Frontiers in Civil and Hydraulic Engineering, Volume 2: Proceedings of the 8th International Conference on Architectural, Civil and Hydraulic Engineering (ICACHE 2022), Guangzhou, China, 12–14 August 2022 9781032471532, 9781032471549, 9781032382470, 9781032382579, 9781003344209, 9781032471556, 9781032471617, 9781003384830

Table of contents :
Cover
Title Page
Copyright
Table of contents
Preface
Committee members
Structural seismic technology and risk assessment monitoring
Calculation and study of the stability of oblique under-crossing tunnels
1 INTRODUCTION
2 ENGINEERING SITUATIONS
3 LOADS AND LOAD COMBINATIONS
4 SETTLEMENT DISPLACEMENT SIMULATION DURING THE CONSTRUCTIONSTAGE
5 CALCULATION RESULTS OF SECONDARY LINING OF MAIN TUNNEL IN USINGSTAGE
6 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Study on monitoring and early warning technology of road slope deformation
1 INTRODUCTION
2 METHODS
3 RESULTS
4 CONCLUSION AND DISCUSSION
ACKNOWLEDGEMENTS
REFERENCES
FRP constraint steel UHPC composite column bending bearing capacity analysis
1 INTRODUCTION
2 COMPUTATIONAL ASSUMPTIONS AND CONSTITUTIVE RELATION
3 FOR CALCULATING THE ULTIMATE BEARING CAPACITY FOR BENDING
4 CONCLUSION
REFERENCES
Study on the influence of spatial variability of tensile strength on ground settlement
1 INTRODUCTION
2 GENERATION OF THE RANDOM FIELD
3 NUMERICAL MODEL
4 ANALYSIS OF SIMULATION RESULTS
5 CONCLUSIONS
ACKNOWLEDGEMENT
REFERENCES
Research on the structural deformation law of subway station induced by difference of foundation bearing capacity
1 INTRODUCTION
2 NUMERICAL COMPUTATIONAL MODELS AND ANALYSIS METHODS
3 ANALYSIS OF NUMERICAL CALCULATION RESULTS
4 CONCLUSIONS
REFERENCES
Finite element dynamic analysis of a new prefabricated anti-collision wall
1 INTRODUCTION
2 ENGINEERING CONDITIONS
3 NUMERICAL ANALYSIS MODEL OF ANTI-COLLISIONWALL
4 MODELLING ASPECTS
5 WORKING CONDITIONS
6 ANALYSIS OF INFLUENCING FACTORS
7 WELDING STRESS
8 CONCLUSIONS
REFERENCES
Research on hot spots of drag reduction and vibration reduction of cylinder flow based on CiteSpace
1 INTRODUCTION
2 LITERATURE CHARACTERISTICS OF DRAG REDUCTION AND VIBRATIONREDUCTION AROUND CYLINDER
3 RESEARCH TRENDS AND PROSPECTS
4 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Application analysis of extrusion and expanded pile in electric power engineering
1 INTRODUCTION
2 ANALYSIS OF LOAD-BEARING APPLICATION OF SQUEEZE-EXPANDED DISKPILES IN POWER ENGINEERING
3 CONTRASTIVE ANALYSIS OF BEARING PERFORMANCE OF STRAIGHT PILE ANDEXTRUSION-EXPANDED DISK PILE
4 LOAD TRANSFER MECHANISM OF SQUEEZED AND EXPANDED DISK PILE
5 CONCLUSIONS
REFERENCES
Analysis of ultimate bearing capacity of prestressed concrete box Girder Bridge
1 INTRODUCTION
2 SPACE STRESS CHARACTERISTICS OF CONCRETE BOX GIRDER BRIDGE
3 ULTIMATE BEARING CAPACITY OF BOX SECTION UNDER ASYMMETRIC LOAD
4 BRIDGE CASE VERIFICATION
5 CONCLUSION
REFERENCES
Research on the blast and impact resistance of FRP panels
1 INTRODUCTION
2 STUDY ON EXPLOSION/IMPACT RESISTANCE OF PURE FRP PLATE
3 STUDY ON EXPLOSION/IMPACT RESISTANCE OF FRP COMPOSITE PLATE
4 EXPERIMENTAL RESEARCH METHOD
5 NUMERICAL SIMULATION STUDY
6 SUMMARY OF NATIONAL NORMS
7 CONCLUSIONS
REFERENCES
Research and application of adaptive bentonite waterproof blanket
1 GENERAL INSTRUCTION
2 RESEARCH PROGRESS OF BENTONITEWATERPROOF BLANKET AT HOME ANDABROAD
3 APPLICATION OF BENTONITEWATERPROOF BLANKET AT HOME AND ABROAD
4 IMPROVED BENTONITE TECHNOLOGY
5 RESEARCH ON IMPROVED BENTONITEWATERPROOF BLANKET TECHNOLOGY
6 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Analysis of traveling wave effect on the seismic response of the spatial cable surface suspension bridge
1 INTRODUCTION
2 BASIC PRINCIPLES OF DYNAMIC RESPONSE ANALYSIS METHODS
3 FINITE ELEMENT MODELING AND SEISMICWAVE SELECTION
4 ANALYSIS OF LONGITUDINAL SEISMIC TRAVELINGWAVE EFFECTS
5 CONCLUSIONS
REFERENCES
Research on the application of enabling technology for river basin hydro-junctions operation safety monitoring system
1 INTRODUCTION
2 MONITORING SYSTEM AND ITS ENABLING TECHNICAL ARCHITECTURE
3 ENABLING TECHNOLOGIES AND THEIR APPLICATIONS
4 CONCLUSIONS
REFERENCES
Risk assessment method for subway-crossing shield tunnel based on ground loss ratio
1 INTRODUCTION
2 PROJECT OVERVIEW
3 RISK ASSESSMENT METHOD FOR SUBWAY-CROSSING SHIELD TUNNEL
4 CASE STUDY
5 CONCLUSION
REFERENCES
Application of steel strand tension technology in the construction of bridge bearing platform
1 INSTRUCTION
2 PROJECT OVERVIEW
3 PROCESS OPTIMIZATION OF BEARING PLATFORM PULL ROD
4 CHECKING CALCULATION OF FORCE AND ELONGATION OF PULL ROD
5 ECONOMIC COMPARISON AND SELECTION
6 CONCLUSION
REFERENCES
Research on the influence of foundation pit excavation on upper span tunnel
1 INTRODUCTION
2 ENGINEERING BACKGROUND
3 PLAXIS 2D FINITE ELEMENT CALCULATION RESULTS AND ANALYSIS
4 CONCLUSION
REFERENCES
Three-dimensional finite element analysis of the influence of graded slope excavation on the adjacent existing diversion tunnel
1 INTRODUCTION
2 PROJECT OVERVIEW
3 THREE-DIMENSIONAL FINITE ELEMENT MODEL AND PARAMETERS
4 FINITE ELEMENT ANALYSIS
5 CONCLUSION
REFERENCES
Traffic noise monitoring and sensitivity modeling of control measures for a highway service area
1 INTRODUCTION
2 METHODOLOGY
3 RESULTS AND DISCUSSION
4 CONCLUSION
ACKNOWLEDGMENT
REFERENCES
Effects of the installation parameters on the compressive performance of helix stiffened composite piles in soft clay
1 INSTRUCTION
2 TEST OVERVIEW
3 RESULTS AND DISCUSSION
4 CONCLUSION
ACKNOWLEDGEMENTS
REFERENCES
Simulation analysis of waterlogging in mountain city
1 INTRODUCTION
2 MODEL BUILDING
3 RESULTS ANALYSIS
4 CONCLUSIONS
REFERENCES
Treatment technology and effect analysis of highway tunnel collapse in rich-water and soft surrounding rock
1 INTRODUCTION
2 RESEARCH BACKGROUND
3 OVERVIEW OF TUNNEL COLLAPSE
4 TUNNEL COLLAPSE TREATMENT PLAN
5 EFFECT ANALYSIS
6 CONCLUSION
REFERENCES
Influences of sluice foundation pit excavation based on monitoring and numerical analysis
1 INSTRUCTIONS
2 PROJECT OVERVIEW
3 MONITORING DATA ANALYSIS
4 FINITE ELEMENT SIMULATION
5 CONCLUSION
ACKNOWLEDGEMENTS
REFERENCES
Optimization of acoustic transit-time flowmeters installed in short converging intakes of a pump station
1 INTRODUCTION
2 MODEL SET-UP
3 NUMERICAL SIMULATION RESULTS
4 FLOW RATE CALCULATION
5 DISCUSSION
6 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
A safety analysis of temporary anchor-tension system for immersed tube in the Shenzhen-Zhongshan link
1 INTRODUCTION
2 PROJECT OVERVIEW
3 LAYOUT OF TEMPORARY ANCHOR-TENSION SYSTEM
4 TEST LOADING
5 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
A Geofencing-based dynamic supervision technology for highway engineering construction site
1 INTRODUCTION
2 DESIGN OF THE DYNAMIC SUPERVISION TECHNOLOGY
3 PERSONNEL ANDWORKPLACE MAPPING DATABASE
4 GEOFENCING-BASED DYNAMIC SUPERVISION TECHNOLOGY
5 APPLICATION SCENARIOS
6 CONCLUSION
REFERENCES
Research on the function-oriented method for delimiting coastal setback lines in China
1 INTRODUCTION
2 INNOVATIVE ELEMENT OF COASTAL ZONE SETBACK LINE DELINEATIONMETHOD
3 CLASSIFICATION OF COASTAL ZONE USES AND FUNCTIONS
4 DELINEATION METHOD OF COASTAL SETBACK LINE BASED ON FUNCTIONALUSE CLASSIFICATION
5 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Natural vibration characteristics and stability analysis of radial steel gate
1 INTRODUCTION
2 RADIAL STEEL GATE MODEL
3 NATURAL VIBRATION CHARACTERISTICS OF THE ARC GATE
4 STABILITY ANALYSIS OF RADIAL STEEL GATE
5 CONCLUSION
REFERENCES
Short-term prediction of runoff based on wavelet noise reduction and LightGBM coupling
1 INTRODUCTION
2 WAVELET NOISE REDUCTION
3 LIGHTGBM TIME SERIES PREDICTION
4 CASE STUDY
5 CONCLUSIONS
ACKNOWLEDGMENT
REFERENCES
Research on construction monitoring technology of suspended shape up-stiffened steel truss bridge based on incremental launching
1 INTRODUCTION
2 PROJECT SUMMARY
3 FINITE ELEMENT SIMULATION
4 MONITORING DURING CONSTRUCTION
5 CONCLUSION
REFERENCES
Influence of central buckle on static and dynamic performance of super-span suspension bridge
1 INSTRUCTIONS
2 ENGINEERING BACKGROUND AND ANALYSIS MODEL
3 INFLUENCE OF CENTRAL BUCKLE PARAMETERS ON THE STATIC AND DYNAMICPERFORMANCE OF THE STRUCTURE
4 CONCLUSION
REFERENCES
Passive cooling measures—the thermosyphon embankment techniques of roads on plateau permafrost
1 GENERAL INTRODUCTIONS
2 ENGINEERING PROBLEMS ROSE IN PERMAFROST CONSTRUCTION
3 THE EFFICIENT COOLING EFFECT OF THERMOSYPHON
4 COMBINATION OF VARIOUS COOLING TECHNIQUES
5 THERMOSYPHON EMBANKMENT IMPROVEMENTS
6 CONCLUSION
REFERENCES
Research on compaction quality monitoring technology of the embankment based on continuous compaction indices
1 INTRODUCTION
2 CONTINUOUS COMPACTION INDICES CMV AND VCV
3 ROLLING EXPERIMENT OF THE EMBANKMENT
4 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Design and practice of deformation monitoring of seawall during construction
1 INTRODUCTION
2 MONITORING CONTENT
3 SECTION LAYOUT
4 INSTALLATION AND COLLECTION
5 DEFORMATION ANALYSIS
6 PREDICTION OF SETTLEMENT DEFORMATION OF SEAWALL
7 CONCLUSIONS
REFERENCES
Crack control of hydraulic dam mass concrete pouring based on image feature
1 INTRODUCTION
2 STUDY ON A CRACK CONTROL METHOD OF MASS CONCRETE POURING
3 EXPERIMENTAL ANALYSIS
4 CONCLUSION
REFERENCES
Smart city construction and resource sustainability
Research on key technologies of intelligent site management platform
1 GENERAL INSTRUCTIONS
2 DATA ANALYSIS TECHNOLOGY BASED ON-SITE MANAGEMENT PLATFORM
3 DATA ANALYSIS PROCESS
4 ADVANTAGES OF INTELLIGENT SITE MANAGEMENT SYSTEM
5 CONCLUSION
REFERENCES
Optimization of building design and contribution to sustainable development
1 INTRODUCTION
2 METHODOLOGY
3 EXPERIMENTS AND NUMERICAL RESULTS
4 CONCLUSIONS
REFERENCES
Reconstruction technology of residential ecological architecture in China Zhuang nationality
1 INTRODUCTIONS
2 ECOLOGICAL ARCHITECTURES AND THE STYLE AND CHARACTERISTICS OFCHINESE ZHUANG NATIONALITY FOLK DWELLINGS
3 RECONSTRUCTION TECHNOLOGY OF RESIDENTIAL ECOLOGICALARCHITECTURE IN CHINA ZHUANG NATIONALITY
4 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Advancements in super cool roofs
1 INTRODUCTION
2 SUPER COOL ROOF
3 CONCLUSION
REFERENCES
Visual analysis of flood control and drainage texts based on CiteSpace
1 INTRODUCTION
2 RESEARCH METHOD
3 RESULTS AND ANALYSIS
4 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Energy saving test and analysis of rural traditional residence in cold region of China
1 INTRODUCTION
2 EXPERIMENTS ON THE RESIDENCE
3 BUILDING ENERGY DISSIPATION ANALYSIS
4 ENERGY-SAVING SCHEME
5 CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Discussion on the application of green and low-carbon concept in large-scale complex buildings
1 INTRODUCTION
2 DISCUSSION ON THE APPLICATION OF GREEN AND LOW-CARBON CONCEPTS INLARGE-SCALE COMPLEX BUILDINGS
3 RESEARCH AND DESIGN EXPERIMENTS BASED ON THE APPLICATION OFGREEN AND LOW-CARBON CONCEPTS IN LARGE-SCALE COMPLEXBUILDINGS
4 EXPERIMENTAL ANALYSIS BASED ON THE APPLICATION OF GREEN ANDLOW-CARBON CONCEPTS IN LARGE-SCALE COMPLEX BUILDINGS
5 CONCLUSIONS
REFERENCES
Author index

Citation preview

FRONTIERS IN CIVIL AND HYDRAULIC ENGINEERING, VOLUME 2

Frontiers in Civil and Hydraulic Engineering focuses on the research of architecture and hydraulic engineering in civil engineering. The proceedings feature the most cutting-edge research directions and achievements related to civil and hydraulic engineering. Subjects in the proceedings including: • • • • • •

Engineering Structure Intelligent Building Structural Seismic Resistance Monitoring and Testing Hydraulic Engineering Engineering Facility

The works of this proceedings can promote development of civil and hydraulic engineering, resource sharing, flexibility and high efficiency. Thereby, promote scientific information interchange between scholars from the top universities, research centers and high-tech enterprises working all around the world.

PROCEEDINGS OF THE 8TH INTERNATIONAL CONFERENCE ON ARCHITECTURAL, CIVIL AND HYDRAULIC ENGINEERING (ICACHE 2022), GUANGZHOU, CHINA, 12–14 AUGUST 2022

Frontiers in Civil and Hydraulic Engineering Volume 2 Edited by

Mohamed A. Ismail Department of Civil Engineering, Miami College of Henan University, China

Hazem Samih Mohamed School of Civil Engineering and Geomatics, Southwest Petroleum University, China

First published 2023 by CRC Press/Balkema 4 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN e-mail: [email protected] www.routledge.com – www.taylorandfrancis.com CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business © 2023 selection and editorial matter, Mohamed A. Ismail and Hazem Samih Mohamed; individual chapters, the contributors The right of Mohamed A. Ismail and Hazem Samih Mohamed to be identified as the authors of the editorial material, and of the authors for their individual chapters, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers nor the authors for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. Library of Congress Cataloging-in-Publication Data A catalog record has been requested for this book SET ISBN: 978-1-032-47153-2 (hbk) ISBN: 978-1-032-47154-9 (pbk) Volume 1 ISBN: 978-1-032-38247-0 (hbk) ISBN: 978-1-032-38257-9 (pbk) ISBN: 978-1-003-34420-9 (ebk) DOI: 10.1201/9781003344209 Volume 2 ISBN: 978-1-032-47155-6 (hbk) ISBN: 978-1-032-47161-7 (pbk) ISBN: 978-1-003-38483-0 (ebk) DOI: 10.1201/9781003384830 Typeset in Times New Roman by MPS Limited, Chennai, India

Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Editors and Contributors, ISBN 978-1-032-47155-6

Table of contents Preface Committee members

ix xi

VOLUME 2 Structural seismic technology and risk assessment monitoring Calculation and study of the stability of oblique under-crossing tunnels Qing Zhang, Yao Zhao, Ziming Gao, Hongchao Wang & Zichuan Han

3

Study on monitoring and early warning technology of road slope deformation Renjie Wu, Zheng Li, Wengang Zhang, Tao Hu, Shilong Xiao, Yangjun Xiao, Luyu Zhang, Sheng Zhang, Dengsui Zhang & Xuxing Zhang

9

FRP constraint steel UHPC composite column bending bearing capacity analysis Yongshuai Li, Shaopeng Lei & Yi Tao

15

Study on the influence of spatial variability of tensile strength on ground settlement Lu Wang, Jinming Li, Yang Lv & Chao Jiang

21

Research on the structural deformation law of subway station induced by difference of foundation bearing capacity Cao Wang, Guodong Li, Wenbin Xiao & Fengting Li Finite element dynamic analysis of a new prefabricated anti-collision wall Chengtao Cui, Pengfei Xie, Wei Yang, Junbin Zhang, Jie Liu & Ying Wang Research on hot spots of drag reduction and vibration reduction of cylinder flow based on CiteSpace Zhihao Fang & Dongfeng Li

29 34

48

Application analysis of extrusion and expanded pile in electric power engineering Lixing Ma, Kai Han, Kai Xue & Qian Li

54

Analysis of ultimate bearing capacity of prestressed concrete box Girder Bridge Yang Hou, Caopeng Hui, Liu Liu & Dongxu Zhao

63

Research on the blast and impact resistance of FRP panels Zeyu Xie

72

Research and application of adaptive bentonite waterproof blanket Bingyao Duan, Xingyue Zhang, Yangyang Wu, Chaoxi Lai & Nana Liu

80

Analysis of traveling wave effect on the seismic response of the spatial cable surface suspension bridge Jiepeng Zhang & Kongliang Chen

86

Research on the application of enabling technology for river basin hydro-junctions operation safety monitoring system Zuqiang Liu, Shuangping Li, Min Zheng, Yiming Chen, Huawei Wang & Yonghua Li

93

Risk assessment method for subway-crossing shield tunnel based on ground loss ratio Zhuyin Wen, Nian Liu, Guangming You, Jianfeng Hou & Lei Jiang v

103

Application of steel strand tension technology in the construction of bridge bearing platform Yanchao Zhang, Pengyuan Yao & Yundong Ma Research on the influence of foundation pit excavation on upper span tunnel Jin Pang, Hequan Zhao, Ting Bao, Lingchao Shou & Lifeng Wang

116 122

Three-dimensional finite element analysis of the influence of graded slope excavation on the adjacent existing diversion tunnel Qinchuan Wang, Xian Chen, Hong Zheng & Wanting Zhao

129

Traffic noise monitoring and sensitivity modeling of control measures for a highway service area Yanqin Wang, Dongxiao Yang, Minmin Yuan, Xianwei Wei & Xiaochun Qin

135

Effects of the installation parameters on the compressive performance of helix stiffened composite piles in soft clay Xiangjun Lin, Wei Jin, Hao Qi, Zhenqin Zhang, Wenlong Ding & Chengyu Guo

146

Simulation analysis of waterlogging in mountain city Xinke Liu, Shouping Zhang, Wanting Bao, Yifan Zhou & Qian Gao

158

Treatment technology and effect analysis of highway tunnel collapse in rich-water and soft surrounding rock Jing Xiao, Dejie Li, Weisheng Rao, Xutao Zeng & Juntao Zhu

164

Influences of sluice foundation pit excavation based on monitoring and numerical analysis Xiaodong Fan, Yingfang Ge & Zhen Zhang

171

Optimization of acoustic transit-time flowmeters installed in short converging intakes of a pump station Peng Zhang, Heming Hu, Qisen Miao, Yiqing Gong & Jingqiao Mao

179

A safety analysis of temporary anchor-tension system for immersed tube in the Shenzhen-Zhongshan link Shenyou Song, Heng Han, Guoping Xu, Qingfei Huang, Minghu Liu & Bin Deng

190

A Geofencing-based dynamic supervision technology for highway engineering construction site Cheng Yang, Yu Cheng, Wei Zheng, Chun-feng He, Wei Chen, Li-bo Bai & Shu-hai Lin

198

Research on the function-oriented method for delimiting coastal setback lines in China He Zhang, Yang Yu, Yantong Li & Haoru Ye

203

Natural vibration characteristics and stability analysis of radial steel gate Jing Dong, Yuhang Bai, Duofei Pei & Junfa Zhang

211

Short-term prediction of runoff based on wavelet noise reduction and LightGBM coupling Pingan Ren, Li Mo, Jianzhong Zhou, Yongchuan Zhang & Hui Qin

224

Research on construction monitoring technology of suspended shape up-stiffened steel truss bridge based on incremental launching method Mingcheng He, Guifen Liu & Yang Wang

230

Influence of central buckle on static and dynamic performance of super-span suspension bridge Fengchao Guo, Huaimao Yang & Yunhua Zhou

237

vi

Passive cooling measures—the thermosyphon embankment techniques of roads on plateau permafrost Ziyi Wang, Tianyi Ye & Yuhang Chen

246

Research on compaction quality monitoring technology of the embankment based on continuous compaction indices Yuanlong Song & Mingpeng Li

258

Design and practice of deformation monitoring of seawall during construction Hai Zhao & Linsong Yang

266

Crack control of hydraulic dam mass concrete pouring based on image feature Xiaogang Li

279

Smart city construction and resource sustainability Research on key technologies of intelligent site management platform Nana Liu, Geng Chen & Yingjia Wang

287

Optimization of building design and contribution to sustainable development Yiran Wang

293

Reconstruction technology of residential ecological architecture in China Zhuang nationality Cong Lu, Nenglang Huang & Haocheng Luo

299

Advancements in super cool roofs Dongdong Tian

305

Visual analysis of flood control and drainage texts based on CiteSpace Siyi Peng, Dongfeng Li, Shiming Liu, Yifan Zhu & Bin Cheng

310

Energy saving test and analysis of rural traditional residence in cold region of China Chen Lin, Xiaotong Peng, Shuai Zhou & Dingyu Chen

317

Discussion on the application of green and low-carbon concept in large-scale complex buildings Yan Yu

322

Author index

328

vii

Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Editors and Contributors, ISBN 978-1-032-47155-6

Preface Hosted by GuangzhouAssociation ofYoung Technologists & Scientists and Guangdong-HongkongMacao Great Bay Area (Guangdong) Talent Hub, the 2022 8th International Conference on Architectural, Civil and Hydraulic Engineering (ICACHE 2022) was successfully held on August 12–14, 2022 in Guangzhou, China. ICACHE 2022 is an annual conference and has been held consecutively in the past seven years, providing a platform for the presentation of technological advances and research results in related fields. We had the honor of having invited Prof. Mohamed A. Ismail from Miami College of Henan University, Canada to serve as our Committee Chair. The conference was composed of keynote speeches and oral presentations, attracting 200 leading researchers, engineers and scientists from all over the world. Firstly, keynote speakers are each allocated 30–45 minutes to hold their speeches. Then in the next part, oral presentations, the excellent papers selected are presented by their authors one by one. During the conference, three distinguished professors invited address their keynote speeches. Among them, Assoc. Prof. Hazem Samih Mohamed from Southwest Petroleum University, Egypt performed a thought-provoking speech on the Rehabilitation of Corroded Tubular Joints with CFRP Laminates. One of the significant challenges confronting the researchers is extending and enhancing the bearing capacity and service life of tubular structures. Therefore, this presentation focused on the rehabilitation of corroded offshore tubular joints by utilizing Carbon Fiber Reinforcement Polymers CFRP laminates as strengthening materials, corrosion inhibition techniques, and a fatigue life extension approach. Moreover, Assoc. Prof. Mianheng Lai from Guangzhou University, China addressed a speech on the title High-Performance Steel Slag Concrete Material and Structure. To solve the problem of concrete’s unsoundness, steel slag concrete-filled-steel-tube (SSCFST) column was proposed, in which the concrete’s expansion would activate larger confining stress, and thereby enhance the overall behavior of the column. And a theoretical load-strain model was developed to predict the mechanical behavior of traditional CFST and SSCFST columns. Their brilliant speeches had triggered heated discussion in the conference. And every participant praised this conference for disseminating useful and insightful knowledge. The proceedings of ICACHE 2022 are a compilation of the accepted papers and represent an interesting outcome of the conference. These papers feature but are not limited to the following topics: Engineering Structure, Structural Seismic Resistance, Monitoring and Testing, Intelligent Building, Smart City, etc. All the papers have been checked through rigorous review and processes to meet the requirements of publication. We would like to express our sincere gratitude to all the keynote speakers, peer reviewers, and all the participants who supported and contributed to ICACHE 2022. Particularly, our special thanks go to the CRC Press / Balkema – Taylor & Francis Group, for all the efforts of its colleague in publishing this paper volume. We firmly believe that ICACHE 2022 had turned out to be a forum for excellent discussions that enable new ideas to come about, promoting collaborative research. Committee of ICACHE 2022

ix

Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Editors and Contributors, ISBN 978-1-032-47155-6

Committee members Committee Chair Prof. Mohamed A. Ismail, Department of Civil Engineering, Miami College of Henan University, Canada Program Committee Prof. Tetsuya Hiraishi, Kyoto University, Japan A. Prof. Hazem Samih Mohame, Southwest Petroleum University, Egypt A. Prof. Mohammad Arif Kamal, Aligarh Muslim University, India A. Prof. Aeslina Abdul Kadir, Universiti Tun Hussein Onn Malaysia, Malaysia Ph. D. Dayang Zulaika Binti Abang Hasbollah, Universiti Teknologi Malaysia, Malaysia Asst. Prof. Hamza Soualhi, University of Laghouat, Algeria Senior Lecturer Mohammadreza Vafaei, Universiti Teknologi Malaysia, Malaysia Senior Lecturer Au Yong Cheong Peng, University of Malaya, Malaysia Senior Lecturer Nor Hasanah Binti Abdul Shukor Lim, Universiti Teknologi Malaysia UTM, Malaysia Senior Lecturer Libriati Zardasti, Universiti Teknologi Malaysia, Malaysia Technical Committee Prof. Dr. Mohammad Bin Ismail, Universiti Teknologi Malaysia, Malaysia Prof. Ir. Dr. Hj. Ramli Nazir, Universiti Teknologi Malaysia, Malaysia Prof. Dr. Muhd Zaimi Bin Abd Majid, Universiti Teknologi Malaysia, Malaysia Prof. Lu, Jane Wei-Zhen, City University of Hong Kong, Hong Kong, China Prof. Mingqiao Zhu, Hunan University of Science and Technology, China Prof. QingXin Ren, Shenyang Jianzhu University, China Prof. Bing Li, Shenyang Jianzhu University, China Prof. Jianhui Yang, Henan Polytechnic University, China Prof. Changfeng Yuan, Qingdao University of Technology, School of Civil Engineering, China A. Prof. Bon-Gang Hwang, National University of Singapore, Singapore A. Prof. Zhu Yuan, School of Architecture, southeast University, China A. Prof. Chaofeng Zeng, Hunan University of Science and Technology, China A. Prof. Weijun Cen, Hohai University, China Asst. Professor Dr. Shah Kwok Wei, National University of Singapore, Singapore Dr. Shaoyun Pu, Southeast University, China Dr. Zhongzheng Lyu, Dalian University of Technology, China Dr. Mohd Rosli Mohd Hasan, Universiti Sains Malaysia, Malaysia Dr. Kim Hung Mo, University of Malaya, Malaysia Dr. Yuen Choon Wah, University of Malaya, Malaysia Dr. Huzaifa Bin Hashim, University of Malaya, Malaysia Dr. Suhana Koting, University of Malaya, Malaysia Dr. Sharifah Akmam Syed Zakaria, Universiti Sains Malaysia, Malaysia Dr. Xian Zhang, School of Architecture of Southeast University, China Dr. Zhiming Chao, University of Warwick, UK Dr. Jun Xie, School of Architecture and Art Central South University, China Dr. Derek Ma, University of Warwick, England Dr. Ning Xu, Department of Science and Technology Development Shanghai Ershiye Construction CO., LTD., China Dr. Hongchao Shi, Chengdu Technological University, China Dr. Li He, Wuhan University of Science and Technology, China xi

Structural seismic technology and risk assessment monitoring

Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Calculation and study of the stability of oblique under-crossing tunnels Qing Zhang, Yao Zhao & Ziming Gao Kunming Railway Construction Company of China Railway No. 8 Engineering Group Co., Ltd., Kunming, Yunnan, China

Hongchao Wang∗ & Zichuan Han College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao, Shandong, China

ABSTRACT: The new constructing tunnel passing through the existing operating tunnel usually causes a certain settlement of the tunnel during the operation period. According to the typical working conditions of new tunnel oblique under-crossing the existing operating tunnel, relying on the north station of Qingdao subway line 8 oblique under-crossing line 3 project, a calculation model was established through MIDAS GTS NX and ANSYS software, respectively. The maximum settlement value and the corresponding position of the overlying tunnel after the excavation of the left and right tunnels of the new line 8 during the construction stage are studied, and the bending moment and axial force at different positions of the lining structure in using stage are studied, respectively. The results show that the existing tunnel has a certain settlement when excavating the tunnel close to an existing tunnel. But the settlement amount is less. During continuous construction, the settlement, bending moment, and axial force at different positions can meet the deformation requirements under normal construction measures. It provides a reference for the safe construction and lining design of the new tunnel oblique under-crossing the existing operating tunnel.

1 INTRODUCTION With the large-scale construction of urban subways in China, the construction conditions of subway tunnels tend to be complex, and new lines generally under-crossing existing operating lines, thus causing many new tunnel stability problems. Relevant scholars have carried out lots of research on the stability of tunnel excavation, Gattinoni et al. studied an example in the central alps considering tunneling in landslide areas connected to deep-seated gravitational deformation (Gattinoni 2019). Lee et al. computed three-dimensional tomography tunnel assessment of allograft anatomic reconstruction (Lee 2019). Wang et al. have done a critical state analysis of the instability of shield tunnel segment lining (Wang 2020). Chiu et al. studied the lining crack evolution of an operational tunnel influenced by slope instability. The above studies mainly study the force and deformation characteristics of the tunnel itself, but the interaction between the new tunnel and the existing tunnel is less involved. (Chiu 2017) This paper aims at the typical working conditions of new tunnels that obliquely under-cross the existing operating tunnel, relying on the north station of Qingdao subway line 8 oblique undercrossing line 3 project, a calculation model was established through MIDAS GTS NX and ANSYS software, respectively. The maximum settlement value and the corresponding position of the overlying tunnel after the excavation of the left and right tunnels of the new line 8 during the construction stage are studied, and the bending moment and axial force at different positions of the lining structure in using stage are studied, respectively. It provides the basis for tunnel stability analysis. ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-1

3

2 ENGINEERING SITUATIONS Qingdao North Subway Station is the transfer station of Metro Lines 1, 3 and 8. Line 3 is laid to the east after leaving Qingdao north subway station, and folds to the northeast after about 200 m. Line 8 is laid on both sides of Line 3 after leaving Qingdao North Station. The left line of Line 8 under-crossing the right line of Metro Line 3 at about 250 m behind Qingdao North Station. The plane angle is about 16. At the intersection of the line, the mileage of line 8 is DK47+584.615 on the left, and that of line 3 is K24+199.772 on the right. Then, the left line of line 8 under-crossing the left line of Metro Line 3 with a plane angle of about 17. The mileage of Line 8 at the intersection of the line is DK47+628.174 on the left, and that of line 3 is K24+151.263 on the left. The distance between line 3 is 10.235∼13 m. The plane line type is the circular curve and transition curve. The vertical section slope is 13‰ (lower in the west and higher in the east). The mining method is adopted. The buried depth of the vault is 5.1∼13.5 m. The line is mainly located in moderately weathered granite strata, and the thickness of overburden is 0.4∼11.5 m. The structure of Line 3 is the horseshoe section. The outside diameter of the initial support design is 6.3m wide and 6.3m high, and the thickness is 300 mm. The support form is a single row small pipe at arch + anchor bolt on the side wall + grid steel frame/section steel frame. The inner diameter design size of the secondary lining is 5.1–m wide and 5.33–m high and 300–mm thick. The total length of the interval line of line 8 is 99.232m. The mining method is adopted for construction. The interval tunnel is laid in the form of a single hole and single line, with a spacing of 37 m. The plane line type is a straight line. 3 LOADS AND LOAD COMBINATIONS Calculation was performed mainly according to the risk sources of Line 8 under-crossing Line 3 in the section from Qingdao North Railway Station to Cangkou Station. The support parameters and the lining safety of tunnel structures of Line 8 and Line 3 are checked and calculated, including the strength, crack width and construction stability. The load combination is carried out according to different working conditions of the construction stage, using stage and special load effects. (1) Fundamental combination during construction stage: permanent load + variable load (2) Using stage: Fundamental combination: permanent load + variable load Accidental combination: permanent load + variable load + earthquake loading The load combinations of serviceability limit state adopt quasi-permanent combinations to calculate. 4 SETTLEMENT DISPLACEMENT SIMULATION DURING THE CONSTRUCTION STAGE In order to predict the impact on Metro Line 3 during the interval tunnel excavation, a threedimensional numerical calculation method was adopted to simulate the construction. The integrated model established by Midas GTS NX is shown in Figure 1. To eliminate the influence of the boundary effect and completely simulate the influence of left and right line excavation on Metro Line 3, the calculation model is 65 m along the direction of Metro Line 3, and 94.4 m in the vertical direction. The height of the model is 42 m, and the top of the double-line tunnel is about 21 m from the surface. A full fixed constraint is applied to the bottom of the geometric model, and a vertical sliding constraint is applied to both sides. The surface of the model is a free boundary. The calculated parameters of rock and soil strata are evaluated in combination with the geological exploration report and related engineering experience. 4

Figure 1.

Model meshing.

In the calculation, the right tunnel is excavated first, and the left tunnel is excavated later. Excavation is as follows: right line upper section excavation – right line upper section initial support – right line under section excavation – right line under section initial support – excavation on the left line upper section after 20 meters on the right line – left line upper section initial support – left line under section excavation – left line under section initial support. According to the calculation results, after the right line tunnel excavation is completed, the maximum displacement of Line 3 occurs in the left line interval of Line 3 closest to Line 8. The maximum displacement is 0.074 mm, as shown in Figure 2. After the left line excavation is completed, the maximum displacement of Line 3 is 0.283 mm, and the displacement cloud diagram is shown in Figure 3.

Figure 2.

Displacement cloud diagram after right line excavation is completed.

5

Figure 3.

Displacement cloud diagram after left line excavation is completed.

According to the calculation results, Line 3 will produce a certain settlement during the excavation of the interval tunnel, but the settlement amount is less. During continuous construction, the settlement can meet the deformation requirements under normal construction measures. 5 CALCULATION RESULTS OF SECONDARY LINING OF MAIN TUNNEL IN USING STAGE The tunneling method in this section adopts fully covered waterproofing. The lining of a fully covered waterproof section bears all soil and water loads, which are determined by the load-structure method. The structure size and reinforcement are calculated and determined by the internal force envelope diagram obtained by the load-structure method. Because the longitudinal size of the tunnel is very long, and the transverse size is very small, it can be simplified as a plane strain problem and calculated horizontally for each extension meter. The load-structure model was adopted for calculation, and the secondary lining is simulated by a two-dimensional beam element. The beam element width is unit width, and the beam height is actual lining thickness. The secondary lining is made of C45 concrete, the elastic modulus is 33.5 GPa, the Poisson’s ratio is 0.2, and the weight is 25 N·m−3 . The surrounding rock resistance is simulated by the spring element. The applied range and quantity of the spring are adjusted and optimized according to the deformation of the structure in the trial calculation. Only when the structure produces displacement pointing to the direction of the surrounding rock, the spring element is added. The elastic resistance coefficient of the surrounding rock is selected according to the lateral and vertical bed coefficients of the surrounding rock measured. The structure size and reinforcement are calculated and determined by the envelope diagram of internal force obtained by the load structure method. The reinforcement was calculated by the ANSYS program and the crack width of the structure was checked. The top of the calculation sectional tunnel is covered with 26.7–m soil. The weighted average value of the horizontal foundation bed coefficient of the ground is 100.0 MPa/m. The vertical foundation bed coefficient of the ground is 120.0 MPa/m. The thickness of the vault and arch wall lining is 350 mm, and that of the abut is 350 mm. The C45 concrete and HRB400 reinforcement were used. 6

ANSYS finite element program analysis results are as follows: Without considering the water pressure conditions, the fundamental combination calculation results are shown in Figure 4 and Table 1. The bending moment and axial force at different positions, such as vault, spandrel, hance, abut and arch bottom, meet the safety requirements.

Figure 4. The bending moment diagram and axial force diagram of the fundamental combination.

7

Table 1. The calculation results of fundamental combination (Without considering the water pressure). Position

Bending moment (N·m)

Axial force (N)

Reinforcement design (per meter)

Vault Spandrel Hance Abut Arch bottom

2.77E+05 8653.8 −28551 −50481 68616

−1.44E+06 −1.68E+06 −2.10E+06 −2.30E+06 −2.36E+06

6.7C25 6.7 C25 6.7 C25 6.7C25 6.7C25

6 CONCLUSION (1) According to the condition of the new tunnel under-crossing the existing tunnel, the calculation model is established through the Midas GTS NX software, and the maximum settlement value and the corresponding position of the overlying tunnel after the excavation of the left and right tunnels of the new tunnel are obtained successfully. (2) According to the problem of the lining design of the main tunnel in the using stage, the bending moment and axial force at different positions of the lining structure were obtained through ANSYS software analysis, which provided the data basis for lining design. (3) Future research should focus on the support method for the new excavation tunnel.

ACKNOWLEDGMENTS The first author would particularly like to acknowledge my team members for their wonderful collaboration and patient support. Authors would first like to thank the referee’s valuable advice.

REFERENCES Chiu Y, Lee C, Wang T. Lining crack evolution of an operational tunnel influenced by slope instability. (2017) Tunnelling and Underground Space Technology, 65: 167–178. Gattinoni P, Consonni M, Francani V, Leonellicd G, Lorenzob C. (2019) Tunnelling in landslide areas connected to deep seated gravitational deformations: An example in Central Alps (northern Italy). Tunnelling and Underground Space Technology, 93: 103100. Lee D W, Park I K, Kim M J, Kim W J, Kwon M S, Kang S J, Kim J G, Yi Y. (2019) Three-Dimensional computed tomography tunnel assessment of allograft anatomic reconstruction in chronic ankle instability: 33 cases. Orthopaedics & Traumatology: Surgery & Research, 105 (1): 145–152. Wang S, Wang X, Chen B, Fu Y, Jian Y, Lu X. (2020) Critical state analysis of instability of shield tunnel segment lining. Tunnelling and Underground Space Technology, 96: 103180.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Study on monitoring and early warning technology of road slope deformation Renjie Wu∗ Chongqing Chengtou Road and Bridge Administration Co. Ltd., Chongqing, China School of Civil Engineering, Chongqing University, Chongqing, China

Zheng Li Chongqing Chengtou Road and Bridge Administration Co. Ltd., Chongqing, China

Wengang Zhang School of Civil Engineering, Chongqing University, Chongqing, China

Tao Hu, Shilong Xiao, Yangjun Xiao, Luyu Zhang, Sheng Zhang, Dengsui Zhang & Xuxing Zhang Chongqing Chengtou Road and Bridge Administration Co. Ltd., Chongqing, China

ABSTRACT: In road traffic construction, the large-scale excavation and the restrictions by geological and geomorphic conditions cause frequent accidents, posing a serious threat to road construction and operation safety. High-quality monitoring and early warning of road slope deformation are the focus of disaster prevention and control. The research results can improve the monitoring and early warning ability of road slope deformation, save the losses caused by disasters, and provide technical support for governments at all levels and relevant departments to implement sustainable development planning and decision-making. It can be of great significance in disaster reduction and bring economic, social, and environmental benefits.

1 INTRODUCTION China has a vast territory and complex terrain. Three types of topographies, namely, the plateaus and mountainous and hilly areas account for about 65% of the land area. The complex and changeable geomorphic conditions have made China one of the countries with the most serious geological disasters and the Chinese the most threatened group in the world. There are many types of geological disasters in China, including landslide, collapse, debris flow, surface subsidence, ground fissure, and land subsidence. Landslides and collapses respectively account for about 70% and 20% of the total geological disasters. In the past four years, geological disasters have occurred frequently in China, resulting in serious damage. In particular, the number of geological disasters from 2018 to 2020 witnessed significant growth. The number of geological disasters in 2019 increased by 108.4% compared with that of 2018, and the number of geological disasters in 2020 increased by 26.8% compared with that of 2019 (Figure 1). The monitoring and early warning of road slope deformation have been important work since a long time ago, not only to ensure the accuracy of monitoring project data but also to ensure the safety of site laying equipment and of construction workers. Slope deformation monitoring and early warning systems can provide an efficient and safe data management platform for road slope ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-2

9

Figure 1.

Statistics of geological disasters in China from 2018 to 2021.

monitoring and early warning and emergency rescue. It is a concrete manifestation of improving disaster prevention ability comprehensively and strengthening the construction of a disaster prevention and preparedness system. It is also a concrete measure to implement the national policy of improving the quality and level of transportation service and strengthening the construction of transportation safety supervision and emergency guarantee system.

2 METHODS The deformation monitoring of road slopes has been started since the 1950s. At first, limited by instruments and technologies, the monitoring can only be operated manually based on experience to observe the surface change, hydrological conditions, and crack width at a certain time to obtain relevant data to determine whether these slopes were stable. Yer with the progress of science and technology, the research on road slope deformation monitoring and early warning has made some achievements. 2.1 Road slope deformation monitoring Based on the relationship between rainfall and landslide, geological conditions of landslide-prone areas, and real-time monitoring data of regional network rainfall, Keefer (1987) used the slope stability model to predict the possibility of landslides during a rainstorm. Sardroud (2012) discussed a new landslide monitoring technology. According to radio frequency identification (RFID) technology and combined with ultrasonic sensors, the groundwater level in slope and landslide-prone areas was accurately identified and monitored. GSM was used to transmit the monitoring data to the central data management library, and the collected data were used for slope stability analysis to 10

provide a real-time sensitivity map. And GSM would be automatically alarmed when the landslide occurred. Feng (2016) developed a non-contact photogrammetry system, which could detect the deformation and final failure of the slope before failure. It provided the deformation mode of the section and the whole surface and generated the velocity map when the slope was rapidly damaged. Based on the monitoring data of crack gauge and total station, Loew (2017) developed an early warning system, which obtained early warning, general public warning, and evacuation thresholds. The early warning data covered about 10 years, and it supplemented the information of similar fault events in the past. Wang (2019) analyzed the deformation law of the slope by monitoring the surface deformation and the internal displacement of the rock during the slope excavation. Monitoring points were set to monitor the surface deformation of the slope. Multi-point displacement meter and inclinometer were installed to monitor the internal deformation of the slope. And the results showed that the slope was stable before excavation, and the slope displacement and internal displacement tended to converge in a short time after excavation. Lin (2019) used the variation of the TDR waveform and the calculation of the reflection coefficient integration method to determine the position and size of shear deformation in a landslide to monitor the position and size of potential slope movement in a landslide. 2.2 Road slope deformation warning system Based on the existing monitoring methods, Hosseyni (2011) used GIS to analyze the collected data, combined with RFID and motion-sensitive sensors for road slope landslide monitoring and early warning. Chen (2012) established the time series prediction model of road slope displacement without cohesive soil, constructed the membership function based on distance measurement, and established an effective method for predicting future displacement of slope based on monitoring data to judge slope stability. Segoni (2015) developed a set of landslide prediction systems. Through the reverse analysis of the records from 2004 to 2010, the verification test was carried out. The regional early warning system could correctly predict the accurate position of 83% of landslides according to the rainfall threshold. Fendi (2019) established a landslide monitoring system with a resolution ratio of 1 mm and a measurement range of 1 mm to measure soil movement and soil moisture. Then the early warning was provided through an alarm. Zhou (2019) analyzed the purpose and structure of road slope monitoring and early warning and developed the road slope monitoring and early warning system from the expression layer and service layer. Chung (2019) proposed a slope real-time monitoring framework based on TDR technology, which could observe multiple large-depth landslide surfaces timely and was helpful for effective early warning. Based on landslide EWS, Wu (2020) used Ad-Hoc technology to design a fast deployment monitoring system (FDMS) to monitor landslide displacement for real-time prediction. Thein (2020) analyzed the inducements of road slope landslides and established a landslide monitoring system based on a wireless sensor network. The system displayed the corresponding signal at the relay station and sent the alarm message to the mobile phone for early warning. Fang (2020) developed monitoring and early warning equipment based on topographic and hydrological information and landslide area change, established new landslide monitoring and early warning indicators, and strengthened the hardware and software construction of the local disaster response center.

3 RESULTS In summary, the early warning method of road slope deformation has undergone changes from field inspection of group prevention and measurement to remote automatic monitoring and early warning, and from single monitoring to syncretic monitoring and essential monitoring. Due to different types and modes of slope deformation and failure, the monitoring methods adopted are also different (Figure 2). As far as monitoring methods and contents are concerned, commonly used methods at present are displacement monitoring, stress-strain monitoring, groundwater dynamic monitoring, surface water dynamic monitoring, ground sound monitoring, environmental factor 11

monitoring macroscopic phenomenon monitoring by using a theodolite, level gage, rangefinder, total station, electronic theodolite, photoelectric rangefinder, optical fiber, other instruments and equipment through a laboratory test, mathematical fitting, numerical simulation, and field test.

Figure 2.

Monitoring equipment for slope deformation.

In recent years, with the continuous improvement of monitoring methods and the diversification of monitoring instruments, China has made many achievements in slope deformation monitoring and prediction. However, in the past decade, the successful prediction rate of geological disasters such as slope landslides and collapses was less than 4% annually. Road slope geological disasters are characterized by suddenness and complexity, which makes it difficult to unify monitoring and early warning methods and ensure high reliability. At present, the threshold and early warning ideas are usually adopted in the actual monitoring and early warning projects yet without primary consideration of the evolution of slope deformation, resulting in a high false alarm rate of early warning. At the same time, a large number of studies are mainly concentrated on the early warning model. In the actual monitoring and early warning, monitoring methods are often not optimized, monitoring methods are not perfect, monitoring data are abnormal, and so on. In the monitoring process, the authenticity and reliability of data are extremely important, which directly affects the success of early warning and prediction. Nowadays, there is still a lack of effective research on the quality evaluation system and standards of monitoring data. In addition, because there are many slope collapse monitoring instruments and monitoring types, and the monitoring data are multi-source, the previous research on the integration and call of monitoring data was not enough. Therefore, how to solve the real-time organization and distribution of massive monitoring data, and how to build an efficient real-time and intelligent monitoring data management platform for slope collapse are the primary problems to be solved in the establishment of road slope monitoring and early warning system.

4 CONCLUSION AND DISCUSSION In road construction, due to the influence of terrain, it is inevitable to have high fill and deep excavation which result in a large number of road slopes. These slopes are affected by load, rainfall, temperature changes, unreasonable survey, design, construction, and other factors, causing slope deformation and failure and affecting road traffic safety. Mastering the influencing factors and failure characteristics of road slope deformation and failure and studying the slope deformation mechanism and its evolution process are of great significance to analyze slope stability. 12

Considering the diversity of slope types, the collection and transmission of deformation data are also different, so monitoring equipment and methods should be reasonably selected. For multisource real-time monitoring data, a data integration method is established, and the monitoring data of different types and instruments are integrated into the real-time monitoring database. Monitoring data are usually not directly used in the calculation of prediction and early warning and need to be preprocessed. Therefore, it is necessary to study the processing methods of abnormal data (missing data, noise, and filtering). The adaptability of each processing method should be analyzed. Different methods for data processing should be selected to realize the automatic identification of various monitoring data and to provide data support for automatic real-time warnings. In addition, it is necessary to study the warning model, threshold, and warning level to ensure the effective operation of real-time monitoring. At present, there are still many uncertain factors in the monitoring and early warning of road slope deformation, so the monitoring and early warning technology still need to be further explored and studied. ACKNOWLEDGEMENTS This work was supported by the Natural Science Foundation of Chongqing under Grant [Number cstc2021jcyj-bshX0028]. The authors’ sincere thanks also go to the reviewers and editors for their valuable comments and advice, which improved the quality of the paper. REFERENCES Chen, Y.Y., Wang, S.W., Chen, N., Long, X.Q. & Tang, X.R. 2012. Forecasting cohesionless soil highway slope displacement using modular neural network. Discrete Dynamics in Nature and Society 2012: 1–15. Chung, C.C. & Lin, C.P. 2019. A comprehensive framework of TDR landslide monitoring and early warning substantiated by field examples. Engineering Geology 262: 105330. Fang, Y.M., Chou, T.Y., Hoang, T.V., Bui, Q.T., Nguyen, D.B. & Nguyen, Q.H. 2020. New landslide disaster monitoring system: Case study of Pingding Village. Applied Sciences 10(19): 6718. Fendi, A.P., Nanang, M.Y. & Gembong, W.A. 2019. Landslide early warning system based on arduino with soil movement and humidity sensors. Journal of Physics: Conference Series 1153(1): 012034. Feng, T.T., Mi, H., Scaioni, M., Qiao, G. & Lu, P., et al. 2016. Measurement of surface changes in a scaleddown landslide model using high-speed stereo image sequences. Photogrammetric Engineering & Remote Sensing 82(7): 547–557. Hosseyni, S., Bromhead, E.N., Majrouhi, S.J., Limbachiya, M. & Riazi, M. 2011. Integrated RFID and sensor technologies for effective landslide monitoring and early warning. ISEC 2011-6th International Structural Engineering and Construction Conference: Modern Methods and Advances in Structural Engineering and Construction. 633–638. Keefer, D.K., Wilson, R.C., Mark, R.K., Brabb, E.E. & Brown, W.M., et al. 1987. Real-time landslide warning during heavy rainfall. Science (New York, N.Y.) 238(4829): 921–925. Lin, Y.S., Chen, I.H., Ho, S.C., Chen, J.Y. & Su M.B. 2019. Applying time domain reflectometry to quantification of slope deformation by shear failure in a landslide. Environmental Earth Sciences 78(5): 123. Loew, S., Gschwind, S., Gischig, V., Keller-Signer, A. & Valenti, G. 2017. Monitoring and early warning of the 2012 Preonzo catastrophic rockslope failure. Landslides 14(1): 141–154. Sardroud, J.M., Hosseyni, S., Bromhead, E.N. & Riazi, M. 2012. Automated landslide monitoring and warning using radio frequency identification technology. International Journal of Safety and Security Engineering 2(2): 118–130. Segoni, S., Lagomarsino, D., Fanti, R., Moretti, S. & Casagli N. 2015. Integration of rainfall thresholds and susceptibility maps in the Emilia Romagna (Italy) regional-scale landslide warning system. Landslides 12(4):773–785. Thein, T.L.L., Sein, M.M., Murate, K.T. & Tungpimolrut K. 2020. Real-time monitoring and early warning system for landslide prevention in Myanmar. 2020 IEEE 9th Global Conference on Consumer Electronics 2020: 303–304.

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Wang, Y.Q., Zhang, S.B., Chen, L.L., Xie, Y.L & Wang, Z.F. 2019. Field monitoring on deformation of high rock slope during highway construction: A case study in Wenzhou, China. International Journal of Distributed Sensor Networks 15(12): 1–15. Wu, Y.B., Niu, R.Q., Wang, Y. & Chen, T. 2020. Fast deploying monitoring and real-time early warning system for the Baige landslide in Tibet, China. Sensors 20(22): 6619. Zhou, X.R., Zheng, K., Shi, Q.H. & Sheng, J.X. 2019. Research on highway slope monitoring and warning system. IOP Conference Series: Materials Science and Engineering 569: 042002.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

FRP constraint steel UHPC composite column bending bearing capacity analysis Yongshuai Li∗ , Shaopeng Lei & Yi Tao Xi’an University of Architecture and Technology, Xi’an, China

ABSTRACT: According to the experiment and numerical simulation, the FRP confined steel reinforced UHPC (FCSRU) composite column under a high axial compression ratio has a good seismic mechanics performance and can be applied to many high-rise building structures. In recent years, the research related to FRP constraints and steel reinforced concrete composite columns has been increasing in recent years, but most of them focused on the composite column axial compression. In this paper, mathematical and mechanical tools are used and the superposition method is adopted to analyze the FCSRU bending bearing capacity of the composite columns.

1 INTRODUCTION The combination of FRP-constrained steel UHPC has both the advantages of the steel-UHPC columns and FRP material. It can be used as a new structure with superior performance to be applied in high-rise buildings and large span bridges and can also be used as a new reinforcement scheme applied to the existing old buildings. The research on FRP constraint steel UHPC composite columns is still very scarce, and there are only a few studies on the axial compression performance with no systematic study of various factors on FRP constraint bending steel composite columns or the influence of shear bearing capacity (Han 2005; Xiao 2000). Therefore, based on the experiment and numerical simulation, the high-performance FRP constraint force performance and failure mechanism of a concrete column under different loads are examined, and the calculation method of composite column bearing capacity is put forward.

2 COMPUTATIONAL ASSUMPTIONS AND CONSTITUTIVE RELATION The following assumptions about the FCSRU bending bearing capacity of composite column derivation analysis are used for calculation. (1) Flat section assumption (Zhou 2006). Under the action of external load, the cross-section of each point linear change appears to strain along the section height direction. (2) The tensile strength of UHPC is not reckoned. For UHPC, due to internal steel fiber, the tensile strength was bigger than ordinary concrete. Yet in the process of the test, it was found that UHPC, under the restriction in FRP, had no larger deformation. Thus the tensile strength of UHPC can be ignored. ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-3

15

(3) The package h-beam uses the ideal elastic-plastic model, as shown in Figure 1. And its stress and strain relation are as follows (Jiang 2007). ⎧ ⎪ ⎨ −fsd σs (ε) = Es ε ⎪ ⎩ fsd

Figure 1.



 ε ≤ −εy   |ε| < εy   ε ≥ εy

(1)

Steel stress-strain curve.

(4) UHPC in FCSRU composite column is restrained circumferentially by FRP pipe. This constraint will increase the limit of UHPC compressive strength. And the compressive stress-strain curve relationship of UHPC is built based on the UHPC stress-strain relationship curve proposed by Lam and Teng (Li 2005; Teng 2005), which are calculated as follows. ⎧ 2 ⎪ ⎨ E ε − (Ec − E2 ) ε 2 c  4fco σ= ⎪  ⎩ fco + E2 ε

(0 ≤ ε ≤ εt )

(2)

(x ≥ 1)

εt =

2fco Ec − E 2

(3)

E2 =

fcc − fco εcc

(4)

fl =

2ffrp,t tfrp d

(5)

Ec is the elastic modulus of unconstrained concrete; E2 constrains the slope of the second straight section of the concrete stress-strain for FRP; ffrp,t and tfrp are the annular ultimate tensile strength and thickness of the FRP tube; d is the diameter of the constrained concrete; fl is the circular binding force provided for FRP; fco is the cylindrical compressive strength for unconstrained concrete; fcc is the compressive strength of the cylinder constraining concrete. (5) For FRP pipe, a linear elastic material, when the strain reaches the ultimate strain εf , the fiber breaks and can’t continue to provide annular constraint for the internal UHPC. Its stress-strain relationship is measured by the test and the mathematical expression is shown below.  σf =

Ef ε 0

16

ε < εf ε > εf

(6)

3 FOR CALCULATING THE ULTIMATE BEARING CAPACITY FOR BENDING 3.1 The value of the section M-N The bending bearing capacity of the combination column can be seen as the superposition of the mechanical properties of the FRP pipe, UHPC, and H-beam, as shown in Equations (7) and (8). The UHPC axial force and bending moment under the compression state (Nci,c , Mci,c ), the axial force and bending moment of the yield part of H-shaped steel under pressure (Ns,c , Ms,c ), the axial force and bending moment of the unyielding part of H-shaped steel under pressure (Ns ,c , Ms ,c ), the axial force and bending moment of the yielding part of H-shaped steel in the tensile state (Ns,t , Ms,t ), the axial force and bending moment of the unyielding part of H-shaped steel under pressure (Ns ,t , Ms ,t ), and the axial force and bending moment of FRP pipe in the tensile state (Nfrp,t , Mfrp,t ) are all included. N = Nfrp,c + Nci,c + Ns,c + Ns ,c − Nfrp,t − Ns,t − Ns ,t

(7)

M = Mfrp,c + Mci,c + Ms,c + Ms ,c + Mfrp,t + Ms,t − Ms ,t

(8)

The values of the axial force and bending moment should also satisfy Equation (9). Where, ei is the initial eccentricity, ei is the sum of the additional eccentric distance and the load eccentric distance, e0 is the eccentric distance of the vertical load for the center of gravity of the crosssection and ea is the additional eccentricity. The value is larger than 1/30 and 20mm of the eccentric cross-sectional size. M =N · e

(9)

e i = e0 + e a

(10)

3.2 The section size of the bias On the basis of the flat section assumption, the combined column section is defined as the tensile side steel flange of the tensile type when the large eccentric compression is destroyed. And the opposite is the small eccentric compression failure and the failure state when the transition from large bias to small bias is the boundary compression failure. Whether large bias failure or small bias failure occurs, UHPC on the pressure side can achieve its corresponding ultimate pressure strain. The specific discriminant method of size bias is as follows.

Figure 2.

Limit damage section strain distribution.

If the boundary of the cross-section is damaged by compression, the tensile side of the steel flange would yield at the same time, and the UHPC would be under pressure failure, according to Figure 2. The strain distribution of the combined column section in this state is shown in Figure 2, which also provides the inner edge of the steel flange of the tension side. The height of the outer edge of the UHPC pressure zone is h0 , the height of the bounding pressure zone is xcb , the UHPC limiting pressure strain is εcu , the section steel limit pulls strain is εsy , the section steel yield stress 17

is fy , and Esy is the elastic modulus of the section steel. The relative boundary pressure zone can be known from the geometric relationship. The formula is as follows. ξ=

xcb εcu 1 1 = = = f h0 εcu + εsy 1 + εεcusy 1 + εcu yEsy

(11)

Where εcu , fy , Esy , all material properties, are measured by tests, and the cross-sectional form is known h0 . The only determination is the height of the cross-sectional pressure zone in the event that the boundary failure can be found according to this formula. The value xcb is the actual occurrence of bending failure. If x < xcb , then a large bias failure occurs. On the contrary, if x > xcb , then a small bias failure occurs. If the neutral axis height is known, the only determining factor is the corresponding axial force N. With the axial tensile lateral movement, the N value increases monotonously. Therefore, the value of N and the neutral axis height became known. If the axial force N is known, it can be concluded that among them, the height of the shaft shows discriminatory bias. 3.3 Large eccentric loading damage section bending bearing capacity calculation Figure 3 is the FCSRU composite column with large eccentric compression failure stress distribution. D in the figure in the center of the neutral axis to the cross-section when bending failure. Through FRP pipe, UHPC and the superposition of the internal force of the h-beam provided all the damage conditions of axial force and bending moment. The specific calculation process is as follows.

Figure 3.

Stress distribution when the large eccentric loading damage.

The axial forces and bending moments of FRP pipes under the pressure of large eccentric compression are shown in the following Equations (12), (13), (14), and (15), where εfrp,c is the ultimate compressive strain of the FRP tube, R is the inner diameter of the FRP tube, tfrp is the thickness of the FRP tube, Efrp is the modulus of elasticity of FRP tubes, and εfrp,t is the tensile strain for FRP tubes. π Rα (12) tfrp Nfrp,c = εfrp,c Efrp 180   √R2 −d 2

tfrp 2 2 Mfrp,c = εfrp,c Efrp √ R −d −d + (13) tfrp dx 2 − R2 −d 2  

π Rα (14) tfrp Nfrp,t = εfrp,t Efrp π (R + tfrp )2 − R2 − 180     √   R R

tfrp R2 − x 2 2 2 R −x −d + tfrp dx (15) d− tfrp dx + 2 √ Mfrp,t = εfrp,t Efrp 2 2 −R R2 −d 2 And α = arccos Rd is the angle system. 18

For UHPC, under the constraint of an FRP, the pipe cross-section deformation occurs. When the UHPC stress serves as the uneven distribution, the material the equivalent stress and strain relations is as follows. xc is for practical compressive zone height, β1 for the coefficient of equivalent compression zone height, α1 for equivalent rectangular stress coefficient, and fci for the constraint of UHPC. Constraints on the stress-strain relationship of the UHPC curve using Lam and Teng are suggested by FRP confined concrete stress-strain curve. UHPC under large eccentric loading damage on the axial force and the bending moment are indicated by the following Equations (16) and (17). 

Nci,c

Mci,c



πR2 arccos R−βR1 xc = α1 fci − (R − β1 xc ) R2 − (R2 − β1 xc )2 (16) 180     √R2 −(R−β1 xc )2 

 √R2 − x2 R β1 2 2 = α1 fci √ R − x − (R − β1 xc ) − + 1− xc dx (17) 2 2 2 − R2 −(R−β1 xc )2

For the built-in H-beam, the steel stress at cross-section deformation of tension and compression trapezoidal distribution is suitable for steel height H. tw is for the thickness of the flange, bw for the flange width, hs for tension within the flank edge boundary from the neutral axis height, ts for the thickness of the flange, dn for tensile flank flange outer boundary from the neutral axis height, and yn for steel yielding some height. Under large eccentric loading damage, steel on the tension side and pressure side of yield and yield for part of the axial force and bending moment are shown in Equations (18), (19), (20), (21), (22), (23), (24), and (25). Ns,c = fy bw tw + fy ts (yn − tw )  tw 1 + fy ts (yn − tw )(2dn − tw − yn ) Ms,c = fy bw tw dn − 2 2 1 fy ts (dn − yn ) 2 1 = fy ts (dn − yn )2 3 = fy bw tw + fy ts [H − dn − (dn − yn ) − tw ]  tw 1 = fy bw tw H − dn − + fy ts [H − dn − (dn − yn ) − tw ] (H − tw − yn ) 2 2

(18) (19)

Ns ,c =

(20)

Ms ,c

(21)

Ns,t Ms,t

1 fy ts (dn − yn ) 2 1 = fy ts (dn − yn )2 3

(22) (23)

Ns ,t =

(24)

Ms ,t

(25)

4 CONCLUSION Based on the FCSRU force mechanism of the composite column under bending load derived from its cross-section bending bearing capacity, the concrete results are as follows. (1) Based on the flat section assumption and the cross-section of each material’s stress-strain relations, the FCSRU combination column section size bias discriminant formula is deduced. (2) The mathematical deduction of composite column size bias damage occurs according to the bending bearing capacity calculation formula of a cross-section. 19

REFERENCES Han K.S. (2005). Testing study on the behavior of high-strength concrete column confined by carbon fiber sheet [D]. Dalian: University of Technology. JiangT. &Teng J. G. (2007). Analysis-oriented stress–strain models for FRP–confined concrete [J]. Engineering Structures, 29(11): 2968–2986. Li J. H. (2005). Study on the performance of steel reinforced high-strength concrete columns under low cyclic reverse loading [D]. Xi’an: 53–60. Teng J. G. & Chen J. F. & Smith S. T., et al (2005). FRP strengthened RC structures [M]. Beijing: Chinese Architecture and Building Press, 2–5. Xiao Y. & Wu H. (2000). Compressive behavior of concrete confined by carbon fiber composite jackets [J]. Journal of Material in Civil Engineering, 12(2): 139–116. Zhou L & Wang L G & Li S (2008). Calculation of positive cross-section bearing capacity of FRP-constrained SRHC bending components [J]. Journal of Northeastern University (Natural Sciences Edition), (03): 108–111.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Study on the influence of spatial variability of tensile strength on ground settlement Lu Wang∗ , Jinming Li∗ , Yang Lv∗ & Chao Jiang∗ SHCCIG Caojiatan Mining Co., Ltd., Yulin, China

ABSTRACT: To investigate the influence of spatial variability of tensile strength on ground deformation caused by excavation, the tensile strength is selected as a random variable that has a log-normal distribution. The random field is discretized by Karhunen-Loève expansion and then mapped to the numerical model. The Monte-Carlo method is carried out by a finite difference algorithm to discuss the influence of the variability of the tensile strength on ground settlement. The results show that the stochastic analysis will yield larger mean values of deformation at the midpoint of the ground surface than the deterministic analysis. The influence of the tensile strength on the deformation of the model is mainly limited in the tensile failure zone of the upper part of the excavation zone. This local influence causes the coefficient of variation. The auto-correlation distance of the tensile strength has a small effect on the probability density function and the cumulative distribution function of the deformation at the midpoint of the ground surface.

1 INTRODUCTION After mining (Hu et al. 2014) and underground excavation (Wang et al. 2008), the original equilibrium state of the rocks and soils around the excavated area is disrupted. This effect will cause continuous or discontinuous surface deformation at the ground surface if it developed to the surface (Sun et al. 2009). The surface deformation caused by underground excavation will cause a series of engineering problems such as the cracking of houses and road damage (Tong et al. 2004). To avoid the impact of underground excavation on structures near the surface, accurate prediction of ground settlement in the extraction area is needed for reasonable design, construction, and management planning of excavation projects. The existing methods for predicting ground settlement mainly include the empirical formula method, the analytical method, and the numerical simulation method (Tong et al. 2004). To simplify the calculation, these methods usually assume that the physical and mechanical properties of the underground space are homogeneous. However, rocks and soils often exhibit significant spatial variability. Vanmarcke (Vanmarcke 1983) proposed the random field theory to describe the spatial variability of geotechnical parameters. Many scholars have conducted extensive research on slope stability (Griffiths and Fenton 2004), reinforced soil (Khan and Dasaka 2020), retaining walls (Fenton et al. 2005), foundation bearing capacity (Kasama and Whittle 2004), and other issues by applying the random field theory. These studies have shown that the spatial variability of rocks and soils has a significant influence on the mechanical behavior of rock-soil bodies and engineering structures. In recent years, the influence of spatial variability of rock-soil bodies on ground settlement has been paid attention to by scholars. Li et al. studied the effect of spatial variability of elastic modulus ∗ Corresponding Authors: [email protected], [email protected], [email protected] and [email protected]

DOI 10.1201/9781003384830-4

21

on ground settlement caused by tunnel construction. Xiao et al. (2017) studied the effect of cohesion and internal friction angle on ground settlement, and the study showed that the variability of ground deformation increased with the increase of spatial correlation length. All the above studies use the conventional Mohr-Coulomb model. In the conventional Mohr-Coulomb model, material failure under tension may produce excessive expansion or volume increase. Thus, this model is not suitable for simulating tensile damage due to excavation. To solve this problem, the Mohr-Coulomb Tension Crack model (Cheng and Damjanac 2021) was developed by assuming that the tensile plastic strain is reversible and can prevent the generation of compressive normal stress before crack closure. This model can better simulate the tensile damage caused by excavation. Compared with the MohrCoulomb model, the tensile strength is introduced to control the mechanical performance of the material in the Mohr-Coulomb Tension Crack model when the material is under tension. At present, the influence of the variability of this parameter on surface deformation is unclear. In this paper, the effect of the spatial variability of the tensile strength on excavation-induced ground settlement is discussed. In this paper, the tensile strength is assumed to be a random variable that has a log-normal distribution. Then the random field is discretized by Karhunen-Loève (K-L) expansion. The MonteCarlo method is carried out by a finite difference algorithm to discuss the influence of the variability of the tensile strength on ground settlement.

2 GENERATION OF THE RANDOM FIELD The random field theory can effectively model the variation of soil property. The statistical characteristics of soil property can be characterized by mean function, variance function, covariance function, auto-correlation function, etc. In the random field analysis, discretization methods are needed to generate samples of soil properties for each element of the numerical model (Liu et al. 2019). Random field discretization methods which are commonly used include the turning bands method, spectral method, local average method, Karhunen-Loève (K-L) expansion method, etc. In this paper, the K-L expansion method is used to generate the random field due to its high computing efficiency. Based on the K-L expansion method, the random field can be expressed as (Liu et al. 2019): R(x) = µlnR +

N 

σlnR λi fi (x) ξi ,

(1)

i=1

where x is the position vector, ξi is a set of uncorrelated standard normal variables, andN is the number of expansion terms. In this paper, the tensile strength is assumed to have a log-normal distribution. Thus, the mean µlnR and standard deviation σlnR can be expressed as: 1 2 µlnR = lnµ − σlnR , 2    σlnR = ln 1 + σ 2 .

(2)

(3)

In addition, λi and fi (x) denote the eigenvalues and eigenfunctions of the auto-correlation function. The exponential auto-correlation function is used in this paper:   x1 − x 2 2 ρ (x1 , x2 ) = exp − θ where θ is the auto-correlation distance. 22

3 NUMERICAL MODEL To discuss the effect of spatial variability of tensile strength on surface settlement, a two-dimensional excavation model established by Cheng and Damjanac is used in this paper. The model is 100m long and 60m deep. A horizontal cut with width w=30m and height h=1m is excavated in the lower part of the model, as shown in Figure 1. It is assumed to have roller boundaries at the bottom and sides of the model. The Mohr-Coulomb Tension Crack model is used to describe the mechanical behavior of soil. Except for the tensile strength, the physical and mechanical properties of the model are shown in Table 1.

Figure 1. The geometry of the horizontal cut model. Table 1. The physical and mechanical properties of the model (Cheng & Damjanac 2021, Itasca 2017). Parameters

Value

Density ρ (kg/m3 ) Shear modulus G (Pa) Bulk modulus K (Pa) Cohesion C (Pa) Internal friction angle φ (◦ )

2500 4×107 3×107 1×1020 0

The mean value of tensile strength of the model is assumed to be 2000 Pa. The coefficient of variation and correlation length are two indicators that characterize the spatial variability of the tensile strength. Therefore, the influence of these two indicators on surface settlement will be considered comprehensively in this paper. The numerical simulation conditions are listed in Table 2. Table 2. The numerical simulation conditions. Case number

Coefficient of variation δ

θ /w

T0 T1 T2 T3 T4 T5 T6 T7 T8 T9

0 0.02 0.2 0.5 0.02 0.2 0.5 0.02 0.2 0.5

0 0.1 0.1 0.1 1.0 1.0 1.0 3.33 3.33 3.33

23

As shown in Table 2, T 0 is the deterministic analysis and T 1 − T 9 are the stochastic analysis. For the stochastic analysis condition, the random field is discretized by the K-L expansion introduced in the previous section. Then the discrete random tensile strength parameters are assigned to the corresponding elements. Figure 2 shows the frequency distribution histogram of tensile strength of one realization in T1, together with the estimated log-normal distribution. As shown in Figure 2, it can be seen that the tensile strength generated from K-L expansion follows a log-normal distribution.

Figure 2. The frequency distribution histogram of tensile strength of one realization in T1.

Stochasticity analysis was performed by Monte-Carlo simulation. The number of simulations was first determined based on the convergence of mean values and standard deviation of surface deformation. Figure 3 shows convergence trends of mean values and standard deviation of the deformation at the midpoint of the ground surface with the number of simulations. It can be seen that the mean values and standard deviation reach convergence when the number of simulations is greater than 600. Therefore, to ensure the convergence of Monte-Carlo simulation, 1000 random realizations are performed for each case.

Figure 3. Convergence trends of mean values and standard deviation of the deformation at the midpoint of the ground surface with the number of simulations.

24

4 ANALYSIS OF SIMULATION RESULTS 4.1 The mean value of the deformation at the midpoint of the ground surface Figure 4 shows the mean values of the deformation at the midpoint of the ground surface for the 10 simulation cases listed in Table 1. It can be seen that the mean values of the deformation at the midpoint of the ground surface obtained from the stochastic cases (T1-T9) are smaller than those obtained from the deterministic case (T0). This phenomenon indicates that for strata with spatial variability in tensile strength, the deterministic analysis may yield conservative results when the tensile strength exhibits a strong spatial variability.

Figure 4. The mean values of the deformation at the midpoint of the ground surface.

As shown in Figure 4, for the stochastic cases, the mean values of deformation at the midpoint of the ground surface reach the lowest value when θ/w = 1.0 at a given coefficient of variation. This indicates that excavation may produce larger settlements when the auto-correlation distance and excavation width are essentially the same. When the auto-correlation distance is much smaller than the excavation width, areas of high and low values of tensile strength will alternate in high frequency in the upper area of excavation. On the other hand, when the auto-correlation distance is much larger than the excavation width, the distribution of the tensile strength in the upper area of the excavation will be more uniform. When the correlation distance is comparable to the excavation width scale, the tensile strength in the upper area of the excavation may produce continuous lowvalue areas of tensile strength, thus reducing the mean value of settlement at the midpoint of the round surface.

4.2 Reliability of deterministic analysis For the stochastic analysis cases (T1-T9), each random realization corresponds to a random field of tensile strength. The probability density curves of deformation at the midpoint of the ground surface for each case can be obtained by Monte-Carlo simulation, as shown in Figure 5. It can be seen that for different cases, the probability density curves of deformation at the midpoint of the ground surface show a similar pattern. For all stochastic analysis cases, the deformation at the midpoint of the ground surface is mainly distributed in the range from −0.10m to −0.16m. 25

Figure 5.

Probability density curve of deformation at the midpoint of the ground surface.

To evaluate the reliability of the deterministic analysis, it is necessary to discuss the probability Pc . The deformation at the midpoint of the ground surface obtained by stochastic analysis exceeds the deterministic analysis. In this paper, the probability cumulative curves of the surface center point settlement among the deformation at the midpoint of the ground surface are plotted, as shown in Figure 6. It can be seen that the probability cumulative curves of the deformation at the midpoint of the ground surface for each case show a similar pattern. And as shown in Figure 6, Pc reaches the minimum value of 48.0% for T8 and the maximum value of 59.3% for T9.

Figure 6.

Probability cumulative curves of the deformation at the midpoint of the ground surface.

26

4.3 Analysis of element stress state From the above analysis, the spatial variability of the tensile strength has less influence on the probability density curve and the probability accumulation curve of the deformation at the midpoint of the ground surface. To investigate this phenomenon, the tensile strength distribution and the stress state of the element were analyzed. As shown in Figure 7(c), a low-value zone is distributed in the upper part of the failure zone for the realization of T9-115, and thus the maximum deformation is obtained in the T9 case. In the realization of T9-863, the tensile strength in the failure zone is around 2000 Pa, and thus the minimum deformation is obtained in the T9 case.

Figure 7. Tensile strength distribution and stress state distribution for different realizations.

Although the spatial variability of the tensile strength has a certain effect on the ground deformation, it can be seen from Figures 7(b), (d), (f) that the tensile failure zones obtained from T0, T9-115, and T9-863 are the same. This indicates that the spatial variability of the tensile strength has little effect on the tensile failure zone. According to the Mohr-Coulomb Tension Crack model, the tensile strength controls the mechanical behavior of the element when it is subjected to tension. When the element is not in tension, the tensile strength has little effect on the mechanical behavior of the element. Thus, the effect of tensile strength on the deformation of the model is limited to the failure zone in the upper part of the excavation. Thus, a low value of tensile strength in the failure zone will produce a large surface deformation. However, the local influence of the tensile strength leads to a small influence on the coefficient of variation and the auto-correlation distance on the probability density curve and the probability cumulative curve of the deformation at the midpoint of the ground surface. 27

5 CONCLUSIONS This paper discusses the influence of spatial variation of tensile strength on excavation-induced surface settlement. The findings from this study are as follows: (1) Compared to deterministic analysis, the stochastic analysis will yield larger mean values of deformation at the midpoint of the ground surface. For the same coefficient of variation, a larger mean value of deformation at the midpoint of the ground surface will be obtained when the correlation distance is comparable to the excavation width scale. (2) The spatial variability of the tensile strength has a small influence on the probability density curve and the probability accumulation curve of the deformation at the midpoint of the ground surface. (3) There is a 48% chance that the ground deformation obtained from the stochastic analysis will exceed the ground deformation obtained from the deterministic analysis. (4) The spatial variability of the tensile strength has little effect on the size of the tensile failure zone of the excavation model. The influence of the tensile strength on the deformation of the model is mainly limited in the tensile failure zone of the upper part of the excavation zone. This local influence causes the coefficient of variation, and the auto-correlation distance of the tensile strength has a small effect on the probability density function and the cumulative distribution function of the deformation at the midpoint of the ground surface. ACKNOWLEDGEMENT Thanks for the support of research on surface subsidence patterns and ecological management technology of large mining height coal working face generation SHCCIG Caojiatan Mining Co., Ltd. (CKH/ZXKJ-2020-010). REFERENCES Chao, S., Jing-shan, B., Hong-shuai, L. (2009). Study on influencing factors of ground settlement over the mined-out area. Journal of Jilin University. Earth Science Edition, 3, 498–502. Cheng, Z., Damjanac, B. (2021, June). Extension of Mohr-Coulomb Model considering opening and closure of tension cracks. In 55th US Rock Mechanics/Geomechanics Symposium. OnePetro. Fenton, G.A., Griffiths, D.V., Williams, M.B. (2005). Reliability of traditional retaining wall design. Geotechnique, 55(1), 55–62. Griffiths, D.V., Fenton, G.A. (2004). Probabilistic slope stability analysis by finite elements. Journal of Geotechnical and Geoenvironmental Engineering, 130(5), 507. Hu, J.Y., Li, S.L., Lin, F., Peng, F.H., Yang, S., Yu, Z.F. (2014). Research on disaster monitoring of overburden ground pressure and surface subsidence in the extra-large mined-out area. Rock and Soil Mechanics, 35(4), 1117–1122. Itasca Consulting Group Inc. (2017). FLAC3D6.0 Manual: Examples (An. Excerpt from FLAC3D Help); Itasca Consulting Group Inc.: St. Paul, MN, USA. Kasama, K., & Whittle, A.J. (2011). Bearing capacity of spatially random cohesive soil using numerical limit analyses. American Society of Civil Engineers. Khan, M.R., Dasaka, S.M. (2020). Spatial variation of ground vibrations in ballasted high-speed railway embankments. Transportation Infrastructure Geotechnology, 7(3), 354–377. Liu, Y., Li, J., Sun, S., Yu, B. (2019). Advances in Gaussian random field generation: A review. Computational Geosciences, 23(5), 1011–1047. Thomson, D.J. (1983). Random fields: analysis and synthesis. Tong, L.Y., Liu, S.Y., Qiu, Y., Lei, F.G. (2004). Current research state of problems associated with mined-out regions under the expressway and future development. Chinese Journal of Rock Mechanics and Engineering, 23(7), 1198–1202. Wang, K.Z., Li, Z.K., Wang, A., Fu, S.Y. (2008). Study on physical model test and deformation law of surrounding soil for shallow metro station chamber. Chinese Journal of Rock Mechanics and Engineering, 27(Supp. 1), 2715–2720. Xiao, L., Huang, H., Zhang, J. (2017). Effect of soil spatial variability on ground settlement induced by shield tunneling. In Geo-Risk 2017 (pp. 330–339).

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on the structural deformation law of subway station induced by difference of foundation bearing capacity Cao Wang & Guodong Li Power China Municipal Construction Group Co., Ltd, Tianjin, China

Wenbin Xiao & Fengting Li∗ School of Civil Engineering and Water Conservancy, Shandong University, Jinan, Shandong, China

ABSTRACT: The special geological structure in the city has brought huge technical difficulties to the design and construction of subway stations. Using the numerical calculation and analysis method, the structural deformation law of the subway station is studied by discussing the difference in the bearing capacity of the subway station foundation. The main conclusions and suggestions are as follows: (1) The vertical deformation trend of the station structure is that obvious settlement deformation occurs first from the top of the station structure. With the expansion of the scope of action or the reduction of the bearing capacity of the foundation, the deformation and scope of the station gradually increase to the station floor and column. (2) With the increasing proportion of the station’s soft soil foundation, the maximum settlement of the station floor continues to increase, and the dangerous position gradually moves from the station side wall to the middle, which affects the standing column of the vehicle. (3) For the construction of subway stations in special strata, the special stratum foundation treatment should be carried out first to meet the design requirements of the bearing capacity of the subway station; at the same time, in the construction process of the subway station, in addition to the conventional foundation pit monitoring, the station structure deformation monitoring should be added.

1 INTRODUCTION The urban subway project has become a way and method to solve the problem of urban traffic congestion in large and medium-sized cities along the southeast coast of China. However, in these cities, weak strata, upper soft and lower hard strata, and discontinuous strata are widely distributed, and these geological structures have brought huge technical difficulties to the design and construction of subway stations. Special soils such as soft soil, frozen soil, and expansive soil are often encountered in underground engineering construction. Among them, soft soil is the most likely one to cause differences in the bearing capacity of station foundations. When the subway station is built under geological conditions with different foundation bearing capacities, it is easy to cause the deformation and cracking of the floor structure of the station. Li Zhi (Li 2019) used the spring back recompression method to accurately calculate the deformation of the substrate. Lu Linhai (Lu 2021) established a three-dimensional numerical model considering the interaction of soil and structure, and the whole process of foundation pit construction is simulated, in which the supporting structure and the main structure were combined. Liu Li (Liu 2014) compared the bearing capacity results of the deep-buried strip foundation with the calculation results of the code formula by the numerical calculation method, and the insufficiency of the code is analyzed to correct the calculation method of the bearing capacity depth of the deep-buried strip foundation and ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-5

29

the side strip foundation. Zhang Qiaohui et al. (Zhang 2021) used FLAC 3D numerical calculation software to study the influence of double foundation pit excavation on the displacement of existing station structures. Rong Bing et al. (Rong 2015) analyzed the complex surrounding environment and reserved conditions of Hongmiao Station based on Beijing Metro Line 14 Hongmiao Station. From the above analysis, it can be seen that the differences in the external environmental factors of the subway station structure can easily lead to the deformation and instability of the station structure. Discussing the difference in the bearing capacity of the subway station foundation and studying the deformation law of the subway station structure, it has certain guiding significance and application value for the design and construction of the subway station.

2 NUMERICAL COMPUTATIONAL MODELS AND ANALYSIS METHODS 2.1 Numerical computation model This paper assumes that the cross-sectional size of the subway station model is 20.8×13.5m and the length is 52m. The diameter of the standing column of the car is 0.8m, the distance between the columns is 8m, and there are 14 columns in total. The station is divided into upper and lower floors, namely the top, middle, bottom, and side walls. The thickness of the top and bottom plates is 0.9m, the thickness of the middle plate is 0.4m, and the thickness of the side walls is 0.7m. The upper and lower sections of the column are bound to the station respectively, and this constraint condition can make the two deform together, which is closer to the actual project. In ABAQUS, the C3D8 unit is used to simulate each part of the station. The grid size of the station roof, bottom, middle and side panels is 1m, and the grid size of the car stand is 0.4m, with a total of 8560 units.

Figure 1.

Numerical calculation model of the subway station.

2.2 Numerical calculation and analysis method The station adopts an elastic model, and the station model adopts the following assumptions in the numerical simulation: 1. Each part of the unit in the model adopts uniform and isotropic material; 2. The influence of groundwater is ignored; 3. The station model is horizontal and represents infinity. 30

The difference in the bearing capacity of the station foundation is simulated by applying pressure with different reduction coefficients to different lengths of the station floor. The side walls and roof of the station are constrained to move in the normal direction, and the lengths of the pressure applied are 20%, 40%, and 60% respectively. For the length of the station floor, the reduction factors are 0.5 and 0.25, respectively.

3 ANALYSIS OF NUMERICAL CALCULATION RESULTS Figure 2 shows the difference map of the foundation bearing capacity of the subway station (without reduction). When the proportion of soft soil in the station foundation is 20%, the station floor at this position has obvious vertical settlement, and the settlement value reaches 2.8mm. When the proportion of the soft soil part of the station foundation is 40%, the range of uneven settlement of the station floor increases, and gradually transitions to the middle of the floor. The maximum settlement reaches 48.6mm, which is an obvious increase. When the proportion of the soft soil of the station foundation is 60%, the settlement range of the station floor will be larger again, and uneven settlement of the middle plate and columns of the station will also occur, with the maximum settlement value of 55.1mm.

Figure 2.

Differences in bearing capacity of subway station foundations (without reduction).

31

When there are uneven strata in the lower part of the subway station floor, and the bearing capacity of the foundation is different, it is easy to cause uneven settlement of the structure, thus causing structural cracking. The vertical deformation trend of the station structure is that the obvious settlement deformation occurs first from the top of the station structure. With the expansion of the scope of action or the reduction of the bearing capacity of the foundation, the deformation and scope of the station gradually expand to the station floor and columns.

Figure 3. The proportion of soft soil foundation in subway stations is 20%.

Figure 4. The proportion of soft soil foundation in subway stations is 40%.

Figure 5. The proportion of soft soil foundation in subway stations is 60%.

As shown in Figures 3–5, the simulations are carried out for different lengths of soft soil foundations and different bearing capacities of subway stations. When the proportion of the soft soil foundation of the subway station is 20%, and the reduction factor of the bearing capacity is 0.5, the maximum settlement of the station floor will be 5.60mm, and when the reduction factor of the bearing capacity is 0.25, and the maximum settlement of the station floor reaches 11.21 mm, the floor settlement of the station will increase by 100.1%. When the proportion of the soft soil foundation of the subway station is 40%, and the bearing capacity reduction factor is 0.5, the maximum settlement of the station floor will be 97.2mm. When the bearing capacity reduction factor is 0.25, and the maximum settlement of the station floor reaches 194.6 mm, the floor settlement of the station 32

will increase by 100.2%. When the proportion of the soft soil foundation of the subway station is 60%, and the bearing capacity reduction factor is 0.5, the maximum settlement of the station floor will be 110.1mm. When the bearing capacity reduction factor is 0.25, and the maximum settlement of the station floor reaches 220.3 mm, the settlement of the floor of the station will increase by 100%. Therefore, as the proportion of the station’s soft ground continues to increase, the maximum settlement of the station floor continues to increase, and the dangerous position gradually moves from the station side wall to the middle, which in turn affects the vehicle standing column.

4 CONCLUSIONS The special geological structure in the city has brought huge technical difficulties to the design and construction of subway stations. Using the numerical calculation and analysis method, the structural deformation law of the subway station is studied by discussing the difference in the bearing capacity of the subway station foundation. The main conclusions and recommendations are as follows: (1) The vertical deformation trend of the station structure is that obvious settlement deformation occurs first from the top of the station structure. With the expansion of the scope of action or the reduction of the bearing capacity of the foundation, the deformation amount and scope of action gradually expand to the station floor and columns. (2) As the proportion of the station’s soft soil foundation continues to increase, the maximum settlement of the station floor continues to increase, and the dangerous position gradually moves from the station side wall to the middle, which affects the standing column of the vehicle. (3) For the construction of subway stations in special strata, the special stratum foundation treatment should be carried out first to meet the design requirements of the bearing capacity of the subway station; at the same time, in the construction process of the subway station, in addition to the conventional foundation pit monitoring, the station structure deformation monitoring should be added.

REFERENCES Li Zhi. (2019). Calculation and processing method of soft soil foundation deformation of subway station [J]. Urban Rail Transit Research, 5:111–115. Liu Li. (2014). Calculation and method of foundation bearing capacity of strip foundation for deep-buried station[J]. Special Structure, 31(1):83–87. Lu Linhai, (2021). Sun Hong, Wang Guofu, Xu Qianwei. Deformation of deep foundation pit combined with support and main structure of subway station [J]. China Railway Science, 42(1): 9–14. Rong Bing, (2015). Wu Lanting, Zeng Deguang. Analysis of key points of structural engineering design of underground reserved stations [J]. Municipal Technology, 33(2): 32–39. Zhang Qiaohui, (2021). Jiang Xiaolei. Deformation analysis of double foundation pit excavation in soft soil area...its influence on the structure of existing subway stations [J]. Comprehensive Utilization of Fly Ash, 35(6): 51–57.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Finite element dynamic analysis of a new prefabricated anti-collision wall Chengtao Cui, Pengfei Xie, Wei Yang, Junbin Zhang & Jie Liu Sinohydro Bureau 14 Co., Ltd Kunming, Yunnan Province, China

Ying Wang∗ Xi’an University of Technology Xi’an, Shaanxi Province, China

ABSTRACT: To study the safety problem when the vehicle accidentally hits the anti-collision wall, a specific project has been analyzed and calculated as an example. The finite element model of anti-collision wall and vehicle has been established, and the ABAQUS platform has been used to carry out dynamic numerical analysis and calculation on this model. The impact of external factors on the impact results in the collision process has been analyzed by changing the impact speed, impact angle, vehicle mass, and other external factors. At the same time, the welding connection stress of each part of the anti-collision wall has been studied to determine whether it meets the safety requirements specified in the specification. The results have shown that the greater the collision speed is, the greater the collision angle, the greater the impact force of the vehicle on the anticollision wall, and the greater the displacement will be. When the vehicle has hit the anti-collision wall, the welds among the components of the anti-collision wall are in the elastic stage, meeting the requirements of the specification.

1 INTRODUCTION The anti-collision wall is an indispensable part of roads and bridges, whose function is to ensure the safety of vehicles. The anti-collision wall can not only absorb the energy generated by a vehicle collision and reduce the damage to vehicles and personnel but also has the function of visual orientation (Qiu 2015). In recent years, the prefabricated anti-collision wall has gradually become the first choice in the project because of its convenient construction and a high degree of industrialization. With the rapid development of China’s economy and science and technology, prefabricated concrete bridge crash walls are becoming more and more popular in China. Many unique and innovative achievements have emerged in the field of bridge crash wall structure and performance research (Qiu 2015; Zhang 2019). The anti-collision wall has played an important role in road traffic safety, in which mechanical properties directly affect the safety and stability of roads and bridges. The fabricated anti-collision wall was analyzed based on the dynamic load case. The impact of the anti-collision performance on the new assembled anti-collision wall was analyzed under different collision conditions, which evaluated the anti-collision performance of the new assembled anti-collision wall (Qiu 2015). Based on the obtained finite element dynamic calculation results, the weld connection parameters between the new anti-collision wall and the bridge deck and the prefabricated baffle have been analyzed, and its safety and reliability have been tested, which provides a reference for improving the construction quality of the project. ∗ Corresponding Author:

34

[email protected]

DOI 10.1201/9781003384830-6

2 ENGINEERING CONDITIONS The Erbao road project of Guizhou Shuanglong airport economic zone was taken as the research object. The design speed was 40 km/h, and the bridge section was 0.5 m (crash barrier) +17.5 m (roadway) +0.5 m (crash barrier) =18.5 m. The installation method is shown in Figure 1.

Figure 1.

Structural installation type of prefabricated anti-collision wall.

3 NUMERICAL ANALYSIS MODEL OF ANTI-COLLISION WALL 3.1 Dynamic analysis theory There are two kinds of dynamic analysis problems: explicit algorithm and implicit algorithm. The explicit algorithm was adopted. The central difference method was used for the explicit time integration. For the multi-degree-of-freedom system, the stepwise calculation formula of the central difference method is    1 1 1 2 1 [M ] [M ] [M ] [K] [C] [C] {u} {P} {u} {u}i−1 + − = − − − i+1 i i t 2 2 t t 2 t 2 2 t (1) 35

[M ], [C], and [K] are the mass matrix, damping matrix, and stiffness matrix of the system respectively; {u}i and {p}i are the displacement vector and external load vector of the system at time ti , respectively. 3.2 Structural contact nonlinear model In ABAQUS, the contact problem is simulated by setting contact pairs on the contact surface. For the structural form of this research object, the surface-to-surface contact element was selected for calculation. In the surface-to-surface contact model, surfaces are divided into master surfaces and slave surfaces. The selection of master-slave surfaces has a great influence on contact convergence and accuracy (Qiu 2015). 4 MODELLING ASPECTS 4.1 Finite element model of anti-collision wall According to the engineering construction design drawings, the finite element model of the vehicle’s newly assembled collision system was established with one section of the collision wall and three sections of the collision wall as a whole along the vehicle flow direction. The model of the anticollision wall is shown in Figure 2.

Figure 2.

Model of anti-collision wall.

4.2 Vehicle finite element model According to literature (Zhang 2019), vehicle modeling is divided into cars and large trucks. The structural dimensions of the car are 3.6 m long, 1.4 m wide and 1.5 m high, and the vehicle mass is 1.5 T respectively. The structural dimensions of the large truck are 7.5 m long, 2 m wide and 2.4 m high. The vehicle mass is 10 T and 14 T respectively. The total mass of the vehicle is controlled by the mass density of the material (Qiu 2015). The simplified model of the vehicle is shown in Figure 3.

Figure 3. Vehicle model.

4.3 Material model The model of 2-line skin was used for steel bars and steel plates, and the plastic damage model was used for concrete. Based on the static constitutive model of concrete, the influence of the strain rate strengthening effect is considered by modifying the mechanical indexes such as compressive strength and tensile strength, realizing the simulation of the dynamic behavior of concrete (Zhang 2019). 36

5 WORKING CONDITIONS 5.1 Factor design of specimen working condition In the process of simulating the oblique collision between the vehicle and the anti-collision wall, the vehicle weight, vehicle speed, and collision angle are the three major factors of the initial conditions of the anti-collision wall. The specific working conditions are shown in Table 1. Table 1. List of specific external factors. Number

Vehicle mass (t)

Collision speed (km/h)

Collision angle (◦ )

M1V1θ2 M1V2θ2 M1V3θ2 M1V1θ1 M1V1θ3 M2V1θ2 M3V1θ2

1.5 1.5 1.5 1.5 1.5 10 14

40 60 80 40 40 40 40

20 20 20 15 25 20 20

5.2 Fundamental assumption In the process of finite element simulation of the new prefabricated anti-collision wall, the following assumptions are usually adopted (Zhang 2019): • The friction between the vehicle and the pavement or the anti-collision wall is not considered; • The local deformation caused by vehicle collision is not considered, and only the deformation and damage of the anti-collision wall are considered; • Ignoring the influence of wheel rolling on the vehicle in the process of vehicle operation, this paper uses the translation of vehicle wheels instead of wheel rolling; • It is assumed that when the vehicle collides with the crash wall, the vehicle body moves in a plane without considering the vertical rotation and soaring of the vehicle; • It is assumed that the possible contact between the vehicle and the crash wall in the collision is the front end and rear end of the vehicle.

6 ANALYSIS OF INFLUENCING FACTORS 6.1 Single span anti-collision wall 6.1.1 Collision velocity The displacement cloud diagram of the newly assembled anti-collision wall under different collision velocities was obtained through finite element calculation, as shown in Figures 4-6. The peak impact force and maximum dynamic deformation of the newly assembled anti-collision wall after being impacted by the vehicle were shown in Table 2, and the displacement time history curve was drawn as shown in Figure 7. From the comparison of the displacement time-history curve and displacement cloud, it could be seen that the displacement of the anti-collision wall was 0. When the car collided with the anticollision wall, the displacement of the anti-collision wall reached the maximum instantly. After the car collided, the displacement decreased gradually. When the vehicle velocity changed from 40 km/h to 80 km/h, the peak impact force increased by 99.99%. The maximum displacement deformation increased by 99.37%. 37

Figure 4. 40km/h Displacement cloud (Unit: m).

Figure 5. 60km/h Displacement cloud (Unit: m).

Figure 6. 60km/h Displacement cloud (Unit: m).

Table 2. Impact results of different impact speeds. Number

Vehicle mass(t)

Collision speed (km/h)

Collision angle (◦ )

Peak impact force (KN)

Maximum dynamic deformation (mm)

M1V1θ2 M1V2θ2 M1V3θ2

1.5 1.5 1.5

40 60 80

20 20 20

569.98 855.22 1139.95

1.58 1.76 3.15

Figure 7.

Displacement time-history curve.

6.1.2 Collision angle The displacement cloud diagram of the newly assembled anti-collision wall under different collision angles was obtained through finite element calculation, as shown in Figures 8-10. The peak impact force and maximum dynamic deformation of the newly assembled anti-collision wall after being impacted by the vehicle were shown in Table 3, and the displacement time history curve was drawn as shown in Figure 11. When the car collided with the anti-collision wall, the displacement of the anti-collision wall reached the maximum instantly. After the car collided, the displacement decreased gradually. When 38

Figure 8. 15◦ Displacement cloud (Unit: m).

Figure 11.

Figure 9. 20◦ Displacement cloud (Unit: m).

Figure 10. 25◦ Displacement cloud (Unit: m).

Displacement time-history curve.

Table 3. Impact results of different impact angles.

Number

Vehicle mass(t)

Collision speed (km/h)

Collision angle (◦ )

Peak impact force (KN)

Maximum dynamic deformation (mm)

M1V1θ2 M1V1θ1 M1V1θ3

1.5 1.5 1.5

40 40 40

15 20 25

431.32 569.98 704.29

1.50 1.58 2.50

the vehicle collision angle changed from 15◦ to 25◦ , the peak impact force increased by 63.29%, and the maximum displacement deformation increased by 66.67%. 6.1.3 Vehicle mass The displacement cloud diagram of the newly assembled anti-collision wall under different vehicle masses was obtained through finite element calculation, as shown in Figures 12-14. The peak impact force and the maximum dynamic deformation of the newly assembled anti-collision wall after being impacted by the vehicle were shown in Table 4, and the displacement time history curve was drawn as shown in Figure 15. When the car collided with the anti-collision wall, the displacement of the anti-collision wall reached the maximum instantly. After the car collided, the displacement decreased gradually. When the vehicle mass changed from 1.5 T to 14 T, the peak impact force increased by an order of magnitude, and the maximum displacement deformation was increased by more than three times. 39

Figure 12. 1.5 T Displacement cloud (Unit: m).

Figure 15.

Figure 13. 10 T Displacement cloud (Unit: m).

Figure 14. 15 T Displacement cloud (Unit: m).

Displacement time-history curve.

Table 4. Impact results of different vehicle masses.

Number

Vehicle mass (t)

Collision speed (km/h)

Collision angle (◦ )

Peak impact force (KN)

Maximum dynamic deformation (mm)

M1V1θ2 M2V1θ2 M3V1θ2

1.5 10 14

40 40 40

20 20 20

569.98 3799.84 5319.78

1.58 2.84 4.02

6.2 Three-span anti-collision wall This part studied the anti-collision performance of a three-span anti-collision wall under different influence factors. 6.2.1 Collision velocity The displacement cloud diagram of the newly assembled anti-collision wall under different collision velocities was obtained through finite element calculation, as shown in Figures 16-18. The peak impact force and maximum dynamic deformation of the newly assembled anti-collision wall after being impacted by the vehicle were shown in Table 5, and the displacement time history curve was drawn as shown in Figure 19. 40

Figure 16. 40 km/h Displacement Figure 17. 60 km/h Displacement cloud (Unit: m). cloud (Unit: m).

Figure 18. 60 km/h Displacement cloud (Unit: m).

Table 5. Impact results of different impact speeds.

Number

Vehicle mass(t)

Collision speed (km/h)

Collision angle (◦ )

Peak impact force (KN)

Maximum dynamic deformation (mm)

M1V1θ2 M1V2θ2 M1V3θ2

1.5 1.5 1.5

40 60 80

20 20 20

569.98 855.22 1139.95

2.14 2.40 2.63

Figure 19.

Displacement time-history curve.

When the car collides with the anti-collision wall, the displacement of the anti-collision wall reached its maximum instantly. After the car collided, the displacement decreased gradually. When the vehicle speed changed from 40 km/h to 80 km/h, the peak impact force increased by 99.99%, and the maximum displacement deformation increased by 22.90%. 6.2.2 Collision angles The displacement cloud diagram of the newly assembled anti-collision wall under different collision angles was obtained through finite element calculation, as shown in Figures 20-22. The peak impact force and maximum dynamic deformation of the newly assembled anti-collision wall after being 41

impacted by the vehicle were shown in Table 6, and the displacement time history curve was drawn as shown in Figure 23.

Figure 20. 15◦ Displacement cloud (Unit: m).

Figure 21. 20◦ Displacement cloud (Unit: m).

Figure 22. 25◦ Displacement cloud (Unit: m).

Table 6. Impact results of different impact angles.

Number

Vehicle mass (t)

Collision3 speed (km/h)

Collision angle (◦ )

Peak impact force (KN)

Maximum dynamic deformation (mm)

M1V1θ2 M1V1θ1 M1V1θ3

1.5 1.5 1.5

40 40 40

15 20 25

431.32 569.98 704.29

1.34 2.14 2.72

Figure 23.

Displacement time-history curve.

When the car collided with the anti-collision wall, the displacement of the anti-collision wall reached the maximum instantly. After the car collided, the displacement decreased gradually. When the vehicle collision angle changed from 15◦ to 25◦ , the peak impact force increased by 63.29%, and the maximum displacement deformation was increased by 1.02 times. 42

6.2.3 Vehicle mass The displacement cloud diagram of the newly assembled anti-collision wall under different vehicle masses was obtained through finite element calculation, as shown in Figures 24-26. The peak impact force and maximum dynamic deformation of the newly assembled anti-collision wall after being impacted by the vehicle were shown in Table 7, and the displacement time history curve was drawn as shown in Figure 27.

Figure 24. 1.5 T Displacement cloud (Unit: m).

Figure 25. 10 T Displacement cloud (Unit: m).

Figure 26. 15 T Displacement cloud (Unit: m).

Table 7. Impact results of different vehicle mass.

Number

Vehicle mass (t)

Collision speed (km/h)

Collision angle (◦ )

Peak impact force (KN)

Maximum dynamic deformation (mm)

M1V1θ2 M2V1θ2 M3V1θ2

1.5 10 14

40 40 40

20 20 20

569.98 3799.84 5319.78

2.14 3.82 5.36

Figure 27.

Displacement time-history curve.

When the car collides with the anti-collision wall, the displacement of the anti-collision wall reaches the maximum instantly. After the car collides, the displacement decreases gradually. When the vehicle mass changes from 1.5 T to 14 T, the peak impact force increases by an order of magnitude, and the maximum displacement deformation is increased by 1.5 times. 43

7 WELDING STRESS To study the welding connection stress of each part on the anti-collision wall, it was necessary to analyze whether the tensile stress, compressive stress, and shear stress at the welding joint meet the weld strength design value specified in the specification (She 2021), optimizing the welding connection parameters between the anti-collision wall and the bridge deck and the outer baffle. 7.1 Weld parameters In the finite element simulation of the weld connection, the material of the steel plate was Q235 steel, the yield strength was fy = 235N/mm2 , the elastic modulus E was 2×105 N/mm2 , and the Poisson’s ratio was 0.3. The yield strength of the weld was fy = 265N/mm2 , the ultimate yield strength was fy = 370N/mm2 , the elastic modulus E was 2×105 N/mm2 , and the Poisson’s ratio was 0.3. When considering material nonlinearity, the weld constitutive model adopted a bilinear model. 7.2 Design of fillet weld In this paper, this fillet weld was designed in two ways, namely the equilateral right angle fillet weld and the double V-shaped groove fillet weld. Their shapes were shown in Figure 28. The finite element model of the weld was shown in Figure 29.

Figure 28.

Fillet weld.

Figure 29. Weld finite element model.

7.3 Result analysis Through the simulation of finite element equilateral right angle fillet weld, the stress cloud of the steel plate and the weld is shown in Figure 30. The time history diagram of weld stress was shown in Figure 31. The stress intensity of steel plate and weld at elastic stage and yield stage was shown in Table 8. 44

Figure 30.

Finite element results of equilateral right angle fillet weld (Unit: Pa).

Figure 31.

Stress time history of fillet weld and steel plate.

Table 8. Data of right angle fillet weld. Material

Yield strength/MPa

Ultimate strength/MPa

Pre-collision strength/MPa

Collision time strength/MPa

Steel plate Weld

235 265

370 370

0 0

14.75 0.220

The stress time history analysis of equilateral right angle fillet weld and steel plate showed that the stress intensity of steel plate and weld before collision were both 0. When the car collided at 1.78 s, the stress intensity of the steel plate was 14.75 Mpa, and the stress intensity of the weld was 0.220 Mpa. The steel plate and weld were still in the elastic stage. Through the stress intensity analysis of the steel plate and weld in the elastic stage, it was found that the weld strength and the steel plate strength increase together. 45

Through the simulation of the V-groove fillet weld of the finite element, the stress intensity of the steel plate and weld was shown in Figure 32. The time history diagram of weld stress was shown in Figure 33. The stress intensity of the steel plate and weld in the elastic stage and yield stage was shown in Table 9. When the car collided at 1.78 s, the stress strength of the steel plate was 12.61 Mpa, and the stress strength of the weld was 7.96 Mpa. The steel plate and weld were still in the elastic stage. Through the stress intensity analysis of the steel plate and weld in the elastic stage, it was found that the weld strength and the steel plate strength increase together. Table 9. Data of right V-groove fillet weld. Material

Yield strength/MPa

Ultimate strength/MPa

Pre-collision strength/MPa

Collision time strength/MPa

Steel plate Weld

225 265

370 370

0 0

12.61 7.96

Figure 32.

Finite element results of double V-groove weld (Unit: Pa).

Figure 33.

Stress time history of double V-groove weld and steel plate.

46

8 CONCLUSIONS The anti-collision wall is calculated and the following conclusions are obtained: (1) Under the condition that other influencing factors remain unchanged, by changing the collision speed, collision angle, and vehicle mass of the car, it could be concluded that the greater the collision speed, collision angle, and vehicle mass are, the greater the impact force on the anticollision wall and the displacement deformation will be. In general, the maximum dynamic deformation of the prefabricated anti-collision wall was less than or equal to 100mm, and all working conditions met the specification requirements. (2) In the process of fillet weld finite element analysis, the weld strength increased with the increase of steel plate strength, indicating that the weld strength and steel plate strength increased together. According to the specification, the design grade of weld strength was 215 Mpa, and the maximum weld stress was 7.96 Mpa, which was less than the grade II weld strength. The weld met the strength requirements. REFERENCES And A.B., Idelsohn S.E. Oñate, et al. Analysis of reinforced concrete structures using ansys nonlinear concrete model [J]. International Journal of Fracture – Int. J. Fracture, 1998, 25(44): 105–112. Barauskas R., Abraitiene A. Computational analysis of the impact of a bullet against the multilayer fabrics in LS-DYNA [J]. International Journal of Impact Engineering, 2007, 34(7): 1286–1305. GB 50010-2010, code for design of concrete structures [S]. GB 50017-2017, Code for Design of Steel Structure [S]. GB 50661-2011, Steel Structure Welding Code [S]. Itoh Y., Liu C., Kusama R. Dynamic simulation of collisions of heavy high-speed trucks with concrete barriers [J]. Chaos Solitons and Fractals, 2007, 34(4): 1239–1244. JTG B05-01-2013, Highway Guardrail Safety Performance Evaluation Standard [S]. JTG/T D81-2006, Design Rules of Highway Traffic Safety Facilities [S]. JTJ 023-1985, Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts [S]. Macdonald D.J, Engineer S. Precast concrete barrier crash testing final report [J]. Design Standard, 2001, 46(32): 72–76. Neves R.R, Fransplass H, Langseth M, et al. Performance of some basic types of road barriers subjected to the collision of a light vehicle [J]. Journal of the Brazilian Society of Mechanical Sciences & Engineering, 2018, 40(6): 274. Niu H.X. Research on the Structure of BridgeAnti-collisionWall and ItsAnti-collision Property [D]. Chongqing Jiaotong University, 2021. Prochowski L. Analysis of displacement of a concrete barrier on the impact of a vehicle. Theoretical model and experimental validation [M]. German and Italian lyrics of the Middle Ages. Anchor Press, 2010: 71–6. Qiu J.K. Crashworthiness of existing RC parapets with sustainable rehabilitation [D]. Harbin Institute of Technology, 2015. Ross Jr. H.E, Sicking D.L, Zimmer R.A, Michie J.D. NCHRP Report 350: Recommended procedures for the safety performance evaluation of highway features [R]. Transportation Research Board. Washington DC. 1993. Shahrouz J. Ghadimi. Sandra N. Gutierrez. Integrating guardrail system preservation policies into asset management practices development of a performance-based model [J]. Transportation research record, 2017, 82(2646): 49–56. She C.L, Su K.L, Zhang C.X, Tan L.H. Finite element numerical simulation of steel plate welding temperature field and stress-strain field [J]. Welding Technology, 2021, 50(04): 16–20. Wang Z.C, Zhang G.H, Wang W.H.Anti-collision performance and numerical analysis of prefabricated concrete anti-collision wall [J]. Northern Communications, 2022(04): 12–17. Zhang H., Sun T., Zhang J.X. Dynamic finite element analysis of the new type of prefabricated concrete anti-collision wall [J]. Northern Communications, 2019(07): 1–4+9. Zhao M., Zhang Y. Mechanical model and simulation calculation of reinforced concrete guardrail system impacted by cars [J]. Journal of Civil Engineering, 1994(06): 56–61.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on hot spots of drag reduction and vibration reduction of cylinder flow based on CiteSpace Zhihao Fang Zhejiang Ocean University, Zhoushan, China The Key Laboratory for Technology in Rural Water Management of Zhejiang Province, Zhejiang University of Water Resources and Electric Power, Hangzhou, China

Dongfeng Li∗ The Key Laboratory for Technology in Rural Water Management of Zhejiang Province, Zhejiang University of Water Resources and Electric Power, Hangzhou, China

ABSTRACT: The flow around a cylinder is basic and complex. In recent decades, experts and scholars have done a lot of research and made outstanding achievements in the field of drag reduction and vibration reduction. To understand the development process of drag reduction and vibration reduction around the cylinder, this paper takes the literature in Web of Science as the research object and uses CiteSpace software to draw the knowledge map of drag reduction and vibration reduction around the cylinder from the aspects of keyword co-occurrence. By analyzing the amount and content of papers published over the years, the research on drag reduction and vibration reduction around the cylinder can be roughly divided into three stages, further analyzing the trend of the research on drag reduction and vibration reduction around the cylinder and summarizing the evolution law and development trend of drag reduction and vibration reduction around the cylinder. 1 INTRODUCTION The flow around the column can be seen everywhere in life. For example, the wind blows over the pier, and the water flows around the pier, leaving many eddies. However, when the fluid flows through the building, it produces fluid-structure coupling, which makes the structure vibrate, and may damage the structure itself. In addition, the flow resistance is also an important factor in the damage to the structure. It is of great significance to study drag reduction and vibration reduction around a cylinder. However, there is no literature specifically describing this field at present. Therefore, this paper takes the paper literature in Web of Science as the object and carries out matching retrieval and analysis and research by taking the subject words “flow around a cylinder” and “drag reduction and vibration reduction” as the subject, keywords, and titles. After systematic retrieval, matching, and elimination of repetitive documents, 270 relevant documents were finally screened out in this study, and the effective documents were exported in Refworks format. In terms of research methods, CiteSpace software is used for literary analysis. The literature of ScienceNet is imported into the software, and CiteSpace software is used for keyword co-occurrence and cluster analysis. Author analysis is studied, and the corresponding knowledge map is obtained.

2 LITERATURE CHARACTERISTICS OF DRAG REDUCTION AND VIBRATION REDUCTION AROUND CYLINDER 2.1 Temporal distribution of documents The first stage is 1992-2008. At this stage, the number of documents issued is small, and it is in the initial stage of computer technology. Therefore, there is no advanced technical support, and the ∗ Corresponding Author:

48

[email protected]

DOI 10.1201/9781003384830-7

content of the research is relatively basic. Hara et al. (1992) experimentally compared the influence of bubbles on the vibration of two cylinders installed in series with a pitch diameter ratio of 1.5 and 3.0, and preliminarily explained the mechanism of cylinder vibration (Lam, Lin, 2008). Munshi et al. (1998) applied moving surface boundary layer control (MSBC) to drag reduction and vortexinduced vibration suppression of spar cylindrical structures, and achieved good results (Munshi, Modi, Yokomizo, 1998). Hover et al. (2001) simulated the effect of protrusion by attaching metal wires to the smooth cylinder wall. The test found that for static cylinders, the effect of drag reduction and vibration reduction was very significant (Hover, Tvedt, Triantafyllou, 2001). Lam & Lin (2008) studied the cross flow under wave cylinders with different wavelength ratios, and the research showed that the resistance coefficient of wave cylinders was less than that of corresponding cylinders (Lam & Lin 2008). Assi & Bearman (2008) eliminated vortex-induced vibration (VIV) by using a free rotating two-dimensional control board, and the generated resistance coefficient was about 70% of that of an ordinary cylinder, providing a new idea of vibration reduction (Assi, Bearman, 2008). The second stage is from 2009 to 2014. Srinil (2009) analyzed the vortex-induced vibration of Catenary Risers in the ocean current by establishing a model, which significantly reduced the amount of calculation of numerical simulation in drag reduction and vibration reduction (Srinil et al. 2009). Huang (2011) found through experiments that the spiral groove could effectively suppress the transverse flow vibration amplitude caused by eddy current, reducing its amplitude by 64%. In the range of subcritical Reynolds numbers tested in the study, the drag reduction rate of the fixed cylinder was also as high as 25% (Shan 2011). Korkischko & Meneghini (2012) gave the experimental results of the flow around a cylinder with moving surface boundary layer control, combining vortex-induced vibration suppression and drag reduction (Korkischko & Meneghini 2012). Zou et al. (2014) conducted a three-dimensional numerical simulation on two cylinders arranged in series. When the spacing ratio was greater than or equal to 4, the effect of drag reduction and vibration reduction was obvious (Zou et al. 2013). The third stage is after 2015. At this stage, the annual number of articles published remained high, with an average of more than 30 articles per year. Silva-Ortega et al. (2015) studied the suppression effect of vortex shedding by plane cylinders surrounded by two, four, and eight smaller control cylinders. The experiment found that the drag reduction effect of four control cylinders was the best (Silva-Ortega et al. 2015). Silva-Ortega & Assi (2017) studied the use of a configuration column composed of eight non-rotating control cylinders to suppress the vortex-induced vibration of larger cylinders, providing a direction for further vibration reduction (Silva-Ortega & Assi 2017). Dash et al. (2020) analyzed its influence on the vortex by adjusting the length of the splitter plate around the cylinder. Through the analysis, it was found that the drag reduction effect with the length of 4D was the best (Dash et al. 2020). Wang et al. (2020) proposed a drag reduction design method for box girders based on the bionic method, which could not only reduce the resistance but also improve the utilization of energy (Wang et al. 2020). Ma et al. (2021) proposed an arched device installed on the leeward side of the cylinder to reduce the resistance of the cylinder and reduce vortex shedding (Ma et al. 2021). Xu et al. (2022) used 3D printing to form a porous structure on the surface of the cylinder, resulting in the suppression of vortex shedding and the reduction of resistance (Xu et al. 2022).

2.2 Research team analysis Figure 1 shows the map of national cooperation. The national cooperation network reflects the attention and degree of cooperation among various countries in the research of cylinder drag reduction and vibration reduction. It can be seen from the figure that China pays the highest attention to this field, followed by the United States. From the perspective of the connection among countries, the connection is relatively weak, indicating that countries still need to strengthen cooperation. Figure 2 shows the map of the research authors. It can be seen from the figure that there are 273 statistical authors and 347 network connections. The network density is 0.0093, network modularity Q = 0.4281, and average contour value S = 0.7567. Among them, the network density indicates the strength of the cooperative relationship between authors, and the closer it is to 0, the weaker the relationship will be. Network modularity indicates the strength of the network community structure. The larger its value is, the better the network clustering result will be, and the faster the propagation speed between

49

Figure 1.

Research country cooperation map.

nodes in the network will be. The average contour value indicates the internal homogeneity of a cluster group after network clustering. The closer its value is to 1, the higher the homogeneity of this cluster group in the network will be. It can be seen that the network density of the author’s cooperation network in the field of drag reduction and vibration reduction around a cylinder is small, the tightness of network nodes is low, the network modularity is high, and the network clustering result is good.

2.3 Keyword analysis The following figure is the keyword co-occurrence map. There are 320 keywords in the field of drag reduction and vibration reduction around a cylinder, with 1908 network connections. The network density is 0.0374, with a low network density. Keyword font size indicates the frequency of keywords.

Figure 2.

Map of research authors.

50

The larger the keyword font is, the higher the frequency of keywords will be. It can be seen intuitively from the figure that words such as circular cylinder and drag reduction appear frequently.

Figure 3.

Keyword co-occurrence map.

Table 1. High-frequency keywords and their frequencies. High-frequency words

Frequency

High-frequency words

Frequency

Circular cylinder Drag reduction Vortex induced vibration Wake Flow Suppression Drag Reduction Vortex-induced vibration Bluff body

88 64 58 55 46 43 40 36 30 29

Induced vibration Flow control Dynamics Vortex shedding Numerical simulation Force Viv Square cylinder Passive control Simulation

28 25 23 22 22 21 20 20 19 17

3 RESEARCH TRENDS AND PROSPECTS To better tap the research trend of drag reduction and vibration reduction around cylinders, the following figure shows the sudden detection of the top30 keywords from 2012 to 2022. From the figure, it can be seen that the sudden intensity of low Reynolds number and bluff body is high, reaching 3.24 and 3.23 respectively. Synthetic jet, airfoil, operation, cross flow, and force will last until 2022 and may continue in the future. Future research trends are as follows: New drag reduction measures will be sought. At present, a series of studies have been made on the surface of structures, such as attaching metal wires, adding spiral grooves, and other measures. The research on bionic surface drag reduction in the marine environment has been relatively mature. Bionic surface drag reduction technology has a very high application value, and it plays an important role in

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Figure 4.

Sudden detection of keywords among drag reduction and vibration reduction.

the navigation body in the sea whether it can be applied to structures, or superhydrophobic surfaces are used to reduce the resistance of structures. The combination of various drag reduction measures will be realized. At present, most of the research done is a single drag reduction measure. In the future, the research will be carried out from a single drag reduction method to a variety of drag reduction methods, organically combining a variety of drag reduction methods and enhancing the effect of drag reduction through the matching of drag reduction methods and parameter control. It will be an important trend in future research. The mechanism of drag reduction cannot be ignored. At present, the research on drag reduction mostly focuses on the effect of drag reduction, and the revelation of the drag reduction mechanism is still lacking, which still needs attention. The study of bluff body flow will continue to deepen. As a classical problem in fluid mechanics, bluff body flow has been studied a lot, but the mechanism of wake vortex generation has not been fully understood. Therefore, for a long time, the research will still focus on bluff body flow and vortex-induced vibration suppression methods. In addition, with the emergence of new structures such as trapezoidal structures, numerical simulations should be carried out. If the research results meet the expected effect, it can replace the traditional structure. Although the traditional vortex-induced vibration suppression methods have been very detailed, there is still room for further excavation. In addition, new suppression methods still need to be explored. How to find a new inhibition method with high efficiency and low cost is the focus of long-term research. It is possible to achieve breakthroughs in the field through artificial intelligence. With the rapid development of technology, the application of artificial intelligence enriches the research methods of fluid mechanics and can provide more powerful technical support. New technologies and methods are bound to accelerate progress and breakthrough in the research field. At present, it has been realized to establish a model by importing data to the machine and then studying the flow field under other working conditions. Throughout the history of computer development, the research on drag reduction and vibration reduction around cylinders has achieved continuous breakthroughs with the continuous improvement of computer technology. In the future, artificial intelligence and machines will be more advanced, and the method of combining machine learning with physical models will play a great auxiliary role in this field.

4 CONCLUSION Combined with statistical analysis, knowledge map, literature research, and other methods, this paper combs and shows the development history of the field of drag reduction and vibration reduction around cylinders and the evolution track of research hotspots. The analysis shows that this field is in

52

a relatively mature period of research, and the research is hot in recent years. Various countries also attach great importance to it. However, the cooperation between countries is not close, so international cooperation and exchanges should be strengthened in the future. In the era of rapid development of science and technology, how to make drag reduction and vibration reduction technology keep pace with the times and move it from laboratory research to practical large-scale application still needs continuous exploration and research.

ACKNOWLEDGMENTS This research was supported by the Funds Key Laboratory for Technology in Rural Water Management of Zhejiang Province(ZJWEU-RWM-202101), the Joint Funds of the Zhejiang Provincial Natural Science Foundation of China (No. LZJWZ22C030001. No. LZJWZ22E090004), the Funds of Water Resources of Science and Technology of Zhejiang Provincial Water Resources Department, China (No.RB2115, No.RC2040), the National Key Research and Development Program of China(No.2016YFC0402502), and the National Natural Science Foundation of China (51979249).

REFERENCES Assi, G.R.S., & Bearman, P.W. (2008). VIV Suppression and Drag Reduction with Pivoted Control Plates on a Circular Cylinder. ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. Dash, S.M., Chavda, S.D., & Lua, K.B. (2020). A Study on the Wake Regime Control and Drag Reduction Using Single Splitter Plate for a Flow Past a Semicircular Cylinder. In Advances in Mechanical Engineering (pp. 97–105). Springer, Singapore. Hover, F.S., Tvedt, H., & Triantafyllou, M.S. (2001). Vortex-induced vibrations of a cylinder with tripping wires. Journal of Fluid Mechanics, 448, 175–195. Korkischko, I., & Meneghini, J.R. (2012). Suppression of vortex-induced vibration using moving surface boundarylayer control. Journal of Fluids and Structures, 34, 259–270. Lam, K., & Lin, Y.F. (2008). Large eddy simulation of flow around wavy cylinders at a subcritical Reynolds number. International Journal of Heat and Fluid Flow, 29(4), 1071–1088. Ma, W., Du, Z., Zhang, X., Liu, Q., & Liu, X. (2021). A novel drag reduction and vortex shedding mitigation measure for a circular cylinder in the subcritical regime. Fluid Dynamics Research, 53(1), 015504. Munshi, S.R., Modi, V.J., & Yokomizo, T. (1998, May). Drag reduction and vibration control of a spar-type cylindrical structure through boundary-layer control. In The Eighth International Offshore and Polar Engineering Conference. OnePetro. Shan, H. (2011). Viv suppression of a two-degree-of-freedom circular cylinder and drag reduction of a fixed circular cylinder by the use of helical grooves. Journal of Fluids & Structures, 27(7), 1124–1133. Silva-Ortega, M., & Assi, G.R.D.S. (2017). Suppression of the vortex-induced vibration of a circular cylinder surrounded by eight rotating wake-control cylinders. Journal of Fluids and Structures, 74, 401–412. Silva-Ortega, M., Assi, G.R., & Cicolin, M.M. (2015, May). Hydrodynamic Force Measurements on a Circular Cylinder Fitted with Peripheral Control Cylinders: Preliminary Results on the Development of VIV Suppressors. In International Conference on Offshore Mechanics and Arctic Engineering (Vol. 56482, p. V002T08A062). American Society of Mechanical Engineers. Srinil, N., Wiercigroch, M., & O’Brien, P. (2009). Reduced-order modeling of vortex-induced vibration of the catenary riser. Ocean Engineering, 36(17–18), 1404–1414. Wang, Y., Cheng, W., Du, R., & Wang, S. (2020). Bionic drag reduction for box girders based on ostracism cubicles. Energies, 13(17), 4392. Xu, Z., Chang, X., Yu, H., Chen, W.L., & Gao, D. (2022). Structured porous surface for drag reduction and wake attenuation of cylinder flow. Ocean Engineering, 247, 110444. Zou Lin, Guo Congo, Xiong can. (2013). Flow characteristics of the two tandem wavy cylinders and drag reduction phenomenon [J]. Hydrodynamic Research and Progress Series B.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Application analysis of extrusion and expanded pile in electric power engineering Lixing Ma∗ , Kai Han∗ , Kai Xue∗ & Qian Li∗ Design Center, Economic and Electrical Research Institute of Shanxi Electrical Power Company of SGCC, Taiyuan City, Shanxi Province, China

ABSTRACT: The economic benefits of squeeze-expanded disk pile technology are very significant. Based on the geological distribution of a power project in Taiyuan, Shanxi Province, this paper analyzes the bearing effect and application of the squeeze-expanded disk pile, and draws the conclusion that the 5.1m-6m support disk affects the ultimate bearing capacity. The key force is the key force, and the bearing capacity is increased by 67.03%, showing the characteristics of friction multi-pivot end-bearing piles as a whole. The increase of the friction force on the upper and lower sides obviously lags behind that of the support disk, thereby enhancing the bearing capacity of the extruded and expanded support disk pile. Not prominent. The displacement of the soil layer at the top of the disk makes the top of the supporting disk separate from the soil to form a free surface, and the soil undergoes overall penetration shear failure.

1 INTRODUCTION The technology of extruding and expanding the disk pile was born in the 1980s. It is a new type of pile innovated on the basis of the original cast-in-place pile of equal sections. The pile includes four parts: the pile body, several load-bearing squeezing and expanding disks, multiple branches, and the compacted soil layer around the pile, as shown in Figure 1. Due to the distribution characteristics of branches and bearing disks, the stress range of the pile body is expanded, and the effect is similar to the root system of a tree (Mohan 1969). The comprehensive technical and economic benefits of squeezing and expanding the supporting disk pile are also considerable. The soil bearing capacity of a single pile is generally about two times that of ordinary piles, and a large number of materials will be saved. Out: In terms of construction consumables such as concrete, the bored pile is 1.73 times that of the extruded and expanded pile foundation, which is close to 2 times. It reduces the consumption caused by raw material processing and transportation, avoids various pollutions such as dust, waste gas, and noise, and indirectly contributes to comprehensive social benefits such as environmental protection and resource conservation. Generally speaking, under the design conditions of the same bearing capacity, the raw materials are saved by 30%–60%, and the project cost is reduced to 20%–30%. The comprehensive technical and economic analysis and comparison are shown in Figure 2 (Mohan 1967); (Bruce 1986).

∗ Corresponding Authors: [email protected]; [email protected]; [email protected] and [email protected]

54

DOI 10.1201/9781003384830-8

Figure 1. The structure of squeezed branch pile.

Figure 2.

Comprehensive technical and economic analysis of squeezed branch piles and ordinary piles.

2 ANALYSIS OF LOAD-BEARING APPLICATION OF SQUEEZE-EXPANDED DISK PILES IN POWER ENGINEERING 2.1 The physical model of the closed contact surface of the extruded and expanded branch pile The extruded and expanded disk piles are friction-type end-bearing piles, so the friction simulation of the contact surface is particularly important in the finite element simulation. The closed contact surface can transmit the tangential friction force. ABAQUS believes that when the friction force is less than the limit value, the contact surface is in a bonded state. On the contrary, there will be relative sliding. The friction model is divided into the following two points: (1) Ultimate shear stress The user can specify the maximum allowable shear stress value in specific cases to meet the simulation requirements. (2) Elastic slip deformation “Elastic slip deformation” defines the allowable value of deformation in the case of surface bonding, which solves the original calculation obstacle without shear deformation. ABAQUS determines the slip amount according to the element length on the contact surface (the default value is 0.5% of the element length, which can be set by yourself), and then automatically selects the stiffness in the penalty friction calculation method, as shown in Figure 3 (Simek 1989). 55

Figure 3.

Elastic slip deformation concept.

In this paper, in order to simplify the calculation, the pile-soil, pile-consolidated body, and consolidated body-soil default to “hard contact,” and the principle of selecting the subordinate surface of the main control surface is: pile>consolidation body>soil body. The contact surface model of each model component adopts the Coulomb friction model, and its friction relationship is shown in Figure 4, and the meaning of the formula is shown in Formula 1.

Figure 4.

Schulting friction model.

2.2 Parameter setting under weak stratum in power engineering Two sets of two-dimensional, axisymmetric finite element models of straight piles and extruded and expanded branched disk piles are established for simultaneous comparison. Taking the distribution of most of the geological conditions in Shanxi Province as an example, a soil environment dominated by silty clay is uniformly set to simulate power engineering. In the soft stratum, we apply a vertical uniform load to the top of the pile in 10 levels, extract the Q-s curve part in the calculation result and the distribution diagram of the axial force of the pile body under each level of load, compare the bearing capacity of the single pile of the two models, and analyze the load transfer mechanism and pile top settlement law of each pile type: Table 1. Selection and arrangement of pile foundation for squeezed branch. Pile diameter d

Bearing plate height h

400–500 600–700 800–1100

500 700 900

56

In this model, only one support plate is set in the sand layer of 5.1m, which meets the requirements of technical regulations. The foundation soil layer is set to 3 layers, 0–4m is silty clay, 4–10m is sandy soil, and below 10 is silty clay layer. According to the indoor geotechnical test, the density, elasto-plasticity, and Mohr-Coulomb parameters of the three layers of soil are respectively assigned, and its material properties are defined, as shown in Table 2. Table 2. Model parameter.

Type

Elastic modulus (KPa)

Pile Silty clay Sand

3*107 6800 3*104

µ

Weight (kN/m3 )

Cohesion (kpa)

Internal friction angle (◦ )

0.2 0.3 0.25

25 18 18

20.76 0

19.62 30

3 CONTRASTIVE ANALYSIS OF BEARING PERFORMANCE OF STRAIGHT PILE AND EXTRUSION-EXPANDED DISK PILE In this paper, the vertical loads on the top of the piles are applied to the two groups of models according to the above steps. There is no discontinuous iteration in the monitoring of the calculation process, and the convergence is good. Then, based on the ABAQUS post-processing module, the single pile top load-settlement relationship curve is output, as shown in Figure 5:

Figure 5.

Q-s curve of three models.

It can be seen from the table that under the same stratum environment, the ultimate bearing capacity of the straight pile is 421.93kN, and the bearing capacity of the squeezed-expanded disk pile is 1279.88kkN, which is 67.03% higher than that of the straight pile, and the bearing capacity enhancement effect is very significant. From the trend of the Q-s curves of the two pile types, before kN400kN, the curves of the straight pile and the squeezed-expanded disk pile basically overlapped, showing a straight line trend, indicating that the pile body and soil were both in the elastic stage and did not yield. At around 500kN, since the bottom of the pile is silty clay, the end resistance of the straight pile is 57

very small, and it is easy to cause penetration damage, and the curve shows a steep drop. With the continuous increase of settlement, the soil enters the plastic failure stage, and the extruded and expanded branched disk piles reach the ultimate bearing capacity and cannot continue to bear (Fleming, 1993); (D. Mohan 1967). 4 LOAD TRANSFER MECHANISM OF SQUEEZED AND EXPANDED DISK PILE For the extraction of the axial force of the pile body of the axisymmetric element, we can pick up the node path of the model in the post-processing module, and then extract the vertical stress of the node based on the built path, and convert it into the axial force value to make a chart. 4.1 Distribution characteristics of axial force of pile body The figure reflects the axial force distribution of the pile body under various loads. The load transfer curve of the squeezed-expanded disk pile shows a different transfer law, and the axial force changes significantly in a certain area of the pile body. It can be seen from the figure that the axial force distribution decreases from the top of the pile to the bottom of the pile under each level of load, and there is an obvious jump and abrupt decrease in the support plate with a depth of 5.1m-6m. In the process of downward transfer, the lateral friction resistance of the straight pile on the upper section of the support plate is consumed first. When the support plate is transferred to the position of the support plate, the support plate disperses the load and transfers the load to the high-bearing soil layer at the bottom of the plate. The sudden reduction in the axial force in the figure is completely. It is shared by the bottom soil of the pan, thereby weakening the resistance of the pile end. This reveals the bearing characteristics of the squeezed-expanded disk pile, which is also the reason for the high bearing capacity of the squeezed-expanded disk pile.

Figure 6. Axial force distribution diagram of all levels of load.

4.2 Bearing characteristics of the support plate From the axial force distribution characteristics in the above figure, it can be inferred that it is precise because of the addition of the construction process of extrusion and expansion that it has 58

a great influence on the load transmission and axial force distribution, and is the key to its high bearing capacity. Next, based on the axial force distribution diagram, we start with the load sharing value of each pile section, and further analyse the effect of the friction resistance of the support plate and the pile side (Bruce 1986).

Figure 7.

Squeezed branch pile load sharing value.

Figure 8.

Squeezed branch pile load sharing percentage.

The above figure shows the load sharing of the extruded and expanded support disk piles. From the perspective of the total cycle of the loading process, the front part of the loading is mainly borne by the side mold resistance and end resistance, and the support disk only contributes 27% of the bearing capacity. With the increase of the load, the load carried by the support plate is rising steadily, and the growth rate is far greater than the side resistance and end resistance, while the side mold resistance of the upper and lower sections gradually tends to be stable. Due to the excellent characteristics of the support plate to control settlement, the settlement is slow. Growth has limited end-to-end resistance. When the sixth level of load is reached, the load borne by the support plate reaches nearly 40%, which has stabilized. At the end of the loading stage, the support plate bears 39.7% of the load, and the pile end only accounts for 17.11% due to the distribution of the weak clay layer. 4.3 Bearing characteristics of pile side friction resistance This paper mainly analyses the frictional resistance on the upper side and the frictional resistance on the lower side at a depth of 0m–5.1m and 6m–12m. On the whole, although the side friction resistance is increasing linearly, the growth rate is very small compared to the support plate, and 59

it gradually becomes flat. In the initial stage of loading, the frictional resistance on the upper side increases rapidly and plays a key role in the total frictional resistance of the extruded and expanded branched pile. The performance is limited, and the proportion is getting smaller and smaller. At the end of the loading period, the pile side resistance no longer increases. For the upper side frictional resistance, the volatilization lag of the lower side frictional resistance is slightly lower than that of the upper side frictional resistance, and the growth rate of the two is basically the same, and has been in a state of slow growth. (Fu 1999) 4.4 Analysis of soil displacement field of squeezed and expanded pile The vertical displacement field of soil extracted by ABAQUS is shown in the figure. After the ground stress is balanced, the displacement of the bottom of the support plate is very small, which indicates that the support plate compacts the soil during the process of expanding into a plate, which is in line with engineering practice. Gradually, with the increase of the load, the support plate disperses the load to the soil layer at the bottom of the plate, and the displacement of the soil layer on the top of the plate makes the top of the support plate separate from the soil to form a free surface, and the bottom soil of the plate shows regular settlement as a whole (Liu 1996). There is a certain law in the distribution of the displacement field along the pile body in the early stage, without too much obvious concentration, and the expansion angle of the displacement field gradually becomes smaller and smaller, and finally the displacement is concentrated at the position of the support plate and the bottom of the pile, and the overall penetration shear of the soil occurs the vertical displacement field of soil extracted by ABAQUS is shown in the figure. After the ground stress is balanced, the displacement of the bottom of the support plate is very small, which indicates that the support plate compacts the soil during the process of expanding into a plate, which is in line with engineering practice. Gradually, with the increase of the load, the support plate disperses the load to the soil layer at the bottom of the plate, and the displacement of the soil layer on the top of the plate makes the top of the support plate separate from the soil to form a free surface, and the bottom soil of the plate shows regular settlement as a whole. There is a certain law in the distribution of the displacement field along the pile body in the early stage, without too much obvious concentration, and the expansion angle of the displacement field gradually becomes smaller and smaller, and finally the displacement is concentrated at the position of the support plate and the bottom of the pile, and the overall penetration shear of the soil occurs, cut damage (Simek 1989); (Fleming 1993).

Figure 9. Analysis of soil displacement field.

60

Figure 10. Analysis of soil displacement field of squeezed and expanded pile.

5 CONCLUSIONS 1) From the model analysis and calculation, we concluded that the 5.1m-6m support plate is the key to affecting the ultimate bearing capacity of the pile, and it carried most of the resistance during the early load application process, and the 1800kN pile top load The lower support plate shares nearly 40% of the vertical force, and tends to be stable, and the growth is no longer obvious. The whole presents the characteristics of friction multi-fulcrum end-bearing piles. 2) The increase of frictional resistance on the upper side of 0m-5.1m and the frictional resistance of the lower side of 6m-12m obviously lags behind that of the support plate, and the enhancement effect on the bearing capacity of the extruded and expanded support plate pile is not outstanding. 3) The displacement of the soil layer at the top of the disk makes the top of the support disk separate from the soil to form a free surface, and the bottom soil of the disk shows regular settlement as a whole. Finally, the displacement is concentrated at the position of the support disk and the bottom of the pile, and the soil body undergoes overall penetration and shearing. 61

REFERENCES Bruce, “D.A. Ground Engng V19”, N4, May 1986, P9–15 [J]. International Journal of Rock Mechanics & Mining Sciences & Geomechanics Abstracts, 1986, 23(6):240–0. Bruce, International Journal of Rock Mechanics & Mining Sciences & Geomechanics Abstracts, 9–15, 1986. D.Mohan, “Bearing Capacity of Multi-under Reamed Piles”, 1967. Fleming, W.G.K. “The improvement of pile performance by base grouting”. In. Proc. Instn. Giv. Engers, 1993(8):88–93. J.L. Liu, J.C. Zhu. Building Science.02.13–18. 1996. Mohan. D., Murthy V.N.S., Jain G.S. “Design and Construction of Multi-under Reamed Piles”, Proc.7th, Int. Conf.s.m.& FE, Mexico, 1969. Mohan D., “Bearing Capacity of Multi-under Reamed Piles”, Proc. 3th, Asian Conf.s.m.& FE Kaifa, Vol.1, No.1, 1967. Simek, J., Verfel, J., Sedlecky, O., Holousova, T. “Improvement of the pile bearing capacity”, Proceedings of the International Conference on soil Mechanics and Foundation Engineering, v2, 1989:1031–1034. Simek J., Verfel J., Sedlecky O., Holousova T. Proceedings of the International Conference on soil Mechanics and Foundation Engineering, 1031–1034,1989. X.D. Fu. Bridge construction. 10. 52–55. 1999.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Analysis of ultimate bearing capacity of prestressed concrete box Girder Bridge Yang Hou∗ & Caopeng Hui Beijing Xinqiao Technology Development Co., Ltd, Beijing, China

Liu Liu & Dongxu Zhao Henan Anluo Expressway Co., Ltd., Zhumadian Henan, China

ABSTRACT: Prestressed concrete box girder bridges have been widely developed in China due to their clear mechanical properties and good economic indicators. However, the calculation of the ultimate bearing capacity of prestressed concrete box girder bridges has simplified the box section to a T section. This method is reasonable under symmetric loading, but it is not applicable to box girder bridges under asymmetric loading. Therefore, in this paper, the traditional formula for the ultimate bearing capacity of box girder bridges is modified, and the formula for the ultimate bearing capacity of box girder bridges under asymmetric loads is obtained and verified by finite element calculation software.

1 INTRODUCTION With the development of China’s economy, road transportation is becoming increasingly busy, and overloaded transportation frequently appears driven by economic interests. Many vehicles have exceeded the limit imposed by the bridge, especially under the effect of eccentric loading, one side of the prestressed box girder bridge first reaches the conditional ultimate bearing capacity, which leads to the collapse of the entire bridge in recent years (Fan 2003). However, the current standards, such as Specifications for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts, calculate the ultimate bearing capacity of the bridge and are generally equivalent to the box section as a T section. By default, when the structure is damaged, all materials of the entire section have reached the limit state; however, in practice, only a part of the material reaches the ultimate bearing capacity when the structure is damaged under the effect of over-limit and partial load. At this time, the formula provided by the specification cannot be used to calculate the ultimate bearing capacity of the structure, so it is necessary to modify the formula of the specification. Box-section members have the characteristics of larger section size and longer flange cantilever length. These characteristics make most box-shaped members have different force and deformation characteristics in terms of normal cross-section bending resistance, oblique cross-section shears resistance, and torsion resistance (Li 2015). The conclusions obtained from the tests of smaller-sized T-shaped or I-shaped cross-section members and whether the generalized design calculation formulas can be used for large box-shaped cross-section members deserve serious consideration.

∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-9

63

2 SPACE STRESS CHARACTERISTICS OF CONCRETE BOX GIRDER BRIDGE The spatial effect of the bridge is actually relative to shallow and narrow beams that meet the flat section assumption, have open sections, and only consider vertical shear stress. When the bridge’s wide span is relatively large, the flat section assumption is no longer satisfied, and the box beam is a statically indeterminate section, so the spatial effect is very significant (Ji 2016; Ma 2019; Wu 2008; Ye 2014; Yang 2011; Yuan 2009; Zheng 2015). 2.1 Spatial effects of box girder The concrete box girder bridge is a space structure. In a large-span wide box girder structure, the spatial effect is relatively significant, and it is difficult to accurately reflect it through the calculation of a plane beam tie beam element (Yang 2011). In this case, the spatial effect of the box girder must be considered. The deformation of the box girder under eccentric loading is shown in the figure.

Figure 1.

Sectional deformation of box girder subjected to eccentric loads.

According to the deformation diagram of the box girder section under the eccentric load (Figure 1), it can be seen that the spatial effect of the concrete box girder bridge can be expressed by the stress of the cross-section in both directions: Normal longitudinal stress: σZ = σM + σW + σdw ; Longitudinal shear stress: τ = τK + τM + τW + τdW ; Transverse normal stress: σe = σdt + σc ; σM —Normal stress in longitudinal bending under eccentric loading; σW —Free torsional normal stress under eccentric loading; σdw —Distortion warping normal stress under eccentric loading; τK —Longitudinal bending shear stress under eccentric loading; τM —Free torsional shear stress under eccentric loading; τW —Constrained torsional shear stress under eccentric loading; τdW —Distortional shear stress under eccentric loading; σdt —Distorted lateral bending stress under eccentric loading; σe —Lateral bending stress under eccentric loading. 64

Therefore, under the eccentric load, the box section and the T section have a large difference in stress, especially when the shear bending section is in a complex stress state, the stress of the box section is greater than the T section.

3 ULTIMATE BEARING CAPACITY OF BOX SECTION UNDER ASYMMETRIC LOAD 3.1 Calculation of flexural bearing capacity of the normal section of box section under asymmetric load Taking the box-shaped flexural member without reinforcement in the compression zone as an example, the formula for calculating the bending capacity of the normal section of the flexural member of the prestressed concrete according to Specifications for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts is as follows (1), (2), (3):  x (1) γ0 Md ≤ Mu = fcd bx h0 − 2 The height of the section compression zone is calculated as follows: fsd As + fpd Ap = fcd bx

(2)

And the height x of the compression zone should meet the following requirements: x ≤ ξb h 0

(3)

In the formula: As , fsd —Design values of cross-sectional area and tensile strength of longitudinal non-prestressed steel bars in the tensile zone; Ap , fpd —The design values of the cross-sectional area and tensile strength of the prestressed reinforcement in the tensile zone; fsd —Design value of concrete axial compressive strength; ξb –The relative limit compression zone height of prestressed concrete flexural members; h0 —Effective height of the section. However, when the cross-section reaches the ultimate bearing capacity under the action of a unilateral over-limit vehicle, some materials do not fully reach their breaking strength. The above formula is modified as follows: The formula for calculating the bending capacity of a normal section is:  3x (4) γ0 Md ≤ Mu = φfcd bx h0 − 8 And the height of the compression zone must also meet the requirements of the above formula (3). In the formula: φ—Comprehensive consideration of the concrete participation coefficient of the compression zone when the normal section reaches the ultimate bearing capacity under eccentric loading φ = 0.75. 3.2 Calculation of Shear Capacity of Oblique Section of Box Section under Asymmetric Load According to the formula for calculating the shear bearing capacity of the inclined section of the prestressed concrete flexural member in the Specifications for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts: γ0 Vd ≤ Vu = Vcs + Vpb 65

(5)

Design value of common shear capacity of Vcs concrete and stirrups in inclined section: 

Vcs = α1 α2 α3 0.45 × 10−3 bh0 (2 + 0.6p) fcu,k ρsv fsv

(6)

Design value of shear bearing capacity of prestressed bent steel bar:  Apb sin θp Vpb = 0.75 × 10−3 fsd

(7)

In the formula: α2 —Prestressing factor, for prestressed concrete flexural members, α2 = 1.25. But when the bending moment of the section caused by the combined force of the reinforcing bar and the outer bending moment is in the same direction, or prestressed concrete flexural members that allow cracks to appear, α2 = 1; P—Calculated Reinforcement Percentage of Longitudinal Tensile Bars in Oblique Sections. ρ = 100, ρ = (Ap + Apb + As )/bh0 ; When P > 2.5, P = 2.5; ρsv —Reinforcement ratio of internal stirrups in inclined section, ρsv = Asv b. In actual engineering, prestressed concrete box girder may also use vertical prestressed steel bars (hoops) in the web; at this time should be replaced by the reinforcement ratio ρsv of the vertical prestressed steel bar (hoop bar); Sv —Spacing of vertical prestressed steel bars (hoops) in oblique section (mm); fsv —Design value of tensile strength of vertical prestressed steel bars (hoops); Asv —Cross-sectional area of vertical prestressed steel bars (hoops) arranged in the same section in an inclined section; θp —Angle between the tangent to the horizontal line of the prestressed bent steel bar (at the normal section of the compressed end of the inclined section); Apb —Cross-sectional area of prestressed bent-up steel bars in the same bent-up plane in the oblique section (mm2 ); fpd —Design value of tensile strength of prestressed steel bars. However, when the cross-section reaches the ultimate bearing capacity under the action of a unilateral over-limit vehicle, some materials do not fully reach their breaking strength. The above formula is modified as follows:

Figure 2. Analysis of the cross-section of a box girder subjected to eccentric loads.

V1 + V 2 = V  b + e = Vb V 2

(8) (9)

Combine (8) and (9): Under eccentric load, when the shear failure occurs on one side of the web, the calculation diagram of the component based on the limit equilibrium state is shown in Figure 3. 66

Figure 3.

Schematic diagram of shear calculation for inclined section.

Ts +



fsp Aspi cos θ p = Dc   V2 = Vc + fsv Asvi + fsp Aspi θp    V2 • a = Ts • hs + fsv Asvi Si + fsp Aspi cos θp Spi + fsp Aspi sin θp hpi

(10) (11) (12)

Combining formula (10) and formulas (11), (12), and (13), under the eccentric loading of prestressed reinforced concrete beam bridges, when the shear failure occurs on one side of the web, the shear bearing capacity formula of the inclined section of the flexural member is as follows:   Vc + fsd Asdi + fpb Apbi sin α V= (13) 1 + be 2 It is difficult to accurately calculate the shear capacity of each part, especially the shear capacity of concrete and stirrups. Therefore, the formula for calculating the shear capacity of the structure under eccentric loading In this paper, the calculation formula for the shear capacity of the inclined section of the bending member in the Specifications for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts is modified as shown in formula (15): 



Apb sin θp Vu = α1 α2 α3 0.45 × 10 bh0 (2 + α4 0.6p) fcu,k α5 ρsv fsv + 0.75 × 10−3 fsd −3

(14)

In the formula: α4 —Participation coefficient of ordinary steel bars when the inclined section of the web reaches the ultimate bearing capacity under eccentric loading α4 = 0.5. α5 —Coil participation factor when the inclined section of the web reaches the ultimate bearing capacity under eccentric loading α5 = 0.5.

4 BRIDGE CASE VERIFICATION 4.1 Project introduction A prefabricated box girder is made of C50 concrete, the calculated span is 29.89m, the bridge deck width is 11.5m, and ordinary tensile steel bars are HRB335 and R235. The stirrups are HRB335. The spacing between the stirrups at the beam end is 100mm, and the spacing between the stirrups at the middle section is 200mm. The prestressed tendon is a high-strength, low-relaxation steel strand with a nominal diameter of 15.24mm. Its standard tensile strength is fpk = 1860MPa. The 67

Figure 4.

Schematic diagram of a typical cross-section near a box beam support.

Figure 5. Typical cross-section of box girder span.

tensile control stress is 1395MPa. The dimensions and reinforcement at the mid-span section and 1.5m from the support are shown in Figures 4, 5, 6, and 7. The MIDAS/FEA software is used to establish a finite element model of the prestressed concrete simply supported box girder. The basic material parameters of the model are shown in Table 6. The schematic diagram of the model is shown in Figures 6 and 7. Table 1. Table of basic parameters of the prestressed concrete box girder. Parameter

Concrete

HRB335 Steel

R235 Steel

Prestressed Steel

Density/(KN/m3 )

25 34554 0.2 32.4 2.65 1.0×10−5

76.98 200000 0.3 – 335 –

76.98 210000 0.3 – 235 –

78.5 195000 0.3 – 1860 1.2×10−5

Elastic Modulus/Mpa Poisson’s ratio Compressive strength /Mpa Tensile strength/Mpa Linear expansion coefficient

4.2 Comparative analysis of results When the cross-section of the floor plate is broken in the normal section, the lateral stress distribution of the longitudinal reinforcement, stirrups, and prestressed reinforcement of the floor is shown in Figures 8, 9, and 10. 68

Figure 6. Schematic diagram of prestressed concrete box girder model.

Figure 7. Reinforcement skeleton diagram of prestressed concrete box girder model.

Figure 8. Stress distribution of longitudinal reinforcement in the mid-span floor.

Figure 9. Stress distribution of prestressed reinforcement in mid-span sections.

Figure 10.

Stress distribution of concrete in the mid-span floor.

When the oblique section failure occurs near the load-side web, the lateral stress distribution of the longitudinal reinforcement, stirrups, and prestressed reinforcement of the bottom plate is shown in Figures 11, 12, 13, and 14.

Figure 11. Longitudinal stress distribution of the section floor near the fulcrum.

Figure 12. Stress distribution of section stirrup near the fulcrum.

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Figure 13. Stress distribution of prestressed steel bars near the fulcrum.

Figure 14. Stress distribution of concrete floor under section near the fulcrum.

Based on the above figure, it can be seen that when the prestressed concrete simply-supported box girder reaches the limit bearing capacity under the normal cross-section condition, the strength of the concrete and longitudinally-stressed reinforcing steel materials are fully exerted, and the prestressed steel reinforcement does not reach the standard strength of the material. When the web on one side of the shear bend reaches the limit of the bearing capacity of the oblique section, the concrete almost reaches the standard strength of the material along the entire cross-sectional direction. The stirrups and longitudinally-stressed steel bars have reached the standard strength of the material only near the stressed side; the prestressed steel bars have not reached the standard strength of the material. According to the relevant results of the prestressed concrete box girder given above under the condition of eccentric loading, the results are compared with the theoretical results. Table 2. Bending capacity of the normal section of prestressed concrete box girder (Unit: KN). Load form

Theoretical formula

Finite element calculation

Symmetrical load Asymmetric load

27340 23844

26995 25318

Table 3. Shear capacity of the inclined section of prestressed concrete box girder (Unit: KN) Load form

Theoretical formula

Finite element calculation

Symmetrical load Asymmetric load

13165.62 9855.23

20800 17600

5 CONCLUSION This article summarizes the spatial effects of box girder bridges and explains that there are differences between the force characteristics and T girder bridges. At the same time, by using the finite 70

element method to simulate the load test of the actual bridge and comparing the theoretical formula and the finite element calculation, the following conclusions can be drawn: 1) When the mid-span of the prestressed concrete box girder bridge reaches the conditional ultimate bearing capacity under asymmetric load, the material load in the section is more uniform and consistent with the normal section failure mode under the symmetrical load. However, when the shear bending section reaches the conditional ultimate bearing capacity under the asymmetric load, the failure mode of the web oblique section is greatly different from that under the symmetrical load. 2) When the prestressed concrete box girder bridge reaches the limit bearing capacity under the condition of the normal section under asymmetric load, the stress of the longitudinal ordinary steel bar and floor concrete and the symmetrical load have consistently reached the standard strength of the material. The prestressed steel beam is roughly linearly distributed along the transverse bridge. Therefore, the ultimate bearing capacity of the normal section is reduced under asymmetric load, but the decrease is not obvious, which is basically consistent with the ultimate bearing capacity of the normal section under symmetrical load. However, only half of the stirrups and longitudinal ordinary steel bars have reached the standard strength of the material when the shear bending section of the prestressed concrete box girder bridge reaches the limit bearing capacity of the inclined section under asymmetric load. Therefore, the ultimate bearing capacity of the oblique section under asymmetric load is reduced by about 0.83 times that under symmetric load.

REFERENCES Fan, L.C. (2003). Bridge engineering. China Communication Press, Beijing, China. Ji B.Y., Yu X.L., Yang Z., et al. (2016). Analysis of factors affecting the ultimate bearing capacity of prestressed concrete box girder bridge with large cantilever spread wings. In: Sino Foreign Highway. Li, Y.Y. (2015). Refined space stress analysis and reinforcement research of oblique section of PC box girder bridge. Harbin Institute of Technology. Ma X., Chen B.C., Huang Q.W., et al. (2019). Optimal design of 30 m prestressed ultra high performance concrete small box girder. In: Journal of Fuzhou University (NATURAL SCIENCE EDITION). Wu Y.Y. (2008). Test and analysis of the ultimate bearing capacity of the prestressed concrete box girder. In: Guangdong Civil Engineering and Architecture. Yang, H.Y. (2011). Research on residual load carrying capacity based on lateral distribution and redistribution of damaged RC bridge load. Chongqing Jiaotong University. Ye, Y.J. (2014) Study on the calculation method of multi-chamber wide box girder lateral distribution. Chongqing Jiaotong University. Yuan L., Hu Q., Chen L.Q. (2009). Experimental study on the ultimate bearing capacity of the prestressed concrete box girder. In: Railway Construction. Zheng H. (2015). Experimental study on the shear resistance of concrete box girder. Hunan University.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on the blast and impact resistance of FRP panels Zeyu Xie∗ Xi’an University of Architecture and Technology, Ande College, China

ABSTRACT: As a new reinforcement method, the composite material-reinforced concrete technology has been widely studied and it has been found that this reinforcement technology improves the load bearing capacity and ductility of members, but there are fewer studies on the impact and blast resistance of pure composite materials and composite panels. This paper summarises the relevant research on pure fiber-reinforced plastic (FRP) panels and FRP composite panels by scholars at the domestic and international levels, including several aspects such as blast and impact resistance of pure composite and composite panels, experimental and numerical simulation studies, which provides references for design tests and practical applications of FRP panels in engineering, and put forward the outlook.

1 INTRODUCTION In recent years, terrorist attacks and explosions have repeatedly occurred in many parts of the world, posing a serious threat to public production and the safety of human life and property. As a result, engineers are increasingly concerned with improving the blast resistance of buildings and reducing the damage caused by explosions. With the development of science and technology, various new materials have emerged, among which composite materials have attracted much attention in the aerospace, military and engineering fields due to their light weight, high strength and good corrosion resistance. Composites are new materials using advanced material preparation techniques to optimise the combination of material components with different properties. Composites consist of a matrix and a reinforcement material. Matrix materials can be divided into two categories: metallic and nonmetallic. Metallic matrices are usually used for aluminium, magnesium, copper, titanium and their alloys. Non-metallic matrices are mainly synthetic resins, rubber, ceramics, graphite and carbon. Reinforcing materials are mainly glass, carbon, boron and aramid fibres. The most commonly used composite material in engineering today is FRP (fibre reinforced polymer/plastic), a new type of high-performance composite material in which the reinforcing fibres and matrix (resin) are combined by a forming process such as drawing, winding and moulding (Wu 2017). Commonly used reinforcing fibres include carbon, aramid, glass and basalt fibres, which are known as CFRP, AFRP, GFRP and BFRP respectively, and epoxy, vinyl ester and unsaturated polyester resins are used as matrix materials (Han 2002). Many experimental studies and theoretical analyses have been carried out by domestic and international researchers on the effect of FRP on the blast resistance of structures, and studies have shown that the blast resistance of members strengthened with the material is significantly improved (He 2002; Mosalam 2001; Razaqpur 2006; Wu 2007). In a related study on slabs, to investigate the mechanical properties of conventionally reinforced concrete slabs, Zheng, W. Z. (2022) conducted shear tests on four concrete slab specimens and found a positive correlation between the height of ∗ Corresponding Author:

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[email protected]

DOI 10.1201/9781003384830-10

the shear compression zone and the reinforcement rate of the longitudinal tensile reinforcement above the reference section. Based on the test results, a method was developed to calculate the shear capacity by considering the effect of the ratio of shear to span and the relative height of the shear zone due to the longitudinal tensile reinforcement. Sun, W. B (2009) and Zhang, X. B. (2006) investigated the dynamic behaviour and damage characteristics of conventionally reinforced concrete slabs and found that the extent of collapse damage was related to factors such as load and slab strength characteristics. Many researchers have used high-performance concrete and reinforcement to improve the loadbearing capacity of reinforced concrete slabs. Y, J. H.(2012) conducted an experimental study of high-performance concrete (HPC) reinforced with wire mesh and found that slabs reinforced with 2.15% wire mesh showed the best blast resistance compared to 3% and 5% wire mesh. Kou, J. L. (2020) tested six HDC slabs with fibre of 0.5%, 1.0% and 2.0% and conventional reinforced concrete slabs for impact resistance. The results showed that the HDC slabs had good impact resistance and the HDC slabs with 1.0% fibre had the highest impact resistance. Ahmed, G. H.(2015) investigated the effect of the strength and reinforcement rate of UHPC on the impact resistance of the slabs and found that the impact resistance and stiffness of the UHPC slabs were positively correlated with the strength and reinforcement rate of UHPC. In summary, it can be seen that previous research into the blast and impact resistance of panels has focused on reinforcement rates, the use of high-performance concrete and high-performance reinforcement, with little research into the blast and impact resistance of pure FRP panels and FRP composite panels. However, as research into FRP sheets develops and their use in structures becomes more common, their blast and impact resistance becomes very important. In this context, this paper summarises and analyses several aspects of existing research on pure and composite panels, as well as experimental and numerical simulations, to provide ideas and practical recommendations for future research on FRP composite panels in terms of impact and blast resistance.

2 STUDY ON EXPLOSION/IMPACT RESISTANCE OF PURE FRP PLATE In recent decades, most of the researches on the pure composite plates has focused on their bending, shear and invasion resistance properties and the related equations of the buckling of the constructed plate under combined loads (Chen 2021; Huang 2016; Kopparthi 2021; Zhang 1987). However, there are few studies on the anti-knock and impact performance of pure composite plate. The comprehensive analysis shows that the explosion and shock loads not only produce explosion and shock wave but also shear force. Under high load rate, the damage pattern of the plate is mainly shear damage of the whole structure or the mixed damage of shear and bending, while local shear and local bending damage are more common in short-distance explosion loads (Sun 2008; Yu 2021). However, the pure cladding plate itself is too thin to absorb and consume the energy generated by explosion wave and shock wave, and the shear capacity of the composite material itself is low (Li & Yang 2019), so it cannot be used to resist explosion and impact load alone. The main reason for the poor shear performance of composite materials is that most of them have anisotropic mechanical properties due to the inconsistent laying directions of fiber materials, which leads to poor mechanical properties in the vertical axial direction and low shear strength of composite materials (Yu 2021). The slight impact damage on the surface of the composite plate will also result in a serious decline in ultimate bearing capacity (Ou 2018; Zhang 2021). Therefore, composite material should be used in combination with other materials of the plate to ensure the material makes better use of its advantages and improve the performance of components and structures. In addition, compared with the reinforced concrete slab, the cost of pure composite material is quite high, which is one of the reasons why there is small number of research on the impact and explosion resistance of composite slabs at present.

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3 STUDY ON EXPLOSION/IMPACT RESISTANCE OF FRP COMPOSITE PLATE About composite slabs, the present domestic and foreign researchers mostly focus on the research of fiber composite materials and concrete combination explosion or impact load resistance together. Compared with the steel plate, although the modulus of FRP is not greater than the former, FRP improves the whole stiffness of the plate by tightly covering on the wall surface, for wall provides enough constraints. At the same time, problems such as weak bonding and easy corrosion of steel plate reinforcement are avoided (Chen 2021). Common combination form is sticking outside consolidated with interior consolidation. The reinforcement position of the external reinforcement is mainly the bottom of the plate. The FRP material is attached to the bottom of the plate to resist the tension caused by the explosion/shock wave caused by the reflection of concrete. By comparing the dynamic response characteristics of ordinary reinforced concrete slabs and FRP reinforced concrete slabs, it is concluded that FRP can enhance the anti-blast bearing capacity, integrity and plastic performance of the reinforced concrete structures, inhibit the development of concrete cracks and delay the failure time of structure. Different reinforcement materials have different effects on the dynamic response of the plate under impact/explosion load. Under the same reinforcement mode, the anti-explosion performance of the plate strengthened with CFRP is better than that strengthened with GFRP. Compared with CFRP reinforcement, the protective layer of BFRP reinforced plates is less damaged (Chen 2020; Mohamed 2011; Pan 2011; Yang 2021). In internal reinforcement, FRP bars are placed in concrete slabs instead of traditional steel bars as internal reinforcement to solve the steel corrosion problem in concrete slabs from the root (Sadraie 2019). It is found that the use of FRP bars can improve the anti-blast and impact performance of the member, effectively reduce the plate bottom displacement and inhibit the generation of cracks in the member, ensure the ductility of the member and improve the residual strength (Guo 2011; Yu 2020).

4 EXPERIMENTAL RESEARCH METHOD Experimental research is the most direct way to get results. The test methods of anti-explosion performance are contact explosion, non-contact explosion, drop hammer and jack loading. Impact resistance is mostly measured by dropping hammer impact test, pendulum impact test, MTS rapid loading test, SHPB (Split Hopkison Pressure Bar) test, light gas gun test and explosion impact test (Lai 2015). The experimental results show that cracks appear on the backburst surface of ordinary reinforced concrete slab, the main cracks extend along the diagonal direction of the slab, and a rectangular failure zone appears in the center of the slab, showing typical bidirectional flexural failure characteristics. When the explosion load peak is large, the elliptic collapse appears on the reinforced concrete slab, and the failure mode changes from bending failure to shear failure (Chen 2015). Anti-detonation and impact properties are related to the concrete strength, the reinforcement ratio, the reinforcement strength and the blast distance (He 2021; Lu 2012; Wang 2015, 2018). FRP is usually used to strengthen concrete slab to improve its anti-blast and impact performance. The experimental results show that using CFRP grids, CFRP plates and GFRP plates to reinforce concrete slabs can effectively enhance the bearing capacity and deformation capacity of the slabs and improve the integrity of the slabs. Using BFRP bars, BFRP bars and GFRP bars instead of steel bars into the plate can reduce local spalling and effectively inhibit the generation of cross cracks, significantly reducing the number and width of circumferential and radial fractures (Razaqpur 2006; Sadraie 2019; Yu 2021, 2020; Zhao 2019). FRP sandwich plate has an excellent anti-knock ability, which can greatly improve energy dissipation and reduce the deformation level (Ahmed et al. 2017). To sum up, more tests have been carried out so far to strengthen concrete slabs with FRP, and the advantages of composite slabs in bearing capacity, stiffness and integrity compared with ordinary 74

reinforced concrete slabs have been fully verified. However, more research on combination methods is needed to find out the best combination plate form.

5 NUMERICAL SIMULATION STUDY Many practical problems can not be studied through physical experiment research, at the same time, the blast was finished in a very short period of time and the damage caused by explosion has greatly restricted experimental observations and measurements, which interferes with the accuracy of the experimental data. So through the test of explosion problem, there are many difficult in-depth and meticulous research. Numerical simulation, which is not only influenced by environmental conditions but is lesser, can more easily change simulation (test) conditions of comparison and analysis of simulation results. Under different conditions, calculation parameter combination should be adjusted to find the best parameters, which can be further analyzed to find out the changing trend of the important parameters for use in guiding trials to select a parameter and correction. At the same time, the damage phenomenon in the test process can be carefully observed. Moreover, numerical simulation can also simulate and study problems that are not completely clear in theory. These characteristics make numerical simulation an important means to study explosion mechanics (Shi 19998; Wu 2002, 2008). At present, the commonly used finite element software includes ANSYS/ LS-DYNA, ABAQUS and AUTODYN. In the anti-detonation and anti-impact simulation analysis, the explosion phenomenon, detonation wave propagation and its control process are usually described by fluid dynamics or elastic-plastic dynamics model. Both the finite element method and the difference method can be used for the simulation calculation by Lagrange method and Euler method (Wu 2008). When the variation range of parameters is very small, such as the thickness of the reinforcement layer, the reinforcement method, the bond strength, etc., numerical simulation can get the results more quickly than the test. The simulation results show that CFRP plays an important role in the later stage of concrete crack propagation when the external CFRP strips are used for reinforcement. The thicker the external FRP strips are, the more obvious the effect of resisting crack propagation in the concrete area is. External CFRP plates can enhance the anti-explosion performance of composite plates. The more the reinforcement layer, the better, but there is an optimal number of the reinforcement layer. Under the same reinforcement condition, the anti-explosion condition of the CFRP plate is better than that of GFRP plate. Numerical simulation can not only meet the research needs but also reduce the problems caused by experimental research (Chen 2020; Kong 2018, 2018; Yang 2021).

6 SUMMARY OF NATIONAL NORMS As there is less information available on the relevant standards and formulas for blast resistance, it is recommended here to refer to, compare and analyse foreign standards and the current design standards for punching shear strength of FRP concrete slabs in China (in Table 1). 1) According to the British Code, the shape of the control section is square; according to other standards, the shape of the control section corresponds to the shape of the column head. 2) According to the Canadian Code, if d is greater than 300 mm, Vc must be multiplied by (300/d) 0.25 and fc’ must not exceed 60 MPa. As can be seen from the parameters considered in the equations, the Canadian code is the one with the highest number of factors considered, with the Japanese code being second only to the Canadian code in the number of factors considered. As shown in Table I, the factors affecting the punching capacity of concrete slab-column nodes are defined differently in different countries, such as the location of critical sections, the effect of dimensions, reinforcement criteria and the location 75

Table 1. Summary of calculation formulae by country National (normative codes)

Formula V p ≤ (0.7βh ft + 0.25σpc,m )ηbo,0.5d ; η = (η1 , η2 ) min

China (GB50010-2010)

UK BS8110-97

USA ACI1440-15

η1 = 0.4 +

αs d 1.2 βc ; η2 = 0.5 + 4b

o, 0.5d

Vp = 0.79bo,1.5d d



100ρf EF Es

1/3

(400/d)1/4



fcu,k 25

1/3

≤ 0.8bo,1.5d d fcu,k ; ρf = (ρx + ρy )/2 ≤ 3%

 fc bo,1.5d kd; k = 2ρf nf + (ρf nf )2 − ρf nf

nf = Ef /Ec ; Ec = 4750 fc

Vp =

4 5



Vp = 0.18bo,2d dk(100ρf fc )1/3 ≥ Vmin Europe Eurocode2-2004

Vmin = 0.035bo,2d dk 3/2 (fc )0.5 k = (1 + (200/d))0.5 ≤ 2; ρf = (ρx · ρy )0.5 ≤ 2%

Europe Model Code 1990

Canada CAN/CSA-S806-2012

Vp = 0.12ξ 3 100ρf fc bo,2d d ≤ 0.3(1 − fc /250)fc bo d √ ξ = 1 + 200/d(d − in − mm); ρf = (ρx · ρy )0.5   ⎧ ⎫ 2  1/3 ⎪ ⎪ ⎪ Vc1 = 0.028λφc 1 + βc (Ef ρf fc ) bo,0.5d d ⎪ ⎪ ⎪ ⎪ ⎪   ⎨ ⎬ αs d  1/3 Vp = min Vc2 = 0.147λφc bo,0.5d + 0.19 (Ef ρf fc ) bo,0.5d d ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎩ Vc3 = 0.056λφc (Ef ρf fc )1/3 bo,0.5d d ⎭ Vp = βd βp βr fpcd bo,0.5d d/γb βd = (1000/d)1/4 ≤ 1.5(d − in − mm)

Japan JS-1997

βp = (100Ef ρf /ES )1/3 ≤ 1.5 βr = 1 + 1/(1 + 0.25bo /d)

fpcd = 0.2 fc ≤ 1.2MPa

of loads. As a result, inconsistencies may arise between national standards when considering the punching shear capacity of concrete slabs.

7 CONCLUSIONS (1) Pure FRP panels have poor blast and impact resistance, while FRP combination panels can effectively increase the load-bearing capacity of the panels, inhibit the development of 76

cracks and prolong the time of panel damage. Combined forms are mostly externally applied reinforcement and internally reinforced. (2) The blast/impact resistance of the slab is mostly studied by means of experimental research and numerical simulation, and the method selection should take full account into the research conditions and research needs at this stage. (3) The study of punching and shearing of concrete slabs is not uniform across countries, and the choice is made by combining the research needs. The use of FRP panels in buildings that may be subjected to blast or impact loads can reduce the damage to the building and has good engineering prospects.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research and application of adaptive bentonite waterproof blanket Bingyao Duan, Xingyue Zhang, Yangyang Wu, Chaoxi Lai & Nana Liu∗ Chongqing College of Architecture and Technology, Chongqing, China

ABSTRACT: The traditional bentonite waterproof blanket has been used for more than 20 years, but it has many difficulties such as environmental pollution, security risks and application scenarios. The new self-responsive bentonite waterproof blanket developed by the author’s team is a new geosynthetic material, which is self-responsive to pressure, PH, and temperature sodium bentonite waterproof blanket. In this research, a new product is developed by adding high-performance bentonite on the basis of the traditional waterproof blanket. The in-situ controlled polymerization process is adopted to modify bentonite and enforce the intelligent response behavior of bentonite to the changes in water pressure, water seepage, and other factors, so as to achieve an intelligent waterproof effect. This research result is a key step in the application of waterproof blankets in the field of construction, and it can effectively supplement the solution to environmental pollution caused by liquid leakage in the application environment and water seepage in underground building structures.

1 GENERAL INSTRUCTION With economic and social development, the speed of urban construction in China has accelerated significantly, and people’s requirements for quality of life are getting higher and higher. On the one hand, this is reflected in the living environment. The construction of many residential areas is accompanied by artificial water landscapes. On the other hand, a lot of household garbage is produced in terms of living sanitation, and both of them are closely related to the environment. The author focuses on the two aspects mainly because there are often underground garages and other facilities under the artificial water landscape in residential areas, and the waterproofing performance under the waterscape will directly affect the quality of residential areas and the quality of life. Therefore, it is the need for the whole city to use good waterproofing materials for each artificial water body in the city. MSW treatment has always been a key research topic in China’s environment. Sanitary landfill is an easy-to-operate method with a low cost and large capacity (Luan 2003) However, the leachate concentration is high in the garbage, which contains complex organic pollutants and heavy metals, with potential pollution risks to landfill groundwater and surrounding soil (Qian 2010). Therefore, both waterproof and corrosion-resistant materials are essential in the process of urban development. (Jafari 2014) 2 RESEARCH PROGRESS OF BENTONITE WATERPROOF BLANKET AT HOME AND ABROAD Bentonite is also called bentonite. Montmorillonite is the main mineral composition of non-metallic minerals with a content of 85–90%. Some properties of bentonite are also determined by montmorillonite. Montmorillonite can be of a variety of colors such as yellow and green, yellow and ∗ Corresponding Author:

80

[email protected]

DOI 10.1201/9781003384830-11

white, gray, white, and so on, can become dense blocks, and can also be of a loose soil shape, so it will slide when rubbing fingers, with small pieces of water after the volume swells by several times (20–30 times). It will be suspended in the water when being pasty a little. The properties of montmorillonite are related to its chemical composition and internal structure. Montmorillonite is made up of two silicon-oxygen tetrahedron clips and an alumina layer with a 2:1 type of octahedral crystal structure, because its crystal cell layer structure is formed by some cations, such as Cu, Mg, Na, K, etc. The cation with montmorillonite crystal cell function is not very stable and is easily exchanged by other cations, indicating good ion exchange. Abroad, it has been applied in more than 100 departments in 24 fields of industrial and agricultural production, with more than 300 products, so people call it “universal soil”. Bentonite composite waterproof blanket (GCL) is new geosynthetic material (Cho 2010; Shi 2002). It is made of mixed raw materials of graded natural natrium-based bentonite particles and the corresponding admixture. After needling technology and equipment, bentonite particles are fixed between geotextile and plastic weaved cloth and made of blanket waterproof roll materials. The bentonite waterproof blanket not only has all the characteristics of geotechnical materials but also has excellent waterproof (seepage) performance. Moreover, it can be divided into a needle-punched sodium-bentonite waterproof blanket, needle-punched film-coated sodium-bentonite waterproof blanket, and adhesive sodium-bentonite waterproof blanket (JG/T193-2006, Ju 2013; Li 2014). Its waterproof mechanism is that the bentonite particles expand when meting water and form a uniform colloid system. Under the restriction of two geotextile layers, the bentonite changes from disorderly to orderly expansion. The continuous water absorption and expansion result in the compactness of the bentonite layer itself, thus having a waterproof effect. In China, many scholars have studied the preparation of bentonite waterproof blankets and applied them to landfill sites. For example, taking natural sodium-based bentonite as the raw material, when the dosage of sodium hydroxide additive is 0.2%, the dosage of acrylamide is 0.07%, and the water content is 28%, the kneading of fine mud machine is mixed once, and then the film is coated and rolled, and the preparation of bentonite waterproof blanket by this kneading method has the advantages of simple process, strong operability and stable performance (Wang 2019). When the acidity of the solution increases, the permeability coefficient of sodium-bentonite increases by an order of magnitude (Liu 2015). Using natural sodium bentonite as raw material, a certain amount of industrial water is added to react under high temperature and high pressure in a closed environment by mixing it with polymer chemical agents, and then a new GCL is made by vacuum extrusion (Liu 2013). In other countries, sodium carbonate-based bentonite is modified by sodium bentonite and used for seepage control experiments. The results show that the permeability of the sodium bentonite is far lower than the calcium base bentonite, but it has been found through long-term observation that when the sodium bentonite becomes longer, the permeability coefficient will gradually increase, therefore, the sodium bentonite is not suitable for the production of GCL (Katsumi 2008). Under different temperature conditions, the effects of different concentrations of MgCl2 on the permeability of GCL show that the increase in temperature will lead to the decrease of the viscosity of the permeability liquid and increase the permeability of GCL. When anionic and cationic polymers of 1% and 2% are added to GCL, the permeability of GCL decreases by several orders of magnitude (Ozhan 2018).

3 APPLICATION OF BENTONITE WATERPROOF BLANKET AT HOME AND ABROAD When making bentonite MATS, local bentonite resources need to be considered, because the thickness of bentonite in the impermeable layer is about 60-90 cm, which requires a large amount of bentonite for engineering application. Long-distance transportation will increase the cost, which conflicts with the economic factors of using bentonite MATS. In engineering applications, bentonite needs to be added with a large amount of water to prevent it from being loose and failing to meet the impermeability requirements. Therefore, bentonite is seldom used in arid areas. In a complex 81

ionic environment, bentonite pads tend to adsorb pollutants and thus increase their permeability. Generally, the permeability coefficient of bentonite pads is less than 10−7 cm/s. If the permeability coefficient of bentonite increases, the anti-permeability effect will be worse. The recycling of bentonite MATS is particularly difficult because bentonite MATS tends to be in the middle layer during use. The upper and lower layers contain a lot of soil and gravel, and if bentonite MATS fails, it is difficult to repair. The quality of bentonite in each region is different, and the anti-seepage performance of bentonite pads is different, so the engineering quality is difficult to guarantee. When the bentonite waterproof blanket is applied in practical engineering, its anti-seepage effect is mainly related to the following three aspects (Li 2007): its own material, such as bentonite particle size, montmorillonite content in bentonite, bentonite type, etc. If the bentonite in the waterproof blanket is of poor quality or with high impurity content, it cannot effectively prevent seepage; application environment, during the anti-seepage process of the bentonite waterproof blanket, the solution contains harmful substances, if the bentonite in the waterproof blanket cannot effectively adsorb the pollutants in the solution, liquid penetration will be generated, and harmful substances will pollute the surrounding environment. As an anti-seepage material, the bentonite waterproof blanket has lost the significance of environmental protection. In the practical application process, the bentonite waterproof blanket will be affected by the shear stress. If the shear stress is greater than its shear strength, the bentonite waterproof blanket will be damaged, resulting in the loss of anti-seepage performance (Jiang 2005; Wang 2009; Yang 2013). The effect of a bentonite waterproof blanket is much better than a bentonite mat, but there are many problems in a bentonite waterproof blanket. Bentonite waterproof blankets, like bentonite MATS, are particularly susceptible to the influence of the surrounding environment where bentonite adsorbs contamination. The anti-seepage performance of the material will also be reduced, although you can replace the waterproof blanket, this will increase the follow-up cost of the project. Therefore, it is still necessary to upgrade the bentonite waterproof blanket, so that the bentonite in the waterproof blanket is not prone to cation exchange with the pollutants in the surrounding environment, resulting in failure. The result is a waterproof blanket called HDP bentonite, which is made by mixing bentonite with a pre-hydrated solution and then extruded through vacuum filtration and agitation. It has very low porosity. Vacuum extrusion will make bentonite almost parallel in the plane of the plate, and then through the extrusion molding, the vertical hydraulic conductivity of the plate is particularly low. Studies show that the DPH bentonite waterproof blanket has a lower coefficient K than the traditional bentonite waterproof blanket (Dong 2015; Li 2016).

4 IMPROVED BENTONITE TECHNOLOGY The bentonite waterproof blanket studied by the author’s team is based on the improved bentonite developed by Dr. Dong’s team (Dong 2020). The improvement methods are as follows: Using citric acid as a modifier, bentonite is modified primarily; the modified mixture is centrifuged and washed with water until it is neutral. Activated bentonite is obtained after drying. The activated bentonite and silane coupling agent are combined by ultrasonic treatment. After the compound reaction, β-cyclodextrin is added to the mixture for crosslinking reaction. After the crosslinking reaction, a coagulant is added to the mixture, which is centrifuged, washed, and dried successively. Dr. Dong’s research team prepared β-cyclodextrin and bentonite complex by cross-linking polymerization method and then obtained environmentally friendly bentonite. The environmentally friendly bentonite showed good adsorption characteristics for heavy metal ions, and could completely remove heavy metal ions in the waste liquid of heavy metals in a short adsorption time. The water quality after treatment can meet the requirements of class I water body stipulated by GB3838-2002. In addition, the environmentally friendly bentonite has a good adsorption effect on heavy metal ions and oil compounds in the waste drilling fluid, which effectively reduces the biological toxicity of the waste fluid and realizes the harmless treatment of the waste drilling fluid in a real sense. 82

5 RESEARCH ON IMPROVED BENTONITE WATERPROOF BLANKET TECHNOLOGY By using the modified bentonite developed by Dr. Dong, the author’s team successfully developed the adaptive bentonite waterproof blanket after many tests. First of all, the raw material of bentonite waterproof blanket was selected, the double-layer flat woven cloth with more uniform warp and weft tension and higher cloth flatness instead of the traditional circular woven cloth was chosen for the collocation of geotextile, warp and weft tension was more uniform, cloth flatness was higher. The use of plain-woven fabric ensures the consistency of the working thickness of the waterproof blanket, reduces the permeability coefficient, and expands the applicable scenarios such as artificial lakes and building foundations. By optimizing the mass ratio of modifier and controlling the reaction temperature and time, the activation rate of bentonite is increased by 15%, which makes bentonite have stronger adsorption capacity and can effectively adsorb toxic and harmful liquids in the leachate in the environment, thus solving the problem of environmental pollution. Through targeted modification technology, the molecular structure can be directionally changed to realize the arrangement and combination of molecules as required, intelligent response to water pressure, and a controllable structure, which contribute to adaptive groundwater water pressure size and volume expansion up to 30 times, reduce the permeability coefficient, effectively improve its anti-seepage ability, prolong the durability of the building body, and further eliminate the building body security hidden trouble.

Figure 1. Targeted modification technique.

After so many experiments, the author’s research team found that the waterproof blanket made of modified bentonite has advantages in various performance parameters compared with the wellknown bentonite waterproof blanket commonly used in the market, as shown in the following table. Table 1. Comparison of performance parameters between modified bentonite waterproof blankets and traditional bentonite waterproof blankets. The performance parameters

Product

The permeability Application coefficient environment

Well-known brand products A

≤5.0 ∗ 1011

Well-known brand products B Well-known brand products C

Our products

Durability

The average selling price

Features

Apply only in the base environment

50 years

$1.2/m2

Expansibility, cannot adapt to water pressure

≤5.6 ∗ 1011

Apply only in the base environment

50 years

$1.0/m2

Expansibility, pulping, adsorbability

≤4.6 ∗ 1011

Apply only in the base environment

50 years

$1.7/m2

High tensile strength and puncture resistance

≤ 3.7 ∗ 1011

It is widely used in various environments. It is widely used in extreme environments (high water pressure, high humidity).

$1.4/m2

Expansibility, self-response to groundwater pressure changes, recyclable

83

65 years

6 CONCLUSIONS Bentonite resources are abundant in China. The development of new materials for wastewater treatment by bentonite is undoubtedly a feasible way to solve the problem of wastewater treatment containing heavy metals in China. After the bentonite waterproof blanket was introduced into China, it was gradually applied to underground seepage prevention of various projects or landfill in China. However, China is a big manufacturer of metal products, and a huge amount of wastewater with a high concentration of heavy metal ions will be produced in the process of metal manufacturing. The traditional bentonite waterproof blanket has poor impermeability in the wastewater and is easy to fail for a long time. To explore a new type of bentonite waterproof blankets and extend their application to seepage control in wastewater containing heavy metal ions, this research attempts to expand its application environment of liquid leakage caused by environmental pollution and solve the water seepage problems of underground building structures. At present, bentonite waterproof blankets have been widely used in both subway and water conservancy projects in China. It is believed that the application of bentonite waterproof blankets in China will continue to increase. However, there are no reports on various problems after the application of bentonite waterproof blankets in China. This does not mean that there are no problems. China has formulated strict industrial testing standards for the application of bentonite waterproof blankets as soon as possible. Although bentonite waterproof blankets are widely used in various projects, the environment has a great influence on the hydraulic conductivity and durability of bentonite waterproof blankets. There are many studies on the influence of a simple environment, but the influence of complex conditions in China needs to be further studied. Different regions have different requirements for bentonite waterproof blankets due to environmental differences, such as the thickness of bentonite waterproof blankets, bentonite performance, and the selection of geotextiles. China should strengthen the manufacturing process of bentonite waterproof blankets according to the needs of different regions and local production conditions of bentonite waterproof blankets. On the whole, the application cases for bentonite waterproof blankets in China are significantly more than those in foreign countries, and the application scope is also expanding. At present, foreign countries mainly focus on the change of permeability coefficient of bentonite waterproof blankets in the complex solution, the change in bentonite properties, and the reasons why the construction process is easy to induce the failure of bentonite waterproof blankets. China needs to strengthen this part of the work and pay attention to the practical effect of various engineering applications.

ACKNOWLEDGMENTS Thanks to Dr. Wenxin Dong’s team for sharing their research results with the author’s team and providing a lot of technical support in developing the adaptive bentonite waterproof blanket.

REFERENCES Building Industry Standard of the People’s Republic of China (JG/T193-2006), Sodium Bentonite Waterproof Blanket [S]. Cho Y.M. (2010). Investigation of geotechnical and hydraulic aspects of landfill design and operation. Dissertations & Theses Gradworks. Dong Shujuan, SUN Ying, Sun Pengfei (2015). Guangdong chemical industry, 42(12):113–114+130. Dong W.X., Pu X.L., Zhai Y.F. et al. (2020). Treatment of waste drilling fluid with high heavy metal content by β -cyclodextrin/bentonite. Industrial Water Treatment. Jafari N.H., Stark T.D., Rowe R.K. (2014). The service life of HDPE geomembranes subjected to elevated temperatures. J. Journal of Hazardous, Toxic, and Radioactive Waste, 18(1): 16–26. Jiang G.L., Zhang P.P., Jin W.Q., et al. (2005). Processing and application of bentonite. M. Chemical Industry Press.

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Ju J.Y. (2013), Characteristics and quality control of bentonite waterproof blanket. China Non-metallic Mineral Industry Guide, (1):15–18 (in Chinese). Katsumi T., IshiMori H., Onikata M., et al. (2008). Long-term barrier performance of modified bentonite materials against sodium and calcium permeant solutions. Geotextiles and Geomembran, 26(1):14–30. Li J.J. (2014), Waterproof characteristics and construction method of bentonite waterproof blanket. Chemical Industry Management, 2014(9):130. Li J.L. (2016). Metro GCL Construction Technology. C. High-speed Railway and Rail Transit Core New Edition, October, [C]:2016:4. Li Z.B. (2007). Study on anti-seepage effectiveness of geotextile bentonite pad and related mechanism analysis. D. Tongji University. Liu F., Deng N.J. (2013). Development and application of New GCL. Guide of China Non-Metallic Minerals Industry, (04):9–11. Liu Y., Bouazza A., Gates W.P., et al. (2015). Hydraulic performance of geosynthetic clay liners to sulfuric acid solutions. Geotextiles and Geomembranes, 43(1):14–23. Luan Z.H., Wang S.G. (2003). Practical technology for sanitary landfill of refuse. M. Beijing: Chemical Industry Press. Ozhan H.O. (2018). The hydraulic capability of polymer-treated GCLs in saline solutions at elevated temperatures. Applied Clay Science, 161:364–373. Qian X.D., Shi J.Y., Liu X.D. (2010). Design and Construction of Modern Sanitary Landfill (2nd edition). M. Beijing: China Architecture and Architecture Press. Shi Y.Z., Ma S.D. (2002). Journal of Huaqiao University (Natural Science Edition), (02):46–51 (in Chinese). Wang G., Liu Y.Q., Yang H., et al. (2019). Comparison of kneading methods and experimental study of bentonite for a waterproof blanket. Nonmetallic Ore, 5(42):73–75. Wang Y. (2009). Anti-seepage performance of GCL and its application in the landfill. Environmental Engineering, (6):98–101. Yang H.R., Zhang P. (2013). Study on construction measures of new waterproof materials for underground engineering. New Type Construction Materials, 40(01):66–68.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Analysis of traveling wave effect on the seismic response of the spatial cable surface suspension bridge Jiepeng Zhang & Kongliang Chen∗ School of Civil Engineering and Architecture, Wuyi University, Jiangmen, China

ABSTRACT: This study aims to explore the influence of the traveling wave effect on the dynamic characteristics of the spatial cable surface suspension bridge with a single main cable form. Under the background of Xia Sha pedestrian landscape flyover in Jiangmen City, finite element modeling of the spatial rope deck suspension bridge was performed using Midas Civil 2020 software. The effect of the traveling wave effect on the seismic response of the spatial rope deck suspension bridge was investigated through time course analysis. In order to make the results more generally applicable, seven groups of apparent wave velocities from 500 m/s to 6000 m/s were selected for comparative analysis with the calculated results of consistent excitation. The following conclusions were finally drawn: When the apparent wave speed is greater than a certain value, the calculation results of the shear force at the bottom of the tower and the displacement at the top of the tower both gradually converge to the uniform excitation with the traveling wave effect considered. The bending moment response values at the base of the tower and the spanwise displacement response values of the main beam when the traveling wave effect is considered are significantly different from the calculated results of the consistent excitation. It is necessary to consider traveling wave effects in the seismic design of the spatial cable surface suspension bridge.

1 INTRODUCTION Even if the bridge structure is located at a site with stable soil conditions, differences may result from the different arrival time of ground shaking along the longitudinal bridge direction. This causes a phase difference in the input seismic timescale at each support (i.e., traveling wave effect). Current domestic and foreign scholars have mainly focused on traditional suspension bridges to conduct a large number of studies on seismic response analysis. Lin J (2001) proposed that the traveling wave effect of seismic ground motion has considerable influence on the response of large-span structures; Yang W et al. (2020) stated that the seismic design of large-span suspension bridges should focus on the influence of traveling wave effect. However, there is less research on the seismic response of the spatial cable surface suspension bridge. Compared with traditional suspension bridges, the spatial cable surface suspension bridge has a novel structure and the boom is arranged in an inclined manner. And the spatial three-dimensional system is formed between the boom and the main cable and the main girder. This type of suspension bridge has a more complex force situation, which is manifested by the greater sensitivity to dynamic effects (Wu 2022). It is necessary to study the force conditions and seismic response characteristics of the spatial cable surface suspension bridge. With the pedestrian bridge in Xia Sha Park of Jiangmen as the research background, a finite element model of the bridge formation stage was built by the finite element software Midas Civil 2020. Time course analysis was used to analyze the influence of the traveling wave effect of ground vibration on the spatial cable surface suspension bridge. ∗ Corresponding Author:

86

[email protected]

DOI 10.1201/9781003384830-12

2 BASIC PRINCIPLES OF DYNAMIC RESPONSE ANALYSIS METHODS The traveling wave effect can be analyzed by the time domain and frequency domain methods. In this paper, the time domain method is used for the dynamic response analysis. The time difference can be used to present the propagation characteristics of ground shaking by the time domain method. It has the advantage that the calculation principle is simple and easy to use. The disadvantage is that the seismic response of the bridge structure is strongly related to the selected seismic waves. The seismic response analysis results will be different for different seismic waves. Generally, three groups (maximum values must be taken) or seven groups (average values can be taken) of seismic acceleration time intervals are selected for comparative analysis. The equation (Kiureghian 1992) of motion of the bridge structure under a uniformly excited earthquake can be written as: ˙ + Kx = −MX ˙g M¨x + cX

(1)

For bridge structures that require considering traveling wave effects, the equation of motion can be expressed in blocks by equation (1) as:   −1 ¨ ˙ (2) Ms y¨ s + Cs y¨ s + Ks ys = −Ms K−1 s Ksc Xc − Cs Ks Ksc − Csc Xc ˙ c = 0, then the If we assume that the relative velocity is proportional to the damping force, i.e., X above equation can be simplified as: ¨ ¨ Ms y¨ s + Cs y¨ s + Ks ys = −Ms K−1 s Ksc Xc = MsTsc Xc

(3)

¨ c for the seismic The seismic response can be calculated by entering different accelerations X response analysis considering the traveling wave effect. The schematic diagram of the traveling wave effect is shown in Figure 1. Sites A and B represent the support of the bridge structure to the ground. Site C represents the origin of seismic waves. There is a time difference T between the arrival of seismic waves from C to points A and B (Mu 2019), i.e.: T = L/v (4)

Figure 1.

Schematic diagram of traveling wave effect.

3 FINITE ELEMENT MODELING AND SEISMIC WAVE SELECTION 3.1 Project summary Jiangmen Xia Sha pedestrian landscape bridge is a spatial cable surface suspension bridge with a single main cable form and a single-span ground anchored suspension bridge with the arrangement of 24.85 m+92 m+24.85 m=141.7 m. A steel box girder with a bridge width of 4 m is used. The main bridge adopts a single-span suspension bridge system with double main cables and double booms. The main cable adopts two 7-241 finished cables, which are turned 12.14◦ on the plane through the cable saddle at the main tower and finally anchored on the anchor, and the back cable 87

is symmetrically arranged to balance the cable force from east to west. The spacing of booms is 5 m, and the lower end is anchored on the crossbeam. The whole bridge superstructure is made of steel, and the pedestrian landscape flyover in Xia Sha, Jiangmen City is shown in Figure 2.

Figure 2.

Xiasha pedestrian landscape footbridge.

3.2 Finite element model of spatial rope deck suspension bridge In this paper, we use Midas Civil 2020 to model the pedestrian landscape bridge in Xiasha, Jiangmen City. The main span and side span of this bridge model are simulated using girder units, and the material is Q355. The main span of the bridge is a split steel box girder with a single box and single chamber section. The side span is a monolithic steel box girder with a single box and double chamber sections. The material of the main tower is Q355. Simulation is done using beam cells. The tower and the main tower saddle cover adopt a box-shaped variable section. In this suspension bridge, the structural form of a single main cable with two cable faces is used. Its main cable and boom are simulated by the cable unit. 17 pairs of booms are used for the whole bridge. The main cable and boom material are used is 1860 steel strand for simulation. The boom consists of 34 units. The main cable consists of 18 units. The overall model of the bridge is shown in Figure 3.

Figure 3.

Finite element model of spatial rope deck suspension bridge.

3.3 Selection of seismic waves Due to the lack of earthquake records in Jiangmen City, Jianghai District, three different typical seismic waves conforming to the Jianghai District of Jiangmen City are used. The basic data 88

situation is shown in Table 1. Based on relevant information and zoning maps, it is known that the seismic intensity of Jiangmen Jianghai District is 7, the site category belongs to Class II, the design basic earthquake peak acceleration value is 0.10 g (1g=9.8 m/s2 ), and the design earthquake grouping is the first group with Tg=0.35 s. With Taft Lincoln School as an example, the amplitude adjustment factor under E1 seismic action is calculated as follows: PGA = 0.9 8m/s2 ,

0.98 µ = (−0.16)×9.8 = −0.63.

µ=

PGA = ACs Cd Ci

(5)

PGA Amax

(6)

PGA—Design acceleration peak; Amax —Peak acceleration of the original seismic wave; µ—Magnitude adjustment factor; Table 1. Basic data of seismic waves. No.

Wave name

Duration t (s)

Tg (s)

A (g)

µ

1 2 3

Taft Lincoln School San Fernando T2-III-2

54.38 61.84 50.00

0.53 0.27 1.422

−0.16 0.32 −0.69

−0.63 0.31 −0.14

Figure 4.

Seismic wave time course curves.

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4 ANALYSIS OF LONGITUDINAL SEISMIC TRAVELING WAVE EFFECTS The following assumptions are made in the calculation. The source of the earthquake is located at the left anchorage point on the south shore. The clamping angle is 0◦ . Seismic waves propagate from the south coast to the north coast along the longitudinal bridge direction. The effect of time difference is considered in the seismic wave input and the calculation of time difference is based on the apparent wave speed of the seismic wave. In order to analyze the influence of seismic traveling wave effects universally applicable, seven seismic apparent wave velocities of 500 m/s, 1000 m/s, 2000 m/s, 3000 m/s, 4000 m/s, 5000 m/s, and 6000 m/s were selected in turn for comparison and analysis with the calculated results of consistent excitation. The three seismic waves are calculated and analyzed using the nonlinear time course method as seen in Table 1. The base of the bridge tower is used as the control position for seismic force analysis. The main beam span and the top of the tower displacement are used as the control positions for structural displacement analysis. The influence of the traveling wave effect on the seismic response of the above control locations is examined by comparing the variation pattern of seismic response considering the traveling wave effect and consistent input structure.

4.1 Analysis of internal force Figures 5 and 6 show the relationship between the effects of different apparent wave speeds on the internal forces at the bottom of the tower on the south bank side. The following conclusions were drawn: (1) When the apparent wave speed is 500 m/s–2000 m/s. The shear ratio at the tower bottom increases with the increase of apparent wave speed. When the apparent wave speed is 2000 m/s, the shear ratio at the tower bottom reaches the maximum value. When the apparent wave speed is greater than 2000 m/s, the shear ratio at the tower bottom tends to decrease firstly and then increase. When the apparent wave speed exceeds 4000 m/s, the shear ratio at the tower bottom converges gradually under the traveling wave effect to a uniform excitation. (2) When the apparent wave speed is 500 m/s, the bending moment ratio at the tower bottom reaches the maximum value. When the apparent wave speed is 500 m/s–1000 m/s, the bending moment ratio at the tower bottom tends to decrease. When the apparent wave speed is between 1000 m/s and 2000 m/s, the bending moment at the bottom of the main tower tends to increase. When the apparent wave speed is greater than 2000 m/s, with the increase of apparent wave velocity, the bending moment ratio at the tower bottom shows a decreasing trend again.

Figure 5. bottom.

Relationship between the effects of different apparent wave speeds on the shear force at the tower

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Figure 6. Relationship between the effects of different apparent wave speeds on the bending moment at the tower bottom.

4.2 Analysis of displacement Figures 7 and 8 show the relationship between the effects of different apparent wave speeds on the tower top and the span displacement of the main beam on the south bank side. The following conclusions were drawn:

Figure 7. top.

Relationship between the effects of different apparent wave speeds on the displacement at the tower

Figure 8. Relationship between the effects of mid-span displacement of the main beam at different apparent wave speeds.

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(1) The maximum displacement of the tower top is 0. 024 m under consistent excitation. When the apparent wave speed is 500 m/s, the seismic response of the displacement at the tower top varies a lot under consistent excitation and traveling wave effects. When the apparent wave speed is 2000 m/s, the calculation results considering the traveling wave effect start to converge to the consistent input calculation results. (2) The maximum displacement in the mid-span of the main beam is 0. 072 m under consistent excitation with the traveling wave effect considered. The longitudinal displacement response at the mid-span section of the main beam decreases as the apparent wave velocity of the seismic wave increases. When the apparent wave speed is 2000 m/s, the longitudinal displacement in the span considering the traveling wave effect is 0.071 mm, which is approximately equal to the longitudinal displacement in the span of the main beam under uniform excitation.

5 CONCLUSIONS This paper analyzes the seismic response of a spatial cable deck suspension bridge considering the traveling wave effect, which is related to the seismic wave propagation velocity. (1) The influence of the traveling wave effect on the shear response at the tower bottom of a suspension bridge with a small apparent wave speed is considered. However, if the apparent wave speed is large, the influence of the traveling wave effect can be disregarded. (2) When the traveling wave effect is considered, the bending moment at the tower bottom is larger than that of consistent excitation at the apparent wave speed of 500 m/s. It indicates that a low apparent wave velocity has a greater effect on the seismic response of the structure. The effect of the traveling wave effect on the bending moment at the tower bottom is considered to be smaller at the higher apparent wave speed, which is beneficial to the structure. (3) The seismic wave action mode of the traveling wave effect influences the displacement at the tower top. The displacement response value at the top of the main beam tower considering the traveling wave effect is larger than that under the inconsistent excitation when the apparent wave speed is 500 m/s. This result may be caused by the time difference of excitation at each support point when the apparent wave speed is slow. As the apparent wave velocity increases, the results considering traveling wave effects converge gradually with the consistent excitation results. (4) The seismic wave action mode of the traveling wave effect has a significant effect on the longitudinal displacement in the span of the main beam. The longitudinal displacement value in the span of the main beam decreases with the increase of apparent wave velocity under longitudinal seismic action, which is beneficial to the structure.

REFERENCES Kiureghian A.D. (1992). Response Spectrum Method for Multi-Support Seismic Excitations [J]. 21(8):713–740. Lin J.H. (2001). Seismic analysis methods for large-span structures and recent progress [J]. Advances in Mechanics, (03):350–360. Mu Z.Q. (2019). Research on seismic performance of single cable deck suspension bridges [D]. Chongqing Jiaotong University. Wu Z.M. (2022). Seismic response analysis of spatial rope deck suspension bridges [D]. Wuyi University. Wilson E.L. (1996). Three-Dimensional Static and Dynamic Analysis of Structures [J]. Berkley Computers & Structures Inc. Yang W, Hao X.W, Zhang X.M. (2020). Analysis of the influence of traveling wave effect on the seismic response of large-span suspension bridges [J]. Engineering Seismic and Reinforcement Modification, 42(02):100– 106.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on the application of enabling technology for river basin hydro-junctions operation safety monitoring system Zuqiang Liu∗ Changjiang Spatial Information Technology Engineering Co., Ltd, Hubei Water Conservancy Information Perception and Big Data Engineering Technology Research Center, Wuhan, Hubei, China

Shuangping Li∗ Changjiang Spatial Information Technology Engineering Co., Ltd, Hubei Water Conservancy Information Perception and Big Data Engineering Technology Research Center, School of Geodesy and Geomatics Wuhan University, Wuhan, Hubei, China

Min Zheng∗ , Yiming Chen∗ , Huawei Wang∗ & Yonghua Li∗ Changjiang Spatial Information Technology Engineering Co., Ltd, Hubei Water Conservancy Information Perception and Big Data Engineering Technology Research Center, Wuhan, Hubei, China

ABSTRACT: To meet the informatization and intelligence needs of river basin hydro-junctions operation safety management, we study the application of innovative technologies such as Internet of Things, artificial intelligence, big data, and digital twin as enabling technologies for the construction of the operation safety monitoring system from the dimensions of intelligent sensing, data transmission, computational analysis, and interactive services. These applications greatly enhance the intelligence level of the monitoring system, thus laying the foundation for achieving the goal of informatization and intelligence of hydro-junctions operation safety management.

1 INTRODUCTION The smart river basin refers to the comprehensive application of new information technologies in river basin management. The smart dam is one of the most important elements of a smart river basin, which contains comprehensive sensing, real-time transmission, and intelligent processing. Through the deep integration of the physical space and virtual space of human society and hydraulic buildings related to the dam, a dynamic and refined intelligent dam operation management system can be established (Zhong et al. 2015). The smart dam is constructed throughout the three project stages: decision-making, design and construction, and operation and maintenance. The River Basin Hydro-junctions (RBH) operation safety management requires unified management, analysis, and processing of safety-monitoring data, which makes the management and reporting of RBH safety information more standardized and institutionalized. It also has the rolling warning features of “upstream water forecast analysis-reservoir and dam safety assessmentdownstream flood risk warning” (Li et al. 2018). The traditional safety monitoring system can no longer meet the needs of the RBH smart dam construction, and the informatization and intelligence of the RBH safety management have become a new demand (Feng & Li 2016; Nie & Zhang 2016). From the dimensions of intelligent perception, intelligent management, and intelligent services, we can explore the integrated application of innovative technologies such as the Internet of Things ∗ Corresponding Authors: [email protected]; [email protected]; [email protected]; [email protected]; [email protected] and [email protected]

DOI 10.1201/9781003384830-13

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(IoT), Artificial Intelligence (AI), big data, and digital twin as enabling technologies for new generation monitoring systems. The essence of the smart RBH operation safety monitoring system includes: (1) the application of intelligent sensors and instruments to make monitoring technology intelligent; (2) the use of modern information technologies to build a cloud platform that makes the monitoring intelligent; (3) reliance on the monitoring cloud platform to realize intelligent services for the management of monitoring projects and the total life cycle management of dams, etc. This paper comprehensively explores the applications of enabling technologies for building a smart RBH safety monitoring system, which lays the foundation for the application of modern information technologies in monitoring systems.

2 MONITORING SYSTEM AND ITS ENABLING TECHNICAL ARCHITECTURE 2.1 Monitoring system architecture The RBH safety monitoring system is a comprehensive management cloud platform that integrates data collection, data transmission, evaluation, safety warning, and emergency planning. In order to achieve the purpose of centralized management of RBH operation safety, the designed physical architecture of monitoring systems that we have studied and applied in actual projects is shown in Figure 1.

Figure 1.

Physical architecture of the rbh safety monitoring system.

(1) RBH dams: The monitoring objects include hydraulic buildings, geological hazards on the reservoir slopes and earthquakes. (2) Intelligent sensing layer: The site sensing layer is at the bottom of the system and contains intelligent Measurement and Control Units (iMCU) layer and intelligent Sensor (iSs) layer. (3) Information management layer: It is the basic layer for monitoring data management, and is deployed in each reservoir/dam monitoring center. It collects the original monitoring data from the site sensing layer and supports remote data transmission with the integrated service layer. 94

(4) Integrated service layer: The integrated service layer is the RBH monitoring center and data center, which forms information platforms with relevant authorities. Its main task is to conduct a comprehensive evaluation of the RBH operation safety, analyze early warning and abnormal causes, and provide supplementary decision support. 2.2 Monitoring system enabling technology architecture The new information infrastructures and innovative technologies, such as smart sensors, Georobot, IoT, AI, big data, blockchain, GIS+BIM, cloud + edge computing, digital twin, etc., constitute the enabling technologies for the RBH safety monitoring system. We classify these enabling technologies into four major types based on their characteristics. (1) Intelligent perception technologies: Applications of Georobots, iSs, and iMCU lay the foundation for the realization of global intelligence and accurate information sensing. (2) Data transmission technologies: Through LoT and other technologies, the monitoring system can transmit real-time data in both directions, and realize data collection and transmission of monitoring objects as well as feedback for decision making. (3) Computational analysis technologies: The core of the monitoring system relies on accurate modeling and dynamic decision-making based on monitoring data. AI, big data, blockchain, GIS+BIM, digital twin, and cloud + edge computing enable the operationalization of monitoring data and the informatization of monitoring projects. (4) Interactive service technologies: Such technologies can standardize and design the interfaces of monitoring system interactions to meet the needs of intelligent services.

Figure 2.

Monitoring system enabling technology architecture.

In this paper, we mainly study the enabling technologies and their application scenarios, such as Georobot, IoT, AI, big data, blockchain, GIS+BIM, cloud + edge computing, digital twin, and extended reality.

3 ENABLING TECHNOLOGIES AND THEIR APPLICATIONS 3.1 Intelligent perception technologies of Georobot The Georobot is a highly intelligent electronic total station that can automatically search, track, identify and aim at the target with high accuracy (Liu et al. 2011). It can acquire data such as angle, distance, 3D coordinates, and memory images of the target. We have studied the combination of Georobot and automatic monitoring software to realize the automation of measurement data acquisition and processing, which means unattended automatic observation. At present, the polar coordinate method composed of a single Georobot using multiple realtime differencing techniques has been well applied in our dam deformation monitoring and other projects. Due to the limitation of visibility conditions and maximum target recognition distance, 95

the single Georobot can only be used in the deformation monitoring of deformed bodies with good visibility conditions and small deformation areas. We have also studied a multi-Georobot monitoring system. The designed flow of multiple Georobots carrying out real-time grouping and leveling observation networks is shown in Figure 3. The technical difficulties solved include: (1) Multiple Georobots are controlled remotely and intelligently so that each Georobot works with each other and operates in a coordinated network. (2) Unattended automatic measurement and the function of intelligent judgment and processing of target occlusion are realized. (3) The real-time network solution (including a real-time meteorological correction model) for positions of multiple Georobots sites and monitoring points is given to obtain high-precision real-time motion traces of monitoring points.

Figure 3.

Multi-georobot real-time observation network.

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3.2 Data transmission technologies IoT is the basis for front-end connection and data acquisition for monitoring systems, and is a key enabling technology. Based on IoT, it can help to realize the online operation of physical equipment, support the real-time collection and monitoring of physical equipment data, and support the closed-loop control of the virtual world to the physical world in the future digital twin monitoring system. The IoT collects real-time information such as sound, light, heat, electricity, mechanics, chemistry, biology, and location of any object or process that needs to be monitored, connected, and interacted with, through various devices and technologies such as information sensors, radio frequency identification technology, global positioning systems, infrared sensors, and laser scanners. Through various types of possible network access, realize the ubiquitous connection between things and things, things, and people, and realize the intelligent perception, identification, and management of objects and processes (Huang et al. 2020). The traditional dam safety monitoring automation system model is highly compatible with the IoT. In our implemented monitoring automation systems, geodetic instruments buried on the surface of the dam, various types of physical sensors buried inside the dam, and the wired cable, optical fiber, and multiple communication technologies form the dam monitoring system IoT in some ways (Figure 4). In the safety monitoring automation system, the IoT presents a specific model of remote automation. The development of IoT technology has also promoted the progress of the safety monitoring automation system and greatly facilitated the implementation of the full-area intelligent perception technology in the monitoring system.

Figure 4.

IoT data transmission structure of monitoring system.

3.3 Computational analysis technologies 3.3.1 Artificial intelligence According to the dam monitoring data series, models built by applying mathematical methods can effectively reflect the relationship between the dam effect set and the external load set, which is used to simulate and predict the operational state of the dam and to comprehensively evaluate the health of the dam. This method is the most common means to ensure that the dam will operate safely and efficiently. When the relationship between effect variables and independent variables is complex, traditional analytical models are less effective in prediction. Intelligent algorithmic models are developing rapidly with advantageous features such as visualization, networking, and 97

ease of implementation. The neural network model has good learning ability and good properties in self-adaptation and fault tolerance, especially the ability to fit nonlinearities well. The nonlinear transformation of the Support Vector Machine (SVM) model’s inner product function architecture transforms the input space into a high-dimensional space and looks for nonlinear relationships between input and output variables in this high-dimensional space. The dam deformation is affected by temperature, the time factor, and water level, and its deformation value shows a non-linear characteristic. The SVM algorithm is very suitable for the nonlinear prediction of dam deformation. In order to improve the prediction quality by using the characteristic information of different dam deformation prediction methods, an intelligent combination model of dam deformation can be used (Liu 1996; Zhang & Zhang 2021). Based on long-term monitoring data, we conducted a horizontal displacement property analysis of the dam using an intelligent algorithm model (Figure 5).

Figure 5.

Displacement component of the dam calculated by the intelligent algorithm model.

As shown in Figure 5, the intelligent algorithm model objectively analyzes the horizontal displacement of the dam. Horizontal displacement is influenced by multiple causes such as water level, temperature, and aging. The water level component and temperature component have obvious periodic characteristics, while the time effect component tends to be stable. This indicates that the horizontal displacement of the dam is normal. In establishing intelligent algorithm models, AI is very important in model setting and strategy optimization. The establishment of intelligent models for dam monitoring based on artificial intelligence technology is an important development direction. Dam safety monitoring data analysis has gone through three important stages: qualitative analysis represented by expert knowledge and experience, quantitative model analysis represented by statistical models, and machine learning model analysis represented by neural network models and other models. In the future, it is very important to study the hybrid intelligent model analysis method with expert knowledge and experience + various mathematical models + machine learning for the intelligent analysis of dam operation safety. 3.3.2 Big Data Due to the development and application of intelligent monitoring systems for RBH operation safety, the real-time collection of massive multi-source perception information has become a reality. In order to analyze and process the large amount of data generated by the safety monitoring system, large hydropower enterprise group companies have started to build big data centers to centralize the management of the monitoring system of the basin/regional dam group, laying a good foundation for the analysis of the operation safety condition of the dam group, and providing decision support for persons and departments at all levels that are responsible for dam safety. From the characteristics of big data, the amount of monitoring data is still small. However, it is possible to explore the composition and application of monitoring big data from the viewpoint of “big data is all data” (Viktor et al. 2013). RBH dam group monitoring big data can be divided into four dimensions, including survey design construction monitoring data, operation, and maintenance stage monitoring system real-time data, basin reservoir dam operation, and maintenance 98

management data, and social resources data (Li et al. 2019). Using the core correlation analysis method of big data analysis, we can discover patterns, dig knowledge and obtain valuable information from monitoring data, and can better manage and administer these monitoring data. This is important for analyzing the safety state of dams, exploring the effect of various influencing factors on the safety of dams and the rules, evaluating and predicting the safety state of dams, and promoting the safe operation and maintenance of RBH (Figure 6).

Figure 6.

Correlation analysis chart.

In addition, big data processing, storage and analysis technologies can effectively support the operation of the RBH monitoring system. Based on big data, the data generated in real production can be collected, organized, analyzed, and processed to form structured data nutrients that can be supplied to the monitoring system model. Big data can also support intelligent decision-making of the monitoring system model and fully exploit the operational value of the monitoring system. 3.3.3 Digital twin Since its introduction in 2003, the digital twin has begun to explode in various industry sectors in recent years after nearly 20-year development. Similar to the IoT, the digital twin will further drive safety monitoring from intelligence to a higher level of monitoring brain. Li et al (2021) summarized several application scenarios of the digital twin technology in monitoring systems, such as the visual representation of monitoring objects based on realistic 3D models. Digital twin technology builds multiple intelligent models by taking various impact factors affecting the dam as inputs to the physical entity, and deformation and seepage of the physical entity of the dam as outputs. These models are used to characterize the operational mechanisms of the physical entities of the dam and predict the deformation dynamics of the physical entities of the dam, and then compare them with the actual observations of the physical entities of the dam to evaluate the operational status of the physical entities. To study the physical characteristics of dam deformation, we conducted a rapid structural calculation of a dam based on BIM and finite elements (Figure 7). It can be directly switched from the BIM model browsing module to the finite element calculation module to realize online analysis and evaluation of the operation status of the physical dam-foundation system when the external loading conditions of the model change. In our study, deterministic models based on ANSYS structural calculations, hybrid models based on multiple linear regression and ANSYS structural calculations, and visualized finite element simulation software combined with computer simulation techniques are used to realize dam displacement simulation under unfavorable operating conditions such as high temperature and high water level, low temperature and high water temperature, high temperature, and low water 99

Figure 7.

Physical model of the dam.

level. Our method can also be used to simulate unprecedented load conditions, such as overload conditions of the dam operation working can be understood through simulation analysis. 3.3.4 Other enabling technologies (1) Blockchain RBH monitoring systems have features that rely on numerous instruments to monitor object entities, multi-organized data, connected collaborative asymmetric encryption, consensus mechanisms, and smart contracts. Blockchain technology can provide open, transparent, and tamper-evident data for monitoring systems. First, it supports online highly-reliable and trustworthy data, asset sharing, and data visualization and traceability. Second, blockchain cryptographic authentication methods support the security of distributed online data and models and guarantee the robustness of online monitoring systems. Third, it supports the unified consensus of multiple organizations that need to collaborate in the monitoring system by using the distributed consensus mechanism of blockchain. We believe that the blockchain decentralized architecture can be used to continuously record the monitoring data uploaded by monitoring sensors to ensure the security, authenticity, and integrity of the data. A federated blockchain is used to register all data collection units and the central server as authorized nodes. After the monitoring sensors collect data, they transmit the data to the data collection units through the network. After the data collection unit receives the data, it adds a digital signature to the data and then broadcasts it across the network. After other nodes receive the broadcasted data, the consensus algorithm verifies and processes the data before adding it to the blockchain. The federated blockchain structure can be used to store monitoring data, which has features such as preventing single node failure, tamper-proof, and data privacy protection. (2) Cloud Computing The RBH monitoring system involves the storage and computation of large amounts of data (both historical and real-time), which requires a lot of storage and computing power. The development of cloud computing and the decrease in cost are the basis for its application and development in monitoring systems. Based on cloud computing technology, the “monitoring big data resources” can be converted into “monitoring big data assets”, enabling security monitoring to move from business-driven to data-driven. Through the huge computing power and storage resources of cloud computing, it can reveal the correlation relationship that is difficult to show by traditional technologies, and establish a new management mechanism of “talking with data, making decisions with data, managing with data, and innovating with data”. Cloud computing technology can centralize the storage and management of business systems scattered across the country via the Internet. It can provide data sharing services to safety monitoring management and analysts for dam property analysis. Managers can check 100

the real-time operation status of the dam at any time and any place, and get the dam safety monitoring report and safety assessment service, which greatly improves the management efficiency. Based on cloud computing and big data technologies, the monitoring system cloud platform built using SaaS (Software as a Service) model covers data collection, management, compilation, analysis, reporting, inspection, project management, and other functions, providing users with a full life cycle and comprehensive safety monitoring services. (3) Edge Computing In the RBH monitoring system, there are video surveillance data, UAV (unmanned aerial vehicle) remote sensing data, and other data that take up a lot of storage space. Transferring them to cloud storage will take up a lot of network bandwidth and cloud storage resources. Therefore, such data must be stored and processed locally. Uploading processed monitoring results to the cloud can greatly reduce network overhead and storage costs. Using edge computing technology, Liu et al. (2011) built an intelligent real-time monitoring module for water engineering surface diseases in the monitoring system. They stored the videos of dams taken by UAV, fixed surveillance cameras locally, and used dynamic image recognition technology to intelligently identify surface collapse pits, cracks, water seepage, weathering, and corrosion, and uploaded the recognition results to the cloud. In one of our projects, the monitoring data collection, collation, and preliminary analysis of the RBH are done in the in situ dam monitoring center, while the main information received by the RBH monitoring center and data center is the analyzed monitoring data and preliminary analysis results. We think that this pattern can be understood as a typical edge computing model. (4) GIS+BIM A three-dimensional Geographic Information System (GIS) can provide more information on topography, dams, and ancillary facilities by integrating multiple sources of data such as tilt photography data, vector data, and BIM data (Wen, 2021). Combining geography, cartography, remote sensing, and computer science, GIS enables the analysis and processing of spatial information and its visual display. BIM takes various information data related to the project as the basis. Using digital and information technology as the model, Zhou et al. (2018) provided an information base consistent with the actual structure by constructing a virtual 3D model of the construction project. In recent years, as a carrier of intelligent engineering, GIS+BIM has been gradually applied to the design, construction, operation, and maintenance of the hydropower engineering industry. In terms of visual expression of deformation analysis of monitoring objects, the monitoring sensor is integrated into the BIM model as a kind of component bearing information of monitoring results, and then the engineering deformation information is visually expressed through the BIM model. According to the logical connection between adjacent monitoring sensor components in the BIM model, when the geometry or spatial position of one monitoring sensor component changes, the other components can change simultaneously. That is, when the dam deformation monitoring data changes, the intelligent system, and the model components occur in a real-time linkage effect. 3.4 Interactive service technologies of extended reality Extended reality technologies include Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), holography, and other technologies. Among them, AR can superimpose virtual images onto real scenes to enhance reality perception. VR provides an immersive experience of the virtual world. MR can superimpose virtual images onto digitized real images to support a more immersive virtual-reality superimposed effect. Holography can construct a three-dimensional image that blends into the environment through light reconstruction technology. Extended reality technology can provide effective support for monitoring system display. Through the three-dimensional immersion picture, accurate visual decision support is provided. 101

4 CONCLUSIONS The operation safety of RBHs is a worldwide problem. RBH management agencies hope to achieve the following goals by constructing an RBH safety monitoring system: (1) Autonomous safety monitoring, taking corrective action on necessary and simple problems; (2) Autonomous anomaly analysis, searching for hidden safety points and causes based on numerous alarms; (3) Autonomous forecasting, predicting changes and situations based on historical operation data; (4) Intelligent decision-making response, pushing correct response measures based on technical standards, management methods, user preferences, etc. This paper investigates how innovative technologies such as modern smart sensors, Georobot, IoT, AI, big data, blockchain, GIS+BIM, cloud + edge computing, and digital twin can be applied to the RBH operation safety monitoring system as enabling technologies, contributing to the realization of intelligent management of RBH operation safety.

REFERENCES Chen, L. Xinghong, J. & Gang, D. (2011). The technical characteristics of the Internet of Things and its wide application[J]. Science Consulting. 9, 86–86. Feng, T. & Li, X.W. (2016). Characteristics of informatization for dam safety of cascade hydropower plants. Dam & Safety. (1), 6. Huang Z. Liao M.X. Zhang H.Q. Zhang G.B. & Ma S.K. (2020). Prediction of tunnel surrounding rock extrusion deformation based on SVM-BP model with incomplete data. Modern Tunnel Technology. 57(S1), 141–150. Jin, L.L. Ren, X.C. Liu, C.L. & Liu, W.B. (2021). Technology and application of automatic monitoring system by robotic total station based on edge computing. Standardization of Surveying and Mapping. 37(1), 60–65. Li, L. Li, R.H. Liang, X.W. et al. (2018). Research on the development and application of dam safety management information system of reservoirs in Guangxi. Guangxi Zhuang Autonomous Region, Guangxi Zhuang Autonomous Region Institute of Water Resources Science, December 26, 2018. Li, S.P. Liu, Z.Q. Zheng, M. & Li, Y.H. (2021). Research on intelligent monitoring systems of hydraulic engineering based on digital twin. 2021 7th International Conference on Hydraulic and Civil Engineering & Smart Water Conservancy and Intelligent Disaster Reduction Forum (ICHCE & SWIDR). December 29, 2021. Li, S.P. Liu, Z.Q. Zheng, M. & Wang, H. W. (2019). Exploration on Big Data Architecture and its Correlation Analysis for Safety Monitoring in Operation of Basin’s Hydro-junctions. IOP Conference Series: Earth and Environmental Science (EES). Liu, Z.Q. (1996). Compose model analysis and forecasting of engineering deformation tendency. Hydropower and Pumped Storage. 20(3), 11–14. Nie, Q. & Zhang, X.S. (2016). Dam safety management innovation of Yalong River basin with information construction. Dam & Safety. (1). 1. Tian, M.H. & Zheng, H.B. The application of blockchain in the construction of intelligent water resources. Smart City. 7(06), 117–118. Viktor, M.S. Kenneth, C. Sheng, Y.Y. & Zhou, T. (2013). The era of big data. Zhejiang People’s Publishing House. Hangzhou. Wen, F.Y. (2021). Research on visual display technology of dam safety monitoring information based on BIM + GIS. Hydroelectricity. 47(03), 94–97. Zhang, H.M. & Zhang, L.S. (2021). Deep learning method applied to image recognition technology of slope landslide. Technology and Innovation. 1, 1–2. Zhong, D.H. Wang, F. Wu, B.P. & Cui, B. (2015). From digital dam toward the smart dam. Journal of Hydroelectric Engineering. 34(10), 1–13. Zhou, G.L. Hu, W. Xiong, J. (2018) Research on the architecture for the management platform of urban underground utility tunnel operation and maintenance based on BIM and GIS. Intelligent Building and Smart City (01). 64–68+74.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Risk assessment method for subway-crossing shield tunnel based on ground loss ratio Zhuyin Wen∗ , Nian Liu∗ & Guangming You∗ Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., Shanghai, China

Jianfeng Hou∗ Shanghai Chengtou Highway Group Co., Ltd., Shanghai, China

Lei Jiang∗ Shanghai Tunnel Engineering Co., Ltd., Shanghai, China

ABSTRACT: With the accelerating urbanization and development of increasing underground space in China, shield tunnels have been widely applied to underground roads in central urban areas. However, there are many subways, bridge pile foundations, pipelines, and other buildings (structures) in the central urban areas with complex surroundings. Therefore, it will be an unavoidable engineering difficulty for the construction of shield tunnels in the central urban area to cross existing buildings (structures) at a close range, such as tunnels, underground pipelines, and basements. There are few studies on the shield tunnel with an outer diameter of 15 m and above crossing existing buildings (structures). The core concept of numerical simulation of a subwaycrossing shield tunnel is an idealized assumption of main factors and an omission of secondary factors. Consequently, the accuracy of the risk assessment method based on numerical simulation is over-dependent on the experience of engineers. In practical engineering applications, people often have great disputes about numerical simulation results. To solve the above problems, this paper uses the Midas_GTS finite element analysis software to study the risk assessment method for shield tunneling in Shanghai by taking the Shanghai Beiheng shield tunnel with an outer diameter of 15.0 m as an example. As the soil layers in Shanghai are evenly distributed with little difference, construction quality is the main control factor for the risk difference in the construction of the shield tunnel in Shanghai. In this context, this paper proposes to assess construction quality using the ground loss ratio index obtained through the back analysis of the measured data. Meanwhile, the simulation method adopted for back analysis and the ground loss ratio index are also used to assess the risks in shield tunneling. The settlement results of the Shanghai Beiheng shield tunnel under-passing the M11 shield tunnel predicted by the above risk assessment method are consistent with the actual results.

1 INTRODUCTION With the accelerating urbanization in China and the constant development of underground space, shield tunnels have been extensively applied to underground roads in central urban areas. However, the central areas feature complex surroundings, such as numerous subways, bridge pile foundations, basements, pipelines, and other structures and buildings. Therefore, it will be an unavoidable engineering difficulty for the construction of shield tunnels in the central urban area to cross ∗ Corresponding Authors: [email protected]; [email protected]; [email protected]; [email protected] and [email protected]

DOI 10.1201/9781003384830-14

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buildings (structures) such as existing tunnels, underground pipelines, underground passages, and basements at a close range. Increasing attention has been paid to research contents such as settlement rule, ground loss, crossing influence analysis, and deformation monitoring associated with shield tunnel construction. For example, Wang studied the settlement rule of the Shanghai subway articulated shield tunnel crossing the existing buildings such as the Nanbei overpassing pile foundation and school (Wang 2004). Shi et al. studied the settlement rule of Shanghai Dalian Road Yuejiang tunnel mud-water balance shield with an outside diameter of 11.22 m under-passing the pier pile foundation of the Huangpu River (with a vertical clearance distance of 0.46 m) (Shi 2004). Huang et al. studied the construction protection technology of the Shanghai Bund soil pressure balance shield with an outside diameter of 14.27 m laterally traversing the Bund historical buildings (Huang 2010). Ge et al. analyzed the settlement rule of shield crossing the protected buildings by Z-Soil software modeling (Ge 2011). Liu et al. studied the basic mechanical properties of glass fiber reinforcement and its application in shield crossing (Liu 2014). Kong et al. studied the construction technology of small-radius shield (minimum curve radius 350m) crossing buildings (Kong 2018). Guo studied the surface deformation rule caused by a large-diameter soil pressure balance shield based on measured data from Beijing Metro Line 14 (Guo 2013). Zhu analyzed the settlement rule of Tibet South RoadYuejiang tunnel crossing Line M8 at a close range and the causes of the subway outage based on measured data (Zhu 2009). Tang and Jiang respectively studied the settlement rule of the Beiheng mud-water balance shield with an outside diameter of 15.56 m underpass Line 7 and Line 11 of the existing metro tunnel (Jiang 2020; Tang 2018). There are remarkable research results for the crossing of subway shield tunnel with an outside diameter of 6.0 m and rich research results for the crossing of shield tunnel with an outside diameter of 10-14 m. In particular, the analysis of causes for the subway outage for Tibet South Road Yuejiang tunnel crossing Line M8 at a close range has great engineering values. However, there are few studies on the shield tunnel with an outer diameter of 15 m and above crossing existing buildings (structures). Relevant studies mainly focused on the summary of Beiheng tunnel crossing construction. Therefore, this paper uses the Midas_GTS finite element analysis software to study the risk assessment method for shield tunneling in Shanghai by taking the Shanghai Beiheng shield tunnel with an outer diameter of 15.0 m as an example. A method is proposed to assess the implementation risks using the ground loss ratio obtained through the back analysis of the measured data of similar projects.

2 PROJECT OVERVIEW 2.1 General The Shanghai Beiheng shield tunnel is China’s largest underground road project in the central urban area. It starts from Beihong Road in the west and ends at Neijiang Road in the east. This 19.1-km road runs through the central urban area of Shanghai (six districts of Putuo, Changning, Jing’an, Huangpu, Hongkou, and Yangpu). It includes serval laying forms such as underground tunnels, overpasses, and surface roads. The overall length is large, and the environment along the line is complex. The Beiheng shield tunnel has an outside diameter of 15.0 m, a lining thickness of 0.65 m, and a ring width of 2.0 m. It adopts a single-layer lining structure, as shown in Figure 1. The project uses the tunnel shield with an outside diameter of 15.56 m to start from the Zhongjiang Road shield work shaft eastward, pass through the Zhongshan Park shield work shaft with a small curve radius of R=500, move westward, and end at the Shaiwang Factory shield work shaft, with a total length of 6.498 km, as shown in Figures 3 and 4 (Liu 2021). The Beiheng shield tunnel continuously crosses over 200 buildings and underpasses the existing metro Lines 3, 7, and 11 (M3, M7, and M11 for short). The crossing section with M3 is built on a through-type arch suspension bridge. M7 and M11 involve double-tube shield tunnels with an outer diameter of 6.2 m. 104

Figure 1. Segments of Shanghai Beiheng shield tunnel.

Figure 2. BIM of Shanghai Beiheng Shield Tunnel Under-passing Metro Line 11 Tunnel.

Figure 3. Floor plan of shanghai beiheng shield tunnel (Zhongjiang Road Shield Work Shaft to Zhongshan Park Shield Work Shaft).

Figure 4. Floor plan of shanghai beiheng shield tunnel (Zhongshan Park Shield Work Shaft to Shaiwang Factory Shield Work Shaft).

2.2 Beiheng shield tunnel under-passing M11 The Beiheng shield tunnel will underpass the existing metro Line 11 (later referred to as M11) at a close range, and its BIM is shown in Figure 2. M11 is a double-tube shield tunnel with an outside diameter of 6.2 m, a thickness of 0.35 m, an annular width of 1.2 m, and a double-line plane clearance distance of about 6.0 m. The plane projection angle between the center line of the Beiheng shield tunnel and the M11 shield tunnel is about 68◦ C, and the overlapping length is 19.9 m, as shown in Figure 5. It is about 38 m away from the center of the Beiheng shield tunnel. There is a north-south Beiheng ramp shield tunnel with an outside diameter of 7.2 m and a thickness of 0.5m. There is a sewage pipe with an outside diameter of 2.4 m above the lower tunnel of M11. The Beiheng ramp shield tunnel is still under planning. Its outsider diameter, thickness, and line position are not determined yet. 105

Figure 5. Plane position relation of shanghai beiheng shield tunnel under-passing M11.

Figure 6. Vertical position relation of shanghai beiheng shield tunnel under-passing M11.

The relative position relation between the section of the Beiheng shield tunnel and the M11 shield tunnel is shown in Figure 6. The M11 upper tunnel in the underpass is covered by about 20.27 m, and the lower tunnel in the underpass is covered by about 20.52 m. The fracture soil layer of the upper tunnel and lower tunnel belongs to (5)1-layer powder clay. Beiheng shield tunnel in the underpass is covered by topsoil of about 27.62 m. The soil in the shield cutting area is mainly (7) 1-layer powder sand, (7) 2-layer fine powder sand, and (8) 1-1-layer powder clay. Beiheng ramp shield tunnel is covered by topsoil by about 9.82 m, and the vertical clearance distance with the M11 shield tunnel is about 3.5 m. The sewage pipe is covered by topsoil of about 3.93 m and is located in (3)-layers of powder clay. The soil layer between Beiheng shield tunnel and M11 shield tunnel is (5) 1-layer powder clay, (6)1-layer powder clay, and (7) 1-layer powder sand, as shown in Table 1. Table 1. Thickness of soil layer between Shanghai Beiheng Shield Tunnel and the M11 Tunnel.

M11 tunnel

Vertical clearance distance (m)

Thickness of soil layer between the two tunnels (m) (5) 1-powder clay

(6) 1-powder clay

(7) 1-powder sand

M11 upper tunnel M11 lower tunnel

7.48 7.06

1.39 1.17

2.24 2.31

3.85 3.58

3 RISK ASSESSMENT METHOD FOR SUBWAY-CROSSING SHIELD TUNNEL The risks in the construction of subway-crossing shield tunnels are mainly assessed by numerical simulation. The core concept of this method is an idealized assumption of main factors and an omission of secondary factors. For example, the convergence-confinement method (Bemat 1998; Mroueh 2003; Zhu 2000) simulates the ground displacement in each stage of shield tunneling based on the stress release coefficient. This method is heavily dependent on the value of the stress release coefficient in each tunneling stage. But this coefficient has no clear physical meaning, and its accuracy is greatly dependent on the experience of engineers. This results in large discreteness of the simulation results when the convergence-confinement method is used in engineering applications, so it has been widely criticized. The equivalent circle zone method (Gao 2017; Zhang 2006) focuses on the effects of shield tail gap size, grout filling quality, eccentricity level of tunnel boring machine (TBM), and other factors on the stratum displacement and generalizes these factors into 106

a circle of special homogeneous materials with equal thickness outside the lining. This circle of special materials is called the equivalent circle zone. The equivalent circle zone has a specific physical meaning, but its thickness and physical properties are affected by many factors, so it must be artificially assumed. Accordingly, the accuracy of this method also substantially relies on the experience of engineers. The ever-developing concept of “complete emulation” seeks to simulate and emulate the TBM tunneling stages as much as possible. But in practice, it is still required to make many idealized assumptions, such as no fluctuation in the supporting pressure or even distribution of the grouting pressure along the circumferential direction. So, it is difficult to achieve truly complete emulation and widely apply it to engineering due to the huge amount of calculation, great time consumption, and high labor cost. To sum up, at present, the accuracy of numerical simulation of subway-crossing shield tunnels hugely depends on the experience of engineers. In practical engineering applications, people often have great disputes about numerical simulation results. To address the above issue, this paper tries to find a single variable to assess the construction quality of a shield tunnel and use this variable to assess the risks in constructing a subway-crossing shield tunnel through finite element analysis software. The risk level of shield tunneling is mainly affected by geological, geometric, and construction quality factors. Specifically, geological factors refer to the geological conditions of the crossing areas. It determines the construction difficulties and the development law of the disturbed geostress field. Geometric factors refer to geometric information, including tunnel size, intersection angle, and vertical clearance distance. Construction quality factors refer to human factors, including overbreak, TBM posture, and synchronous grouting quality. In numerical simulation analysis, geometric factors are the easiest to implement and control, involving the least controversy. Construction quality factors greatly impact construction processes, workers’ competency, and management level. Making a numerical simulation for them is extremely difficult, so it faces the greatest controversy. All the above simulation methods are used to simplify and explore the construction quality factors. The main controversy about geological factors lies in whether the constitutive model is suitable or not and whether the mechanical property indexes and numerical simulation parameters need to be converted. Shanghai is located in the southeast front of the estuary of the Yangtze River Delta, and its landforms are late. Except for scattered denudated monadnock in the west and south, it is a flat sedimentary and beach plain. The soil layers are evenly distributed. Due to ancient channel cutting, the Powder clay in layer (6) is missing, and the distribution of silty sand in layer (7) changes greatly in some sections. Overall, Shanghai features an even geological distribution with little difference. For that reason, the numerical simulation method, constitutive model, and mechanical property index conversion method can be obtained through the back analysis of the measured data of existing projects. In this case, the influence of geological factors on the risk assessment against the shield tunneling in Shanghai is essentially controllable and real. Likewise, the controversy can also be eliminated by determining the simulation indexes of construction quality factors through back analysis. However, there are numerous construction quality factors, and it is difficult to perform back analysis and simulation for all factors. Hence, finding a single variable to represent the influence of construction quality factors is necessary. Generally speaking, the ground loss (displacement) resulting from shield tunneling is the direct reason for the deformation of existing structures, while the TBM posture, overbreak, and synchronous grouting quality are indirect reasons. The ground loss ratio can be used to evaluate the construction quality factors comprehensively. The ground loss ratio obtained through the back analysis of the measured data is not simply equal to the ratio of actual excavated soil to theoretical excavated soil. Contrarily, it is a quantitative index of shield construction quality and a comprehensive embodiment of factors such as overbreak, TBM posture, and synchronous grouting quality. It must be determined by performing back analysis on the measured data. In this paper, the ground loss is simulated by forced segment displacement, which is generally loaded in two forms, uniform ring (a) and crescent gradient (b), as shown in

107

Figure 7. Schematic diagram of simulation about ground loss.

Figure 8. Plane position relation of Xizangnanlu cross-river shield tunnel under-passing m8 shield tunnel.

Figure 7. For Shanghai, the uniform ring (a) is often used to simulate small shield tunnels, and the crescent gradient (b) is commonly used to simulate shield tunnels with a super-large diameter. To sum up, the geological parameters and ground loss ratio can be obtained by performing back analysis on the measured data of similar subway crossing projects, and the same simulation method can be used to analyze the risk level of the subway-crossing shield tunnel in Shanghai.

4 CASE STUDY 4.1 Ground loss ratio index obtained through back analysis 4.1.1 Survey on an engineering project for back analysis For an accurate assessment of the risk level of the Beiheng shield tunnel underpass, the M11 shield tunnel, a subway-crossing shield tunnel in Shanghai, was surveyed using the assessment method mentioned here. It is found that the case of the Xizangnanlu cross-river shield tunnel (“South Xizang Road Tunnel” for short) under-passing M8 shield tunnel is the closest to the Beiheng shield tunnel project. South Xizang Road Tunnel is divided into the west line tunnel and the east line tunnel, with a plane clearance distance of about 11.4 m. They are tunneled using two slurry pressure balance shield tunnels with an outer diameter of 11.58 m. It has an outer segment diameter of 11.36 m, a lining thickness of 0.5 m, and a ring width of 1.5 m. The single-layer lining structure is adopted. The Metro Line 8 shield tunnel (“M8 shield tunnel” for short) has an outer diameter of 6.2 m, a lining thickness of 0.35 m, and a ring width of 1.2 m. The South Xizang Road Tunnel intersects with the M8 shield tunnel in a “pound sign” shape. Figure 8 shows the relative position relation between them. The angle between centerline projections on the plane of two pairs of tunnels is about 66◦ C. The length of the overlapping section is 28.7 m (Ding 2012; Jiang 2009; Shao 2011; Zhu 2009). Figure 9 shows the vertical position relation between Xizangnanlu and M8 shield tunnels. At the crossing section, the earth covering at the top of the M8 shield tunnel is about 19.5 m thick, and the cross-section soil layers mainly include (5)1−2 powder clay and (6) powder clay. At the crossing section, the buried depth at the top of the South Xizang Road Tunnel is about 29 m, and the soil in the shield cutting area is mainly (7)1−1 powder sand and (7)1−2 fine powder sand. Table 2 shows the strata in the interlayer between Xizangnanlu and M8 shield tunnels. Table 3 shows the measured data of the South Xizang Road Tunnel under-passing the M8 shield tunnel. The shield tunneling of each crossing with the east or west line takes about three days. After each crossing is completed, all the main deformation indexes of the M8 shield tunnel exceed the allowable values. When the east line underpasses the M8 shield tunnel, the faults of the TBM and the grouting system materially extend the shield tunneling time. Consequently, for the existing subway tunnel, the settlement rate reaches 1.88 mm/ring, the maximum differential settlement reaches 5.53 mm, and the maximum settlement reaches 29.6 mm. 108

Figure 9. Vertical position relation of south Xizang Road tunnel under-passing M8 Shield Tunnel. Table 2. The thickness of soil layer between the south Xizang Road Tunnel and the M8 Tunnel.

South Xizang Road Tunnel West line tunnel East line tunnel

The thickness of soil layer in the two tunnels (m)

M8 tunnel

Vertical clearance distance(m)

(6)-powder clay

(7)1−1 powder sand

M8 upper tunnel M8 lower tunnel M8 upper tunnel M8 lower tunnel

2.79 2.89 2.84 2.91

1.16 1.50 1.97 2.30

1.63 1.39 0.87 0.61

Table 3. Measured data of settlement of south Xizang Road Tunnel Under-passing M8 Shield Tunnel. Settlement rate Settlement rate (mm/ring)

Crossing relation West Line Tunnel East Line Tunnel

M8 lower tunnel M8 upper tunnel M8 lower tunnel M8 upper tunnel

Settlement trough

Cutting tunneling

Maximum Shield tail tunneling

Maximum differential settlement (mm)

Minimum radius of settlement (mm)

Trough curvature (m)

width (m)

1.05 1.11 1.88 1.34

0.26 0.88 1.03 1.11

14.52 16.84 29.60 21.16

2.80 2.54 5.53 4.32

1581 2105 901 1201

30 34 26 28

4.1.2 Ground loss ratio obtained through back analysis The Midas_GTS finite element analysis software is used to simulate the process of the South Xizang Road Tunnel underpass the M8 shield tunnel. The dimension of the finite element model is 120 × 120 × 60 m, as shown in Figure 10. In this model, the South Xizang Road Tunnel underpasses the existing M8 shield tunnel at a slope of 4.8%. The horizontal angle between the two tunnels is 56◦ C. The Mohr-Coulomb model has nine soil layers, with physical parameters shown in Table 4. Shield segments are simulated by shell elements. After the initial stress field is formed, the M8 shield tunnel is excavated. After the third stress field is formed, the South Xizang Road Tunnel is excavated. In this model, the ground loss caused by the shield gap and construction control of the shield tunnel is simulated by forced segment displacement. The shield support pressure is simulated 109

Table 4. Soil Layer Division and Parameter Values. S/N

Layer sequence

Soil layer

Thickness(m)

E (kPa)

γ (kN/m3 )

c (kPa)

φ (◦ )

1 2 3 4 5 6 7 8 9

(1)–(2) (3) (4) (5)1−1 (5)1−2 (6) (7)1 (7)2 (8)

Filling soil, Clay Powder clay Silt Clay Powder Clay Powder clay Powder clay powder sand Fine powder sand Powder clay

3 3 4 4 4 5 10 12 11

37000 13700 13300 16450 24900 37250 58750 73700 26500

18.5 17.1 16.9 17.6 18.0 19.4 18.6 18.6 18.1

10 13 12 17 19 43 3 1 20

28.5 16.0 15.4 17.2 20.9 20.4 31.5 33.5 20.1

using the uniformly distributed load. The support pressure doubles the lateral soil pressure at the centerline of the shield.

Figure 10.

Model for Simulating South Xizang Road Tunnel Under-passing M8 Shield Tunnel.

4.1.3 Back analysis results When the above numerical calculation model is used for the trial calculation in back analysis, the relative error between simulation and measured results is less than 0.21%, and the numerical simulation results are shown in Figures 11 to 12. Table 5 shows the ground loss ratio obtained through back analysis corresponding to each working condition. Given the faults of the TBM and the grouting system that occurred when the east line tunnel underpasses the M8 shield tunnel, it can be inferred that the ground loss ratio may be controlled at about 0.4% to 0.5% when the shield tunnel with a super-large diameter is normally tunneled in Shanghai’s soft soil strata. At this time, the crossing construction can ensure the safety of the existing tunnel. 4.2 Numerical simulation of risk assessment of Beiheng shield tunnel The dimensions, parameters, and simulation methods for the numerical simulation of the Beiheng shield tunnel under-passing the M11 shield tunnel must be consistent with that of the South Xizang Road Tunnel under-passing M8 shield tunnel as far as possible. As shown in Figure 13, the model dimension is 120 × 120 × 60 m. In the model, the horizontal angle between the Beiheng shield tunnel and the M11 shield tunnel is 68◦ . The Beiheng shield tunnel underpasses the M11 shield tunnel at a slope of 1.47%. The slope of the M11 upper tunnel is 1.57%, and that of the M11 lower 110

Figure 11.

Simulation Results of West Line Tunnel Under-passing M8 Shield Tunnel.

Figure 12.

Simulation Results of East Line Tunnel Under-passing M8 Shield Tunnel.

tunnel is 1.28%. The Mohr-Coulomb model has nine soil layers, with physical parameters shown in Table 6. Shield segments are simulated by shell elements. After the initial stress field is formed, the M11 shield tunnel is excavated. After the third stress field is formed, the Beiheng shield tunnel is excavated. In this model, the ground loss caused by the shield gap and construction control of the shield tunnel is still simulated by the forced segment displacement. The shield support pressure Table 5. Summary and comparative analysis of back analysis results. Crossing West line tunnel East Line Tunnel

M8 lower tunnel M8 upper tunnel M8 lower tunnel M8 upper tunnel

Actual settlement (mm)

Simulated settlement (mm)

Relative error

Ground loss ratio

−14.43 −16.57 −29.81 −21.46

−14.4 −16.6 −29.8 −21.5

0.21% 0.18% 0.03% 0.19%

0.4% 0.5% 1% 0.5%

111

is simulated using the uniformly distributed load. The support pressure doubles the lateral soil pressure at the centerline of the shield.

Figure 13.

Numerical calculation model of M11.

Table 6. Soil layer division and parameter value S/N

Layer sequence

Soil layer

Thickness (m)

E(kPa)

 (kN/m3 )

C (kPa)

ϕ (◦ )

1 2 3 4 5 6 7 8 9

(1)1 (2)1 (3) (4) (5)1 (6) (7)1 (7)2 (8)1−1

Filling soil Clay Powder clay Silt Clay Powder clay Powder clay Powder Sand Fine powder clay Powder clay

3.2 8.04 5.5 5.8 7.8 3.83 4.88 7.45 12.34

37000 56300 13700 13300 16450 37250 73700 73700 26500

18.5 18.2 17.1 16.9 17.6 19.4 18.6 18.6 18.1

10 3 13 12 17 43 3 1 20

28.5 31.5 16.0 15.4 17.2 20.4 31.5 33.5 20.1

Due to space limitations, this paper only presents the numerical simulation results for a ground loss ratio of 0.50% and a support pressure of 232.0 kPa, as shown in Figure 14. When the Beiheng shield tunnel is close to the M11 upper tunnel, the uplift of the existing tunnel is 4.6 to 4.8 mm. When the Beiheng shield tunnel underpasses the M11 upper tunnel, the settlement of the upper tunnel is -12.0 mm while that of the lower tunnel is -2.8 mm. When the Beiheng shield tunnel completely underpasses the M11 lower tunnel, the settlement of the upper tunnel is -16.0 mm, while that of the lower tunnel is -15.4 mm. The construction control effect of the shield tunnel directly affects the deformation of existing tunnels. Table 7 shows the deformation values of existing tunnels under different ground loss ratios. When the ground loss ratio is less than or equal to 0.50%, the additional maximum settlement deformation of existing tunnels is less than 20 mm after the Beiheng shield tunnel underpasses the M11 shield tunnel, which meets the protection standard for the subway. Compared with the above back analysis results, it can be concluded that the Beiheng shield tunnel can safely underpass the M11 shield tunnel under normal tunneling conditions. At present, the ground loss ratio of the shield tunnel with a super-large diameter can be controlled at 0.3%, so it can be predicted that the additional vertical deformation of existing tunnels will be about 8.8 to 15.4 mm after the Beiheng shield tunnel underpasses the M11 shield tunnel. 112

Figure 14.

Numerical simulation structure of Beiheng Shield tunnel under-passing the m11 shield tunnel.

4.3 Measured data The measured settlement data of the Beiheng shield tunnel under-passing the M11 are shown in Figures 15 and 16. Since tunneling proceeds to the influence scope of M11, the M11 upper tunnel 113

Table 7. Summary of calculation results Crossing

Settlement of M11 shield tunnel (mm)

Ground loss ratio Upper tunnel Lower tunnel

0.30% −9.0 −8.8

0.50% −16.0 −15.4

closer to the crossing area shows a settlement trend, with a maximum settlement of -0.38 mm. As tunneling proceeds to the area underneath the tunnel, the M11 shield tunnel begins to rise. As tunneling proceeds to the next stage, the M11 upper tunnel rises by a maximum of 9.6 mm. As tunneling goes farther and farther from the upper tunnel, the upper tunnel undergoes settlement accordingly, with a settlement of 3.02 mm. The trend of the lower tunnel is largely consistent with that of the upper tunnel. During tunneling, the lower tunnel undergoes a maximum rise of 12.58 mm. As the TBM goes away, the lower tunnel gradually undergoes settlement, with a maximum settlement of 2.2 mm.

Figure 15. Settlement data of Shanghai Beiheng Shield Tunnel Under-passing M11 Upper Tunnel.

Figure 16. Settlement data of Shanghai Beiheng Shield Tunnel Under-passing M11 Lower Tunnel.

According to the measured settlement data, after the shield tunnel with a super-large diameter (Beiheng shield tunnel) underpasses the M11 shield tunnel, the additional maximum vertical deformation of existing tunnels is 12.5 mm, which is essentially consistent with the above numerical simulation results.

5 CONCLUSION In this paper, the finite element numerical simulation analysis method was used to analyze the relationships among the reasonable clearance distance, settlement peak, and ground loss ratio of the shield tunnel with a super-large diameter under-passing existing metro shield tunnels in soft soil strata. The following conclusions were drawn: (1) The risk level of shield tunneling is mainly affected by three factors: geological factors, geometric factors, and construction quality. As the soil layers in Shanghai are evenly distributed with little difference, construction quality is the main control factor for the risk difference in constructing the Shanghai Beiheng shield tunnel. (2) The ground loss (displacement) resulting from shield tunneling is the direct reason for the deformation of existing structures, while the TBM posture, overbreak, and synchronous grouting quality are indirect reasons. Therefore, the ground loss ratio index is obtained through the back analysis of the measured data to assess the overall construction quality. 114

(3) According to the back analysis on the South Xizang Road Tunnel under-passing the M8 shield tunnel, it can be inferred that the ground loss ratio may be controlled at about 0.4% to 0.5% when the shield tunnel with a super-large diameter is normally tunneled in Shanghai’s soft soil strata. (4) Numerical simulation predicts that when the ground loss ratio is controlled at 0.3% to 0.5%, the additional vertical deformation of existing tunnels is about 8.8 to 15.4 mm after the Beiheng shield tunnel underpasses the M11 shield tunnel. The measured vertical deformation is 12.5 mm, which falls within the above prediction range.

REFERENCES Bemat S, Cambou B. Soil-structure interaction in shield tunneling in soft soil [J]. Computer and GeoTechniques, 1998, 22(3/4): 221–242. Ding C.S., Yang X.F. Deformation analysis of shield tunnel undercrossing nearby operation tunnels [J]. Construction Technology, 2012, 41(01): 84–86+91. Gao H.J., He P. Chen Z.Application of equivalent circle zone method in calculation analysis of tunnel excavation [J]. Railway Engineering, 2017, (07): 64–67. Ge S.P., Xie D.W., Ding W.Q., Yang H.J. Simulation and monitoring of shield tunnel undercrossing historic building [J]. Journal of Tongji University (Natural Science), 2011, 39(10): 1463–1467. GuoY.H. Study on Ground surface movement induced by large-diameter earth pressure balance shield tunneling [J]. China Civil Engineering Journal, 2013, 46 (11): 128–137. Huang D.Z., Zhou Y.X., Dai S.M., Chen J. Construction protecting technology of historic buildings adjacently passed by shield in shanghai bund bypass [J]. Construction Technology, 2010, 39(09): 43–46. Jiang H.J. The Study of the Influence on the Existing Tunnel when Passed Beneath by Slurry Shields and the Driving Parameters [D]. Shanghai Jiaotong University, 2009. Jiang L. Analysis on influence of oversized-diameter shield tunneling on rail traffic in soft soil area [J]. Urban Roads Bridges & Flood Control, 2020(04): 189–192+24–25. Kong Q.X. Construction technology for shield tunnel underpassing buildings on a small-radius curve [J]. Project Management, 2018(05): 88–92. Liu J. Basic Mechanical Properties of Glass Fiber Reinforcement and Its Application in Shield Crossing Projects. Beijing, Beijing University of Civil Engineering and Architecture, Marcy 2, 2014. Liu Nian. Optimal clearance distance of super-large-diameter shield tunnel underpassing the existing metro tunnel [J]. IOP Conference Series: Earth and Environmental Science, 2021,783(1). Mroueh H, Shahrour I. a full 3D finite element analysis of tunneling -adjacent structures interactions[J]. Computer and Geo Techniques, 2003, 30: 245–253. Shao H. Analysis on monitoring technique of construction by slurry shield undercrossing the operating metro tunnel [J]. Chinese Journal of Underground Space and Engineering, 2011, 7(06): 1196–1202. Shi H.B., Wu H.M. Construction technique of slurry shield tunneling under pile foundation of wharf [J]. China Municipal Engineering, 2004(02): 32–35+70. Tang X.J. Numerical analysis of large-diameter shield tunneling beneath subway tunnel [J]. Low-Temperature Architecture Technology, 2018, 40(06): 131–133. WangY.Technology of shield tunnelling beside buildings [J]. Underground Engineering andTunnels, 2004(01): 49–51+57. Zhang H.Z., Zhang J.W., Zhai J.Y. Ansys method for deduction of parameters of equivalent circular zone of shield tunnel [J]. Tunnel Construction, 2006, (05):8–10+27. Zhu C.S. Settlement analysis of m8 subway caused by closely cutting through of the south tibet road tunnel [J]. Shanghai Geology, 2009(03): 57–62. Zhu H.H., Ding W.Q., Li X.J. Construction simulation for the mechanical behavior of shield tunnel and its application [J]. China Civil Engineering Journal, 2000, 33(3): 98–103.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Application of steel strand tension technology in the construction of bridge bearing platform Yanchao Zhang∗ Liaoning Railway Vocational and Technical College, China

Pengyuan Yao∗ China Railway Construction Bridge Engineering Bureau Group Co., Ltd, China

Yundong Ma∗ Tunnel Engineering and Disaster Prevention and Control Professional Technology Innovation Center, Liaoning Province, China

ABSTRACT: In order to solve the problem that the quality of concrete construction is affected by the site limitation in bridge construction in some areas and to ensure that the concrete construction is solid inside and beautiful outside, the improvement and innovation of traditional construction techniques are proposed. Combined with the construction technology of the new Fuzhou-Xiamen railway bridge bearing platform, the steel strand is used to replace the round steel or finish rolled rebar as the bearing platform formwork pull rod, which overcomes the difficulties of pulling out the pull rod and leaving the pull rod in the concrete structure when the round steel or finish rolled rebar is used as the pull rod in the traditional technology. The engineering practice shows that the application of steel strand tension technology in the construction of bridge-bearing platforms can meet the design requirements, save the project cost, eliminate the hidden quality accident, and provide a guarantee for later operation safety.

1 INSTRUCTION In the construction of bridge-bearing platforms, in order to fix the formwork, pull rods are usually used for the fixed connection. In the traditional construction process, the round steel or finish rolled rebar is used as the pull rod to fix the bearing platform formwork (Yin 2009). Because the round steel or finish rolled rebar cannot be bent, and its working space is limited by the excavation size of the foundation pit, even if the pull rod is jacketed, the round steel or finish rolled rebar pull rod cannot be pulled out, resulting in that the pull rod cannot be pulled out (He 2016; Wang 2012). The leftover pull rod not only affects the construction quality of the bearing platform, but also the pull rod left inside the bearing platform will form a corrosion channel, especially for the bearing platform partially located in the marine environment without a cover, which will greatly damage its durability. At the same time, the frequent leftover of the pull rod will increase the cost of engineering construction and cause a great waste of resources (Guo 2020; Han 2020; Wang 2018; Zhu 2020). Therefore, traditional construction technology must be improved and innovated to ensure that the concrete construction is solid inside and beautiful outside, so as to provide a guarantee for later operation safety.

∗ Corresponding Authors:

116

[email protected]; [email protected] and [email protected]

DOI 10.1201/9781003384830-15

2 PROJECT OVERVIEW 2.1 Project introduction Fuzhou-Xiamen railway is located in the coastal area of Fujian Province. It starts at Fuzhou Station in the north and ends at Xiamen station in the south. The total length of the main line is 300.483 km and the design speed is 350 km per hour. A project department is responsible for the construction task of about 16.9 km. The bridge, works in this section include two super major bridges, one major bridge and three medium bridges. There are 183 bearing platforms in this section. The bearing platform of the project belongs to mass concrete construction. The construction process requirements for the bearing platform are relatively high, and the construction standards are correspondingly high. Therefore, the combined steel formwork is used for the construction of the bearing platform on site. 2.2 Project features 2.2.1 High construction standard At the beginning of railway construction, the southeast coastal railway company put forward the construction concept of “high-quality projects, intelligent buildings”, with high standards and strict requirements. China’s high-speed rail version 2.0 in terms of quality is built and a benchmark is set for high-speed rail in the new era. The traditional pull rod technology of bearing platforms can no longer meet the requirements of the times. 2.2.2 Poor hydrological conditions The bid section is located in the southeast coastal area, and the bridge site spans a large area of saline-alkali land and a bay area. Some bearing platforms are located in the marine environment without cover. The chloride ion content of groundwater and surface water is far greater than that of the normal construction environment, which seriously affects the appearance and physical quality of the tie rod corrosion. 2.2.3 Difficulties in land acquisition The project is located in the core economic zone of the coastal area in Fujian, with dense housing and factories, and the land acquisition and demolition work are very difficult. There is no temporary land except the land for the railway red line, which leads to the difficulty in foundation pit excavation and the narrow working surface of the cushion cap construction, and the pull rod cannot be pulled out through the traditional pull rod construction technology.

3 PROCESS OPTIMIZATION OF BEARING PLATFORM PULL ROD 3.1 Process optimization In order to reduce the project cost, eliminate quality defects, and ensure the safety and reliability of construction, the new pull-rod material should have the following characteristics: It can be reused to avoid material waste; it has a certain strength to ensure that it can work stably under the action of concrete lateral pressure, vibration impact force and other forces; it has a certain flexibility and is easy to pull out, making it more convenient to install and remove the pull rod. Through the above analysis, the prestressed steel strand is proposed to be used as the pull rod, which has the following advantages compared with the traditional round steel or finish rolled rebar: Materials are easy to obtain because there are a large number of prestressed works in this project, materials do not need to be purchased additionally and can be obtained at any time on site; the material is flexible, which can be installed and removed even when the excavation size of the foundation pit of the bearing platform is limited; it can be recycled to reduce costs and prevent resource wastes; during the installation of pull rods, the pre-tensioning force can be applied to 117

offset the concrete load and construction load, so as to ensure that the formwork is not deformed and that the apparent size of mass concrete meets the standard. 3.2 Specific structure and construction method 3.2.1 Specific structure The length of steel strands is determined according to the structural size of the bearing platform and calculation results, and then they are processed and cut according to the calculated length; Tie plates (Figure 1), length regulators, single hole anchors, and tool clips are purchased or processed according to the actual conditions of the project;

Figure 1.

Structural diagram of tie plates.

The formwork is installed and fixed temporarily; The PVC plastic casing is installed at the pull rod channel in the bearing platform, and the diameter of the casing is slightly larger than the diameter of the steel strand pull rod; The steel strand pull rod is threaded into the PVC plastic sleeve; The internal support of the formwork is reinforced; Tie plates, length regulators (Figure 2), single hole anchors, and tool clips are installed outside the back edge of the formwork;

Figure 2.

Structural diagram of length adjusting bolt.

After the reinforcement is completed, checked, and confirmed, the regulator is adjusted according to the inspection results to achieve the target tightness and stress state; The size and stress condition are rechecked and confirmed, and the preparation is made for concrete pouring. 3.2.2 Construction method Since the pull rod holes are set separately one by one, the use of steel strands is also a single bundle construction. It is noted that the anchorage and tool clips prepared on site are of a single-hole type. The construction diagram of the steel strand pull rod is shown in Figure 3. Wherein, 1-base plate; 2-length adjusting bolt; 3-anchorage; 4-tool clip; 5-formwork back ridge; 6-formwork; 7-PVC casing; 8-steel strand. Installation sequence: 6 → 5 → 7 → 8 → 1 → 2 → 3 → 4. 118

Figure 3.

Construction diagram of steel strand pull rod.

4 CHECKING CALCULATION OF FORCE AND ELONGATION OF PULL ROD 4.1 Checking calculation of the force on the pull rod This study takes the bearing platform of the 149# pier of Anhai Bay super major bridge as an example. The size of the bearing platform is 15.8 m × 10.6 m × 3.5 m. The steel strand with a diameter of 15.2 mm is used as the flexible pull rod, with a transverse spacing of 1.5 m and a longitudinal spacing of 0.9 m. The vertical formwork of the bearing platform is mainly subjected to horizontal forces, mainly including the lateral pressure of concrete and the lateral construction stress load during concrete pouring (Figure 4).

Figure 4.

Load diagram of lateral pressure.

The lateral pressure of concrete is calculated as follows: Pmax = 0.22γc to K1 K2 V 1/2

(1)

Where, γ c –gravity density of concrete, γc = 25 KN/m3 ; t0 – initial setting time of concrete, t0 = 3.5 h according to the actual mix proportion; K1 – additive correction coefficient, K1 = 1.2; K2 – correction coefficient of concrete slump influence, K2 = 1.15; V – concrete pouring speed, V = 1.5 m/h. (2) Pmax = γc h Where h – the height from the calculated height of concrete lateral pressure to the top surface of the concrete. So: P1 = 0.22 × 25 × 3.5 × 1.2 × 1.15 × 1.51/2 = 32.53 KPa, P2 = 5 × 1.3 = 32.5 KPa. The smaller of the two is Pmax = 32.5 kPa. Effective head height h= Pmax /γ c = 32.5 / 25 = 1.3 m, that is, the bearing platform formwork reaches the maximum lateral pressure at 1.3 m from the top. The horizontal load generated by vibration is 4 kPa; The load generated by the dumping of concrete pump truck is 2 kPa; the lateral pressure of fresh concrete is 32.5 kPa. The lateral pressure on the formwork is Pm = 1.2 × 32.5 + 1.4 × (4 + 2) = 47.4 KPa. 119

Then, the tensile force borne by the pull rod is F = Pm · a· b= 47.4 × 1000 × 1.5 × 0.9 = 63, 990 N. The allowable tension of steel strand is Fcapacity = Rb_y · Ay = 1860 × 106 × 140 × 10−6 = 260, 400 N. After comparison, the prestress borne by the steel strand pull rod is far less than its ultimate tensile strength, which meets the stress requirements. 4.2 Calculation of pull rod pretension elongation First, the reinforcement of the bearing platform is bound, then the bearing platform formwork is installed, and finally, the steel strand pull rod system is installed. According to the pretension stress (taken as 60 kN according to the above calculation results), its deformation control amount is calculated, and then the length adjuster is used to adjust the length to make it reach the calculated pretension force. The elongation of 60 kN tension steel strand is calculated as follows: In the long side direction (15.8 m): L =

PL 60000 × 15.8 = = 0.0347m = 34.7mm Eg Ay 1.95 × 105 × 140

(3)

In the short side direction (10.6 m): L =

PL 60000 × 10.6 = = 0.0233m = 23.3mm Eg Ay 1.95 × 105 × 140

(4)

The on-site construction adopts the method of tensioning and prestressing at both ends. That is, the tensioning length at each end of the long side is 17.4 mm, and the tensioning length of each end of the short side is 11.7 mm. In order to avoid stress loss, when tensioning the steel strand pull rod, the actual tensioning length at each end of the long side is 18 mm, and that at each end of the short side is 12 mm. 4.3 Calculation of supporting balance force in formwork 4.3.1 Calculation of compressive strength of internally braced steel pipe During construction, the inner support pipe is installed on the reinforcement skeleton, so its self60000N weight is not considered in the calculation. From [N ]1 = f ∗ A, A = [Nf ]1 = 215MPa = 279.07mm2 is obtained. φ 108 × 6 mm is taken as steel pipe support, with a sectional area of 1922.7 mm2 . 4.3.2 Checking calculation of concrete cushion block The size of the cushion block for bearing platform construction is 2.5 cm × 4.5 cm × 7 cm, with a strength of C60. The diameter of the bearing platform reinforcement is 2 cm, and the contact length is 25% of its perimeter, i. e. L = 2πr/4=1.57 cm. 1 cm is taken in the calculation, and its minimum bearing area is 2.5 cm2 . Then the force that a cushion block can bear is: N = 60 MPa × 2.5 cm2 = 15 kN. Three layers of steel strand pull rods are arranged from the bottom to the top, with a horizontal spacing of 1.5 m and a vertical spacing of 0.9 m. The force distribution of each steel strand pull rod is 1.5 m × 0.9 m = 1.35 m2 . The average number of cushion blocks is 5.4, that is, the pressure shared by each cushion block is 11 kN, which is less than the withstanding pressure of 15 kN, so the compressive strength of cushion blocks meets the requirements. 4.4 Result analysis The pretension force of the steel strand pull rod is greater than the lateral pressure of the concrete and the construction load stress; An appropriate amount of pre-tensioned steel strand can gradually and basically offset the lateral pressure and construction load generated during concrete pouring, ensuring that the formwork deformation is within a controllable range and that the size of the cushion cap meets the design requirements; 120

Before and during concrete pouring, there is always rigid support inside the formwork, ensuring that the formwork is in a state of mechanical balance from the beginning to the end. 5 ECONOMIC COMPARISON AND SELECTION Taking the 149 # pier cap of Anhai Bay super major bridge as an example, the economic benefit is analyzed. The long and short sides are evenly arranged in the horizontal direction. According to the requirements, the horizontal spacing should be less than 1.5 m, and three layers are arranged in the vertical direction. Table 1 shows the cost of round steel pull rods and steel strand pull rods used in the bearing platform through a comparative analysis. Table 1. Cost analysis of round steel tie rod and steel strand tie rod (Monetary unit: RMB Yuan). Type

Details of charges Quantity Total cost of all bearing platforms

Round steel pull rod Processing cost of pull rod screw head Material cost ——

Steel strand pull rod 540 4950 ——

Pull rod cost Cost of length adjusting bolt Cost of anchorage and clip

66,000 32,000 128,000

183 bearing platforms

15 sets of formworks

996,000

294,000

After the construction, the flexible pull rod and other materials are still available, with a certain economic value. Therefore, through the comparative analysis, the use of steel strand flexible pull rods can at least reduce the direct economic investment by RMB 702,000. 6 CONCLUSION By applying the prestress to the steel strand pull rod, it can not only achieve the effect of traditional pull rod construction but also offset the concrete side stress and construction load stress in the construction process. The deformation of the formwork is avoided, and the geometric dimension of the bearing platform meets the design requirements. Compared with the traditional round steel pull rod, the steel strand pull rod is incomparably economical, which not only saves the cost for the project but also avoids the waste of resources. When the excavation size of the foundation pit of the bearing platform is limited, the steel strand pull rod has incomparable flexibility compared with the traditional pull rod, which is simple to pull out and easy to operate, so as to avoid the traditional pull rod leaving in the concrete and affecting the concrete quality. REFERENCES Guo Rongkun. (2020). Discussion on construction technology and quality control of bridge underwater bearing platform. Brick-Tile. 4, 107–108. He N.S. (2016). Prevention of formwork burst in railway bridge pier construction. Railway Engineering. 4, 41–43 + 55. Wang B.S. (2018). Construction technology of bridge deep foundation pit bearing platform. Construction & Design for Engineering. 7, 231–232 + 235. Wang C. & Zhang B.L. (2012). Research on application of steel strand tie rod in formwork reinforcement of deep foundation pit bearing platform of urban light rail bridge. Highway Transportation Technology (Application Technology Edition). 8(2), 151–153. YinY.H. (2009). Optimization design and engineering application of formwork tie rod members. Transpoworld. 9, 93–95. Zhu Y.H. (2020). Key technology of bridge bearing platform. Transpoworld. 17, 175–176.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on the influence of foundation pit excavation on upper span tunnel Jin Pang* Publishers, Chinese, Zhejiang Mingsui Technology Co., Ltd, China

Hequan Zhao* Chinese, China Railway 14th Bureau Group Mege Shield Construction Engineering Co., Ltd, China

Ting Bao*, Lingchao Shou* & Lifeng Wang* Chinese, Zhejiang Mingsui Technology Co., Ltd, China

ABSTRACT: Based on a foundation pit project in Hangzhou, the whole process of foundation pit excavation is numerically analyzed by Plaxis 2D. Combined with the comparison of the measured results, the stress and deformation of the foundation pit envelope structure system and the influence of the foundation pit excavation on the subway below are analyzed. The calculation results all meet the requirements of standard control, indicating that the adopted enclosure structure can effectively control the impact of foundation pit excavation on the surrounding environment. This study can provide a reference for similar projects.

1 INTRODUCTION With the continuous development and utilization of urban underground space in China, more and more foundation pits of new constructions need to be excavated and constructed over existing subway tunnels at a close range (Min 2010). The excavation of the foundation pit will produce an unloading effect, which will lead to the destruction of the original stress balance in the soil, resulting in the uplift deformation and additional stress of the tunnel structure below (Chen 2017; Guo 2017). How to ensure the safe operation of the existing subway is an urgent problem to be solved in the project. Experts and scholars have carried out many studies on the impact of foundation pit excavation on the surrounding environment. Zhong F J et al. (Zhong 2018) studied the protective effect of different reinforcement methods on the uplift of the existing tunnel under the foundation pit. Bi S Q et al. (Bi 2022) analyzed the influence of foundation pit excavation construction on the subterranean tunnel in combination with the actual project. The results show that the initial stage of the tunnel’s floating deformation is greatly affected by the excavation sequence. Wei Z K et al. (Wei 2022) considered that the excavation depth of the foundation pit, the distance between the tunnel and the foundation pit, and the width of the foundation pit are all important factors affecting tunnel deformation through the single-factor and multi-factor analysis. Zheng G et al. (Huang 2014; Li 2011; Zheng 2010) used numerical calculation methods to analyze the influence of foundation pit construction on the deformation and stress of the subterranean tunnel under different positional relationship conditions.

∗ Corresponding Authors: [email protected]; [email protected]; [email protected]; [email protected] and [email protected]

122

DOI 10.1201/9781003384830-16

Each project has its own characteristics. Based on the research background of a subway foundation pit project in Hangzhou, this paper uses the method of numerical simulation to compare with the measured data to analyze the influence of the foundation pit excavation on the envelope structure and the subway below.

2 ENGINEERING BACKGROUND 2.1 Project overview The Genshan East Road crossing the river tunnel project is designed as an urban expressway, including the river crossing tunnel, the comprehensive pipe gallery, the ground connecting line project, and supporting ancillary projects. The total length of the project is 4612.26 m (including the ground connecting line road), and the total length of the tunnel is 4462.26 m (including the shield section of about 3210 m). Among them, the open-cut section near YK0+700 on the Xiasha side is orthogonal to the existing Metro Line 1, and the foundation pit of the open-cut section is shown in Figure 1. It is about 6 m below the proposed tunnel project.

Figure 1.

Plane position relationship between foundation pit and subway tunnel.

2.2 Engineering geological conditions The minimum clear distance between the open-cut tunnel floor and the operating subway tunnel is about 5.2 m, and the soil layers in the interval are, from top to bottom, miscellaneous fill, sandy silt, silt, sandy silt, and silty clay. The mechanical properties of each layer of soil are shown in Table 1. The subway shield tunnel is located in the silt and is not affected by groundwater within the construction area of the site. 2.3 Foundation pit excavation and monitoring plan For the foundation pit enclosure, bored cast-in-place piles are used with a diameter of 800 mm and a spacing of 1000 mm, of which double-row piles are used directly above the subway, and at the waterproof curtain are 2400@1800MJS rotary jet piles. A bored cast-in-place pile with a diameter 123

Table 1. Mechanical property parameters of soil layer. Soil layer

Soil layer name

γ /(kNm−3 )

Eref 50 /MPa

Eref oed /MPa

Eref ur /MPa

c/kPa

ϕ/(◦ )

(1) 0-1 (1) 1 (2) (5) 2 (6) 1 (10) a-1 (11) b-3

miscellaneous fill sandy silt silt sandy silt silty clay silty clay silty clay

17.71 19.5 19.7 19.4 18.7 18.3 18.62

3 19 20.31 13.39 4.9 3.9 5.1

3 19 20.31 13.39 4.9 3.9 5.1

9 57 60.93 40 22 20 15.3

10 6 4 7 14 13 22

12 25 32 23 21 11 15

of 1200 mm is installed in the foundation pit as an anti-uplift pile. The vertical distance between the bottom of the enclosure pile directly above the shield tunnel and the top of the tunnel is greater than 2.0 m, and the elevation of the bottom of the remaining enclosure piles is −21.2 m. The two sides of the shield tunnel are reinforced with portal bodies. MJS rotary jet piles are adopted for the sake of reinforcement. The depth of the foundation pit is reinforced to −21.2 m. The sub-pits are separated by bored piles, and the overall construction sequence is to excavate areas A, B, C, and D of the foundation pit above in sequence. In order to grasp the impact of foundation pit construction on the surrounding environment and subway tunnels, systematic deformation monitoring is carried out on the foundation pit supporting structure, surrounding environment, and subway structure. Among them, the monitoring contents of the foundation pit supporting structure and surrounding environment include 1) horizontal displacement of deep soil; 2) surface settlement behind the wall; 3) supporting axial force, etc. 3 PLAXIS 2D FINITE ELEMENT CALCULATION RESULTS AND ANALYSIS 3.1 Establishment of finite element model According to the engineering geological characteristics of the Genshan East Road crossing the river tunnel in combination with the foundation pit design and construction plan, the PLAXIS 2D finite element software is used for numerical analysis to simulate and calculate the adverse effects of the foundation pit excavation on the surrounding environment and the underground operation of the subway. The HSS model is used to analyze the constitutive relationship of soil, and the soil layer model is established according to the geological survey report. The mesh of the calculation model is shown in Figure 2. The excavation depth of the foundation pit in the model is 9.8 m. Since the foundation pit is geometrically symmetrical along the width direction, a 1/2 foundation pit width model is established. According to the principle of SaintVenant, the impact depth of foundation pit excavation is generally 3-5 times that of the foundation pit excavation depth, so the soil layer boundary is 100 m wide and 50 m deep. Fully fixed constraints are applied to the bottom of the model, and horizontal constraints are applied to the left and right edges. In addition, 20 kPa of the load is applied near the excavation surface of the foundation pit to simulate the construction load. 3.2 Analysis of calculation results According to the actual construction sequence, the calculation steps are set according to the actual construction process during the calculation and analysis, and the model calculation steps are shown in Table 2. When the main construction steps of the calculation model are completed, the vertical displacement cloud map and the horizontal displacement cloud map are shown in Figures 4 and 5. 124

Figure 2.

Model meshing diagram.

Table 2. Construction steps of foundation pit excavation. STEP

Working condition description

STEP

Working condition description

Phase 0 Phase 1

Equilibrium stress field Existing Tunnel Settings

Phase 7 Phase 8

Phase 2

Phase 9

Phase 6

Underground diaphragm wall Settings The first concrete support construction in the middle Middle excavation to the second support bottom Middle second steel support construction Dig in the middle

Intermediate floor casting Construction of the first concrete support on the outside Excavate the outside to the second support bottom

Figure 3.

Vertical displacement.

Phase 3 Phase 4 Phase 5

Phase 10 Phase 11

Construction of the second steel support on the outside Excavation to the bottom

Phase 12

Outer base plate pouring

According to Figure 3, after the excavation of the foundation pit is completed, the position with the largest vertical displacement is at the bottom of the foundation pit, which is mainly due to the excavation of the upper soil mass, and the stress release causes the soil mass to rebound upward. Therefore, in the actual construction process, the monitoring of the deformation of the base should be strengthened, and the uplift deformation of the bottom of the foundation pit can be reduced by pouring the base plate, increasing the stacking load, speeding up the construction progress, and avoiding the too long exposure time of the bottom of the foundation pit. According to Figure 4, the horizontal displacement of soil is the largest near the pit bottom. Figure 5 is a graph of the horizontal displacement of the ground connecting wall after the excavation of the foundation pit is completed. The curves in the figure are the measured and simulated values of the horizontal displacement of the ground connecting wall at different depths. 125

Figure 4.

Horizontal displacement.

Figure 5.

Horizontal displacement diagram of ground connecting wall.

By comparison, it can be seen that the simulated behavior of the horizontal displacement of the ground connecting wall of the model is similar to the measured behavior, indicating that the numerical model is reliable. When the excavation of the foundation pit is completed, the horizontal displacement of the ground connection wall presents a distribution pattern of small in the middle and large at both ends along the depth direction. The finite element simulation value of the maximum horizontal displacement is 9.37 mm, which is slightly larger than the measured value of 4.57 mm.

Figure 6.

Vertical displacement map of the ground surface.

126

Figure 6 is the vertical displacement curve of the ground surface behind the wall after the foundation pit excavation is completed. The curves in the figure are the simulated and measured values of the ground settlement behind the wall. By comparison, it can be seen that the surface settlement shape curve behind the wall is “grooved”. When the foundation pit is excavated to the bottom, the finite element simulation value of the maximum surface settlement behind the wall is -7.04 mm, and the measured value is -6.15 mm. The simulation results are basically consistent with the measured results, which, once again, verifies the reliability of the numerical model.

Figure 7.

Displacement Diagram of the Underground Subway Tunnel.

The finite element simulation analysis can not only effectively reflect the deformation and stress of the envelope structure, but also reflect the influence of the foundation pit excavation on the adjacent operating tunnels. Figure 7 reflects the displacement of the operating tunnel under the foundation pit, and the maximum vertical displacement is 6.37 mm. It can be seen that the excavation of the foundation pit has little effect on the operation of the subterranean tunnel, which meets the requirements of the specification, and when the soil of the foundation pit is unloaded, the tunnel structure is displaced towards the inner side of the foundation pit, further manifesting that the model is reasonable.

Figure 8.

Tunnel monitoring time history curves.

127

Figure 8 shows the time-history curves of the settlement and horizontal displacement of the tunnel bed at some monitoring points. The curve is stepped, reflecting the excavation process of the foundation pit. Among them, the development section is the superposition of the cumulative effect of earthwork excavation and the excavation in the previous stage; the flat section denotes the working condition of erecting supports and pouring the bottom plate; the steeply increasing section corresponds to the long-term exposure of the soil at the bottom of the pit, which causes the bottom of the pit to bulge and affects the working status of the tunnel.

4 CONCLUSION Through the numerical simulation of the foundation pit of Hangzhou Genshan East Road crossing the river tunnel, the deformation characteristics of the foundation pit excavation are compared and analyzed, and the following conclusions are drawn: The excavation of the foundation pit will cause an uplift of the pit bottom. The monitoring of the water level and the base should be strengthened, and the uplift should be prevented and controlled in time. During the excavation of the foundation pit, the maximum horizontal displacement of the ground connecting wall occurs near the excavation surface. After the excavation is completed, the measured maximum displacement of the ground connecting wall is about 0.05% of the excavation depth, which appears near the bottom of the pit. The surface settlement shape curve behind the wall is “grooved”; the measured maximum settlement value is about 0.05% of the excavation depth. The time-history curve of the settlement and horizontal displacement of the tunnel bed is stepped, which corresponds to each working condition during the excavation of the foundation pit.

REFERENCES Bi, S.Q., Gan, B.L. & Liang, Y.H. et al. (2022). Measured analysis of the influence of foundation pit excavation on existing short-range subterranean tunnels. J. Science Technology and Engineering. 22(3), 1198–1204. Chen, S.M., Ou, X.F. & Han, X.F. et al. (2016) Feng Han. Numerical analysis of new foundation pits adjacent to existing subway tunnels. J. Journal of Railway Science and Engineering. 13(08), 1585–1592. Guo, P.F., Yang, L.C. & Yu, Z. (2017). Measured data analysis of subway tunnels under the action of excavation and unloading above. J. Journal of East China Jiaotong University. 34(2): 20–28. Huang, X., Schweiger, H.F. & Huang, H. (2014). Influence of deep excavations on nearby existing tunnels. J. International Journal of Geomechanics. 13(2), 170–180. Li, P., Liu, H.L. & Chen, Y.M. (2011). Analysis of the uplift deformation of the existing subway tunnel in the excavation of the foundation pit. J. Journal of PLA University of Science and Technology. 12 (5), 480–485. Wei, Z.K., Chen, J. & Chen, B. et al. (2022). Research on the influence of soft soil foundation pit excavation on the deformation of adjacent existing tunnels. J. People’s Yangtze River. 53 (6), 198–206. Yan, J.Y. (2010). Discussion on the design and construction of deep foundation pits adjacent to operating subway tunnels. J. Chinese Journal of Geotechnical Engineering. 32(S1), 234–237. Zheng, G. & Wei, S.W. (2010). Numerical analyses of the influence of overlying pit excavation on existing tunnels. J. Journal of the Central South University of Technology. 15(S2), 69–75. Zhong, F.J., Li, W.P. & Xu, X.T. et al. (2018). Analysis of the influence of grouting reinforcement on the deformation of the existing subway tunnel under the foundation pit. J. Modern Tunneling Technology. (S2), 1144–1150.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Three-dimensional finite element analysis of the influence of graded slope excavation on the adjacent existing diversion tunnel Qinchuan Wang*, Xian Chen*, Hong Zheng* & Wanting Zhao* POWERCHINA Chengdu Engineering Corporation Limited, Chengdu, China

ABSTRACT: Taking a slope project to be excavated as an example, this paper mainly analyzes the influence of slope excavation on the deformation and stress of the adjacent existing diversion tunnel by using three-dimensional finite element analysis software, hoping to provide some reference for the finite element analysis of the adjacent influence of similar slope excavation. The results show that the slope excavation has little influence on the deformation of the adjacent existing diversion tunnel, but it has certain influences on the force. Therefore, the construction quality should be strictly controlled and the safety monitoring of the existing diversion tunnel should be strengthened in the process of slope excavation to ensure the good operation of the existing diversion tunnel.

1 INTRODUCTION With the rapid development of infrastructure construction, it is inevitable that there will be existing tunnels around the proposed project, and the construction process will inevitably produce disturbance to the surrounding rock and soil mass, thus causing internal forces and the deformation of the tunnel structure (Guo 2021; Wang 2021). Therefore, in order to ensure the safety of the existing tunnel, impact analysis becomes increasingly important. At the same time, with the continuous development of computer technology, finite element numerical simulation has become a powerful means of solving such problems (Wei 2022; Zhao 2009). Taking a slope excavation project as an example, this paper analyzes the influence of slope excavation on the adjacent existing diversion tunnel by using the three-dimensional finite element analysis software, which provides some reference for the finite element analysis of the adjacent influence of similar slope excavation.

2 PROJECT OVERVIEW The slope to be excavated will be excavated in five stages and ten steps, with a maximum excavation height of about 72 m. Its profile is shown in Figure 1, in which the red tunnel is the existing diversion tunnel and the closest distance from the slope excavation is about 13 m. The shallow layer of the slope is gravel soil (Qcol+dl ), the lower part of the overburden is chlorite 4 schist which is strongly weathered, unloaded, and dumped, and the relatively normal chlorite schist is near the exit section of the tunnel.

∗ Corresponding Authors: [email protected]

[email protected],

DOI 10.1201/9781003384830-17

[email protected],

[email protected] and

129

Figure 1.

Profile of slope excavation.

3 THREE-DIMENSIONAL FINITE ELEMENT MODEL AND PARAMETERS 3.1 Finite element modeling According to the stratum line of this project, a three-dimensional model of the natural slope is established as shown in Figure 2, with a length of 440 m, a width of 350 m, and a height of 290 m. The rock mass adopts solid elements, with a total of 103,111 nodes and 385,531 elements. The existing diversion tunnel is of the city gate type with a size of 3.1 m×4.0 m, and the model is shown in Figure 3.

Figure 2.

Overall model of the slope.

130

Figure 3.

Model diagram of the existing diversion tunnel.

3.2 Parameter selection The parameters selected in this analysis are set according to the parameters of the investigation report. The parameters of each rock layer of the slope are shown in Table 1, and the parameters of the existing diversion tunnel are shown in Table 2. Table 1. Physical and mechanical parameters of rock and soil mass of the slope. Name of geotechnical body

Bulk density

Gravel soil (Qcol+dl ) 4 Green mud schist (strongly weathered) Green mud schist (weakly weathered) Green mud schist (breezy) F2 fault zone

22.4 26.5 27 27.3 19.5

Cohesion

Internal friction angle

Modulus of elasticity

Poisson’s ratio

22 150 350 600 18

30 26.6 35 42 34

1 1.5 6 10 1

0.2 0.5 0.35 0.3 0.2

Table 2. Lining parameters of existing diversion tunnel. Concrete strength class

Static axial compressive strength (MPa)

Static axial tensile strength (MPa)

Static modulus of elasticity

Poisson’s ratio

C30

20.1

2.01

3.0×104

0.167

4 FINITE ELEMENT ANALYSIS 4.1 Deformation of the existing diversion tunnel In order to analyze the influence of graded slope excavation on the existing diversion tunnel, the lateral node close to the arch shoulder of the slope excavation side is selected as the feature point, and its displacement is monitored to obtain the continuous change curve of the displacement of the slope diversion tunnel with Grade V excavation, as shown in Figure 4. It can be seen from the calculation results that the existing diversion tunnel is far away from the first slope, so it is less affected, and the maximum displacement is only 0.09 mm. The maximum displacement of the existing diversion tunnel caused by the second stage excavation is 0.85 mm, 131

which appears at 34 m. The third-stage excavation causes the most obvious increase in the displacement of the existing diversion tunnel, and the maximum displacement is 2.60 mm. The main reason is that the excavation position of the third stage is close to the tunnel, and the soil disturbance caused by excavation has a great influence on the tunnel. The displacement of the existing diversion tunnel caused by the fourth and fifth stage excavation is 3.86 mm and 3.87 mm, respectively, and the displacement change tends to be stable. In general, the maximum displacement of the existing diversion tunnel appears at 24 m and tends to be 0 after 100 m. The main influence range of excavation on the existing diversion tunnel is 0–80 m.

Figure 4.

Displacement of the existing diversion tunnel near the slope.

After the fifth-stage excavation of the slope, the overall displacement cloud diagram of the existing diversion tunnel is shown in Figure 5. It can be seen from the cloud diagram that the existing diversion tunnel is mainly affected by the slope excavation on the side of the slope, and the maximum displacement is 1.941 mm.

Figure 5.

Displacement cloud of the existing diversion tunnel after slope excavation (top view).

4.2 Stress variation of the existing diversion tunnel In order to better understand the most affected position of the existing diversion tunnel, the stress values inside and outside the roof, bottom, and side walls of the lining structure of the existing diversion tunnel are selected for analysis. The calculation results are shown in Figure 6. From the calculation results, it can be seen that in the initial stage, the stress values everywhere are small; the stress on the inner and outer sides of the roof changes very little, and the maximum value is only about 0.1 MPa. The stress value changes greatly on the inner and outer sides of the side wall, and the maximum value is about 1 MPa. The calculation results of the first principal stress of the existing diversion tunnel after slope excavation at all levels are shown in Figure 7. It can be seen from the calculation results that the first 132

Figure 6.

Trend diagram of stress variation of bottom plate, side wall, and roof during graded slope excavation.

Figure 7.

First principal stress cloud diagram of the existing diversion tunnel during graded slope excavation.

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principal stress of the existing diversion tunnel is only 0.078 MPa when the slope is not excavated. The maximum value of the first principal stress at all levels of excavation is 1.204 MPa, which occurs when the fifth-level slope is excavated without support. According to the maximum principal stress of the existing diversion tunnel and the stress variation trend of each part, the stress state of the existing diversion tunnel is obtained: After the slope excavation is completed, the outer roof is tensioned, and the inner roof is under a pressure; the outer side of the side wall is subjected to pure tension due to slope excavation, but the stress of the inner side has no obvious change. The inner side of the bottom plate is always under a pressure. The outer side wall and the inner side wall are the most unfavorable, which may produce pull cracks.

5 CONCLUSION In this paper, for a slope engineering example, the three-dimensional finite element analysis software is used to conduct the numerical simulation, and three-dimensional finite element models of three-dimensional terrain, slope, and existing diversion tunnel are established, and the following conclusions are obtained. (1) During the graded excavation of the slope, the maximum displacement of the existing diversion tunnel is 3.87 mm, which appears at 24 m; the influence range of slope excavation on the maximum displacement of the existing diversion tunnel is mainly 0–80 m. (2) In the graded excavation process of the slope, the maximum stress of the existing diversion tunnel is 1.204 MPa, the outer roof is tensioned, and the inner roof is under a pressure; the outer side of the side wall is subjected to pure tension due to slope excavation, but the inner side stress has no obvious change. The inner side of the bottom plate is always under a pressure. The outer side wall and the inner side wall are the most unfavorable, which may produce pull cracks. The above analysis shows that the graded slope excavation has a certain influence on the adjacent existing diversion tunnel. Considering the safe operation of the existing diversion tunnel, the construction quality should be strictly controlled during the slope construction, and monitoring facilities should be set up within 0–80 m to ensure the safety of the existing diversion tunnel.

REFERENCES Guo Y.H., Yan M., Song Q., Yuan G., Fu X.B. Influence of deep foundation pit excavation on adjacent high-pressure natural gas pipeline [J]. Chinese Journal of Underground Space and Engineering, 2021, 17(S2):840–847. Liu G.B., Huang Y.X., Hou X.Y. Research and practice on uplift deformation control of metro tunnel in operation under foundation pit [J]. Chinese Journal of Rock Mechanics and Engineering, 2001(02): 202–207. Wang L., Luo Z.H., Zhang H. Three-dimensional finite element analysis of the influence of deep foundation pit excavation on adjacent buildings in a subway station [J]. Building Structure, 2021, 51(S1):1928–1934. Wei Z.K., Chen J., Chen B., Huang J.H. Study on influence of soft soil excavation on deformation of adjacent existing tunnels [J]. Yangtze River, 2022, 53(06):198–206. Zhao D.P., Wang N.Y., Jia L.L. Study on the influence of cutting slope excavation on adjacent existing tunnel [J]. Rock and Soil Mechanics, 2009, 30(05):1399–1402+1408.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Traffic noise monitoring and sensitivity modeling of control measures for a highway service area Yanqin Wang National Environmental Protection Engineering and Technology Center for Road Traffic Noise Control, Research Institute of Highway Ministry of Transport, Beijing, China

Dongxiao Yang College of Civil Engineering, Beijing Jiaotong University, Beijing, China

Minmin Yuan & Xianwei Wei National Environmental Protection Engineering and Technology Center for Road Traffic Noise Control, Research Institute of Highway Ministry of Transport, Beijing, China

Xiaochun Qin* College of Civil Engineering, Beijing Jiaotong University, Beijing, China

ABSTRACT: Highway traffic noise has become a major environmental problem and a serious hazard. This paper takes the Xianrenshan service area of the Shanghai-Nanjing Highway as a case. It firstly analyzes the noise distribution law from the spatial and temporal perspectives of the allround noise monitoring data in the service area and then analyzes and evaluates the sensitivity modeling of traffic control measures based on SoundPLAN software from three perspectives of traffic flow, speed, and vehicle ratio. The results show that the level of highway traffic noise is affected by the difference in the functional area, distance, time, and other factors. Controlling the reasonable traffic flow, speed, and vehicle model ratio can effectively reduce noise pollution. It has important guiding significance in improving the effect of traffic noise pollution control in highway service areas.

1 INTRODUCTION By the end of 2021,ü China had 16 million kilometers of expressways and 528.07 million kilometers of highways nationwide. With the increase in traffic volume and traffic density caused by highway mileage, traffic noise has become the main pollution source in the urban environment (Hamad et al. 2017). According to the research, more than 30% of residents’ life will be affected by road noise (Alexander et al. 2019). Long-term noise exposure may cause a series of health problems (Song et al. 2021). Therefore, it is significant to carry out the monitoring, analysis, simulation, and evaluation of traffic control measures for road traffic noise. Exposure to continuous noise levels beyond 85 dB for 8 h or more may be hazardous (WHO 2005). Therefore, many noise monitoring studies have been conducted at home and abroad. Chebil et al. (2019) conducted a case study of traffic noise levels at four main roads in Monastier, Tunisia, using a sound level meter of type TES-1352H made by the TES, and concluded that the noise level observed was higher than the limits of Tunisia’s environmental standards and the WHO standards. Alam et al. (2020) used a Sound Level Meter (SLM) to analyze and evaluate traffic noise levels as per standard procedures during the day and night’s peak traffic hours. Monitoring results of noise ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-18

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levels show non-compliance with regulatory standards for daytime and nighttime. The noise level is maximum at the centerline of the road, decreases on either side with the distance, and remains above the permissible limits at all locations. Literature review shows that the noise monitoring results of almost all countries have exceeded the acceptable limits. Therefore, road traffic noise is a serious problem, and urgent action is required to control the traffic noise level. Traffic noise models are needed to aid the design of highways and for assessing existing roads (Golmohammadi et al. 2007). These models are used to forecast noise levels in terms of Leq, L10, L90, etc., and can be used to plan proper mitigation measures to reduce traffic noise (Ramírez and Domínguez 2013). On a worldwide scale, many developed countries like the USA, UK, and Germany have developed good models [CoRTN(Delany et al. (1976)), FHWA TNM (Barry and Reagon (1978)), RLS-90 [(Richtlinien für Lärmschutz and Straßen 1990), etc.] to predict noise levels under homogenous traffic conditions. Currently, other developing countries are also conducting experiments to develop nationally appropriate noise prediction models (Lekshmi et al. 2018). Traffic noise prediction modeling trends vary from basic regression models to genetic algorithms, artificial neural networks, convolutional neural networks, fuzzy systems, graph theory approaches, etc. (Suman et al. 2022). However, at present, most domestic and foreign countries focus on the analysis of detection data, and there is no comprehensive study on the monitoring, simulation, and evaluation of traffic control measures of traffic noise. Secondly, there is little research on traffic noise in the service area of important highway nodes. Therefore, the research purpose of this paper is to break through the limitations of the above research and comprehensively analyze the road traffic noise monitoring data and the sensitivity of traffic control measures based on the highway service area to provide a scientific basis for the prevention and control of highway traffic noise and the design and planning of the service area. Through the noise monitoring of the Xianrenshan service area of Shanghai Nanjing Highway, this paper first analyzes the noise distribution law from the perspective of time and space. It then uses the road traffic noise prediction model SoundPLAN to analyze and evaluate traffic control measures’sensitivity from vehicle flow, speed, and vehicle type ratio. The results show that different functional areas, distance, time, and other factors affect highway traffic noise distribution levels. Controlling traffic flow, speed, and vehicle type ratio can reduce noise pollution.

2 METHODOLOGY 2.1 Type area Shanghai-Nanjing Highway, which is part of the national highway G42 Hurong Highway, is also the busiest in China as a fully closed, fully interchanged, high-grade, multi-functional modern highway. This study selects Zhenjiang Xianrenshan Service Area on the Shanghai-Nanjing Highway as a project, which is a comprehensive service area integrating multiple functions such as catering, shopping, accommodation, refueling, and auto repair (Table 1 and Figure 1). Table 1. Details of the service area. Location name

Area

Longitude

Latitude

Remarks

Xianrenshan Service Area

13,000 m2

119.39378

32.04183

Approx. 49 km from Nanjing and 225 km from Shanghai

2.2 Experimental method of noise monitoring According to the “Sound Environment Quality Standard” of the Ministry of Environmental Protection (2008), 11 monitoring points (including the south and north sides of the Shanghai-Nanjing 136

Figure 1.

Location of the Xianrenshan service area in Zhenjiang, Shanghai-Nanjing highway.

Highway) were arranged in different parts of the service area of Zhenjiang Xianrenshan on the Shanghai-Nanjing Highway, and the AW6228 multi-functional integral sound level meter with calibration accuracy strictly meeting the requirements (GB/T 17181-1997, GB/T 3785-2010) of the standard was used for road noise monitoring at different times. The distribution of noise monitoring points is shown in Figure 2.

Figure 2.

Arrangement of monitoring points in the Zhenjiang Xianrenshan service area.

2.3 Sensitivity model of traffic noise control measures Since its promulgation in 1986 by Braunstein + Berndt GmbH software designers and consultants, SoundPLAN has rapidly developed into the world’s leading noise prediction, mapping, and evaluation software and is widely used. This paper uses SoundPLAN software to model, calculate and evaluate the service area of Shanghai-Nanjing Highway Zhenjiang Xianrenshan based on ISO and 11 road standards, a collection of point sound sources, line sound sources, surface sound sources, and other complex sound source environments, and fully consider the reflection and diffraction effects of sound propagation from various facilities within the service area, to analyze the impact of various traffic control measures on the noise of each monitoring point with high accuracy.

3 RESULTS AND DISCUSSION 3.1 Noise distribution at the spatial scale 3.1.1 Noise distribution of different functional partitions To clarify the change law of the sound pressure level with time in various functional zones of the Xianrenshan Service Area of Ning-Hang Highway (Figure 3), the 12 monitoring points were 137

Figure 3.

Variation of sound pressure level with time in various functional zones at monitoring points.

divided into the gas station, restaurant and supermarket, office building front, parking lot, parking lot side and highway access side according to different functional areas, as shown in Table 2. Table 2. Zoning of monitoring points in the Zhenjiang Xianrenshan service area. Monitoring point zoning

Monitoring points

Main audience

Gas stations Restaurants, supermarkets In front of the office building Parking By the highway access road By the parking lot

1 7, 8 2, 9 3, 11 4, 10 5, 6

Staff Passengers, drivers, staff Staff Passengers, drivers Staff Staff

From the overall analysis of Figure 3, the maximum sound pressure level in the Xianrenshan Service Area is 78.9 dB(A), and the lowest sound pressure level is 53.4 dB(A), both of which are located in the 16:00 time period, while the other sound pressure level distributions are mainly concentrated between 60 and 67.5 dB(A). Analyzed from the perspective of different areas, in the areas where the main audiences are passengers and drivers (restaurants, supermarkets, and parking lots, monitoring points 7, 8, 3, and 11), the sound pressure level at each monitoring point is below 70 dB(A) during most of the daytime hours. This is mainly because these monitoring points are far away from the main highway line (140 m to 200 m), and traffic noise is absorbed and reflected by vegetation and hardened road surface during propagation at longer distances, making up for the lack of vegetation. For the personnel working at the gas station (monitoring point 1), the sound pressure level is below 70 dB(A) in most hours of the day, which indicates that the sound environment is relatively good. However, in a few hours, the sound pressure level is higher, which has a greater impact on the staff. Under possible conditions, vegetation planting or sound barriers can be increased at appropriate locations along the highway. For the staff working in the service area, the sound pressure level of monitoring points 2 and 9 are below 65 dB(A) throughout the day. This is mainly because these office areas are far from the main highway line (>200 m). The sound environment in these areas for daytime offices is good and not affected by traffic noise. In terms of the main audience for the service area staff of the highway channel side of the monitoring points 4 and 10, these monitoring points from the main line of the highway are within a distance of 30 m, the sound environment of these monitoring points is strongly affected by highway traffic noise, so its 138

noise fluctuates. When there are more low-speed vehicles passing through, the sound pressure level at these monitoring points is very high; when there are only small cars passing through or traffic flow is small, the noise level of these monitoring points is very low. As for the monitoring points 5 and 6 by the parking lot where the main audience is the service area staff, the sound pressure level is below 65 dB(A) during the whole daytime, which is mainly because the two monitoring points are farther away from the main highway line (about 100 m). More vegetation is planted in the path of sound transmission, which has a greater effect on reducing traffic noise originating from the main highway line. 3.1.2 Noise distribution under distance variation To know the effect of distance change on the noise in the Xianrenshan Service Area, Figure 4 shows the change in the sound pressure level in the service area at monitoring points 4, 3, and 2 (the distance from the edge of the main line of the highway is 23 m, 90 m, and 133 m, respectively).

Figure 4.

Variation of sound pressure level with distance at monitoring points.

From the overall analysis of Figure 3, in the direction of sound propagation, the sound pressure level gradually becomes smaller as the propagation distance increases due to the characteristics of reflection and diffraction of sound waves as well as the absorption of sound waves by vegetation and ground. Specifically, the sound pressure level decreases by about 3 dB(A) when the sound point changes from monitoring point 4 to monitoring point 3 (i.e., when the distance from the edge of the highway mainline increases from 23 m to 90 m), and by about 4 dB(A) when the sound point changes from monitoring point 3 to monitoring point 2 (i.e., when the distance from the edge of the highway mainline increases from 90 m to 133 m). The sound pressure level reduction of the latter is greater than that of the former (even though the distance of the latter increases only by 43 m, while the distance of the former increases by 67 m) mainly because more vegetation is planted between the monitoring point 3 and monitoring point 2, which has a greater effect on noise absorption and dissipation. In the future, in the soundscape design of the service area, under the condition that the planning land permits, for the places that need a quiet sound environment (such as accommodation areas), they can be arranged at a location far away from the main highway line; at the same time, more vegetation is planted to improve the landscape design effect on the one hand and reduce the impact of traffic noise on the other. 3.2 Noise distribution at the time scale The number of test points with sound pressure level values below 65 dB in each time period accounts for the percentage of the 12 test points to illustrate the quietness of the service area; the larger the percentage, the quieter the overall environment of the service area, and the comparison results are shown in Table 3. 139

Table 3. Time distribution statistics of sound pressure level. Number of monitoring points Test time

50–60 dB

60–65 dB

65–70 dB

70–80 dB

Percentage of monitoring points below 65 dB

7:00 8:00 10:00 12:00 14:00 16:00 18:00

5 4 3 2 2 3 0

2 5 6 9 8 4 7

5 1 2 1 2 3 3

0 2 1 0 0 2 2

58.3% 75.0% 75.0% 91.7% 83.3% 58.3% 58.3%

As seen in Table 3, the overall environment of the service area is the quietest at noon during this period. In the two time periods of 16:00 and 18:00, the overall environment of the service area is relatively the noisiest, and the test points with the largest sound pressure level values are test points 4 and 10, with sound pressure level values of 66.9 dB and 74.0 dB, respectively. This is because the test points are located at the side of the highway access and within 30 m of the main highway line, thus further illustrating the influence of different functional zoning and distance in the above study. Therefore, it further illustrates the reliability of the noise impact of different functional zones and distances in the above study. 3.3 Sensitivity assessment of traffic noise control measures 3.3.1 Analysis of sensitivity of traffic flow to noise Assuming that the traffic volume at night is 30% of that during the day, the traffic volume is set to increase from 500 veh/h to 4000 veh/h during the day. The sensitivity of the traffic volume to noise is analyzed from two perspectives: the change in noise source intensity (as shown in Figure 5) and the range of predicted noise values at each sensitive point (as shown in Figure 6). It can be seen that the noise source intensity increases with the increase in traffic volume, and the changing trend of noise source intensity during the day and night is comparable, and the difference between the noise source intensity during the day and night is about 5.5 dB(A); when the traffic volume increases from 500 veh/h to 4000 veh/h, the noise source intensity increases by about 9 dB(A), and the increase becomes slower with the increase in traffic volume base. When the traffic volume increases from 500 veh/h to 1000 veh/h, the increase is 3dB(A), and when the traffic volume exceeds 2500 veh/h, the noise increases by about 0.7 dB(A) for every 500veh/h increase during the day.

Figure 5.

Variation of noise source intensity with traffic volume.

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The variation trend of noise at night and in the daytime at each sensitive point is the same, and the noise at each point is about 5 dB(A) higher during the daytime than at night. The noise increases with the increase in traffic volume, but the increase rate is getting slower. When the traffic volume increases from 500 veh/h to 4000 veh/h, the noise at each point increases by 4–9 dB(A), where the closer the point is to the road, the greater the increase in noise. Regardless of the traffic volume, there are 5 points of daytime noise less than 70 dB(A). The common feature is that they are far away from the road. The remaining 6 points don’t meet the sound environment quality standard when the traffic volume exceeds 2000 veh/h, 2 of them exceed 70 dB(A) regardless of how the traffic volume changes, the common feature of the two points is that they are closer to the road, and the distance of the noise source can be seen on the point. The noise has a great influence on the noise of the point. Regardless of the traffic volume, there are 4 points less than 55 dB(A) for night noise. The road noise at night is more serious than that during the day.

Figure 6.

Variation of predicted daytime (a) and nighttime (b) noise values with traffic volume.

3.4 Analysis of sensitivity of vehicle speed to noise The average speed of each vehicle model during the day (large: 15 km/h, medium: 20 km/h, small: 25 km/h) is used as the reference data for group 1, and it is assumed that the nighttime speed is 10 km/h faster than that in the daytime. The daytime speed increases by 10 km/h to group 7 (large: 75 km/h, medium: 80 km/h, small: 85 km/h). The predicted noise source intensity is shown in Figure 7 and the noise prediction value of each sensitive point is shown in Figure 8. As seen from Figure 7, with the increase in vehicle speed, the noise decreases slowly and then increases rapidly in a straight line. Taking small cars as an example, the noise is the least at an average speed of 45–55 km/h. This is related to the road noise characteristics; when the speed is low (less than 50 km/h), the noise generated by the engine, intake, exhaust, transmission system, and body vibration of the car is the main noise source, and the lower the speed, the higher the natural noise; when the speed is higher (50 km/h–100 km/h), the friction noise between the tires 141

and the road dominates, and the higher the speed, the higher the noise. When the vehicle speed is greater than 100 km/h, the mutual motion of the vehicle body and air in the separation layer causes a strong turbulent field to become the main noise source.

Figure 7.

Variation of source intensity for different vehicle speeds.

As seen from Figure 8, the noise is lowest when the vehicle speed is 45–55 km/h, and the closer the sensitive points are to the road, the greater the noise variation. Regardless of how the vehicle speed changes, the daytime noise at 5 points is below 70 dB(A), and that at 6 points exceeds 70 dB(A) regardless of how the vehicle speed changes. The noise level at 4 points is less than 55 dB(A) at night at all traffic levels.

Figure 8.

Variation of daytime (a) and nighttime (b) noise with vehicle speed.

3.4.1 Analysis of sensitivity of the ratio of small and large models to noise According to different model ratios, the predicted noise source intensity, and the change values of daytime and nighttime noise at each sensitive point are shown in Figures 9 and10. As seen in Figure 9, the variation trend of noise source intensity at night is the same as that of noise source intensity during daytime. With the increase in the proportion of large vehicles, the 142

noise source intensity increases, but the rate of increase becomes slower. For each 10% increase in the proportion of large vehicles, the noise increases by about 2 dB, and all large vehicles are 9 dB louder than all small vehicles.

Figure 9.

Variation of noise source intensity with model ratio.

As seen in Figure 10, the noise at each sensitive point has the same trend as the change in noise source intensity of the road; with the increase in the proportion of large vehicles, the noise becomes larger, but the growth rate becomes slower. All sensitive points are large cars but not small cars when the noise is 6–9 dB greater, where the closer the sensitive point is to the road, the greater the change in noise. Regardless of how the model ratio changes, there are five points with noise less than 70 dB (A) during the day. The noise pollution at night is more serious; the noise level at only 1 point is less than 55 dB (A).

Figure 10. Variation of daytime (a) and nighttime (b) noise value with model ratio.

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4 CONCLUSION Based on the noise monitoring and software prediction simulation of the Xianrenshan Service Area of the Shanghai-Nanjing Highway, this paper analyzes the noise distribution law from spatial and temporal perspectives. It evaluates traffic noise control measures’ sensitivity from three perspectives: traffic flow, vehicle speed, and vehicle ratio. The conclusions are (1) Highway noise varies due to different functional areas, distance, time and traffic flow, speed, car ratio, and other factors. (2) The highway noise and distance function can be approximated as y = −0.0004x2 + 0.0018x + 66.484(R2 = 1). (3) The highway service area is the quietest at 12:00, and it is relatively noisy during 16:00–18:00. (4) When the traffic volume is from 500 veh/h to 4000 veh/h, noise source intensity increases by about 9 dB (A), and the increase with the increase in traffic volume slows down when the traffic volume is from 500 veh/h to 1000 veh/h, with the maximum increase of 3 dB (A). When the traffic volume is more than 2500 veh/h, for every increase of 500 veh/h during the day, the noise source intensity increases by about 0.5 dB (A). Noise source intensity increases by about 0.7 dB(A). (5) The noise is the minimum when the vehicle speed is 45–55 km/h. (6) With the increase in the proportion of large vehicles, the noise source intensity will increase, but the increase becomes slower. (6) When the proportion of large vehicles increases by 10%, the maximum noise increase is 2 dB, and all large vehicles are 9 dB louder than all small vehicles. In summary, this paper realizes a comprehensive analysis of noise monitoring and traffic noise control measures’ sensitivity modeling and evaluation for highway service areas, which provides a scientific guidance method for predicting the comprehensive noise of other similar highway service areas and exploring optimal noise control measures. However, more efforts are needed to achieve comprehensive noise reduction in highway service areas, e.g., controlling traffic demand to regulate traffic flow and thus speed, optimizing the environment for large vehicles to pass, and adopting time-of-day and technical control measures on traffic speed and passage during actual operation.

ACKNOWLEDGMENT The research work was supported by the Opening Project of the National Environmental Protection Engineering and Technology Center for Road Traffic Noise Control (2020-04) and the National Natural Science Foundation of China (Grant No.52078034). The authors are very grateful for the helpful comments of the anonymous reviewers.

REFERENCES Alam P., Ahmed K., Afsar S. (2020). Analysis and evaluation of traffic noise in different zones of Delhi, India SSRN Electron J. Alexander A., El-Aassar A., Macdonald J., et al. (2019). Technical approaches to developing a highway noise programmatic agreement[J]. Transportation Research Record, 2673(1): 102–109. Barry T.M., Reagon J.A. (1978). FHWA highway traffic noise prediction model, FHWA-RD-77. Chebil J., Ghaeb J., Fekih M.A., Habaebi M.H. (2019). Assessment of road traffic noise: A case study in Monastir City. Jordan J. Mech. Ind. Eng. 13(3). Delany M.E., Harland D.G., Hood R.A., Scholes W.E. (1976). The prediction of noise levels L10 due to road traffic. J. Sound Vib. 48(3):305–325. GB/T 17181-1997. Type I, Integral average sound level meter [S]. GB/T 3785-2010. Type I, Electroacoustics sound level meter[S]. Golmohammadi R., Abbaspour M., Nassiri P., Mahjub H. (2007). Road traffic noise model. J. Res. Health Sci. 7(1):13–17. Hamad K., Ali Khalil M., Shanableh A. (2017). Modeling roadway traffic noise in a hot climate using artificial neural networks. Transp. Res. Part D Transp. Environ. 53:161–177.

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Lekshmi S., Nithya K., Priya K.L. (2018). ANN modeling of traffic noise in Quilon-Kochi Highway. IJIRT 4(12) ISSN: 2349–6002. Mann S., Singh G. (2022). Traffic noise monitoring and modeling—an overview[J]. Environmental Science and Pollution Research: 1–12. Ministry of environmental protection of the people’s Republic of China. (2008). GB3096-2008, Acoustic environment quality standard[S]. Acoustic environment quality standard. Ramírez A, Domínguez E. (2013). Modeling urban traffic noise with stochastic and deterministic traffic models. Appl Acoust 74:614–621. Richtlinien für den Lärmschutz an Strassen—RLS 90, Ausgabe1990. Der Bundesminister für Verkehr. Song L.Z., Li Z.Z., Zhang L.T., et al. (2021). Characteristics and prediction of structure-borne noise from urban rail transit bridge-sound barrier system [J]. Journal of Traffic and Transportation Engineering, 21(3): 193–202. World Health Organization (2005). United Nations road safety collabo-ration: a handbook of partner profiles.

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Effects of the installation parameters on the compressive performance of helix stiffened composite piles in soft clay Xiangjun Lin State Grid Lianyungang Power Supply Company, Lianyungang, Jiangsu, China

Wei Jin∗ Lianyungang Zhiyuan Electric Power Design Company, Lianyungang, Jiangsu, China

Hao Qi State Grid Lianyungang Power Supply Company, Lianyungang, Jiangsu, China

Zhenqin Zhang, Wenlong Ding & Chengyu Guo Lianyungang Zhiyuan Electric Power Design Company, Lianyungang, Jiangsu, China

ABSTRACT: The Helix Stiffened Cement Mixing (HSCM) pile is an innovative type of composite pile, and the installed technique can affect the load-bearing performance and bond diameter of the pile. To verify the feasibility of the simultaneous drilling and grouting techniques for HSCM piles in soft clay and to investigate the influence of the installation parameters on the compressive load bearing performance, two sets of model tests were designed in this study, including HSCM piles with the different helix number and drilling speed and comparative helical piles. The test piles were installed in soft clay prepared from kaolinite clay and tested for compressive load-bearing performance and pile geometry to analyze the relationship between the installation parameters of the HSCM piles and the soil-cement column. The test results showed that the simultaneous drilling and grouting techniques were able to form the soil-cement column with the shape of an inverted frustum of a cone around the helical pile, with the average bond diameter of the soil-cement column being approximately 1.17 to 1.36 times the helix diameter. An appropriate increase in the helix number could enhance the integrity and continuity of the soil-cement column by mixing the cement with the soil adequately to improve the installed quality of HSCM piles. Excessive drilling speed could result in inadequate grouted, which reduces the bond diameter and stiffness of the soil-cement column. The compressive ultimate bearing capacity of HSCM piles under the conditions of this paper is 3.83 to 3.93 times that of helical piles. The enlargement of the pile diameter increased the skin resistance. The grouting technique was able to reinforce the soil and increase its strength, thus compensating for the reduction in strength caused by the disturbance of the soil by the helix plate during the rotary process. 1 INSTRUCTION The stiffened composite pile is a kind of composite pile foundation in which rigid piles (precast piles or cast-in-place piles) are reinforced with flexible piles (cement mixing piles) (Wang et al. 2020, Wu et al. 2004). The upper load is transferred to the cement-soil pile body through the pile core and then spreads to the soil around the pile. The cement-soil pile body is used to expand the contact area between pile and soil, thereby improving the bearing capacity of pile foundation (Yu et al. 2022, Zhou et al. 2022), which has been widely used in construction, port, power grid, highway, and railway engineering and other fields. ∗ Corresponding Author:

146

[email protected]

DOI 10.1201/9781003384830-19

The construction of stiffened composite pile usually includes hole forming, mixing grouting, and precast pile stiffening. The construction technology is relatively complex, and its application in construction transformation or rush repair engineering is limited. In order to further improve the bearing capacity and construction efficiency of stiffened composite piles, in recent years, some scholars in China and abroad have adopted special-shaped piles such as spiral piles and bamboo joint piles as pile cores and carried out research (Vickars & Clemence 2000, Zhou et al. 2014, 2013). HSCM pile replaces the traditional rigid pile core with spiral piles and makes use of grouting technology to compensate for the disturbance of soil caused by blades. At the same time, it retains the advantages of the convenient installation of spiral piles, improves the piling process and the interaction of contact surfaces, and improves the construction efficiency and bearing capacity of the stiffened composite pile. The main factors affecting the quality and bearing capacity of the HSCM pile include the design parameters of the screw pile core and the piling process. The grouting process can be divided into pre-grouting, post-grouting, and synchronous grouting. The pre-grouting process is similar to the process of composite stiffened piles. Firstly, the cement-soil mixing pile is used to form holes, and then the screw pile core is screwed to stiffen, which effectively strengthens the screw pile. Srijaroen et al. (2021)used the pre-grouting process to conduct a comparative study on the relationships among the vertical bearing performance, construction efficiency, and construction cost of screw piles, cement mixing piles, and HSCM piles in soft clay. The post-grouting process is to fill the void formed by the screw pile through compaction grouting after the screw pile is installed so that the cement slurry diffuses to fill the void formed by the screw pile and squeezes the soil, and the cement soil is formed after the cement slurry consolidates with the soil (Nabizadeh & Choobbasti 2017). Sakr et al. (2016) formed grouting bubbles in the middle of spiral piles through the postgrouting process and studied the relationship between grouting position and bearing capacity in the sand. Khazaei & Eslami (2017) tested small and medium screw piles in sandy soil using a flat-cut restraint vessel (FCV) before and after grouting. The results show that the bearing capacity of a post-grouting HSCM pile is higher than that of a spiral pile with the same parameters, which is attributed to the improvement of sand friction angle and the increase in the pile shaft size. In the synchronous grouting process, pressure grouting is carried out at the same time of screw pile installation, so as to improve the installation efficiency (Mansour 2019, Zhuang et al. 2021). When Laefer et al. (2005) used the synchronous grouting process to form piles, it was found that the location of the grouting hole would affect the amount of cement slurry. Setting the grouting hole under the blade could save about 20% of cement slurry. Mansour & El Naggar (2021) installed several small HSCM piles in sand using a synchronous grouting process to study the influence of grouting direction and grouting nozzle position on the molding of the soil-cement pile body. Zong et al. (2022) verified the feasibility of HSCM pile synchronous grouting technology through field tests and studied the influence of blade diameter and arrangement on pulling bearing capacity. At present, there are few types of research on the pile-forming test of HSCM piles in soft clay by synchronous grouting process. Since the permeability of cohesive soil is significantly lower than that of sand, it will affect the diffusion of cement slurry, so the pile-forming effect of the synchronous grouting process and the bearing capacity of HSCM piles still need to be studied. Therefore, the scale model test of HSCM piles in soft clay is carried out in this paper. By changing the number of blades and drilling speed of screw piles, the influence of synchronous rotary grouting technology on the pile body and compressive bearing capacity of HSCM piles is studied.

2 TEST OVERVIEW 2.1 Model pile design scheme The model pile used in the test, as shown in Figure 1, involves three different pile types, and the main difference is the number of blades in the same blade segment. The diameter the of central steel tube is DS = 22 mm, and the length of the steel tube LS = 600 mm. The blade diameter is 147

DH = 260 mm, the blade pitch is BH = 10 mm and SHB = 160 mm, and SHB changes with the pile type. The diameter of the grouting hole is 4 mm.

Figure 1.

Conceptual drawing of model piles.

In order to study the influence of synchronous rotary grouting technology on the compressive bearing performance of HSCM piles under different pile formation parameters, two groups of scale model tests were designed, and a total of 8 model piles were selected with different numbers of blades and drilling speeds. Table 1 describes the two groups of test protocols and specific parameters. A standard pile was set as the control group in each group, with the number of blades n = 4, DH = 260 mm, and drilling speed v = 250 mm/min. For the experimental group of the number of blades, two and three-blade model piles were designed as experimental groups. For the drilling speed test group, v = 200 mm/min and v = 300 mm/min constituted the experimental group. Table 1. Test plan of HSCM piles. Test group Blade number

No.

HP-HN-4 HSCM-HN-2 HSCM-HN-3 HSCM-HN-4 Drilling speed HP-DS-250 HSCM-DS-200 HSCM-DS-250 HSCM-DS-300

Number of Blade spacing Drilling rate The way of v (mm/min) pile driving blades N SHU (mm) 4 2 3 4 4

160 480 320 160 160

250 200 250 250 250 200 250 300

Precession – no grouting Synchronous rotary grouting Synchronous rotary grouting Synchronous rotary grouting Precession – no grouting Synchronous rotary grouting Synchronous rotary grouting Synchronous rotary grouting

Numbering rules: pile type-variable-variable value.

2.2 Soil sample preparation and parameters The test was carried out in a model box with dimensions of length (L) × width (W) × height (H) = 1.6 m × 0.6 m × 1.0 m, and the model piles were horizontally arranged along the long edge L, as shown in Figure 2. A drainage system was set up in the model box. A layer of coarse sand was laid at the bottom, and the drainage board was buried in it. After that, geotextile was laid to isolate the soil sample from the coarse sand and ensure the normal drainage and consolidation of the soil sample. The test soil sample was soft kaolin. The prepared soil sample was added to the model box, and the soil parameters were measured after gravity consolidation for 60 days, as shown in Table 2. The 148

Figure 2.

Layout of model piles.

resistance of soil to T-bar is measured by T-bar test, and the undrained shear strength cu of soil can be measured by combining Formula (1), as shown in Figure 3. According to the ratio of cu to effective   vertical stress p (z), ψ = cu /p (z), when ψ is greater than 0.4, it belongs to over-consolidated soil. The ψ of the upper soil in this test is about 1.8, which belongs to overconsolidated soil, but the soil gradually becomes normal consolidated with the increase of depth. cu =

(Ftotal − Frod ) NT AT

(1)

Where, Ftotal : T-type bar resistance, Frod : steel bar resistance, NT : bearing capacity coefficient, set at 10.5 (Gerkus 2016), AT : horizontal projection area of acrylic bar (2320 mm2 ). Table 2. Summary of geotechnical properties of kaolin clay. The proportion of Gs

Moisture content w (%)

Liquid limit WL (%)

Plastic limit WP (%)

The plasticity index IP

The liquid index IL

Severe gamma γ (kN/m3 )

2.8

55–60

78

33

45

0.49–0.6

17.2

2.3 Piling process The piling equipment of the HSCM pile is shown in Figure 4. The equipment consists of three parts: grouting system, rotary pile system, and control system, which can carry out pressure grouting at the same time as the model pile is rotated. The cement slurry is transported to the top of the central steel pipe through the pump machine and grouting pipe and is ejected from the grouting hole, realizing the synchronous rotary grouting process. The grouting pressure can be adjusted by the control system. The rotary pile system is composed of hinges, rotary joints, and servo motors to realize the conversion of mechanical energy to kinetic energy. By adjusting the speed of the servo motor through the control system, the installation torque and downward pressure force can be changed to adjust the drilling speed. The top of the central steel pipe is bolted to the extension to secure the through-hole. 149

Figure 3.

Undrained shear strength of kaolin clay.

The piling process of the HSCM pile is shown in Figure 5, which mainly includes the following steps: (1) connect the model pile to the extension section and align the construction point; (2) add the configured cement slurry to the grouting system, and adjust the drilling speed and grouting pressure; (3) start the grouting equipment and drilling equipment and screw the model pile until it reaches the design depth; (4) stop the installation and carry out in situ rotary spray until the mud emerges from the soil surface; (5) separate the model pile from the extension. A flexible joint is used between the top of the central steel pipe and the extension to ensure that separation will not interfere with the model pile. The test water-cement ratio is 0.5, 0.2% water reducing agent is added to increase the fluidity, and 4% accelerating agent is added to appropriately improve the setting rate of cement slurry.

Figure 4.

Installation machine of model piles.

2.4 Loading scheme In the loading test, the displacement method was used to control the loading, and the moving rate was 1 mm/min, as shown in Figure 6. The motion controller (TC55H-LA) was used to pull the weight, and the load was continuously applied to the loading plate and transferred to the pile top. The test was stopped when the pile top displacement reached 10 mm. Tension and pressure sensors are respectively installed on the upper part of the weight and the top of the pile to ensure the accuracy of the data. When measuring pile top displacement, a displacement sensor (LVDT) should be installed at the lower part of the loading plate. Since the loading plate cannot maintain 150

Figure 5.

Installation procedure of hscm piles.

an absolute level, even slight displacement will lead to large errors, and three LVDT should be set to ensure accurate data.

Figure 6.

Loading tests.

3 RESULTS AND DISCUSSION 3.1 Analysis of pile forming effect After the loading test, all test piles were pulled out, and the bonding diameters DT , DM , DB of each HSCM pile at the buried depths of 0 mm, 300 mm, and 600 mm were measured, and the average bonding diameter DAv = ((DT + DM + DB )/3) was obtained, as shown in Figure 7. The shape of the cement soil pile is shown in Figure 8. According to the measurement results of pile diameter in Figure 7, the size of bond diameter decreases with the increase in buried depth, making the soil-cement pile body an inverted round table. The results show that the shape of the soil-cement pile is influenced by spiral blades and the pile-forming process. In the process of rotary grouting of screw piles, cement slurry and soil are constantly mixed by spiral blades to form cement soil. The upper cement soil is stirred more fully so that the integrity of cement soil pile is better. With the increase in pile side earth pressure and cu , the diameter of hole formation decreases with depth, which is similar to the research results of Wang (2014). The pile diameter measurement results of the experimental group with a certain number of blades are shown in Figure 7 (a). The DAv of HSCM-HN-2, HSCM-HN-3, and HSCM-HN-4 is about 1.311.33 times that of DH . Since the position of pile diameter measurement is close to the spiral blade, 151

Figure 7.

Bond diameters of HSCM piles.

Figure 8.

Test piles after extraction: (a) Helix number test sets, (b) drilling speed test sets.

the DAv of the test pile is relatively close. According to the observation of the cement-soil pile body in Figure 8 (a), HSCM-HN-4 has the best pile quality with high integrity and continuity, while HSCM-HN-2 and HSCM-HN-3 present a threaded distribution on the surface of the pile body, and there is a gap between the threads. The above results show that the integrity of the soil-cement pile is related to the number of spiral blades. When the upper part of the grouting hole lacks spiral blades, the cement and soil cannot be fully mixed, and the cement consolidates along the track of the rotating spiral blades at the bottom, resulting in the gap in the pile body and reducing the integrity and the contact area between the pile and soil. 152

As shown in Figure 8 (a), in the absence of the spiral blade distribution area, the soil-cement mixing effect is poorer, making it difficult to form a cavity and leading to the increase in HSCMHN-3 bond diameter. Suddenly, a mutation point P1 appears, which reduces the continuity of the cement-soil pile. At a close distance to the upper position of spiral vane, a mutation point P2 appears, and the bond diameter increases again at this time. The above results show that the existence of spiral blades will affect the continuity of soil-cement piles. There is no mutation point in the cement-soil pile body of HSCM-HN-2, and its drilling speed v = 200 mm/min is less than the pre-set value (250 mm/min), which makes the grouting amount higher than other test piles, indicating that the grouting amount will also affect the continuity of the cement-soil pile body. The pile diameter measurement results of the drilling velocity test group are shown in Figure 7 (b). The cement slurry dosage of HSCM-DS-250 and HSCM-DS-200 is 2.9 L and 3.2 L, respectively, and their DAv is 1.33 and 1.36 times of DH , respectively. The measurement results are close to each other, indicating that when the grouting amount is appropriate, further reducing the drilling speed (increasing the grouting amount) has little effect on the bond diameter. When the drilling speed is further increased, the amount of grouting will be insufficient, and the cement-soil mixing is not sufficient, which reduces the bond diameter. The DAv of HSCM-DS-300 is 14.3%, being less than that of HSCM-DS-250. Comparing the cross sections of HSCM-DS-250 and HSCM-DS-300 (Figure 9), the whole pile body is composed of three parts: cement, steel pipe, and soil-cement. The soil-cement integrity of HSCM-DS-300 is lower than that of HSCM-DS-250, indicating that the large increase in drilling speed will affect the bond diameter. Comparing the cement-soil pile body of HSCM-HN-3 and HSCM-DS-300, the grouting amount of HSCM-DS-300 is reduced, but the cement-soil pile body is still continuous, indicating that the number of spiral blades will affect the continuity, and the continuity of the cement-soil pile body is affected by the coupling of several factors.

Figure 9.

Bond diameter of HSCM piles.

3.2 Load bearing performance analysis 3.2.1 Parameter analysis The load-displacement curves of test piles in the experimental group of blade number and drilling speed are shown in Figures 10 (a) and (b). The whole loading proceeds in three stages: linear, nonlinear and plastic. Part of the curve in nonlinear stage presents short plastic damage, and then returns to the nonlinear stage, this is because in the forming process of a cement shell layer on the pile soil surface, some of the load is shared during loading until the brittle failure leads to a sudden increase in the displacement of the pile body. As part of the test pile load-displacement curve in the failure stage has no obvious turning point, the ultimate bearing capacity is determined based on the failure to reach such a turning point, and the diameter of the cement-soil test pile diameter changes with depth. The limit bearing capacity 153

Figure 10.

Bond diameters of HSCM piles.

cannot be accurately judged through the sedimentation method (Bayesteh et al. 2021). This article adopts the double tangent method of graphic structures (Wu et al. 2018) to determine the ultimate bearing capacity of the load-displacement curve. The extension of the initial tangent line and the intersection of the line with a slope of 14.3 mm/100N are regarded as the ultimate load of the load-displacement curve, and the results are shown in Table 3. Table 3. Test plan of HSCM piles.

No.

Ultimate compressive bearing capacity Pult (N)

Displacement (mm)

Initial stiffness (N/m)

HP-HN-4 HSCM-HN-2 HSCM-HN-3 HSCM-HN-4 HP-DS-250 HSCM-DS-200 HSCM-DS-250 HSCM-DS-300

141 469 513 540 105 438 413 380

1.03 4.03 6.27 3.38 0.70 3.76 4.84 4.03

2.63 × 104 4.21 × 104 2.88 × 104 3.57 × 104 1.49 × 105 1.51 × 105 3.54 × 104 1.20 × 104

According to the loading test results of the experimental group of the number of blades, Pult of HSCM-HN-4 is 15.14% and 5.26% higher than that of HSCM-HN-2 and HSCM-HN-3, respectively. Reducing the number of blades will lead to the reduction of the pile-soil contact area of 154

the soil-cement pile, which is attributed to the presence of the clearance on the surface of the soil-cement pile. According to the load-displacement curve, the initial stiffness of HSCM-HN-3 is slightly lower than that of HSCM-HN-4, indicating that the number of spiral blades has an impact on the formation of the soil-cement pile. The initial stiffness of HSCM-HN-2 is slightly higher than that of HSCM-HN-4. Due to the large grouting amount of HSCM-HN-2, the elastic modulus of soil-cement test pile is increased and the stiffness of the pile is improved. According to the loading test results of the drilling rate test group, HSCM-DS-200 reaches the highest Pult , which increases by 6.05% and 15.26% compared with that of HSCM-DS-250 and HSCM-DS-300, respectively. Combined with the pile diameter measurement results, although the DAv of HSCM-DS-200 and that of HSCM-DS-250 are close, the difference in DB is about 6.11%, which leads to the relatively low bearing capacity of the end of HSCM-DS-250. According to the load displacement curve, the initial stiffness of HSCM-DS-200 is greater than that of HSCM-DS250. Since the cross-sectional areas of the two are similar, the increase in elastic modulus of the soil-cement pile improves the stiffness.

3.2.2 Comparison of pile forming process The Pult of the HSCM pile is 3.83–3.93 times higher than that of the screw pile under the same pile formation parameters. Combined with the pile diameter measurement results, the synchronous precession grouting process forms a cement-soil column around the screw pile, increases the pile diameter, improves the pile side friction, improves the strength of the reinforced soil, makes up for the blade in the process of precession degradation caused by the disturbance of soil strength, and significantly enhances the compressive bearing capacity of the bored pile. In order to further analyze the influence of the piling process on the bearing capacity of HSCM piles, this paper collects relevant data and compares the test results of domestic and foreign scholars. The ratio of ultimate bearing capacity of the HSCM pile and the screw pile under the same test parameters is taken as the control basis, as shown in Table 4. The comparison results show that the ultimate bearing capacity of the spiral pile is improved by the grouting process to different degrees, and the bearing capacity is greatly improved by post-grouting and synchronous rotary grouting processes, which mainly depends on soil parameters and the forming effect of the cement soil. Due to the differences in the design parameters of each test, including grouting pressure, drilling speed, steel pipe diameter, blade size, blade arrangement, blade number, and grouting hole location, the formation of the diameter of soil-cement pile will be affected, leading to differences in the test results under the same pile formation process. This paper only verifies the feasibility of the synchronous rotary grouting process under a scale test, but the influence of the pile formation process on the soil-cement pile body under different parameters needs to be further studied. Table 4. Comparison of load-bearing performance. Pile processing method

Literature

Ratio of ultimate bearing capacity

Soil

Loading

Prior to grouting Local front grouting After grouting

Srijaroen et al. (2021) Srijaroen et al. (2021) ZHAO0 (2021) Khazaei & Eslami (2017) Vickars & Clemence (2000) Sakr et al. (2016) This paper Zong et al. (2022) Mohajerani et al. (2016)

1.24 1.04–1.21 2.31 2.29 1.51 1.24–1.86 3.83–3.93 2.63 3.00–3.17

Marine soft soil Marine soft soil Silty clay Sandy soil Alluvial soil Sandy soil Soft clay Marine soft soil Sandy soil

Compressive Compressive Compressive Compressive Compressive Pulling Compressive Pulling Compressive

Local post grouting Synchronous rotary grouting

155

3.3 Theoretical calculation In order to further provide a reference for the design method of HSCM piles, Mansour (2021) and Zong (2022) carried out theoretical calculation on the design method of HSCM piles and compared it with the test results in this paper. Equation (2) was used to obtain the calculated bearing capacity Q of HSCM piles, and the results are shown in Table 5. The comparison results show that the deviation between the calculated bearing capacity of HSCM pile and the test value is within 15%. Q = Qshaft + Qbearing = π DAv αcu Ls + Nc DAv αcu

(2)

where: Q is the calculated value of compressive bearing capacity; Qshaft stands for the calculated side friction resistance; Qbearing is the calculated terminal bearing; α is the bonding coefficient, which is taken as 1 in this paper0 (Zong et al. 2022). Nc is the compressive bearing capacity coefficient in clay, which is taken as 9 in this paper (Mohajerani et al. 2016). Table 5. Calculated compressive bearing capacity of HSCM piles. Calculated lateral friction

Calculated terminal

Calculated bearing

No.

resistance Qshaft (N)

bearing force Qbearing (N)

capacity Q (N)

Q − Pult Pult (%)

HSCM-HN-2 HSCM-HN-3 HSCM-HN-4 HSCM-DS-200 HSCM-DS-250 HSCM-DS-300

396 395 401 332 326 286

138 137 142 140 135 104

534 532 543 472 461 390

13.86 3.7 0.56 7.76 11.6 2.63

4 CONCLUSION Through scale model tests, the feasibility of the composite pile forming process with screw pile core strength is verified, and the compressive bearing characteristics of the composite pile with screw pile core strength are analyzed through compressive bearing performance tests and pile body geometry size tests. The conclusions are as follows: 1) Synchronous precession grouting process can form a cement-soil pile body around the screw pile, increase the pile diameter, improve the pile side friction, improve the strength of the reinforced soil, make up for the blade in the process of precession degradation caused by the disturbance of soil strength, and significantly enhance the compressive bearing capacity of the bored pile. 2) Appropriately increasing the number of blades can improve the integrity and continuity of the soil-cement pile body, so as to improve the pile forming quality of composite piles with screw pile core strength. 3) The large increase in drilling speed will lead to insufficient grouting amount, reduce the diameter and stiffness of the soil-cement pile body, and thus reduce the pile forming quality of composite piles with screw pile core strength.

ACKNOWLEDGEMENTS This research is supported by Jiangsu State Grid Science and Technology Project under Grant No. J2021033. 156

REFERENCES Bayesteh H., Fakharnia M.A., Khodaparast M. (2021). Performance of driven grouted micropiles: Full-scale field study. J. International Journal of Geomechanics. 21(2): 04020250. Gerkus H. (2016). Model Experiments to measure yield thresholds and trajectories for plate anchors and develop a new anchor concept. D. United States: The University of Texas at Austin. Khazaei J. & Eslami A. (2017). Postgrouted helical piles behavior through physical modeling by FCV. J. Marine Georesources & Geotechnology, 35(4): 528–537. Laefer D.F., Menninger N.E., Hernandez W.E. (2005). Grouting patterns and possibilities with helical piers. C.//Presented at Underground Construction in Urban Environments: Specialty Seminar, ASCE Metropolitan Section Geotechnical Group and the Geo-Institute of ASCE, May 11-12, 2005, New York City. American Society of Civil Engineering (ASCE). Mansour M.A. (2019). Performance of Pressure Grouted Helical Piles Under Monotonic Axial and Lateral Loading. D. Mansour M.A. & El Naggar M.H. (2021). Optimization of grouting method and axial performance of pressure grouted helical piles. J. Canadian Geotechnical Journal, 59(5): 702–714. Mohajerani A., Bosnjak D., Bromwich D. (2016). Analysis and design methods of screw piles: A review. J. Soils and Foundations, 56(1): 115–128. Nabizadeh F. & Choobbasti A.J. (2017). Field study of capacity helical piles in sand and silty clay. J. Transportation Infrastructure Geotechnology, 4(1): 3–17. Nabizadeh F. & Choobbasti A.J. (2017). The performance of grouted and un-grouted helical piles in sand. J. International Journal of Geotechnical Engineering, 13(6): 516–524. Sakr M.A., Nazir A.K., Azzam W.R., et al. (2016). Behavior of grouted single screw piles under inclined tensile loads in sand. J. Electronic Journal of Geotechnical Engineering, 21(2): 571–592. Srijaroen C., Hoy M., Horpibulsuk S., et al. (2021). Soil–Cement Screw Pile: Alternative Pile for Low- and Medium-Rise Buildings in Soft Bangkok Clay J. Journal of Construction Engineering and Management, 147(2): 04020173. Vickars R.A. & Clemence S.P. (2000). Performance of helical piles with grouted shafts. M//New technological and design developments in deep foundations. 327–341. Wang J., Zhu Z.H., Wang H.Y., et al. (2020). Numerical analysis on lateral bearing capacity of stiffened deep cement mixing piles in clay. J. Journal of Railway Science and Engineering, 17(6): 1382–1389. Wang Z.-F., Shen S.-L., HO C.-E., et al. (2014). Jet grouting for mitigation of installation disturbance[J]. Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 167(6): 526–536. Wu D., Liu H.-L., Kong G.-Q., et al. (2018). Displacement response of an energy pile in saturated clay. J. Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 171(4): 285–294. Wu D., Liu H.-L., Kong G.-Q., et al. (2004). A study on load transfer mechanism of stiffened DCM pile. J. Chinese Journal of Geotechnical Engineering, (3): 432–434. Yu J.L., Xu J.C., Zhou J.J., Gong X.N. (2022). Experimental study on frictional capacity of concrete-cemented soil interface of concrete-cored cemented soil column J/OL. China Civil Engineering Journal: 1–13. DOI:10.15951/j.tmgcxb.21121264. Zhao Y. (2021). Experimental study and design method of compressive bearing capacity of grouting helical pile. D. Jinan: Shandong University. Zhou J.J., Wang K.H., Gong X.N., et al. (2014). Bearing capacity and load transfer mechanism of static drill rooted nodular piles. J. Rock and Soil Mechanics, 35(5): 1367–1376. Zhou J.-J., Wang K.-H., Gong X.-N., et al. (2013). Bearing capacity and load transfer mechanism of a static drill rooted nodular pile in soft soil areas. J. Journal of Zhejiang University Science A, 14(10): 705–719. Zhou M., Li Z., Han Y., et al. (2022). Experimental study on the vertical bearing capacity of stiffened deep cement mixing piles. J. International Journal of Geomechanics, 22(5): 04022043. Zhuang X.X., Zong Z.L., Huang Y.H., et al. (2021). Experimental study on the uplift performance of pressure grouted helical pile with GFRP casing in marine soft clay. J. Journal of Jiangsu Ocean University (Natural Science Edition), 30(4): 55–59 Zong Z.L., Zhuang X.X., Huang Y.H., et al. (2022). Experimental study on uplift capacity of pressure grouted helical piles. J. The Ocean Engineering, 40(1): 160–166.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Simulation analysis of waterlogging in mountain city Xinke Liu*, Shouping Zhang*, Wanting Bao*, Yifan Zhou* & Qian Gao* Chongqing Jiaotong University, Chongqing, China

ABSTRACT: This paper takes Jiefangbei Street in Yuzhong District of Chongqing City as the study area to simulate the stormwater process in different return periods. The SWMM model was constructed by two sub-catchment area division methods: iso-current method and Theissen polygon method. The main results are as follows: The sub-catchment area divided by the iso-current method can correct the error caused by the Theissen polygon method, and the accuracy of the model and the simulation results are improved to a certain extent. Surcharge and flooding will occur in the overall pipe network in the study area, but most of the duration is relatively short. The overall ability to prevent waterlogging is good. The results of this paper can provide guidance for the reconstruction of the underground pipe network in the study area.

1 INTRODUCTION With the accelerated global climate changes and urbanization, urban waterlogging has become a new “urban disease” (Wang et al. 2021). With the high development of urbanization, the confluence process of urban floods is accelerated, the confluence time is shorter, and the process of urban floods is faster and fiercer (Anni et al. 2020; Zhang et al. 2016). Therefore, the effective simulation of the urban rain flood process has become one of the research hotspots in hydrology. SWMM is a dynamic rainfall-runoff simulation model, which is mainly used to calculate the runoff volume and water quality in urban areas. The SWMM model has been widely used in the urban hydrological simulation (Hou et al. 2019). In the process of SWMM model construction, it is an important step to delimit the sub-catchment area, and different partitioning methods will affect the simulation results to a certain extent (Lei et al. 2010; Liang et al. 2019; Qin et al. 2016). In practical research, the sub-catchment division method should be selected based on the characteristics of the study area (Xiang et al. 2020). The study area in this paper is located in the mountainous city—Chongqing, where the ground elevation difference is large, the confluence speed is fast, and the time for rainwater to reach the drainage outlet is different. However, the total flow in the confluence model is calculated by the product of the runoff per unit area and the area, which leads to a higher calculated runoff than the actual flow reaching the drainage outlet (Li 2021). Therefore, the iso-flow time method and Theissen polygon method were combined to draw the molecular catchment area to solve the problem of the large gap in the catchment time. At the same time, the Tyson polygon method was directly used to draw the molecular catchment area to establish the comparison group model, and the simulation results of the two groups of models were compared and analyzed. And the performance of nodes and the pipe network in the study area under heavy rain in different return periods was explored.

∗ Corresponding Authors: [email protected], [email protected], [email protected], [email protected] and [email protected]

158

DOI 10.1201/9781003384830-20

2 MODEL BUILDING 2.1 Visual part 2.1.1 Nodes and conduit network The node and conduit network data obtained from relevant departments were simplified, and finally, 1234 conduits and 1128 nodes were obtained, including 7 outlets, all of which were free flow without gates. At the same time, all the data of the conduit network in the study area were obtained and distributed in the model. 2.1.2 Sub-catchment area The iso-current method and Thiessen polygon method are combined to draw the sub-catchment area. The specific division steps of the sub-catchment area are as follows: (1) Calculation of net rain flow time τ of grids Formula (1) is used to calculate the net rain flow time τ of grids one by one. τ=

l a · Sib

(1)

where l is the route length of surface water flowing through the grid. Si is the slope in the direction of the outflow of certain water. a is a parameter with a dimension of velocity. b is a power function parameter, reflecting the impact of the slope size on the flow rate. When b = 0, the flow velocity is evenly distributed in the whole watershed and has nothing to do with the slope. (2) Calculation of confluence time t of grids According to the grid computing elevation from the low to high order. For the first grid, the runoff flow time τ1 is the confluence time t1 . The grid is the outlet of the watershed. For the ith grid, the confluence time tj of grid j with the lowest elevation among the 8 surrounding grids has been calculated. The confluence time ti of the ith grid can be calculated by adding tj to the net rain flow time τj of the i (th) grid. (3) Sub-catchment area division The equal flow time surface can be obtained by combining the same grid set. The sub-catchment area is delimited by the Thiessen polygon method with rainwater well as the node inside the constant flow time surface. Then, the confluence time in the same sub-catchment area is relatively consistent. The sub-catchment area corresponds to the rainwater well one by one, and the runoff in the sub-catchment area enters the underground pipe network via the rainwater well. A total of 1128 sub-catchment areas are drawn, and each sub-catchment area corresponds to a rainwater wellhead. After the sub-catchment area division is completed, data such as area, impervious area ratio, and characteristic width of each sub-catchment area are also distributed in the model. The isochrones model is displayed in Figure 1. 2.2 Non-visual part 2.2.1 Precipitation According to the rainstorm formula for Yuzhong District of Chongqing published by Chongqing Urban and Rural Development Commission, the formula is as follows: q=

1132 (1 + 0.958 lg P) (t + 5.408)0.595

(2)

where q is the rainstorm intensity, L/(s·hm2 ); P is the design recurrence period, years; t is the rainstorm duration, min. The Chicago rain pattern is used to generate the rainfall history with 1, 2, 5, 20, and 50 years of return. The duration of the rainstorm is all 120 min, and the peak ratio is 0.45. The rainstorm process line is shown in Figure 2: 159

Figure 1.

SWMM model of isochrones method.

Figure 2.

Rainstorm process lines at different return periods.

2.2.2 Land use The urbanization degree of the study area is very high, and the underlying surface has been almost all hardened. The land use is divided into four types: green space, road, roof, and hardened pavement. As the study area is highly urbanized, the green space area is relatively small. Roads, roofs, and hardened surfaces in the study area are considered impervious.

3 RESULTS ANALYSIS 3.1 Result comparison between the two groups The continuity errors of the two groups of models are between 1.1% and 2.1%, which meets the accuracy requirements of the model. In the same return period, the precision of simulation results can be improved. With the decrease in the rainstorm return period, the iso-current method can improve the accuracy of the model better. The results show that the model of the sub-catchment area using the iso-current method meets the accuracy requirement and can be used in the simulation of storm floods in mountainous cities. In the same return period, the peak runoff of the model is slightly smaller than that of the comparison group. The error of the Theissen polygon method can be corrected. 160

Using the iso-current method to delineate the sub-catchment area can reduce the overflow ratio of nodes and conduits in the simulation results to a certain extent. The overflow simulation of nodes and conduits can provide a basis for the design and modification of the system. Reducing the overflow ratio can avoid paying too much attention to less problematic conduits. The continuity error of calculation is listed in Table 1. Table 1. Continuity error of calculation. Return period (year) 1 2 5 20 50

Model

Continuity error of calculation (%)

Peak runoff (m3 /s)

Reduction proportion of node surcharge (%)

Reduction proportion of conduit surcharge (%)

Isochronous model Comparison model Isochronous model Comparison model Isochronous model Comparison model Isochronous model Comparison model Isochronous model Comparison model

1.988 2.022 1.799 1.804 1.499 1.517 1.246 1.246 1.13 1.132

48.9 48.97 63.26 63.34 82.25 82.33 110.98 111.07 129.96 130.06

0.57

0.32

1.38

0.73

0.81

0.81

0.73

0.81

0.41

0.65

3.2 Analysis of iso-current model results 3.2.1 Node surcharge situation With the increase in the return period, the proportion of surcharge nodes increases gradually. Most overflows subside within 30 minutes, but 10–20% of the nodes are overflowed for longer than an hour. The depth of node surcharge increases with the increase in the return period. The nodes with long surcharge time and large surcharge depths can be adjusted in the subsequent project to reduce the occurrence of urban waterlogging. The proportion of conduit section surcharge is higher than that of node surcharge, exceeding 50% in the return period of one year, and gradually increases with the increase in the return period. However, most of the surcharge situations can be alleviated within 30 minutes, and 5%–10% of the water level of the conduit can be maintained for 30 minutes to more than an hour above the normal full flow of the conduit. Between 2% and 8% of the conduits, the capacity constraints range from 30 minutes to more than an hour. If the conduits in the study area are modified, this part of the conduits can be reconstructed preferentially. The node and conduit surcharge situation is listed in Table 2. Table 2. Node and conduit surcharge situation.

Return period (year)

Number of surcharge nodes

Number of nodes with surcharge time greater than 1 h

1a 2a 5a 20a 50a

515 610 731 831 889

153 183 216 259 280

Average depth of the node surcharge (m) 0.92 0.95 0.95 1.01 1.03

Number of surcharge conduits

Number of conduits with a water level higher than normal full flow and time greater than 1 h

Number of conduits with capacity constraints greater than 1 h

668 755 866 956 1005

72 83 102 110 120

28 35 46 50 52

161

3.2.2 Node flooding situation Compared with the proportion of node surcharge, the proportion of node flooding is decreased greatly. According to the return period from small to large, the proportion of node flooding is 18.35%, 22.7%, 29.08%, 37.94%, and 42.73%, and gradually increases. With a return period of 1 year, about 1.68% of nodes will have flooding for more than one hour, and with a return period of 50 years, this proportion will increase to 3.9%. The flooding of nodes is relatively good, which will not cause great losses to urban life and the economy. The node flooding situation is listed in Table 3. Table 3. Node flooding situation. Return period (year)

Number of flooding nodes

Proportion of flooding nodes (%)

Number of nodes with flooding time longer than 30 min

Number of nodes with flooding time longer than 1 h

Average total water accumulation volume (103 m3 )

1 2 5 20 50

207 256 328 428 482

18.35 22.70 29.08 37.94 42.73

29 37 43 54 61

19 21 29 39 44

0.123 0.147 0.165 0.188 0.203

4 CONCLUSIONS In this paper, the waterlogging simulation analysis of a mountainous city is performed, and the isochrones method of the sub-catchment area is applied to establish the SWMM model. At the same time, the Thiessen polygon method is directly used to establish the comparison group model, the same rainfall data is used for the simulation, and the possible waterlogging situation in the study area under different return periods is explored. The main conclusions are as follows: (1) The isocurrent time method is used to delineate the sub-catchment area so that the time of surface runoff reaching the outlet of the basin in the same catchment area is basically the same. To a certain extent, the model accuracy is improved, the peak flow of simulated runoffs is reduced, and the surcharge of nodes and conduits is reduced, proving that it is reasonable to divide the sub-catchment area by using the iso-current method, and the error caused by the Thiessen polygon method can be corrected so that the confluence process calculated by the model is more consistent with the actual confluence law. (2) The surcharge and flooding accumulation of nodes and conduits in the study area increases with the increase in the rainfall return period, and the overall situation is not serious. However, in the event of rainfall with a long return period, urban waterlogging may occur, but the area with a long time of waterlogging will be less subjected to waterlogging. If it is necessary to replan the underground pipe network in the study area to enhance its drainage capacity, the results of this study can be taken for reference.

REFERENCES Hossain Anni, A. & S. Cohen, et al. (2020). “Sensitivity of urban flood simulations to stormwater infrastructure and soil infiltration”. Journal of Hydrology (Amsterdam) 588: 125028. Hou J.M. & Li D.L., et al. (2019). Effects of initial conditions of LID measures on runoff control at residential community scale [J]. Advances in Water Science, 30(01):45–55. Lei X.H. & TianY., et al. (2010). General catchment delineation method and its application into the middle route project of china’s south-to-north water diversion [J]. Transactions (Hong Kong Institution of Engineers), 2010,17(2):27–33. Li D.S. & Xu L.J., et al. (2021). Catchment division method and flooding simulation analysis of mountainous and Hilly cities [J]. China Water & Wastewater, 37(01):109–113.

162

Liang X.G & Wu Z.G, et al. (2019). Influence of subcatchment partitioning on SWMM’s low impact development simulation [J]. China Water & Wastewater, 35(06):1–5. Qin P. & Lei K., et al. (2016). Impact of sub-catchment size delineation on urban non-point source pollution simulation using SWMM [J]. Environmental Science & Technology, 39(06): 179–186. Wang, H. & Mei, C., et al. (2021) Current status and prospects of the treatment of urban water-related problems in China [J]. China Water Resources, (14):4–7. Xiang N. & Li L.W., et al. (2020). Research on the influence of watershed division method on hydrological simulation results based on model analysis [J]. China Rural Water and Hydropower, (04):87–91. Zhang J.Y & Wang, Y.T, et al. (2016). Discussion on the urban flood and waterlogging and causes analysis in China [J]. Advances in Water Science, 27(04):485–491. Zhang Y. Control of urban waterlogging should have a broad pattern [N]. China Ocean News.

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Treatment technology and effect analysis of highway tunnel collapse in rich-water and soft surrounding rock Jing Xiao*, Dejie Li*, Weisheng Rao*, Xutao Zeng* & Juntao Zhu* CCCC Second Harbor Engineering Co., Ltd, Wuhan, Hubei, China

ABSTRACT: To solve a series of problems such as poor self-stability of surrounding rock, construction difficulties and high risk of treatment after the collapse of tunnels in water-rich and soft strata, ensure safe and rapid passage through the collapse section, and avoid secondary collapse, taking the Dongfengshan Tunnel under construction on Fuzhou National Highway G316 as the background, this paper analyzes the causes of the tunnel collapse, and puts forward targeted collapse treatment measures, and analyzes the treatment effect combined with numerical simulation and field monitoring data. The analysis results show that the tunnel collapse is the result of multiple factors. The main reason is that the water rich in sandy strongly weathered strata intensifies softening and reduces the strength of the surrounding rock. The weak initial support parameters of the tunnel, the poor construction quality of the middle pipe shed and the lack of attention to the monitoring and measurement data aggravate the occurrence of tunnel collapse. Combined with the actual situation of the collapse section, the comprehensive treatment technology of sandbag backfills + temporary support reinforcement, surface grouting and backfill treatment + small pipe radial grouting, large pipe shed + locking anchor pipe in the tunnel can safely pass through the collapse area.

1 INTRODUCTION With the increasing scale of tunnel construction in China, highway and railway tunnels gradually develop into mountainous areas with complex geological conditions. Due to the influence of various factors, such as geological factors, hydrological and meteorological factors, design support parameters, and construction factors, tunnel collapse accidents occur from time to time, endangering the life safety of construction personnel, and delaying the construction period, resulting in huge economic losses. Therefore, the proposed targeted collapse prevention and treatment measures are directly related to the safety of tunnel construction. Tian et al. (2020) summarized various treatment measures in tunnel construction and analyzed the safety of tunnel structures combined with a numerical simulation method. Gao (2016) took grade IV surrounding rock tunnel as the research object and evaluated the safety of primary support structure in the process of landslide treatment by numerical simulation. Yang et al. (2020) relying on the Shenzhen Outer Ring Expressway Tunnel, proposed a comprehensive treatment scheme of sandbag backfill, small pipe radial grouting, tunnel face grouting and concrete arch protection at the bottom of the collapse given the collapse accident at the entrance section. Shu et al. (2017) used the method of field measurement and statistical analysis to analyze the causes of tunnel collapse caused by middle bench excavation. Xu et al. (2021) studied the characteristics and evolution law of tunnel collapse by a similar model test based on the soil-sand interbedded tunnel. ∗ Corresponding Authors: [email protected], [email protected], [email protected], 806176479 @qq.com and [email protected]

164

DOI 10.1201/9781003384830-21

The above studies on highway tunnel collapse are mostly concentrated on the mechanism of collapse or the treatment measures of collapse. Based on analyzing the causes of the tunnel collapse, targeted treatment measures are put forward. Finally, there are few studies on evaluating the effect of collapse treatment through numerical simulation and field monitoring. Therefore, this paper takes the Dongfengshan Tunnel under construction on National Highway G316 as the engineering background, analyzes the mechanism of the water-rich soft rock tunnel collapse, puts forward the comprehensive treatment technology of tunnel collapse, and evaluates the treatment effect by combining numerical simulation and field monitoring.

2 RESEARCH BACKGROUND The Dongfengshan Tunnel entrance is located in the Changle District of Fuzhou City, which crosses Dongfengshan underneath. Double-hole bidirectional eight-lane main road tunnel is arranged in the middle, and a double-hole bidirectional four-lane auxiliary road tunnel is arranged on both sides, belonging to a separate small spacing tunnel. The minimum spacing between the left auxiliary tunnel and the left main tunnel is only 12.9 m, as shown in Figure 1. The total length of the main road tunnel is 4048.5 m, according to the first-grade highway and urban expressway standard construction and the design speed is 80 km/h. The total length of the auxiliary road tunnel is 4,093 m, according to the second-grade highway and urban secondary trunk standard construction and the design speed is 40 km/h. The maximum excavation span of the main tunnel is 20.22 m, and the maximum excavation height is 13.81 m. The maximum excavation span of the auxiliary tunnel is 12.18 m, and the maximum excavation height is 10.03 m. According to the geological mapping and drilling data, the geological conditions of the shallow buried section are complex. The surrounding rock of the tunnel portal section is mainly composed of slope silty clay, residual clay, fully weathered granite and sandy strongly weathered granite. The structure is relatively loose and the strength is low.

Figure 1.

Site layout of Dongfengshan tunnel.

3 OVERVIEW OF TUNNEL COLLAPSE Due to the unique engineering characteristics of fully weathered granite and sandy strongly weathered granite strata, engineering disasters such as deformation and cracking of primary support, the collapse of tunnel face, intrusion of primary support and surface cracks occur frequently during tunnel construction. Collapse description: when the left auxiliary tunnel of the tunnel was excavated to FZK6 + 217.1 by the three-step reserved core soil + temporary inverted arch excavation method on December 30, 2020, due to the increase of water content in the stratum, the working face slipped, and the core soil was extruded outward by about 5 m, as shown in Figure 2. The maximum settlement of the tunnel is 1.3 m, the circumferential cracks appear in the initial support, and the arch frame is distorted. 165

Figure 2. Core soil extrusion and initial support distortion.

Figure 3.

Cracks on the ground.

Large-scale cracks occurred on the ground and the surface subsidence is about 20 cm∼100 cm, as shown in Figure 3.

4 TUNNEL COLLAPSE TREATMENT PLAN 4.1 Cause of collapse After the collapse of the tunnel, by comparing the design drawings, observing the surrounding rock and the mountain on the top of the cave, and checking the construction records, it is believed that the reasons for the collapse mainly include the following three aspects. 1) Construction factors. On the one hand, it includes the construction quality of the middle pipe shed. In the first cycle of the left auxiliary tunnel, the pipe shed construction pile number is FZK6+200.9, the length is 12 m, and 89 (wall thickness 5 mm) seamless steel pipe is used. Due to the sudden collapse of the tunnel, the reserved deformation amount was not enlarged in advance when the steel frame was erected, so the first circulation pipe shed was not set with a pipe shed studio, resulting in a large setting angle. In addition, when erecting several steel frames near the working surface of the pipe shed, the pipe shed needs to be cut to ensure the reserved deformation, which leads to the weakening of the scaffolding effect of the pipe shed. In addition, the grouting effect is poor and does not reinforce the surrounding soil. On the other hand, monitoring data is not valued. Before the tunnel collapsed, the vault settlement data was abnormal, and the construction workers had no strong safety awareness, so they continued to excavate the tunnel face without taking effective control measures. 2) Design factors. Due to the incomplete geological survey work in the early stage and the lack of a thorough understanding of the surrounding rock properties and geological conditions, the strength of the I20b steel arch frame used in the design is weak, resulting in the deformation and distortion of the I-beam, resulting in a large settlement. 3) Geological factors. The sandy strongly weathered granite stratum is a typical mechanically unstable stratum with a loose structure, and poor self-stabilizing ability after excavation, and it is easily softened in contact with water and becomes slimy. Due to the aggravation of water-rich strata in the collapsed section, if the support is not carried out in time, the water accumulation in the arch foot is neglected or the construction quality is not paid attention to during the construction process, large deformation or even collapse is likely to occur. 4.2 Landslide treatment The overall treatment plan for this landslide is as follows: the core soil is backfilled with sandbags, and reinforced with diagonal bracing and vertical bracing; a water intercepting ditch is set on the surface, and surface cracks are grouted and backfilled; the large deformation section and pipe shed studio expansion section are reinforced by small pipe radial grouting to increase the stability of surrounding rock; the large pipe shed guard arch and the studio are constructed, and then the large 166

pipe shed is built in the hole; the arch frame of the large deformation section is replaced. And the locking anchor pipe is added; the excavation of the tunnel body is restored, and the second lining will be constructed after the conditions are met. The specific implementation process is as follows. 1) Backfill back pressure and temporary support Sandbags are used to backfill the upper and middle steps. Due to the extrusion displacement of the face, the sandbags and the vault are not closely attached. C25 concrete is used to spray and compact the gaps. And make 89 mm locking foot anchor pipe grouting on the left and right sides of the arch of each arch frame. 2) Surface cracks and collapse treatment The intercepting ditch is set up around 6 m from the surface subsidence area, and the damaged drainage system is restored; grouting the cracks with cement slurry, and filling the cracks tightly. To protect the surface vegetation, the slurry is stopped when it reaches 6 m below the surface, and the remaining cracks are manually compacted with backfill. The subsidence area is backfilled with loess, and the backfill is about 20 cm higher than the surrounding surface. 3) Grouting reinforcement of small pipes in large deformation sections The deformation section and the excavation section of the large pipe shed studio are reinforced by radial grouting with 42 (wall thickness 4 mm) small conduits, the small conduits are 5 m long, the circumferential spacing is 1m, and the longitudinal spacing is 1.2 m. The surrounding soil is consolidated. 4) Construction of large pipe shed The original middle pipe shed could not solve the problem of large deformation of the tunnel, and then it was converted to a large pipe shed for support, as shown in Figure 4. First of all, it is necessary to carry out earthwork backfilling in front of the large deformation section, and build a pipe shed construction platform. The supporting parameters of the large pipe shed are shown in Table 1 below. The large pipe shed adopts two types of steel pipes of 4 m and 6 m, and the steel pipes are connected by a thread. The pipe shed grouting slurry adopts cement slurry, and the water-cement ratio is 0.8:1∼1:1. According to the field grouting test, the grouting pressure is controlled at 1MPa.

Figure 4.

Field support effect of large pipe shed.

Table 1. Design support parameters of large pipe shed. Pipe shed 108 mm×6 mm hot finished seamless steel pipe

Section length

Length

Circumferential spacing

Extrapolation angle

Number of circumferential arrangement roots

4 m, 6 m

30 m

30 cm

1∼3◦

54

5) Temporary support removal and arch replacement in large deformation section After the grouting of the large pipe shed is completed, the temporary steel support of the large deformation section shall be removed, and the arch frame of the initial support encroachment shall 167

be removed and replaced to ensure the thickness and construction quality of the secondary lining. In addition, the arch-changing section is constructed by the upper and lower steps method, and the initial support steel frame is changed from I20b to I25b to ensure the safety of force; the advanced support adopts 42 (wall thickness 4 mm) small conduit, 3.5 m in length and 0.3 m in circumferential spacing, the longitudinal spacing is 2.4 m, and the extrapolation angle is 10◦ ∼13◦ . At the same time, a 89 mm locking foot anchor pipe is set at the arch foot of each arch frame, the length is 5 m, and the deformation is controlled. 5 EFFECT ANALYSIS 5.1 Numerical simulation analysis Using computational simulation software, a three-dimensional tunnel model is established to analyze the deformation and stress characteristics of the tunnel during the construction process after landslide treatment, to evaluate the effect of landslide treatment. 5.1.1 Model building According to the actual geological conditions of the Dongfengshan Tunnel, a calculation model is established. To reduce the influence of the boundary, the two sides and bottom of the model are 4 times the diameter of the hole, and the size of the entire model is 114 m × 50 m × 79 m (length × width × height), as shown in Figure 5, only gravity is considered in the calculation. Using fixed boundary conditions, the left and right sides of the model are constrained by horizontal displacement, the bottom is constrained by vertical displacement, the surface is a free boundary, and the Mohr-Coulomb model is used as the constitutive model. The surrounding rock and supporting structure are simulated with solid elements. The calculation excavation method is the upper and lower step method.

Figure 5.

Overall model diagram.

5.1.2 Material parameter selection To simplify the calculation, the effect of the leading large pipe shed is equivalent to a 0.5 m supporting structure, and the effect of the small pipe grouting is equivalent to the strengthening of the physical and mechanical parameters of the surrounding soil. In addition, the elastic modulus of the steel arch is incorporated into the shotcrete according to the principle of equivalent bending stiffness. The surrounding rocks of the calculation model are silty clay on the slope, fully weathered granite and sandy strongly weathered granite from top to bottom. The numerical calculation parameters are shown in Table 2. 5.1.3 Analysis of numerical results To eliminate the influence of boundary conditions, the middle section of the model is selected for analysis. 1) Initial support stress After the calculation is completed, the minimum principal stress nephogram, the maximum principal stress nephogram and the maximum shear stress nephogram of the initial support are shown in Figures 6–7. 168

Table 2. Calculation parameters of surrounding rock and supporting structure. Category

Elastic modulus/MPa

Poisson ratio

Internal friction angle/◦

Cohesion/ kPa

Density/ kg/m3

Diluvial silty clay Completely decomposed granite Sandy strongly weathered granite Pipe shed reinforcement area Initial support

3.65 40 70 28000 31000

0.45 0.45 0.34 0.2 0.2

17 25 35

25.1 25 35

/

/

1660 1900 2000 2400 2500

Figure 6. Minimum principal stress nephogram of primary support (Pa).

Figure 7. Maximum principal stress nephogram of primary support (Pa).

Figure 8. Vertical displacement nephogram of surrounding rock (m).

Figure 9. Horizontal displacement nephogram of surrounding rock (m).

A negative minimum principal stress indicates compressive stress, and a positive maximum principal stress indicates tensile stress. It can be seen from the figure that the initial support structure has stress concentration on the left and right sides of the arch and wall feet. The maximum compressive stress is 3.91 MPa, which does not exceed the design value of compressive strength of C25 shotcrete (13.5 MPa), and the maximum tensile stress is 0.97 MPa, which does not exceed the design value of tensile strength of C25 shotcrete (1.3 MPa). This shows that the initial support is not damaged after the treatment measures are adopted, and the stress is safe. 2) Tunnel deformation law After the calculation is completed, the vertical displacement nephogram and the horizontal displacement nephogram of the surrounding rock are shown in Figure 8 and Figure 9 respectively. It can be seen from the figure that the change trends of the vault subsidence and the surrounding convergence are basically the same. Before the tunnel excavation reaches the monitoring section, the deformation of the surrounding rock is small, and then gradually increases. Finally, the deformation tends to be stable because the entire section is closed into a ring. The final cumulative settlement of the vault is 22.8 mm, and the peripheral convergence value is 26.7 mm. 5.2 Field monitoring data analysis After the tunnel collapse is treated, monitoring is carried out according to a section of 5 m. To accurately analyze the treatment effect of landslide, the typical section FZK6+205 was selected for analysis, and the change curve of monitoring point deformation and time is shown in Figure 10. 169

It can be seen from Figure 10 that the vault settlement and the surrounding convergence of section FZK6+205 begin to converge and tend to be stable within 20 days. Finally, the maximum vault settlement is 31.5 mm and the maximum surrounding convergence is 23.4 mm, both of which are basically consistent with the numerical calculation results, indicating that the landslide treatment technology adopted by the Dongfengshan Tunnel has a good effect.

Figure 10. The curve of deformation—time variation of monitoring points.

6 CONCLUSION Aiming at the Dongfengshan Tunnel, this paper analyzes the causes and mechanisms of the tunnel collapse, and on this basis puts forward a comprehensive treatment technology for the collapse of the tunnel passing through the water-rich sandy and strongly weathered granite section. Finally, according to the numerical simulation and monitoring measurement data, the treatment effect is evaluated. The main conclusions are as follows. 1) The main reason for the collapse of this tunnel is that the surrounding rock of the collapsed section is water-rich sandy soil-like strongly weathered granite. Due to the intensified water-rich stratum, the surrounding rock is further softened and the strength of the surrounding rock is reduced. In addition, the initial support parameters of the tunnel are weak, and the poor construction quality of the middle pipe shed and the lack of attention to monitoring measurement data aggravated the occurrence of tunnel collapse. 2) Based on the analysis of the causes of collapse, the comprehensive treatment technology of sandbag backfills + temporary support reinforcement, surface grouting and backfill treatment + small pipe radial grouting, large pipe shed + locking anchor pipe in the cave is proposed. According to the numerical simulation and field monitoring data, the application effect of comprehensive treatment technology is obvious, which can provide a scientific basis for the design and construction of similar water-rich sandy stratum tunnels.

REFERENCES Gao H.T. (2016). Safety evaluation of primary support structure during collapse treating of a large cross-section railway tunnel. Tunnel Construction, 36(06): 756–761. Shu D.L., Yang J.M. and Zhu L.C. (2017). A study of deformation law of tunnel surrounding rock and primary support in xigeda formation. Tunnel Construction, 37(12): 1544–1549. Tian Z.Y., Tian S.Z., Yang F., et al. (2020). Engineering measures and safety evaluation of baizhang tunnel passing through flow plastic water-rich fracture zone. Modern Tunnelling Technology, 57(02): 176–183. Xu H.Y., Wang Z.J., Chen C.J., et al. (2021). Model tests on characteristics and evolution of tunnel collapse in soil-sand interbedded strata. Chinese Journal of Geotechnical Engineering, 43(06): 1050–1058. Yang L., Jiang H., Chen P.S., et al. (2020). Treatment measures for collapses of the shallow-buried highway tunnel with large cross-section and its effects analysis. Modern Tunnelling Technology, 57(06): 207–213.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Influences of sluice foundation pit excavation based on monitoring and numerical analysis Xiaodong Fan Haining Water Conservancy Construction Management Co., Ltd, Haining, Zhejiang, China

Yingfang Ge Zhejiang Water Conservancy and Hydropower Engineering Quality and Safety Management Center, Hangzhou, Zhejiang, China

Zhen Zhang* Zhejiang Guangchuan Engineering Consulting Co. Ltd. Hangzhou, Zhejiang, China

ABSTRACT: Taking the foundation pit of Luotang River East Gate Station as the research object, the enclosure structure of the foundation pit adopts two rows of C30 bored cast-in-place piles + C30 pressure top beam and cap beam, and the water-stop curtain adopts a single row of threeaxis cement mixing piles. Through the on-site monitoring and numerical simulation analysis, the impact on the surrounding environment during the excavation process of the foundation pit is studied, and the settlement and the deep layer horizontal displacement are mainly analyzed during the excavation process. The numerical simulation results are very close to the field monitoring results. The excavation of the foundation pit with this enclosure structure has little impact on the surrounding environment. Before construction, the finite element software can be used to simulate and verify the excavation process of the foundation pit. 1 INSTRUCTIONS With the mature development of the relevant theory of foundation pit engineering, the analysis of the impact of deep foundation pit excavation on the surrounding area has become the focus of research by domestic and foreign experts and scholars (Gu 2017; Huang 2015; Xie 2015; Xu 2019). During the excavation of deep foundation pits, the surrounding soil will inevitably be disturbed and the soil layer will be deformed, resulting in uneven settlement of the upper buildings. Every year, foundation pit collapses occur in my country, causing serious economic losses and even casualties (Deng 2010; Gu 2018; Wang 2019). To fully understand the impact of construction on surrounding buildings and structures, and to adjust construction parameters in real-time according to monitoring information to ensure the safety of surrounding buildings and structures, it is very necessary to observe the settlement of buildings during the construction period (Liu 2021; Qu 2019; Zhang 2018; Zhou 2020). The Luotang River polder project is mainly composed of three parts: dykes, sluice, and sluice station. 16.70km of new dykes, 28 sluice gates and 8 gate stations were built. Among them, the Luotang River East Gate Station is a large (2) type pumping station, and the pumping station is grade II, and the maximum excavation depth of the foundation pit is about 13.60m. To ensure the construction safety of the foundation pit and the safety of surrounding buildings, monitoring is carried out during the excavation of the deep foundation pit, and measures are taken in time to control its deformation and settlement. ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-22

171

2 PROJECT OVERVIEW 2.1 Engineering geology (1) Composition and characteristics of foundation soil According to the geological survey report, the soil layers within the excavation depth of the foundation pit from top to bottom are: II1 layer of clay: brownish yellow, yellow, plastic to a soft plastic state, medium compressibility, sometimes high compressibility, with bedding, see plant rhizomes, commonly known as the surface crust. III1 layer of silty clay: gray to blue-gray, with a small amount of organic matter, saturated, fluid-plastic, and high compressibility. IV1 layer of silty clay: dark green to grayish yellow, partially grayish green, with a small amount of iron and manganese oxidation spots, hard plastic to a plastic state, medium compressibility. VI1 layer of clay: gray, with a small amount of organic matter, saturated, soft plastic to fluid plastic, medium to high compressibility. (2) Engineering geological evaluation The mechanical properties of layer II1 silty clay are relatively good, but the thickness is thin; III1 silty clay has high compressibility, low strength soft soil with poor properties and large thickness, which is stable for the foundation settlement and anti-slip of the gate station. Control soil layer; IV1 layer of silty clay has good mechanical properties and large thickness; VI1 layer of silty clay has poor mechanical properties and large thickness, with a thin clay layer interposed therebetween. 2.2 Engineering excavation and support scheme The average elevation of the foundation pit site is 2.50 m, the deepest excavation bottom elevation is −11.10 m, and the maximum excavation depth is about 13.60 m. The design level of the foundation pit is Level 1. The water-stop curtain adopts a single row of triaxial cement mixing piles. The first row of bored cast-in-place piles is 18.0 m long, 800 mm in diameter, and 1000 mm in pitch, and the second row is 20.0 m in length, 800 mm in diameter, and 3000 mm in pitch, and the triaxial cement mixing pile has a cement content of 15%. The length is 8.9 m; the pile diameter is 700 mm; the pile spacing is 500 mm. To improve the integrity of the enclosure structure and provide supporting reaction force for the support system, C30 pressure beams and cap beams are set on the top of the enclosure cast-in-place piles. The dimensions of the top beam and the cap beam are 1.0 m (width) × 0.6 m (height) and 0.8 m (width) × 0.6 m (height) respectively; the cross-sectional diagram of the foundation pit enclosure is shown in Figure 1. The excavation sequence of the foundation pit is as follows: (1) Leveling the construction site of the foundation pit; (2) Construction of cement mixing piles, and construction of bored cast-in-place piles after completion; (3) Waterproofing layered grading excavation, excavation on the left bank to −3.3 m elevation, the right bank is excavated to −3.1 m elevation, and the top beams and cap beams on the top of the double-row piles are constructed; (4) After the strength of the top beams and cap beams reaches 80% of the design strength, excavation in the precipitation layered wind zone to the base pit. 2.3 Foundation pit monitoring scheme The main monitoring items for the foundation pit include slope surface settlement monitoring, enclosure surface settlement monitoring, soil deep horizontal displacement monitoring, enclosure deep horizontal displacement monitoring and groundwater level monitoring. The monitoring floor plan is shown in Figure 2. 172

Figure 1. The cross-sectional diagram of the foundation pit enclosure.

Figure 2. The monitoring floor plan.

3 MONITORING DATA ANALYSIS 3.1 Deep horizontal displacement The horizontal displacements CX-01 and CX-10 of the deep tops on the left and right sides and the horizontal displacements CX-04 and CX-08 of the deep layers on the left and right sides of the 173

foundation pit along the elevation curve are shown in Figure 3. The monitoring information of the deep horizontal displacements is shown in Table 1. After the excavation of the foundation pit is completed, the maximum horizontal displacement of the deep top of the slope is −3.81 mm and −5.62 mm, and the elevations are −7.5 m and −2.5 m; the maximum horizontal displacement of the deep layer on both sides of the foundation pit is −6.47 mm and −6.62 mm respectively, with elevations of −3.0 m and −4.0 m. Table 1. Statistical table of deep horizontal displacement monitoring information (up to the completion of foundation pit excavation).

Station

location

Number

Max Displacement Elevation (m)

1 2 3 4

left slope right slope left pit right pit

CX-01 CX-04 CX-08 CX-10

−7.5 −3.0 −4.0 −2.5

Maximum displacement (mm)

Maximum displacement speed (mm/d)

−3.81 −6.47 6.62 −5.26

0.10 0.04 0.47 0.03

3.2 Subsidence After the excavation of the foundation pit is completed, according to the on-site measured data, the cumulative settlement of the surface settlement measurement points WY-01 and WY-10 at the top of the slope is 12.08 mm and 10.98 mm, respectively, and the cumulative settlement of the measurement points WY-04 and WY-08 on both sides of the foundation pit. They are 4.08 mm and 3.52 mm respectively, which are both less than the alarm value of 0.25% H=34 mm, which meets the design and specifications and requirements. 4 FINITE ELEMENT SIMULATION In this paper, Midas finite element analysis software is used to carry out a step-by-step simulation analysis of foundation pit excavation and support. 4.1 Calculation model and working conditions (1) Computational model The calculation boundary is shown in Figure 4. Take about 1.5 times the excavation span of the foundation pit on the left and right sides, and take the bottom to 10m below the bottom elevation of the enclosure pile; the left and right sides and the bottom are fixedly restrained. (2) Calculation parameters The overall model of the foundation pit is established by finite element software. The physical and mechanical parameters of each soil layer from top to bottom are shown in Table 2. The bored piles, capping beams and cap beams adopt elastic constitutive; The pressure in the soil material is much smaller than its compressive strength, so the linear elastic constitutive relation is adopted for the cement mixing pile. (3) Calculation conditions The calculation is simulated in 5 working steps: 1) In the current in-situ initial stress field, the groundwater table is 0.5 m below the surface; the surface elevation is 2.5 m; the groundwater table elevation is 2.0 m; 2) Construction of cast-in-place piles and mixing piles; 3) Precipitation to −4.3 m elevation, grading and excavation, left bank excavation to −3.3 m elevation, right bank excavation to −3.1 m elevation, construction of double row pile top pressure beam and cap beam; 174

Figure 3.

Horizontal displacement along elevation curve.

175

Figure 4.

Excavation of foundation pit completed model illustration.

Table 2. Soil calculation parameter value table.

II1 III1 IV1 VI1

soil layer name

wet density kN/m3

Cohesion C (kPa)

friction angle ψ (◦ )

constitutive model

clay silty clay silty clay clay

20.0 18.0 22.0 18.0

21.0 10.2 25.0 9.8

18.2 12.6 16.0 10.7

MMC MMC MMC MMC

4) Precipitation to −7.6 m elevation, excavation to −6.6 m elevation; 5) Precipitation to −9.9 m elevation, excavation to −8.9 m elevation. 4.2 Analysis of calculation results (1) Deep horizontal displacement After the excavation of the foundation pit is completed, the cloud map of the deep horizontal displacement of the excavation and unloading is shown in Figure 5. The maximum horizontal displacement of the deep depth on the side of the foundation pit is 7.68 mm and the elevation is −6.6 m; the maximum horizontal displacement of the deep layer at the top of the slope is 6.56 mm and the elevation is −17.5 m; the results of the finite element simulation are very close to the measured values, and are slightly larger than the measured maximum deep horizontal displacement.

Figure 5.

Deep horizontal displacement cloud map of foundation pit excavation.

(2) Analysis of Surface Subsidence After the excavation of the foundation pit is completed, the surface settlement cloud diagram of the excavation and unloading is shown in Figure 6. The maximum surface settlement of the foundation pit is 12.1 mm, which is located on the edge of the foundation pit; the surface settlement value of the slope top is 3.10 mm; The measured value is very close. 176

Figure 6.

Ground settlement cloud map of foundation pit excavation.

5 CONCLUSION From the analysis of the measured data and the finite element calculation results, it can be known that: (1) During the excavation of the foundation pit, both the surface settlement and the horizontal displacement of the deep layer are small, and the current foundation pit enclosure structure design meets the design and specification requirements. (2) According to the finite element analysis results, the deep horizontal displacement value and surface settlement data are very close to the field monitoring data. Therefore, before construction, the excavation process of the foundation pit can be simulated as a whole by the finite element software to verify the envelope structure. Whether the requirements for safe excavation are met. During the entire excavation process of the deep foundation pit, when the excavation reaches the bottom of the pit, the horizontal displacement value of the deep layer and the surface settlement reaches a peak value. The collapse of the foundation pit causes unnecessary losses.

ACKNOWLEDGEMENTS At the end of the paper, Thank you for the support of the Fund project: Zhejiang Provincial Department of Water Resources Science and Technology Program (RC2081).

REFERENCES Chen Wang, Yan Qin, Hongqi Liu, et al. Analysis and treatment of a foundation pit collapse [J]. Construction Technology, 2019, 48 (07): 18–20. Chengjie Xu. Research on the Impact of Deep Foundation Pit Excavation on the Surrounding Environment [D]. Jilin University of Architecture, 2019. Chengping Qu, Minghui Ye, Haofang Sun. Deformation monitoring and numerical simulation analysis of a deep foundation pit of a project [J]. Construction Technology, 2019, 48 (22): 59–62. Houcheng Liu, Guo Qijun. Research on deformation monitoring and numerical analysis of subway deep foundation pit based on ABAQUS [J]. Geotechnical Foundation, 2021, 35 (01): 72–75. Jiacheng Gu. Research on Continuous Failure Mechanism of Multi-channel Horizontal Support System in Foundation Pit [D]. Zhejiang University of Science and Technology, 2018. Meiting Gu. Analysis of Factors Affecting Settlement of Adjacent Buildings by the Excavation of Foundation Pit of Qianshan Road Station of Hefei Metro [D]. Anhui Jianzhu University, 2017. Min Deng, Yong Liu. Analysis of the collapse accident of a foundation pit slope [J]. Shanxi Architecture, 2020, 46 (05): 66–68.

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Peng Zhou. Deep Foundation Pit Excavation Monitoring and FLAC3D Simulation Analysis of a Subway Station in Lanzhou [D]. Lanzhou University of Technology, 2020. Shaoshi Huang. Analysis of the Influence of the Excavation of the Foundation Pit of Fengyang Road Station on the Surrounding Buildings D. Anhui Jianzhu University, 2015. Shaowen Zhang. Deformation Monitoring and Numerical Simulation Analysis of Subway Foundation Pit in Suzhou Soft Soil Area [D]. Wuhan University of Technology, 2018. Yunhuan Xie. Analysis of the Impact of Deep Foundation Pit Excavation on the Surrounding Environment. Tung Wah University of Technology, 2015.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Optimization of acoustic transit-time flowmeters installed in short converging intakes of a pump station Peng Zhang* College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, China Guangdong Polytechnic of Water Resources and Electric Engineering, Guangzhou, China

Heming Hu* National Institute of Metrology, Beijing, China

Qisen Miao*, Yiqing Gong* & Jingqiao Mao College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, China

ABSTRACT: The acoustic transit-time (ATT) is an actual online flow measuring technique that is appropriate for vertical tubes, open channels, and even short junctions of pumping houses. Several valid concordance computing methods have been suggested and taken in the flow calculation referring to tubes and open channels, but for the flow of short convergent inlets because of its complex geometry; thus, further improvement is needed. In this paper, the complex flow field of the measured section is researched numerically. The precision of the ATT flowmeter mounted in a short convergent inlet of the pump station is studied by the CFD tool. Taking the sensitivity of water flow in the measurement section into account, the fore cabin structure is of great importance. The calculation area also includes access channels and curved culverts. The influence of the flow field in different working conditions on measurement performance is analyzed and the system deviation is assessed. The results show that the indicated flow obtained by the two computing methods is about equivalent to the normative flow given by FLUENT, and the range of difference is roughly within 9%. The influence of the integral algorithm and path angle on standard flow calculation is taken into consideration. It is worth noting that there is no obvious difference between the calculated indicated flows at all kinds of path angles (∼1%). This study helps improve the flow integration algorithm.

1 INTRODUCTION The water resources are distributed in various regions, and the construction of water conservancy projects such as the south-north water diversion is increasing day by day. For such a huge water distribution project, flow measurement is vital to measure the gross flow. ATT is an actual online flow measurement method (JJG1030-2007, 2007). Flow is computed through acoustic signals transmission and receiving along the diagonal of the flow. It is important to note that the traffic fusion algorithm is bound to be comparable with mounting conditions. The conventional flow merging algorithm has been broadly applied and proved in vertical pipes and open channels. Nevertheless, for adjustable transverse section tubes, for instance, short convergent intakes in pumping stations, the variable cross-section range requires to be transformed to vertical tubes before the conventional

∗ Corresponding Authors: [email protected], [email protected] and [email protected]

DOI 10.1201/9781003384830-23

[email protected],

[email protected],

179

algorithm can be used. You need to evaluate and control the accuracy loss of the results caused by domain transformations. The Qianliulin pump station is the third stage of the Miyun reservoir diversion project of the South-to-North Water Diversion Project. The ATT flowmeter is mounted on its short convergent inlet to measure flow. The flow measurement system adopts an 8-channel structure, that is, 2 cross sound planes, and each sound plane has 4 channels. That is, 16 probes are mounted on each side of the convergence culvert. The culvert part is vertical, but it changes along the flow direction (the section tends to decrease), that is, the bottom and top surfaces are not horizontal, leading to a threat to the flow computation of the ATT flowmeter. A more integrated 3D appearance of the culvert flow field could be obtained by calculating hydrodynamics (Hug et al. 2012, 2015; Marushchenko et al. 2016; Wang et al. 2012). A full understanding of flow field details is crucial for optimizing flow integration algorithms and evaluating installation effects (Hu et al. 2015). In this thesis, the improved CFD model could be used for provoking the convergent inlet input stream in a pump station with an ATT flowmeter. After contrasting with the observed data, the system deviation of the traditional merging algorithm is quantitated. The effect of flow distribution on flow meter performance in various working conditions is analyzed, and the influence of different integral algorithms on standard flow rates is discussed.

2 MODEL SET-UP As 4 perpendicular axial-flow pumps are mounted in the Qianliulin pump station, a multipath ultrasonic flow measuring system with ATT flowmeters was mounted at four short convergent intakes to monitor the pump station flow ratio, which can be shown in Figure 1.

Figure 1.

Installation position of the ATT flowmeters.

With the help of 3D Solidworks, the geometric model of the intake position of the Qianliulin pump station could be measured well and established as soon as possible. The flow characteristics of the measured profile are very sensitive to the inflow situations, which are influenced by the wide forebay structure, narrow upper flow passage, and the geometry between them. Therefore, place the inlet (upstream boundary) is not close to the inlet. Thus, the computational domain consists of an approach channel, a forebay, four short converging intakes, and their curves (Figure 2). The governing equations are the continuity equation and Reynolds-averaged Navier-Stokes equation. The k-ε turbulence model is used to shut the equations. FLUENT software is used to calculate the flow field. The finite volume method is used to discretize governing equations, and the time 180

second-order implicit scheme, diffusion second-order central difference scheme, and the like are adopted. SIMPLEC method could be adopted for solving the speed-pressure coupling puzzle. The numerical simulation’s convergence criterion is defined as 104 . In computing, almost 7 million structured grids are used and can be beneficial for constructing grid systems. Where the local refinement technique is used to accurately approximate the area around the wall. The whole domain consists of 6 parts: diversion channel, forebay, and 4 convergent intakes (Figure 2). The front cross-section of the shunt river is regarded as the inlet to the entire calculating section, where the unified velocity boundary uses fixed values at 1 m/s. According to the design conditions, the water depth is set at 1.65 m, and the flow condition is relatively stable. It is assumed that the water surface is a rigid cap. It means that the free water surface is adopted as the symmetrical plane available for all kinds of variables. The outlet is situated in the mounting part of the pump blade, set as the pressure outlet (with the relative pressure being equal to 0), and the rest left of the boundary is set as the wall surface, which is processed by the standard wall surface function.

Figure 2.

Sketch of the computational domain within the Qianliulin pump station.

3 NUMERICAL SIMULATION RESULTS 3.1 The approach channel For knowing the flow patterns of open channels, front bays, and culverts, Figure 3 shows the 3D streamlines of computing regions. Under the constraint of the sidewall, the mainstream flows to the fore tank. As the cross-section area changes, the main flow velocity decreases. The mainstream is later filled into the front part of the side inlet, forming a countercurrent zone and damming zone. Vortices can be seen next to the gate (Figure 4). 181

Figure 3.

The three-dimensional streamlines of the simulation domain.

3.2 The side entrance With the decrease of intersecting surface area and the increase of speed, inertia, gravity, and sidewall roughness act together to form centrifugal force. Under the combined action of different kinds of forces, the direction of flow changes a lot. When mainstream fluid flows, the pressure of side water increases while the internal pressure drops, and the lateral speed drops while the internal speed increases due to centrifugal force and wall constraints. Therefore, the lateral curve tends to spread, and the inner curve tends to contract. The reverse is true when the main flow flows forward from the curve into the forward cabin. The diffusion trend causes the flow to leave the sidewall, forming a vortex region. The flow inertia reinforces the influence, resulting in the displacement of the main flow. The occurrence of flow separation reduces the cross-section of the forebay significantly, resulting in irregular longitudinal speed distribution.

3.3 The forebay The front bay consists of 4 passageways by 3 separate docks. Because the upstream water deflects at the bend, transverse flow occurs. Under certain conditions, with the help of three piers, the flow area is reduced and speed is increased for preventing bias of the main flow and enhancing flow patterns (Figure 5). The deviation of the main flow will lead to the irregular distribution of water flow on both sides of the channel. The flow on the left moves to the other side of the channel, the right flow moves to the other side of the channel, and the one in the middle part are positioned in an even manner. 182

Figure 4.

Velocity distribution in the approach channel.

Due to the blocking action of the solid retaining wall, the flow generates two right-angle backflows at the top of each passage, resulting in eddy currents at the upper junction between the front cabin and the inlet.

Figure 5.

Velocity distribution in the forebay.

183

3.4 The converging intakes and elbow-shaped culverts Due to the bias of the main flow, uneven flow is generated on each side of the channel. The flow in the intake is deflected to the right as the right side of the fluid flows to the left. The solid wall creates a bias in the flow direction and produces a secondary flow horizontally. The spiral flow is taken as the result of combining the main and secondary flows. With the cross-section decreasing, the flow pattern is required to be regulated, and the distribution of pressure and velocity tends to be uniform. The flow changes in both inlets are all the same. In terms of the middle inlet, the distribution of pressure and velocity seems to be parallel and balanced. In the transition from a straight vertical part to a rounded part, the flow turns about 90 degrees. Under the action of centrifugal force, the inner elbow has low pressure and high speed. There is an area of low pressure along the inner ring of the elbow. However, because of the reduction of the elbow section, no adverse flows (such as flow separation) occurred with high pressure and low speed over the elbow. The flow rate and pressure distribution are strictly regulated owing to changes and effects on shape and centrifugal force (Figure 6).

Figure 6.

Velocity distribution in the elbow-shaped culverts.

4 FLOW RATE CALCULATION The mounting effect refers to the flow error that may occur due to the disturbance of the flow field. The flow error resulting from the mounting effect should be calculated by using indicated flow rate and standard flow rate (Hu et al. 2015). The indicated flow ratio can be gained by a path speed-weighted average based on the numerical flow field in line with every acoustic pathway. 4.1 Calculation of indication flow rate For measuring function, the projection speed vproj is confirmed by the transit time difference between the upstream acoustic pulse and the downstream one. The average axial speed of the path could be computed by the path angle. First, two methods of calculating indicated flow rate are introduced further. The main difference between them refers to the method of calculation vproj . The indication flow ratio is used for calculating the general process: (1) Extracting the geometrical information (x, y, z coordinates) and the following speed elements (u, v, w) of each path. (2) Computing the average speed of each element (u, v, w) according to the trapezoidal rule. 184

Figure 7.

Path positions within the converging intake.

(3) Computing the axial velocity component vax in line with the axial flow direction, and the lateral speed element vtrans regular to the axial flow orientation. (4) Calculation of vax _ proj and vcross vax_proj = vx · cos(ϕ)

(1)

vcross = vz · sin(ϕ)

(2)

Plane A : vproj_A = vax_proj + vcross

(3)

Plane B : vproj_B = vax_proj − vcross

(4)

Plane A : vax_A = vproj_A /cos (ϕ)

(5)

Plane B : vax_B = vproj_B /cos (ϕ)

(6)

(5) Calculation of vproj

(6) Calculation of vax

(7) Calculation of vax-mean We must get the average speed of the channel lines; pitch points are suitable by the trapezoidal integral method. (8) Calculation of vaxial-l 1 − (vax_A /vax_B ) tanλl = (7) tanϕA + (vax_A /vax_B ) · tanϕB vaxial_l = 0.5 · (vA ·

1 1 + vB · ) 1 − tanφ · tanλl 1 + tanϕ · tanλl

(8)

vcross_l = vaxial_l · tanλl

(9)

(9) Calculation of vcross-l (10) Calculation of Q When it refers to the right-angled flow path, the flow ratio is generally computed by GaussLegendre integrating approach and the right-angled optimizing integrating approach (OWIRS). Q=

BH  · ωi · Vi 2 185

(10)

Another method for calculation vproj is the dot product method. The vi refers to the line averaged velocity vector and vproj share the same method named projection method referring to the acoustic path. Consequently, vproj could be transmitted as follows:     (11) vproj = νi · l / f · l 

where flow unit vector f = ( f1 , f2 , f3 ) is mainstream direction; and the direction of path unit 

vector l = (l1 , l2 , l3 ) is from the upstream transducer to the downstream transducer. As a consequence, the most vital matter is to get the average flow along the channel. The position of the channel line is decided by the coordinates at each end. The scattering speed of the 3D flow field could be integrated into the channel line. As the nodes on the channel line are not equivalent, the average speed of the line is not equivalent, but it still needs to be computed according to the formula and line integral. The PCHIP method is admitted in the process of fitting to avoid the problem of local overestimation or underestimation resulting from linear fitting. 4.2 Calculation of standard flow rate FLUENT can supply the flow of a section directly through a built-in integration algorithm. In this part, we will simply compare the computed indicated flow with the standard flow ratio imparted by FLUENT. In Table 1, deviation 1 represents the error between indicated flow 1 and the standard flow ratio. However, deviation 2 refers to the error between the indicated flow 2 and the standard flow ratio. Table 1. Comparison of flow rates (m3 /s) and deviations.

Standard flow rate Indication flow rate 1 Deviation 1 Indication flow rate 2 Deviation 2

Intake 1

Intake 2

Intake 3

Intake 4

9.151081 8.428355208 57.89% 8.6673641 5.28%

9.159491 8.399345108 68.29% 8.671708686 5.32%

9.090051 8.302570938 58.66% 8.545200751 5.99%

9.009708 8.299416513 68.18% 8.512635795 5.51%

The results show that the indicated flow obtained by the two algorithms is about equivalent to the standard flow ratio imparted by FLUENT, and the deviation ratio is within 9%. Nevertheless, the deviation between them is large and worth further discussion. 5 DISCUSSION Water resource measuring and monitoring guarantee water resource utilization, basically, rational dispatching and safety control. The ultrasonic flow measuring device is a noncontact instrument (Kalmus, 1954). Due to its advantages of convenient carrying and installation, high measurement accuracy, and multichannel configuration, it is more and more used, especially for large-diameter flow fields in Hydraulic Engineering (Meng 2016). Therefore, how to enhance the precision of ultrasonic flow measurement devices has always been a hot issue in related research fields (Hosten et al., 2001; Jackson et al. 1989; SIgA et al. 1994). As an accuracy instrument, the transit time ultrasonic flow measuring device has many factors affecting its measurement precision, mainly including TDOA measurement, geometric parameter calibration, and integration algorithm. With the help of simulation, the precision of this technology being applied to the rectangular convergent inlet is studied (Hu et al. 2010). 186

5.1 Choice of standard flow ratio The standard velocity is the outcome of the cross-sectional area and the average velocity of the area. Although FLUENT can supply flow rate for some purposes, the most credible model is probably triangulation-based conformity (Hu et al. 2015). Therefore, we draw the velocities of all nodes of the measured section when it refers to the numerical flow field, and then the Delaunay triangulation method is applied to set up triangular grids (Figure 8). The axial velocities of each grid are average ones. The standard flow rate is the total of all the flows on the triangular mesh.

Figure 8.

Integration base on delaunay triangulation.

Whether enough sound pathways would be put into use in the digital flow field to count the indicated flow ratio. If the truncation error is really small, the indicated flow ratio should be the same as the actual one. Figure 9 analyzes the flow calculated by Delaunay trigonometric survey way (8.93 m3 /s), FLUENT (9.15 m3 /s), and Gaussian integration (9.02 m3 /s from the example of 20-path). As the number of paths increases, the computed flow rate is close to that solved by the other two ways. Generally speaking, the comparative difference between Delaunay trigonometric survey way and Gauss merging way is lower (∼0.79% with the increase of pathway number). It is obvious that at any rate, seven channels are sufficient to produce a calculated flow rate which is considered as the standard one.

Figure 9.

The calculated flow rates and the relative difference.

187

5.2 Effect of path angles Sound pathway angle means the angle of intersection between the sound path and intake axis. The ATT flowmeter at the inlet of the former Liulin Pump station has two path angles that are totally different (53˚ and 65˚). We calculate the flow rate at different path angles of four inlets and compare it with the standard flow rate given by the gaussian integral way (20 paths). Tables 2 and 3 show the outcomes of applying regulated and normative weighing factors, separately. It is worth noting that there is no obvious distinction between the computed indicated flows with pathway angles different (∼1%). Table 2. Calculated flow rates with different path angles (adjusted weighting coefficients).

20-path flow rate (m3 /s) Path angle 53◦ (m3 /s) Relative difference 1 Path angle 65◦ (m3 /s) Relative difference 2 Relative difference between 2 angles

Intake 1

Intake 2

Intake 3

Intake 4

9.02 8.74 −3.10% 8.68 −3.77% −0.69%

9.05 8.75 −3.31% 8.75 −3.31% 0

8.96 8.72 −2.68% 8.67 −3.24% −0.57%

8.89 8.60 −3.26% 8.49 −4.50% −1.28%

Table 3. Calculated flow rates with different path angles (standard weighting coefficients).

20-path flow rate (m3 /s) Path angle 53◦ (m3 /s) Relative difference 1 Path angle 65◦ (m3 /s) Relative difference 2 Relative difference between 2 angles

Intake 1

Intake 2

Intake 3

Intake 4

9.02 9.24 2.44% 9.17 1.66% −0.76%

9.05 9.25 2.21% 9.25 2.21% 0

8.96 9.23 3.01% 9.18 3.01% −0.54%

8.89 9.08 2.14% 8.98 1.01% 1.10%

Based on the CFD model (Zhao et al. 2013), this paper conducts a numerical study on the flow field inside the pump station, including the inlet channel, front bay, and measured inlet. The measured path velocity distribution characteristics in the collected inlet are analyzed, the measuring precision of two different flow calculation models in the collected inlet is compared, and the system deviation is assessed shortly (Hu et al. 2011). Later, we will talk about how to choose standard flow rates by applying various integrated algorithms, and the influence of path degrees (Zhang et al. 2015). The research can take full advantage of the flow rate integration algorithm and enhance the precision of ATT flowmeters.

6 CONCLUSION The impact of the flow distribution field on the accuracy of ATT measurement shown in various conditions is studied, and it indicates that the indicating flow ratios being obtained from two algorithms are about equivalent to the normal flow rate immediately imparted by FLUENT, and the deviation is less than 9%. Especially, the relative divergence between Delaunay trigonometry and Gauss integral is small (∼0.79% with the increase of path number). It is evident that the lowest seven channels are sufficient to manufacture computed flow being taken as standard flow. All kinds of integrated algorithms are applied to compare the planned rate of flow: the Delaunay trigonometric survey way (8.93 m3/s), FLUENT (9.15 m3/s), and Gauss merging way with 188

enhancing path number (9.02 m3/s from the case of 20-path). The results show that, as the number of paths increases, the calculated flow rate becomes closer to that of the other two methods.

ACKNOWLEDGMENTS We sincerely thank the anonymous reviewers for providing insightful comments that have significantly improved our paper. This work was supported by the National Key Research and Development Program of China under Grant No. 2019YFE0109900.

REFERENCES Hosten, B. and Vulovic, F. (2001) “High-frequency transducers and correlation method to enhance ultrasonic gas flow metering”, Flow Measurement and Instrumentation 12.3(2001): 201–211. Hu, H.M., Meng, T. and Wang, C. (2011) “Theoretical analysis of integration error of ultrasonic flowmeter in the disturbed flow condition”, Acta Metrological Sin-Ica 32.3(2011): 198–202. Hu, H.M., Wang, C. and Meng, T. (2010) “Integral method of the multichannel ultrasonic flowmeter and its accuracy analysis”, Chinese Journal of Scientific Instrument 31.6(2010): 1218–1223. Hu, H.M., Zhang, L., Meng, T. and Wang, C. (2015) “Mechanism Analysis and Estimation Tool of Installation Effect on Multipath Ultrasonic Flowmeter”, 9th ISFFM.2015. Jackson, G.A., Gibson, J.R. and Holmes, R. (1989) “A three-path ultrasonic flowmeter for small-diameter pipelines”, Journal of Physics E: Scientific Instruments 22.8(1989): 645–650. JJG1030-2007: Ultrasonic Flowmeters, National Verification Regulation, 2007. Kalmus, H.P. (1954) “Review of scientific instruments”, Electronic flowmeter system 25(1954): 201–206. Marushchenko, S., Gruber, P. and Staubli, T. (2016) “Approach for acoustic transit time flow measurement in sections of varying shape: Theoretical fundamentals and implementation in practice”, Flow Measurement and Instrumentation 49(2016): 8–17. Meng, D.D. (2016) “The principle and application of multichannel ultrasonic flowmeter”, Instrumentation 23.8(2016): 24–16. Silvan, H., Thomas S. and Peter G. (2012) “Comparison of Measured Path Velocities with Numerical Simulations for Heavily Disturbed Velocity Distributions”, 9th IGHEM. 2012. Spiga, M. and Morini, G. L. (1994) “A symmetric solution for velocity profile in laminar flow through rectangular ducts”, International Communications in Heat and Mass Transfer 21.4(1994): 469–475. Wang, C., Meng, T., Hu, H.M. and Zhang, L. (2012). “Accuracy of the ultrasonic flow meter used in the hydro-turbine intake penstock of the three gorges power station”, Flow Measurement and Instrumentation 25(2012): 32–39. Zhang, J.D., Zheng, D.D., Zhang, T., Zhao, D. and Li, B. (2015) “Optimization of numerical integration method for multi-path ultrasonic flowmeter”, Control and Instruments in Chemical Industry 2(2015): 144–147. Zhao, H.C. and Peng, L. H. (2013) “Simulation accuracy using CFD investigations of flowrate measurement”, Journal of Tsinghua University (Science and Technology) 53.7(2013): 1052–1056.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

A safety analysis of temporary anchor-tension system for immersed tube in the Shenzhen-Zhongshan link Shenyou Song* Tsinghua University, Shenzhong Link Management Center, China

Heng Han* School of Highway, Chang’an University, China

Guoping Xu*, Qingfei Huang*, Minghu Liu* & Bin Deng* CCCC Highway Consultants Co., Ltd., China

ABSTRACT: The temporary anchor-tension system of the Shenzhen-Zhongshan link is used to temporarily lock the final butt joint. To explore its safety and strength reserve under the design working state, and provide a sufficient basis for the design calculation, this paper designs a group of 1:1 full-scale self-balanced tension model tests. To ensure that the full-scale model can reflect the actual construction deviation, the two-way 5cm pre-deflection is set in advance and the graded loading is carried out. Combined with the finite element method, the author analyzed the stress of the whole process of loading. The results show that the test results are in good agreement with the finite element analysis results, the bearing performance of the temporary anchor-tension system is good, the safety redundancy is large, and the ribbed plate is the weakest member of the whole structure. Under the design load, the maximum Mises stress of the rib plate reaches 187.5 MPa. From the perspective of design safety, it has a 33% strength reserve. From the perspective of the material yield limit, its strength reserve reaches 52%. All components of the temporary anchor-tension system are in an elastic working state.

1 INTRODUCTION With the continuous innovation and development of bridge engineering technology in China, the bridge-Island-tunnel integration scheme has become the main form of sea-crossing bridges (Ge 2019; Song 2020). According to statistics, more than 150 underwater tunnels have been built in more than 20 countries around the world using immersed tunnel technology. At present, more than 10 immersed tunnels have been built or are under construction in mainland China (Liu 2021). The first bridge-Island-tunnel integration project in China, the Hong Kong-Zhuhai-Macao Bridge, has adopted a reinforced concrete immersed tunnel, and its design theory and construction technology also provide a reference for subsequent projects (Xu 2018). The final joint closure of immersed tube tunnel is the landmark node of the whole project. To ensure the accurate connection of the final joint of immersed tube tunnel, designers have proposed a temporary anchor-tension system to lock the adjacent two immersed tubes shortly. However, due to the high risk of underwater construction, if the strength of the temporary anchor-tension system cannot meet the construction requirements, it will have a great impact on the whole project. Therefore, ensuring the safety of the temporary anchor-tension system under various adverse conditions becomes the top priority. ∗ Corresponding Authors: [email protected], [email protected], [email protected], [email protected], [email protected] and [email protected]

190

DOI 10.1201/9781003384830-24

At present, many scholars at home and abroad have analyzed and discussed the strength of structures or temporary components. The main research methods include numerical simulation, finite element simulation analysis, and model tests. Hu (2016) usedANSYS finite element modeling to check and compare the strength of the comb seal and pass damping seal and studied the influence of different structural parameters on the strength of the pass seal structure. After finite element analysis, it is considered that the pass damping seal designed according to the third strength theory meets the strength requirements and practical engineering needs. Zhang (2019) proposed a new baffle vane impeller structure based on the water surface vector propeller and proposed a mathematical analysis model to solve the blade principal stress based on this structure. The third strength theory and ANSYS finite element software are used to calculate the impeller stress. Comparing the theory with the simulation results, it is found that the theoretical solution of the principal stress is basically consistent with the simulation value. Xu (2021) provided a simple and efficient method for the strength design and verification of thrust ball bearing components based on Hertz theory and the law of energy conservation through the force analysis of thrust ball bearing components on the whole vehicle. Through the comparison between the vehicle test and the impact strength calculated by this method, the experimental results are highly consistent with the calculated results, which verifies the effectiveness of this calculation method. Wang (2018) proposed a metallined carbon fiber reinforced resin (CFRP) hydraulic cylinder barrel. The mechanical model of the CFRP cylinder is established, and the strength theory of the CFRP cylinder is derived on the basis of the composite laminate theory. Using ABAQUS finite element software for stress analysis and strength failure criteria for strength check, the results preliminarily proved the feasibility of CFRP as a lightweight material for hydraulic cylinders. Liu (2019) used traditional methods and finite element software to check the strength of the gear with the largest load on the planetary reducer. The results show that the Von-Mises equivalent stress based on the fourth strength theory calculated by the finite element method can be better used as the check criterion than the traditional tooth root strength check method based on the beam theory. To sum up, there are many methods and theories for structural strength verification, and it is most important to select the strength theory suitable for the specified materials. In this paper, the general finite element software ABAQUS is selected and combined with the full-scale model test. The fourth strength theory criterion, Von Mises strength theory, is used to analyze and verify the safety of the temporary anchor-tension system.

2 PROJECT OVERVIEW The upstream of the Shenzhen-Zhongshan link is 30 km away from Humen Bridge, and the downstream is about 38 km away from Hong Kong-Zhuhai-Macao Bridge. The project starts from the airport interchange of the Guangzhou-Shenzhen Riverside Expressway, connects with Guangzhou-Shenzhen Riverside Expressway, connects with the Shenzhen Bao’an International Airport Expressway through the proposed Guangzhou-Shenzhen Riverside Expressway branch line project, crosses the Pearl River Estuary westward, lands on Zhongshan Ma’an Island, ends at Hengmen interchange, and connects with Zhongshan-Yangchun Expressway. The standard construction of an eight-lane expressway is adopted, and the design speed is 100 km/h. The project consists of tunnels, bridges, artificial islands, and submarine interchanges, with a total length of about 24 km. The general layout of the whole line is shown in Figure 1. The tunnel is 6,845 m long, of which the immersed section is 5,035 m long. It adopts a steel shell concrete composite structure, an integral pipe joint, and a longitudinal rigid structural system, and the number of pipe joints is 32. Among them, there are 26 standard pipe joints, and the length/weight of standard pipe joints is 165 m/76,000 t; for 6 non-standard pipe joints, the length/weight of nonstandard pipe joints is 123.8 m / 70,000 t. Outsourcing size of standard pipe joint: 46 m × 10.6 m, maximum pipe joint width: 55.46 m. The upper section of the island is 1,810 m long and adopts a reinforced concrete structure. There are two artificial islands on the east and west of the whole 191

Figure 1.

General layout of the whole line.

line. The East Island is 930m long and the West Island is 625 m long. The vertical section layout is shown in Figure 2.

Figure 2.

Vertical section layout of Immersed tunnel.

3 LAYOUT OF TEMPORARY ANCHOR-TENSION SYSTEM For the pumping and drainage between the pushing-out section and the adjacent pipe joint, in order to prevent the GINA water stop rebounding from the adjacent pipe joint, the pulling rod system is used to temporarily lock the pushing-out section. Due to the complex stress condition of the immersed tube structure and the influence of construction deviation at the joint position, to ensure the pressure of the water stop, the temporary tension rod system of the final joint must be safe and reliable. Therefore, the model test research and strength verification of the temporary tension rod system of the final joint under different working conditions are carried out to ensure the safety of the structure. The general layout of the temporary anchor-tension system is shown in Figure 3.

4 TEST LOADING 4.1 Calculation parameter selection The mechanical behavior parameters and strength indexes of various materials used for verification and calculation are taken in accordance with the Specifications for Design of Highway Steel Bridge 192

Figure 3.

General layout of the temporary anchor-tension system.

(JTG D64—2015). Since the tension rod is special steel composed of multiple metals, the relevant calculation parameters are provided by the tension rod supplier. See Table 1 for the calculation parameters of all materials.

Table 1. Material calculation parameter. Component

t/d (mm)

Material

E(MPa)

ν

fd (MPa)

fy (MPa)

Rib plate Anchor plate Backing plate Tension rod

50 40 40 65

Q390C Q390C Q390C 40CrNiMoA

206000 206000 206000 209000

0.3 0.3 0.3 0.3

280 295 295 785

390 390 390 835

4.2 Finite element analysis The general finite element software ABAQUS is used to model and analyze the anchor-tension system. The base plate in the model is simulated by a spatial S4R shell element, and the other components are simulated by a C3D8R three-dimensional solid element. Boundary conditions are fixed at one end and pushed out at the other end. The interaction between plates is applied according to the actual contact situation, and the interaction of face-to-face tying is used to simulate welding. The finite element model is shown in Figure 4.

Figure 4.

Finite element model of the temporary anchor-tension system.

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The stress-strain curve of steel adopts bilinear isotropic strengthening theory, the material properties are taken according to Table 1, and the Von-Mises yield criterion is adopted. The stress distribution of the anchor-tension system under the design load is shown in Figure 5.

Figure 5.

Von-Mises stress nephogram of the temporary anchor-tension system (unit: MPa).

4.3 Test layout Place the full-scale model horizontally on the rigid roller, which can be used for the test bench to slide freely along the length of the tension rod. A 500 t hydraulic jack is used to carry out self-balanced jacking loading between the two test benches. To accurately simulate the installation deviation of immersed tubes in the construction process, the two test benches are pre-biased 5 cm vertically and horizontally before the start of the test, and all members of the test are monitored to ensure the safety of the test.

Figure 6.

Static load test layout.

The general arrangement of the static load test is shown in Figure 6. According to the results of finite element theoretical analysis, strain flower measuring points are arranged in the area with large stress changes, and the arrangement of measuring points is shown in Figure 7. A dial indicator is arranged between the two benches to test the ejection amount. The loading and testing of the test site are shown in Figure 8. 4.4 Result analysis According to the Von Mises yield criterion, the equivalent stress at each measuring point of the temporary anchor-tension system can be obtained by using the measured strain of the test. The variation trend of the maximum stress measuring point of each member with the load under the 194

Figure 7.

Layout of measuring points.

Figure 8.

Test loading and testing.

design load is shown in Figure 9, and the measured safety reserve of each member is shown in Figure 10. It can be seen from Figure 9 and Figure 10 that in the process of loading from zero level to one time of design load, the stress of all measuring points basically shows a linear change trend with the load, indicating that under the action of the design load, all components of the temporary anchortension system are in an elastic working state, meeting the requirements of the design bearing capacity. The maximum measured stress of the anchor plate is the 17# measuring point, which is located at the lower edge of the U-shaped groove arc. The measured stress value reaches 183.1 MPa, the design safety reserve is 37.9%, and the elastic limit safety reserve is 53.1%. The maximum measured stress of the rib plate is 5# measuring points, and the measured stress reaches 187.5 MPa. The design safety reserve is 33.0%, and the elastic limit safety reserve is 51.9%. The maximum measured stress of the tension rod is the R2# measuring point, and the measured stress reaches 195

Figure 9.

Variation trend of maximum stress of each component with loading.

Figure 10.

Residual safety reserve of each component under design load.

345.3 MPa. The design safety reserve is 56.0%, and the elastic limit safety reserve is 58.7%. The above data shows that all components have different degrees of safety reserves, among which the safety reserves of the tension rod are slightly larger, and the elastic limit safety reserves of all components are more than 50%.

5 CONCLUSIONS In this paper, a group of full-scale self-balanced tension model tests is designed for the temporary anchor-tension system of the immersed tube in the Shenzhen-Zhongshan link, and the following conclusions are drawn in combination with finite element analysis: 196

(1) Under the design load, the temporary anchor-tension system has good bearing performance and sufficient safety reserves. The full-scale model test data are reliable and are in good agreement with the finite element calculation values. (2) The rib plate is the weakest member of the whole structure. In terms of engineering application, its strength reserve reaches 51.9%, but from the perspective of design safety, its strength reserve is only 33.0%. In addition, the finite element calculation model shows that the stress concentration at the fillet weld at the front end of the rib plate is obvious. Therefore, the welding process should be strictly controlled during construction, and if necessary, the rib plate should be filleted to avoid stress concentration.

ACKNOWLEDGMENTS The authors acknowledge the support from the Key Field R & D Program Project of Guangdong Province (2019B111105002).

REFERENCES Ge Y.J. & Yuan Y. (2019). State-of-the-art technology in the construction of sea-crossing fixed links with a bridge, island, and tunnel combination. Engineering. 5(01): 35–49. Hu H.L., He L.D., Huang W.C. & Tu T. (2016). A structural strength analysis of labyrinth seal and hole-pattern seal. China Sciencepaper. 11(11): 1275–1278. JTG D64 (2015). Specifications for Design of Highway Steel Bridge. Liu K.W. & Zhang Q. (2019). Research of the checking and judging method of the key parts of the double input planetary reducer. Journal of Mechanical Transmission. 43(1): 5. Liu L.F., Lin W. & Yin H.Q., et al. (2021). Construction of immersed tunnel engineering in the world and development status of immersed tunnel technology in China. China Harbour Engineering, 41(08): 71–79. Song S.Y., Guo J., Su Q.K. & Liu G. (2020). Technical challenges in the construction of bridge-tunnel seacrossing projects in China. Journal of Zhejiang University-Science A (Applied Physics & Engineering). 21(07): 509–513. Wang Z.N., Cheng K.S. & Zhang C.C. (2018). Structural development and strength theory research of hydraulic cylinder CFRP Tube. Chinese Hydraulics & Pneumatics. (7): 7. Xu G.P. & Huang Q.F. (2018). General design of shenzhen-zhongshan river-crossing link project. Tunnel Construction. 38(4): 627–637. Xu Z.C., Sun G.Z. & Zhang W.B. etc. (2021). Impact strength checking and bench test for thrust ball bearing assembly in automobile suspension. Bearing. (10): 6. Zhang Y., Lv J.G., Liu J.H., Zhao Z.L. & Dai Z.G. (2019). Research on strength check of baffle impeller structure. Journal of Ordnance Equipment Engineering. 40(09): 169–172.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

A Geofencing-based dynamic supervision technology for highway engineering construction site Cheng Yang, Yu Cheng, Wei Zheng, Chun-feng He, Wei Chen & Li-bo Bai Zhejiang Supervision on Highway and Water Transportation Construction Engineering Co., LTD, Hangzhou Zhejiang, China

Shu-hai Lin* Beijing Chixin Technology Development Co., Ltd. Beijing Fengtai, China

ABSTRACT: This paper proposes a geofencing-based supervision technology for highway engineering construction sites, to improve the highway project quality, safety and intelligence level. First, a carefully designed mobile app for daily site management is developed and delivered to all the project’s participants, including the project owner, construction manager, supervisor and construction site workers. This app helps project participants to better handle site work and record the necessary position information at the same time. Second, a geographic database is established with geographic information and management process data collected from the app. By geofencing technology, several dynamic supervision scenarios are realized such as personnel fulfillment management, location-based risk warning, position and orientation tracking, and data visualization. Finally, the technology aforementioned is put into practice on a highway project in Zhejiang Province, China. The practice shows that geofencing-based dynamic supervision could tackle the traditional obstacles in site management including site worker control, fulfillment evaluation, human resources allocation, and risk warning.

1 INTRODUCTION Highway construction occupies an important position in China’s economic development. However, the current highway construction work is still based on traditional personnel on-site verification, management efficiency is low. In the digital age, a possible solution consists in making use of information technologies, such as mobile internet and location services. Geographic Information System (GIS), as a computer system that integrates the functions of collecting, storing, managing, analyzing, displaying, and applying geographic information, has greater advantages in analyzing and processing massive geographic information data and is widely used in the engineering field (Ali 2020). Al-Mansoori et al. proposed a GIS-enhanced pavement management system based on the construction of the Babylon Highway in Iraq, to achieve a graded warning of pavement maintenance and avoid the expansion of damage to road infrastructure (Al-Mansoori 2020). Budzy´nski et al. applied GIS technology to road infrastructure safety inspection and identified important factors affecting road infrastructure safety through the collection, analysis, and visualization of pavement management and maintenance data (Budzy´nski 2018). In terms of positioning and trajectory tracking, Li et al. proposed a traffic mode identification method based on GPS trajectory data and GIS information (Li 2021). Sharma et al. proposed location planning and scheduling based on geolocation information (Bansal 2018). Li et al. based on GIS information technology (Li 2021), realized the early warning and monitoring function for the ∗ Corresponding Author:

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418837579@qqcom

DOI 10.1201/9781003384830-25

safety hazards during the construction of the track project and provided the staff with information such as location, distance, and trajectory. Zeeshan et al., and Hatamleh et al. applied GIS technology to improve the management issues involved in the solid waste disposal processes such as sorting, transportation, and track tracking (Hatamleh 2020; Zeeshan 2018). Irshaid et al. achieved automatic identification of travelers’ activities and itineraries by applying GIS technology (Irshaid 2021). This study proposes a geofencing-based dynamic supervision technology for highway engineering construction sites. The engineering construction data is dynamically collected and mapped through the project supervision system. By processing and analyzing the collected data, a visualization management control map (VMCM) is established to realize personnel fulfillment management, location-based risk warning, position and orientation tracking, and data visualization. Further, this technology is put into practice on a highway project in Zhejiang Province, China, and helps solve several management obstacles on construction sites. 2 DESIGN OF THE DYNAMIC SUPERVISION TECHNOLOGY This study aims to establish a set of efficient and intelligent personnel work management schemes by using information technology and digital technology. As shown in Figure 1. the dynamic supervision technology studied in this paper is mainly composed of data collection, data analysis, and visualization display. The technology route steps are as follows: • Engineers provided their identification information to build a database of personnel information. • Based on the geographic location information of the project structure and the progress of node projects, the database of mainline and node projects was constructed. • The personnel information was associated with the engineering database to construct the personnel-workplace database, which was used for personnel information calibration. • A project supervision system, including quality, safety, environmental, and other management modules, was established to collect work data. • Based on GIS and the collected data, the visual management control map (VMCM) was established to realize personnel information calibration, location-based risk warning, position and orientation tracking, data visualization, etc.

Figure 1.

Dynamic supervision technology route.

199

3 PERSONNEL AND WORKPLACE MAPPING DATABASE 3.1 Creation of personnel dataset The project team collected, entered, and audited the information of the performance personnel and established the personnel information dataset. Person IDs were also automatically assigned to each individual to ensure that the information was unique. 3.2 Creation of workplace dataset The determination of nodal works is crucial in the process of construction, they can be determined by the list of nodal works submitted by the construction unit. The geographical location of nodal works could be determined according to the coordinated result list in the project field survey report, or use RTK for on-site point collection. Based on the personnel dataset and workplace dataset, the personnel-workplace database was established to clarify personnel responsibilities and regional division of labor.

4 GEOFENCING-BASED DYNAMIC SUPERVISION TECHNOLOGY 4.1 Dynamic collection of personnel location data GPS data of personnel locations were collected at a fixed frequency (1/300Hz, adjustable) through cell phone fusion positioning technology, and the data was returned to the back-end server for storage in real time. In addition, based on the personnel-workplace mapping database, the personnel ID was used as the classification primary key to associate the corresponding workplace and mainline fence. 4.2 Early warning method based on personnel location information Based on the dynamically recorded status of the personnel fence, early warning messages are pushed to the staff who are not on the fence for a certain period, to regulate the work behavior of personnel. The personnel’s location information points within the fence were filtered by data mining and analysis. Personnel working hours were determined by aggregating the aforementioned data. The analysis data was summarized to form a statistical table of personnel work status. 4.3 Visualization management control map (VMCM) Based on the aforementioned personnel-workplace database, the VMCM was constructed using the Mapbox GL JS library to provide the location and tracking of the workplace and personnel, as shown in Figure 2. 4.3.1 Visualization of mainline and workplace fence The supervisory control area, including mainline fences and workplaces, was established by dynamically associating GPS data in the personnel-workplace database. This technology allowed for rapid positioning of key projects and information overview display. 4.3.2 Position and orientation tracking By dynamically associating personnel geographic location information, the personnel were dynamically displayed on the VMCM to achieve accurate positioning of personnel. The VMVC could record the GPS data of personnel in a certain interval section and realize the dynamic mapping of personnel movement trajectory, which was convenient for personnel tracking. The deviation of the personnel trajectory is corrected by the inverse distance weighting method, and the attributes of the unknown points are determined according to the attributes of the adjacent points. Assuming that 200

Figure 2.

Visualization management control map.

the point to be interpolated in the space is P (xp , yp , zp ), and there are n discrete points Qi (xi , yi , zi ) in the neighborhood of point P, the attribute zp of point P is interpolated by the inverse distance weighting method to ensure the accuracy of the position. See Equation 1 below: zP =

n 

n  1 / k [d [d (x, y)] (x, y)]k i i i=1 i=1

zi

(1)

where di (x, y) = (xP − xi )2 + (yP − yi )2

5 APPLICATION SCENARIOS 5.1 Verification of personnel performance The validity verification of personnel performance behavior mainly contained personnel fence state verification and personnel face recognition verification. The project supervision system provided work platform entrances and could be run on cell phones, and computers. According to the logged-in person account information, the system platform would automatically match personnel organization and work area in conjunction with the aforementioned established person-staff point mapping database. Judgment was made on whether personnel working within the work fence, only the work results within the work fence were valid and could be submitted for approval. In addition, face 201

recognition was also applied to modules such as personnel attendance to ensure the reliability and authenticity of work. 5.2 Application of VMCM The VMCM was designed to visualize engineering information and provide managers with better information tracking and tracing, including rapid positioning of personnel or workplace, display of personnel work trajectories and query of personnel work dynamics, etc. By filtering the name of personnel or workplace on VMCM, managers could quickly locate personnel or workplace. Such as, managers could conveniently query the regular work content of personnel by clicking on the personnel dynamic button provided, they could also dynamically view and master the trajectory of personnel by clicking the personnel trajectory button.

6 CONCLUSION Based on a highway project under construction in Zhejiang Province, China, this study provided a geofencing-based dynamic supervision technology, which solved the personnel management problems in the project construction process. The main research results are as follows. • The personnel-workplace database was established by using the project construction management system to gather and organize the basic information of personnel, mainline, and node engineering. • Based on the dynamic supervision technology and GPS data, the early warning and supervision mechanism was established to ensure the authenticity and effectiveness of personnel performance behavior. • The personnel-workplace visualization management and control map was established to realize rapid positioning of personnel or workplace, visualization of personnel area distribution, personnel location and trajectory tracking, and personnel works dynamic display.

REFERENCES Ali E. Geographic Information System (GIS): Definition, development, applications & components [J]. Department of Geography, Ananda Chandra College. India, 2020. Al-Mansoori T., Abdalkadhum A., Al-Husainy A.S. A GIS-Enhanced pavement management system: A case study in Iraq [J]. Journal of Engineering Science and Technology, 2020, 15(4): 2639–2648. Budzy´nski M., Kustra W., Okraszewska R., et al. The Use of GIS Tools for Road Infrastructure Safety Management [C]//E3S Web of Conferences. EDP Sciences, 2018, 26: 00009. Hatamleh R.I., Jamhawi M.M., Al-Kofahi S.D., et al. The use of a GIS system as a decision support tool for municipal solid waste management planning: A case study of al nuzha district, Irbid, Jordan [J]. Procedia Manufacturing, 2020, 44: 189–196. Irshaid H., Hasan M.M., Hasan R., et al. User activity and trip recognition using spatial positioning system data by integrating the geohash and GIS approaches [J]. Transportation Research Record, 2021, 2675(4): 391–405. Li J., Pei X., Wang X., et al. Transportation mode identification with GPS trajectory data and GIS information [J]. Tsinghua Science and Technology, 2021, 26(4): 403–416. Li M., Yang H. Safety Evaluation of Track Engineering and GIS Management System in Computer Environment [C]//2021 International Symposium on Computer Technology and Information Science (ISCTIS). IEEE, 2021: 1–5. S., Bansal V.K. Location-based planning and scheduling of highway construction projects in hilly terrain using GIS [J]. Canadian Journal of Civil Engineering, 2018, 45(7): 570–582. Zeeshan S., Shahid Z., Khan S., et al. Solid Waste Management in Korangi District of Karachi Using GPS and GIS: A Case Study [C]//2018 7th International Conference on Computer and Communication Engineering (ICCCE). IEEE, 2018: 1–4.

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Research on the function-oriented method for delimiting coastal setback lines in China He Zhang*, Yang Yu* & Yantong Li* School of Architecture, Tianjin University, China

Haoru Ye* China Academy of Urban Planning & Design, Institute of Historical and Cultural Cities, China

ABSTRACT: Under the planning background of the territorial planning reform, this research aims at the unbalanced benefits of regional economy and society and weak awareness of overall planning of sea and land. A method of delimiting coastal zone setback lines based on functional uses is proposed. Firstly, the definition and research connotation of the existing coastal retreat lines are extended to determine the way to delimit the coastal setback lines and the elements of coastal zone setback lines. Then, the functional uses of coastal zones are divided into three categories and eleven subcategories, and the connection between the functional use zoning of the coastal zones and the delimitation of the coastal zone setback lines is established, which lays a foundation for clarifying the management and control methods and subjects in the coastal zone setback line area. After that, combined with relevant studies at home and abroad, and based on the classification of coastal zone functions and uses, this research puts forward the delimitation methods of coastal zone setback lines in different functional areas from three perspectives: the starting line of the coastal zone setback line, the delimitation direction, and the retreat distance. 1 INTRODUCTION Under the background of China’s “multi compliance and integration” land and space planning reform, the work of collating the base map of sea and land space, verifying the marine ecological red line and the “three zones and three lines” of the land area is of positive significance to the overall planning of sea and land space. However, the above spatial planning methods are still not enough to stimulate the advantages of coastal areas in the economy, ecology, geographical location, and landscape, and it is difficult to deal with the negative impact of human intervention and marine disasters on coastal areas with the integration of sea and land. Coastal developed countries such as Europe and the United States take the coastal setback line as a means to control the spatial environment of the coastal zone, which is widely used. It plays an important role in avoiding marine disasters and maintaining the ecological security of the coastal zone. In China, there are still many deficiencies in the delimitation of coastal zone setback lines, mainly including the following three aspects: (1) The research on the correlation mechanism of coastal zone setback line delimitation with different spatial uses and functions is insufficient. (2) Overall consideration of sea and land space is lacking. The research scope is mostly focused on the land or seaside, ignoring the thinking of the “domain” level of the coastal zone. (3) The research on coastal types mostly focuses on the natural coastline, and the research on the setback line of artificial coastline is not sufficient. Therefore, with the help of the research on the delimitation method of coastal zone setback line, coordinating the sea and land spatial elements of coastal zone ∗ Corresponding Authors: [email protected], [email protected], [email protected] and [email protected]

DOI 10.1201/9781003384830-26

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area, determining the retreat distance of coastal zone, and delimiting reasonable control areas will become a useful reference and supplement for the overall management of sea and land. To summarize, this paper explores the key elements of the innovation of the coastal zone setback line’s delimitation method and determines the setback line’s delimitation method by classification in combination with different coastal zone uses and functions. 2 INNOVATIVE ELEMENT OF COASTAL ZONE SETBACK LINE DELINEATION METHOD 2.1 Starting line Determining the starting line of the coastal setback line is the first step in the delimitation of the coastal setback line. Different countries and scholars have different calibration positions and definitions for the starting line of the coastal setback line. For example, some parts of Italy take the wave shear point as the starting line of the coastal setback line (Beijing: Ocean Press 1988), while most countries such as Denmark and the United States take the average high tide line as the starting line of the setback line (John 2000). Based on the existing research, Chinese scholars Wen Chaoxiang and Wang Peng (Wang 2012) further discussed and summarized the starting point of the coastline setback line based on the classification of different sediments of the natural coastline. However, the research on the starting line of the coastal setback line of the artificial coastline needs to be supplemented. 2.2 Delimitation direction The Coastal Zone is an ecologically fragile zone highly affected by human activities (Ye 2019), which has many complete ecological units and rich landscape resources. In the period of rapid development, the ocean is transformed into land through disorderly development, utilization, reclamation, and other activities, to continuously expand the land space, resulting in the occupation of marine ecological resources space, the deterioration of the water environment, the reduction of natural coastline and other problems, and irreversible damage to the ecological environment (Li 2021). As an area where land and sea systems coexist, ecological environment protection and resource development, and coastal zone utilization are jointly affected by land and sea. Therefore, the delimitation direction of the coastal setback line should also balance the relationship between the land, sea, and people to realize the overall planning of sea and land space. Most of the existing studies are based on the functional types of the sea area or the negative impact on the land area. They carry out the relevant research on the delimitation of the coastal zone setback line and have strong one-way thinking. The adaptability between the coastal setback line and the functional use of the coastal zone needs to be improved. Therefore, given the above problems, this paper further considers the functional areas and spatial uses of the coastal zone from the perspective of land and sea space planning, integrated research, and management, to provide support for the delimitation of the coastal zone setback line. 2.3 Retreat distance The retreat distance will be classified according to the functional use of the coastal zone. The influencing factors of the retreat distance of the coastal zone setback line in each functional use area will be analyzed, the value proposal or calculation method of the retreat distance of the coastal zone will be given, and the setback line distance will be determined according to different types of space.

3 CLASSIFICATION OF COASTAL ZONE USES AND FUNCTIONS Establishing the functional use classification of the coastal zone is preparatory work for the delimitation of coastal zone setback lines. 204

The functions and uses of coastal zone areas can be divided into three levels: large, medium, and small (Table 1). Large categories can be divided into production, living, and ecological spaces. These three types of space highlight the main functions of coastal zone areas at the regional scale. Within the territorial spatial system of the coastal zone, the three types of functional uses play a supporting role in maintaining the construction of the spatial pattern of the coastal zone and should be controlled differently. However, the functional use division of coastal zones based on a regional scale is not easy to implement control at the meso or micro scale. Therefore, refining the control contents and objects of different functional areas in the coastal zone is still necessary. According to the differences in functions undertaken by sea and land space carriers, the main functions of the middle category are classified twice, and the subdivision of the small category further defines the specific functions and uses of each sea and land space. Table 1. Classification of functional uses in the coastal zone. General category

Middle category

Subclass

Coastal production space

Coastal industrial and mining area

Coastal industrial zone Mineral and energy mining area ——– ——– Fishery infrastructure area Breeding area Submarine pipeline and tunnel area Land for nuclear power plant Reservoir land Sewage disposal area Military zone Scientific research experimental area Cultural relics and historic sites Urban living area Village and town living area ——– Land ecological protection red line area Marine ecological protection red line area General ecological area of land area General marine ecological area

Port terminal area Agricultural production area Fishery production area Infrastructure area

Strategic support area

Coastal living space

Coastal zone ecological space

Other areas General urban living area Tourism and entertainment area Ecological protection red line area General ecological area

4 DELINEATION METHOD OF COASTAL SETBACK LINE BASED ON FUNCTIONAL USE CLASSIFICATION Based on the classification of functional use areas of the coastal zone, this paper studies the delimitation method of the coastal zone setback line, which is divided into the following three steps: firstly, summarize and analyze the starting line of the coastal zone setback line for different types of coastlines; secondly, sort out the marking direction of the functional use area; thirdly, draw up the retreat distance of the coastal zone setback line and clarify the working boundary of management and control. 4.1 Demarcation of the starting line of the coastline setback line From the perspective of coastline types, based on the relevant research on coastline types, this paper summarizes the starting line of the coastline setback line for the natural coastline and artificial coastline, so as to enrich the connotation of the starting line of the coastline setback line. According to the coastline sediment type, the coastline setback line’s starting line can be divided into two types: 205

natural coastline and artificial coastline. The artificial shoreline in the coastal zone is mainly divided into two categories: the artificial shoreline of structures and the artificial shoreline of reclamation. The artificial shoreline of structures is then divided into two categories: the shoreline of coastal structures (seawall, revetment, road, etc.) and the shoreline of vertical or oblique narrow and long structures (approach embankment, jetty wharf, offshore embankment, etc.). In addition to changing the natural properties of the shoreline, the shoreline of impermeable structures with slope structures in the shoreline of coastal structures does not affect the sea-land boundary, and its starting point is still the average high tide level of spring tides for many years. For the convenience of practical application, the coastline of impermeable structures with vertical bank walls and revetment takes the line in front of the embankment top as the starting point. For the coastline of vertical or oblique long and narrow structures, considering the actual marking needs, the starting point is still in the original coastline. The artificial shoreline of reclamation can be divided into four categories: the shoreline of cultivation embankment, the shoreline of Yantian embankment, the shoreline of construction embankment, and the shoreline of land reclamation. The artificial shoreline of the embankment does not form an effective shoreline, and its starting point is still in the original shoreline. The land reclamation shoreline has formed an effective shoreline, and the location of its starting point is the same as the shoreline of coastal structures. See Table 2 and Table 3 for details. Table 2. Determining the calibration position of natural coastline starting points (Zhejiang Provincial Bureau of quality supervision 2019). Shoreline type

Starting line

Bedrock shoreline Sandy shoreline Silt muddy shoreline

Trace line of the sea-land boundary at the mean high tide level of spring tides for many years

Biological shoreline

Closest point of the biological species to the land (sea)

Examples

4.2 Demarcation of the starting line of the coastline setback line This paper holds that the coastline setback line should realize the two-way demarcation of the sea and land space, that is, switching from the demarcation of “one-way land area” on the landward side to the study of “sea and land area” in the coastal zone. This paper will determine the direction of the setback line from three scales: macro, medium, and micro. 4.2.1 Macroscale – two-way delineation At the macro scale, based on the spatial characteristics of coastal areas, the classification and delimitation of land and island spatial units are the first steps in clarifying the direction. Generally, the setback line of the coastal zone is drawn in both directions to the sea and land. When the scale of the available islands is difficult to meet the retreat distance requirements, the retreat distance can be reduced as appropriate, or the whole island can be included in the control area of the coastal setback line. For the islands that have been specified as nonconstructive, they shall be delimited only one way to one side of the sea area. The specific examples are shown in Table 4. 206

Table 3. Determining calibration positions of artificial coastline starting points (Zhejiang Provincial Bureau of quality supervision 2019). Shoreline type Artificial shoreline structure

Reclamation artificial shoreline

Coastal structures

Starting line

Examples

Ramp structure (impervious)

Trace line of the sea-land boundary at the mean high tide level of spring tides for many years

Vertical bank wall and revetment (impervious)

Along the line in front of the embankment top

Vertical or oblique shoreline of long and narrow structures

Starting from the coastline where the structure is located

Artificial shoreline of the embankment

Shorelines affected by ocean dynamics

Reclamation shoreline

According to the specific situation, it is regarded as the artificial shoreline of the structure

Table 4. Direction of the retraction line of the coastal zone at the macro scale. Type

General coastal zone

Islands can be built (insufficient retreat distance), but islands cannot be built

Direction

From the starting line to both sides of the sea and land

Draw a line from the starting line to the seaside

Examples

207

4.2.2 Mesoscale-spatial relationship On the mesoscale level, the island shore relationship in the coastal zone space presents a more complex and diversified type. When the distance between land island units and island units is within the specified retreat distance of the coastal zone setback line, the intersection of coastal zone setback lines of different spatial units will occur. Therefore, on the mesoscale level, the spatial relationship between the land island and island combination should be handled well. Therefore, it is stipulated that when the island and land space units intersect, the connecting line of the peripheral edge line of the setback line to the seaside is taken as the setback line of the coastal zone. The specific example is shown in Table 5.

Table 5. Convergence of the setback line of the coastal zone at the mesoscale level. Land-Island relationship Type

Land to single Island

Land to multi Island

Island-Island relationship

Cohesive mode

4.2.3 Microscale – unidirectional adjustment Because the coastal zone setback line is based on the delimitation of coastal zone functional use areas, different coastal zone functional use areas determine the final direction of coastal zone setback line delimitation. For example, the construction in general urban living areas does not directly occupy or affect the space environment of the sea area, so it only needs to retreat to the land side. Therefore, according to the differences in the spatial use of coastal zone areas for different functional uses, the delimitation directions of the coastal zone setback line can be divided into the landside, seaside, and sea land side. The types of each direction belong to functional areas, as shown in Table 6.

Table 6. Direction of the receding line of the coastal zone in the different functional areas. Delimitation direction Ribbon type

Landward side

Seaward side

Both land and sea

Coastal industrial area, agricultural production area, general urban living area, and general ecological area inland area

General marine ecological area, tourism and entertainment area, and fishery production area

Tourism and entertainment area, sewage disposal area

Type diagram

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Table 7. Basis for initial setback distance. Coastal zone functional area

Initial setback distance (unit: m)

Determination principle of retreat distance

Withdrawal distance considerations

Coastal industrial zone

Balance the economic benefits brought by the proximity to the sea and the economic losses brought by marine disasters

Obvious sea-related characteristics, urban fringe, and relying on ports Strong interference Most of them are artificial shorelines with strong disaster prevention and resistance

80

Agricultural production area

Protect the ecological environment of the natural coastline and the supporting facilities in the agricultural area

Most of them are plain areas, and some of them directly use coastal beach resources with convenient transportation Weak interference Most of them are muddy shorelines with weak disaster prevention and resistance

100

Fishery production area

Control the huge damage to the coastal ecological environment caused by the disorderly development of breeding areas

Most of them are coastal aquaculture; nearshore seawater resources are directly used, causing serious pollution Strong interference Most of them are muddy shorelines and rich in resources

200

General urban living area

Protect the coastal ecological environment and landscape resources, and ensure the safety of residents’ lives and property and the right to be close to the sea

Obvious seaward characteristics Strong interference Most of them are artificial shorelines or natural shorelines with protection projects, having strong disaster prevention and resistance ability

100

Tourism, leisure, and entertainment area

Protect the coastal ecological environment and landscape resources and ensure the accessibility of landscape resources

It has obvious characteristics of being close to the sea and relies on the coastal landscape Strong interference Most of them are sandy gravel and bedrock shorelines, which are rich in landscape resources

120

General ecological area

Ensure the integrity of habitat units in the area

The integrity of the habitat unit is obvious Little interference Mostly natural coastline

150

Ecological protection red line area

Ensure the integrity of habitat units in the area

The integrity of the habitat unit is obvious No interference Mostly natural coastline

300

4.3 Demarcation distance of the coastline setback line The retreat distance will be classified according to the functional use of the coastal zone, the influencing factors of the retreat distance of the coastal zone setback line in each functional use area will be analyzed, and the value proposal or calculation method of the retreat distance of the coastal zone will be given. According to the classification of the function and use of the coastal zone, the retreat distance values of production space, living space, and ecological space are determined, respectively, as shown in Table 7.

209

5 CONCLUSION As an integral part of the territorial space of the coastal zone, the coastal setback line has practical significance for the protection of ecological security, the shaping of landscape style, and the avoidance of disaster risk in the coastal zone. The main conclusions of this paper are as follows: Firstly, the paper summarized the starting line of the coastal setback line for both the natural coastline and artificial coastline, enriching the connotation of the starting line of the coastal setback line. Secondly, the paper coordinated the two-way demarcation of the sea and land space and determined the demarcation directions of the setback line (macro, medium, and micro scales). After sorting out the demarcation directions of different functional areas, the paper summarized three directions (the land side, the seaside, and the sea and land sides). Thirdly, the determination of the retreat distance is not an accurate value, but the retreat range value and calculation idea recommended according to the retreat requirements of different functional areas are accurate, and they should be discussed one by one in the specific delimitation. However, the coastal zone area, especially the marine space and land space, is more threedimensional than the use of space. It is difficult to achieve the three-dimensional governance effect of the coastal zone area only by delimiting and controlling the coastal zone setback line in the twodimensional plane. In future research, based on the reasonable division of the functions and uses of the coastal zone, the coastal zone setback line should be combined with the regional management and control work to carry out layered research on the coastal zone.

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Research on Theory and Method of Sea Reclamation Space Planning Based on Comprehensive Disaster Prevention Constraints (No. 51778404)).

REFERENCES John R, Clark, Wu Keqin, Coastal Zone Management Manual [J], 2000. Li Yun, Fang Jing Research on marine management and planning development of land spatial planning system [J]. South Architecture, 2021(02):45–50. MarineTechnology Branch of the United Nations Economic and Social Council, Coastal Zone Management and Development [M]. Translated by the Policy Research Office of the State Oceanic Administration. Beijing: Ocean Press, 1988. Wang Peng, Cai Yueyin, Lin Xia, et al. Establishment and application of regression line model of coastal buildings – a case study of Dalian City [J]. Ocean Development and Management, 2012, 29(1): 67-70. Ye Shufeng, Wen Quan, What are the characteristics of coastal life community? [J]. China Ecological Civilization, 2019 (4): 20. Zhejiang Provincial Department of Natural resources, Technical Specification for Coastline Survey: DB37/T3588-2019 [S]. Issued by Zhejiang Provincial Bureau of Quality Supervision, 2019.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Natural vibration characteristics and stability analysis of radial steel gate Jing Dong* & Yuhang Bai State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Xi’an, China

Duofei Pei China Energy Engineering Group Shaanxi Electric Power Design Institute, Xi’an, China

Junfa Zhang State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Xi’an, China

ABSTRACT: In order to investigate the natural vibration characteristics and stability of gates, the radial steel gate of a practical project was used as the research object. The radial gate model established by HyperMesh was imported into ABAQUS to calculate the natural vibration characteristics of the gate and analyze the vulnerable position of the gate. In ABAQUS, the stability of the radial steel gate structure was analyzed, the eigenvalue buckling model of the gate under hydrostatic pressure was studied, and the eigenvalue coefficients of the gate under different water depths were obtained. Meanwhile, the nonlinear buckling analysis of the arms under transverse loads was carried out at different positions. The critical load values and instability characteristics of the gate under static water pressure, gravity load, and transverse load acting on different positions were obtained, which could provide references for gate structure design.

1 INTRODUCTION There are various types of steel gate structures, the most popular of which are plane steel gates, radial steel gates, and herringbone steel gates. Among them, radial gates are widely used in engineering because of their excellent flow pattern and flexible opening and closing capability. The safety of radial steel gates is not only related to their own operation and durability but also affects the safety of water conservancy projects. Kim et al. studied the influence of gate opening on the natural vibration frequency and flow velocity (Kim et al 2017). Jijian Lian et al. analyzed the vibration process of the radial gate during flood discharge and elaborated on the vibration mechanism in detail (Lian et al 2020). Seung Oh Lee et al. proposed a method to mitigate the vibration of the gate and verified the finite element analysis results with the experimental results (Lee et al 2018). Yi FeiCai et al. investigated and analyzed that most accidents were caused by arm instability and pointed out the defects of the traditional design (Yi et al 2015). Anami et al. carried out numerical simulation research on the Folsom dam in the accident (Anami et al 2005). Poornakanta et al. analyzed the influence of gate vibration under water flow excitation on gate fatigue life through numerical simulations (Poornakanta et al 2018). Erdbrink et al. combined experimental research with numerical simulations to explore a new method to reduce the cross-flow vibration of bottom-flow hydraulic gates (Erdbrink et al 2014). ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-27

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Kwon focused on adjusting the position of radial gate arms to minimize weight (Kwon et al 2004). Pegios analyzed the static and buckling loads of the plane beam using the finite element method, which was in good agreement with the actual results (Pegios et al 2015). Zhang Jiguang et al. theoretically analyzed the critical load value of spatial structures composed of straight bars under external loads, and programmed and calculated the buckling critical load of arm structures (Zhang et al 1992). Wang studied the characteristics of vibration, holding force, and gate-closing failure during the closing process through physical model experiments (Wang et al 2020). Zhang QL et al. used the finite element method to conduct linear and nonlinear buckling analysis of the arm structure and obtained the first ten-order natural vibration frequencies of the structures (Zhang et al 2014). Zhang Huairen et al. discovered that the stability of the arm can be significantly modified by changing the web thickness of the arm (Zhang et al 2020). In summary, it can be found that the gate is easily affected by external conditions. When the periodic load impacts the gate and the load frequency reaches the multiple relationships of a certain order vibration mode frequency of the gate, the structure is damaged. When the load exceeds the specified load, the hydrostatic pressure load in front of the gate panel is unevenly distributed and the gate undergoes large deformation, causing the uneven stress of the straight arm to be destroyed. Accordingly, taking an actual project in a mountainous area as an example, the frequency and vibration mode of the gate were calculated using the finite element method, which provided references for optimizing the gate scheme. In software, the stability of the radial steel gate structure was analyzed, the eigenvalue buckling model of the gate under hydrostatic pressure was studied, and the eigenvalue coefficients of the gate under different water depths were obtained. Meanwhile, the nonlinear buckling analysis of the arms under transverse loads was studied at different positions. The critical load values and instability characteristics of the gate under static water pressure, gravity load, and transverse load (live load) acting on different positions were obtained, which could provide references for gate structure design.

2 RADIAL STEEL GATE MODEL 2.1 Model introduction The radial steel gate was a double main beam structure with inclined support arms. The composition of the gate included: the gate page structure, the main beam system, the arm structure, and the hinge structure. The structure of the radial gate was shown in Figure 1.

Figure 1. Views of the radial gate.

The opening width, height, and radius of the gate were 12.3 m, 6.3 m, and 7.5 m, respectively. As shown in Figure 2, the gate consisted of 9 beams and 7 longitudinal beams. The main beams and longitudinal beams were I-shaped steel, and the secondary beams were made of channel steel. 212

Figure 2.

Beam system.

2.2 Parameter setting The radial gate was made of Q235 steel with a density of 7848 kg / m3 , the elastic modulus was 2.21 × 1011 MPa, and the Poisson ratio was 0.3. Figure 3 illustrated the true stress-strain constitutive relation curve set by nonlinear analysis. The following was the conversion formula between nominal stress and strain and between real stress and strain. εtrue = ln (1 + εnom )

(1)

σtrue = σnom (1 + εnom )

(2)

where εnom = the nominal strain obtained by a single tensile/compression test, σnom = nominal stress, εtrue = real strain, and σtrue = real stress. The gate page structure, beam structure, and arm structure of the model were shell elements, and the hinged support of the model was the hexagonal element. Binding constraints were set between the gate page and beam system and between the arm structure and beam system to simulate welding connection. The finite element model of the radial gate was shown in Figure 4. The hinge position of the gate can only be allowed to rotate around the Z-axis. The bottom sill of the gate was restrained in the Y direction and both sides of the panel were restrained in the Z direction.

Figure 3. Q235 steel constitutive relation.

Figure 4. Finite element model of the gate.

3 NATURAL VIBRATION CHARACTERISTICS OF THE ARC GATE To analyze the self-vibration characteristics of the gate in an anhydrous state, the natural frequencies of the order from one to nine and corresponding vibration modes were calculated using the Lanczos method. The first nine-order vibration mode displacement clouds of the radial gate was shown in Figure 5. 213

Figure 5.

Natural vibration frequency displacement cloud of nine order gate.

214

Table 1. Description of natural frequency and vibration mode of the gate. Modal number

Frequency/Hz

Characteristics of vibration mode

The first order The Second order

15.241 15.329

The third order

17.171

The fourth order

17.292

The fifth order

25.422

The sixth order

29.598

The seventh order

29.704

The eighth order The ninth order

32.303 33.001

Left and right arm structures near the hinged support bent upwards The right arm structure near the hinged support bent downward and the left arm structure bent upwards Torsional vibration was generated above the panel, the right arm structure bent upwards, and the left arm structure bent downward Radial vibration was generated above the panel, and the right and left arm structures bent upwards Local radial vibration was generated at the left and right sides of the gate page Local vibration was generated at the left and right sides of the gate page, and the oblique supporting arm of the left arm structure bent to the right Torsional vibration was generated above the panel, and the oblique supporting arm of the left and right arm structure bent to the right The oblique supporting arm of the left arm structure bent to the right The oblique supporting arm of the right arm structure bent to the right

*Note: The structure names mentioned in the table were derived from Figure 1.

Figure 5 and Table 1 exhibited that the natural frequency of the radial gate was concentrated in the range of 15.241 Hz to 33.001 Hz, and the main frequency area of water flow fluctuation pressure was mainly distributed between 0 and 20Hz. Resonance is likely to happen. Vibration modes of the radial gate in an anhydrous state were mainly manifested as bending and torsional vibration of the gate page, and bending vibration of the supporting arm and oblique supporting arm. 4 STABILITY ANALYSIS OF RADIAL STEEL GATE 4.1 Working conditions of buckling analysis Condition one was linear eigenvalue buckling analysis of the gate at 6.3, 7, and 8 m hydraulic head, respectively. Conditions two to six were nonlinear buckling analyses under 6.3 m head. And lateral loads at positions one to five were shown in Figure 6.

Figure 6. Diagram of lateral load distribution.

Figure 7. Mechanical diagram of buckling analysis.

4.2 Load condition setting All operating conditions were loaded in front of the panel by hydraulic pressure, and only conditions 2 to 6 were applied with concentrated loads at different positions of support arms. The radial gate 215

was 6.3 m high and the water depth was 6.3m. The gate page was divided into 22 layers according to the height and the water pressure was loaded in layers. The distributed load of the panel was shown in Table 2 and the mechanical diagram of the buckling analysis was shown in Figure 7. Table 2. Distributed load of the panel. Number of panel layers

Water depth pressure/MPa

Number of panel layers

Water depth pressure/MPa

Number of panel layers

Water depth pressure/MPa

1 2 3 4 5 6 7 8

0.00130 0.00409 0.00692 0.00978 0.01269 0.01556 0.01845 0.02141

9 10 11 12 13 14 15 16

0.02431 0.02722 0.03065 0.03354 0.03644 0.03936 0.04217 0.04501

17 18 19 20 21 22 – –

0.04783 0.05064 0.05342 0.56190 0.05853 0.06081 – –

4.3 Eigenvalue buckling analysis In eigenvalue buckling analysis, the most vulnerable form of instability was the low order mode. Therefore, only the first and second-order eigenvalues and buckling modes were used to analyze the eigenvalues of the radial steel gate under different head heights. Buckling modes were shown in Figure 8, and eigenvalue coefficients at 6.3 m, 7 m, and 8 m water pressures were shown in Table 3.

Figure 8.

Buckling modes under hydrostatic pressure.

Table 3. Calculation results of critical water pressure load and eigenvalue coefficients.

Water depth/m

First layer of water pressure /MPa

twenty-second layer of water pressure /MPa

6.3 7 8

0.001304 0.008164 0.017964

0.060812 0.067672 0.077472

First-order eigenvalue coefficient 1.7436 1.2721 0.9173

Second-order eigenvalue coefficient

First layer of critical water pressure /MPa

Second layer of critical water pressure /MPa

1.7458 1.2742 0.9184

0.002274 0.010385 0.016479

0.106032 0.086086 0.071066

Buckling modes were identical under different water pressure. Figure 8 exhibited that the buckling of the radial gate under water pressure was represented by the bending of the near hinge 216

supporting arm. The critical eigenvalue coefficient of the gate was 1.7436 at 6.3 m water depth and 0.9173 at 8 m water depth. It illustrated that the surplus of the gate under water pressure load was not high. 4.4 Nonlinear buckling analysis In buckling analysis, it was usually assumed that the external loads were calculated in a uniform proportion, but in the actual environment, there were both live and permanent loads. Live load varied with external conditions. In this case, the critical value of the live load was calculated using the iteration method: Pb = S × (Pd + K × Pl ) (3) where Pb is the buckling load, S is the buckling load coefficient, Pd is the permanent load, and Pl is the live load. During the iteration, the permanent load was kept unchanged, and the live load was modified. Coefficient S1 was calculated by the permanent load plus the live load, and load coefficient S2 was calculated by the permanent load plus S1 times the live load. Iterated as described above until the buckling load coefficient was close to 1.0. The critical load coefficient for the live load was S1 , S2 …Sn multiplied, and the critical load was the initial live load multiplied by the critical load coefficient. Permanent loads under conditions two to six were the gravity load and 6.3 m water pressure load. 4.4.1 Nonlinear buckling analysis at position one The live load under condition two was the transverse load at position one, and the value was -385 kN. After calculation, the first 20 increment steps were extracted from the results, and the load increment step was negative at step 9. The load began to unload and the structure had become unstable. In step 8, the load coefficient reached its maximum value which was the critical load of the structure, and the load coefficient of step 8 was 0.988536. Through the iteration calculation, the load coefficients from S1 to S5 were 0.1, 0.237, 0.591, 0.741, and 0.989, respectively, so the critical load coefficient was 0.010265 and the critical load value was 3.952 kN. The displacement cloud of the critical buckling state at position one was shown in Figure 9 and the arc length curve of the load coefficient at position one was shown in Figure 10.

Figure 9. Displacement cloud of the critical buckling state at position one.

Figure 10. Arc length curve of the load coefficient at position one.

Figure 9 exhibited that the supporting arm of the radial gate was bent near the hinged support and the displacement near the hinged support was 14.06 mm. Figure 10 presented that when the load coefficient of the last iteration reached its peak value, it was 0.989. The structure was in a critical state of destabilization, the load coefficient decreased gradually and the arc length still increased. 217

Figure 11 showed the displacement cloud of the following incremental steps. When the first position reached a critical buckling state, the load began to unload gradually with the increase of incremental steps, but the deformation at this position increased from 14.06 mm to 37.87 mm, and the arm structure was unstable.

Figure 11.

Displacement cloud of incremental steps 10, 15 and 20.

4.4.2 Nonlinear buckling analysis at position two Live load under condition three was the transverse load at position two, and the value was 278kN. After calculation, the first 20 increment steps were extracted from the results, and the load increment step was negative at step 9. The load began to unload and the structure had become unstable. In step 8, the load coefficient reached its maximum value which was the critical load of the structure, and the load coefficient of step 8 was 1.00376. Through the iteration calculation, the load coefficients from S1 to S4 were 0.384, 0.983, 0.998, and 1.004, respectively, so the critical load coefficient was 0.374434 and the critical load value was 104.09 kN. The displacement cloud of the critical buckling state at position two was shown in Figure 12 and the arc length curve of the load coefficient at position two was shown in Figure 13. Figure 12 exhibited that the first oblique supporting arm of the radial gate was laterally bent. Figure 13 presented that when the load coefficient of the last iteration reached its peak value, it was 1.00376. The structure was in the critical state of destabilization, the load coefficient decreased gradually and the arc length still increased. Figure 14 showed the displacement cloud of the following incremental steps. When the second position reached critical buckling state, the load began to unload gradually with the increase of incremental steps, but the deformation of the first oblique supporting arm increased from 23.06 mm to 121.1 mm, and the arm structure was unstable. 218

Figure 12. Displacement cloud of the critical buckling state at position two.

Figure 14.

Figure 13. Arc length curve of the load coefficient at position two.

Displacement cloud of incremental steps 10, 15 and 20.

4.4.3 Nonlinear buckling analysis at position three Live load under condition four was the transverse load at position three, and the value was 270kN. After calculation, the first 20 increment steps were extracted from the results, and the load increment step was negative at step 8. The load began to unload and the structure had become unstable. In step 7, the load coefficient reached its maximum value which was the critical load of the structure, and load coefficient of step 7 was 1.00938. Through the iteration calculation, the load coefficients from S1 to S4 were 0.355, 0.678, 0.715, and 1.009, respectively, so the critical load coefficient was 0.173642 and the critical load value was 46.88 kN. The displacement cloud of the critical buckling state at position three was shown in Figure 15 and the arc length curve of the load coefficient at position three was shown in Figure 16. 219

Figure 15. Displacement cloud of the critical buckling state at position three.

Figure 16. Arc length curve of the load coefficient at position three.

Figure 15 showed that the supporting arm of the radial gate is bent downward. Figure 16 presented that when the load coefficient of the last iteration reached its peak value, it was 1.0090. The structure was in the critical state of destabilization, the load coefficient decreased gradually and the arc length increased. Figure 17 showed that the displacement cloud of the following incremental steps. When the third position reached critical buckling state, the load began to unload gradually with the increase of incremental steps, but the mid-span position displacement of the arm increased from 17.4 mm to 102.1 mm, the deformation continued to increase, and the arm became unstable.

Figure 17.

Displacement cloud of incremental steps 10, 15, and 20.

220

4.4.4 Nonlinear buckling analysis at position four Live load under condition five was the transverse load at position four, and the value was 247 kN. After calculation, the first 20 increment steps were extracted from the results, and the load increment step was negative at step 13. The load began to unload and the structure had become unstable. In step 12, the load coefficient reached its maximum value which was the critical load of the structure, and load coefficient of step 12 was 0.994076. Through the iteration calculation, the load coefficients from S1 to S3 were 0.536, 0.974, and 0.994, respectively, so the critical load coefficient was 0.518932 and the critical load value was 128.18 kN. The displacement cloud of the critical buckling state at position four was shown in Figure 18 and the arc length curve of the load coefficient at position four was shown in Figure 19.

Figure 18. Displacement cloud of the critical buckling state at position 4.

Figure 19. Arc length curve of the load coefficient at position 4.

Figure 18 exhibited that the second oblique supporting arm bent laterally close to the state page structure. Figure 19 presented that when the load coefficient of the last iteration reached its peak value, it was 0.994. The structure was in the critical state of destabilization, the load coefficient decreased gradually, and the arc length still increased. Figure 20 showed the displacement cloud of incremental step 20. When the fourth position reached critical buckling state, the load began to unload gradually with the increase of incremental steps, the deformation continued to increase, and the arm became unstable.

Figure 20.

Displacement cloud of incremental step 20.

4.4.5 Nonlinear buckling analysis at position five Live load under condition six was the transverse load at position five, and the value was 439kN. After calculation, the first 20 increment steps were extracted from the results, and the load increment step was negative at step 9. The load began to unload and the structure had become unstable. In step 8, the load coefficient reached its maximum value which was the critical load of the structure, and load coefficient of step 8 was 1.00586. Through the iteration calculation, the load coefficients from S1 to S5 were 0.273, 0.636, 0.671, 1.037, and 1.006, respectively, so the critical load coefficient was 221

0.121596 and the critical load value was 53.38 kN. The displacement cloud of the critical buckling state at position five was shown in Figure 21 and the arc length curve of the load coefficient at position five was shown in Figure 22.

Figure 21. Displacement cloud of the critical buckling state at position 5.

Figure 22. Arc length curve of the load coefficient at position 5.

Figure 21 exhibited that the supporting arm bent downward at load application position. Figure 22 presented that when the load coefficient of the last iteration reached its peak value, it was 1.006. The structure was in a critical state of destabilization, the load coefficient decreased gradually, and the arc length increased. Figure 23 showed the displacement cloud of the following incremental steps. When the fifth position reached a critical buckling state, the load began to unload gradually with the increase of incremental steps, but the displacement of the arm increased from 21.3 mm to 84.9 mm, the deformation continued to increase, and the arm became unstable.

Figure 23.

Displacement cloud of incremental steps 10, 15, and 20.

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5 CONCLUSION In this paper, the natural vibration characteristics of the radial gate structure were calculated and obtained. The stability of the gate was analyzed and the following conclusions were drawn: The natural frequency of the radial gate was concentrated in the range of 15.241 Hz∼33.001 Hz. If the vibration frequency of the gate was in this range, resonance was likely to happen. If the gate resonance was a low-order vibration, there was a high probability that the arm structure near the hinged support was bent. If the gate resonance was a higher-order vibration, it was likely that the diagonally braced structure was bent, which needed to be optimized and strengthened. The critical water pressure load coefficients of the radial gate under 6.3 m, 7 m, and 8 m static water pressure were 1.7436, 1.2712, and 0.9173, respectively, and the mode was the supporting arm bending close to the hinged support. The gate operated safely under the designed head, but the surplus of bearing hydraulic load was not high. The critical values of transverse loads at positions one to five were 3.95 kN, 104.09 kN, 46.88 kN, 128.18 kN, and 53.38 kN, respectively. When the critical load was reached, the load began to unload, but the deformation at this point still increased. Comparing the instability modes of each position, the mid-span position of the arm was easier to destabilize than the node position.

REFERENCES Anami, K. Ishii, N. & Knisely, CW. 2005. Hydrodynamic pressure load on Folsom dam tainter gate at onset of failure due to flow-included vibrations. ASME Pressure Vessels and Piping Conference 557–564. Brusewicz, K. Sterpejkowicz-Wersocki, W. & Jankowski, R. 2017. Modal analysis of a steel radial gate exposed to different water levels. Archives of Hydro-Engineering and Environmental Mechanics 64(1). Erdbrink, C.D. Krzhizhanovskaya, V.V. & Sloot, P.M.A. 2014. Reducing cross-flow vibrations of underflow gates: Experiments and numerical studies. Journal of Fluids and Structures. (50): 25–18. Ji, L. Liu, Z. Zhong, W. Xing, F. & Han, MF. 2011. Dynamic instability mechanism and vibration control of radial gate arms. Applied Mechanics and Materials 50–51. Kim, NG. Cho, Yong. & Lee, KB. 2017. Flow-induced vibration and flow characteristics prediction for a sliding roller gate by two-dimensional unsteady CFD simulation. Journal of Mechanical Science and Technology 31(7): 3255–3260. Kwon, Young-Doo. Jin, Seung-Bo. Kim, Jae-Yong. & Lee, Il-Hee. 2004. Structural Engineering and Mechanics 17(5): 611–626. Lee, SO. Seong, H. & Kang, JW. 2018. Flow-induced vibration of a radial gate at various opening heights. Engineering Applications of Computational Fluid Mechanics 12(1): 567–583. Lian, JJ et al. 2020. Analysis of the cause and mechanism of hydraulic gate vibration during flood discharging from the perspective of structural dynamics. Applied Sciences 10(2): 629. Pegios, IP. Papargyri-Beskou, S. & Beskos, DE. 2015. Finite element static and stability analysis of gradient elastic beam. Acta Mechanica 226(3): 754–768. Poornakanta, H et al. 2018. Optimization of sluice gate under fatigue life subjected for forced vibration by fluid flow. Strojnícky casopi–Journal of Mechanical Engineering 68(3): 129–142. Wang, YZ et al. 2020. Characteristics of plane gate vibration and holding force in closing. Applied SciencesBasel 10(17). Yi, FC. & Yun FH. 2015 Research on the radial gate fluid-structure coupling of hydraulic steel gate. Applied Mechanics and Materials 3083:733. Zhang, HR et al. 2021. Analysis of instability accident of the hole radial gate of a reservoir. Technical Supervision in Water Resources (02): 129–133. (in China) Zhang, JG.et al. 1992. Study on spatial buckling load of radial steel gate arm. Journal of Hydraulic Engineering (06): 67–73+80. (in China) Zhang, QL. 2014. Analysis and research on horizontal support structure of arc steel gate arm. Jilin Water Resources (01): 9–11+14. (in China)

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Short-term prediction of runoff based on wavelet noise reduction and LightGBM coupling Pingan Ren, Li Mo∗ , Jianzhong Zhou∗ , Yongchuan Zhang & Hui Qin Huazhong University of Science and Technology, School of Civil and Hydraulic Engineering, China

ABSTRACT: With more and more hydropower stations built and put into operation, the runoff in the river is becoming more and more complex. Runoff is affected by topography, confluence, rainfall, evaporation, and other different conditions. There are more and more noise influencing factors in river runoff series. At the same time, accurate runoff prediction is of great significance for reservoir flood control and beneficial operation. In this paper, aiming at the hydrological noise in river runoff, wavelet transform is used to remove various noise effects of runoff. As a widely used prediction method, LightGBM has been widely applied in many fields. LightGBM is used to predict the hourly flow of Shuibuya Hydropower Station in 2020. The prediction accuracy has been greatly improved. Combining wavelet noise reduction with LightGBM prediction has been proved to an effective method in the short-term prediction of hydropower station runoff and has achieved good results. It has certain engineering application values.

1 INTRODUCTION With the large number of hydropower stations completed and put into operation, river runoff is becoming more and more complex. There are more and more complicated factors affecting runoff. Accurate runoff prediction is the premise of reservoir flood control and benefit regulation. Runoff prediction is becoming more and more important. For this reason, many relevant scholars at home and abroad have conducted a lot of useful researches. It (Sang 2013) introduced wavelet aided de-noising of hydrologic time series. At last, the paper put forward its own views on wavelet transforming and its application prospect in hydrology from three aspects: method research, further application, and combination. To study the influence of noise content on the chaotic characteristics of flow time series, the experiment (Fattahi et al. 2013) analyzed the chaos of river flow time series before and after the application of wavelet de-noising technology. The relationship between the wavelet noise reduction process and the change of chaotic behavior of river flow time series is studied, and a comprehensive chaotic evaluation is carried out. Some scholars (Li et al. 2019) proposed a fully integrated empirical mode decomposition method for underwater acoustic signal de-noising based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), effort-to-compress complexity (ETC), refined composite multi-scale dispersion entropy (RCMDE), and wavelet threshold de-noising. The results show that the de-noised underwater acoustic signal not only eliminates the noise interference, but also restores the topological structure of chaotic attractor more clearly, which lays a foundation for further processing of underwater acoustic signals. Wavelet transform has a good effect on magnetotelluric signal processing (Lu et al. 2019), which can remove noise signals and maintain the energy characteristics of the original signal. Literature (Wang 2014) shows that eliminating the noise of meteorological and hydrological time series is of great significance to improve the accuracy and reliability of extraction, analysis, simulation, and prediction. ∗ Corresponding Authors:

224

[email protected] and [email protected]

DOI 10.1201/9781003384830-28

The model combined singular spectrum analysis (SSA) and a light gradient boosting machine (LightGBM) to achieve high-definition and real-time prediction of regional urban runoff (Cui et al. 2021). The ensemble learning model of LightGBM was adopted to predict the water quality evaluation level (Zhou et al. 2022). The prediction accuracy reached 97.5% and the F1-score reached 97.8%, showing strong prediction ability. A short-term wind energy prediction method based on CNN-LSTM-LightGBM and attention mechanism was proposed (Ren et al. 2022). The local features and time series features of the data are effectively extracted, and the feature weights are reasonably allocated, so the accurate prediction of wind energy can be achieved. Some researchers (Gan et al. 2021) applied LightGBM model to predict the water level in the lower reaches of Columbia River, and the results showed that LightGBM model had a high prediction accuracy. In this paper, a method combining wavelet noise reduction and LightGBM is proposed to predict the runoff of Shuibuya Reservoir in a short term. Some research results have been obtained, proving the effectiveness of the method. 2 WAVELET NOISE REDUCTION In recent years, wavelet theory has been developed very rapidly. Because of its good time-frequency characteristics, its practical application is also very extensive. In the field of de-noising, the wavelet theory has also attracted the attention of many scholars. They applied wavelet to de-noising and obtained very good results. The wavelet de-noising method is an algorithm based on the multi-resolution analysis of wavelet transforming. According to the characteristics that the wavelet coefficients of noise and signal in different frequency bands have different intensity distributions, the basic idea of this method is to remove the wavelet coefficients corresponding to the noise in each frequency band, retain the wavelet decomposition coefficients of the original signal, and then carry out wavelet reconstruction on the processed coefficients to obtain the pure signal.

Figure 1.

Schematic diagram of wavelet transform denoising process.

Compared with other de-noising methods in the past, the wavelet transforming has a better de-noising effect in the case of a low signal-to-noise ratio, and the signal recognition rate after de-noising is higher. The effect is particularly pronounced. The signals observed in practice are usually non-stationary signals with white noise. F(t) = s(t) + e(t)

(1)

where s(t) represents a useful signal, e(t) is the noise signal. The wavelet de-noising method consists of three basic steps: wavelet transforming for noisy signals, performing some kind of processing on the transformed wavelet coefficients, and removing the noise contained in them. The de-noised signal is obtained by inverse wavelet transforming of the processed wavelet coefficients. 3 LIGHTGBM TIME SERIES PREDICTION LightGBM is a gradient lifting framework that uses decision trees as base learners. LightGBM is born for efficient parallel operation. Its light is reflected in the following points: faster training speed, higher memory usage, support of single machine multithreading, multi machine parallel computing, and GPU training, and capable of handling large-scale data. 225

LightGBM uses the histogram algorithm, which occupies less memory and has less complexity in data separation. The idea is to discretize continuous floating-point features into k discrete values, construct a histogram with a width of k, then traverse the training data, and count the cumulative statistics of each discrete value in the histogram. When performing feature selection, it is only necessary to traverse to find the optimal segmentation point according to the discrete values of the histogram. There are many advantages to using the histogram algorithm. The first and most obvious advantage is the reduction of memory consumption. The histogram algorithm not only does not need to store the presorted results, but can also save the value of the feature after discretization. This value is generally enough to be stored in an 8-bit integer, and the memory consumption can be reduced to 1/8 of the original. LightGBM uses a histogram-based split point selection algorithm, and the split criterion is to minimize variance, that is, to maximize variance gain. ⎛  2  2 ⎞ g g i i x ∈O:x x ≤d ∈O:x |d { i ij } { i ij } 1 ⎜ ⎟ + (2) Vj|O (d) = ⎝ ⎠ j j nO nl|O (d) nr|O (d) among, nO =



j

I [xi ∈ O], nl|O =



j

I [xi ∈ O : xi ≥ d], nr|O =



I [xi ∈ O : xi > d].

4 CASE STUDY Qingjiang River, a first-class tributary of the Yangtze River, with a total length of 423 kilometers. The natural drop of Qingjiang River is 1430 meters, the theoretical energy storage of the whole basin reaches 2.9 million kilowatts, the installed capacity of exploitable hydropower resources is 1.77 million kilowatts, and the annual power generation capacity is 9 billion kW·h. The main section of the Qingjiang River is developed in three levels, from bottom to top: Gaobazhou (water storage level 80m), Geheyan (water storage level 200m), and Shuibuya (water storage level 400m, with a total installed capacity of 3.05 million kilowatts, with an annual power generation of 8.1 billion kW·h. In this paper, we take Shuibuya power station as the object of study. The specific locations of the hydroelectric power stations are shown in Figure 2.

Figure 2.

Map of the Qingjiang River.

The normal pool level of Shuibuya reservoir is 400m, the corresponding storage capacity is 4.312 billion cubic meters, the total storage capacity is 4.58 billion cubic meters, and the installed capacity is 1840MW. It is a water conservancy project focusing on power generation and taking into account flood control, shipping, etc. The hourly inflow data of Shuibuya in 2020 is selected for case study. Figure 3 shows the hourly flow data of Shuibuya Hydropower Station in 2020. 226

Figure 3.

Hourly flow data of Shuibuya in 2020.

4.1 Time series prediction using LightGBM The study takes the first 80% of the hourly flow data of Shuibuya in 2020 as the training data, and the last 20% as the test data. LightGBM model is used for short-term runoff series prediction. The correlation coefficient R2 is 0.722971092 and the root mean square error is 68.88606013. The calculation results are shown in the Figure 4 below.

Figure 4.

Prediction results of short-term runoff time series in Shuibuya.

From the above figure, we get the comparison results between the original data and the prediction. Although some prediction results have been achieved, there is still much room for improvement in the prediction effect. 227

4.2 Time series prediction based on wavelet noise reduction and LightGBM coupling The study takes the first 80% of the hourly flow data of Shuibuya in 2020 as the training data, and the last 20% as the test data. The last 20% of the prediction data are used for wavelet noise reduction. Then LightGBM is used to predict the short-term runoff time series. The experimental platform of this paper adopts MATLAB R2021a, where wavelet is sym4, the level is 10, the de-noising method is bayes, the threshold rule is median, and the noise is level independent. The correlation coefficient R2 is 0.856831002 and the root mean square error is 46.59752974. The results after wavelet noise reduction are shown in the following Figures 5 and 6.

Figure 5. Wavelet noise reduction results of hourly flow data in Shuibuya in 2020.

Figure 6.

Prediction results of short-term runoff time series in Shuibuya with wavelet noise reduction.

228

The above figures show the data results obtained from the calculation. After noise reduction, the time series prediction results using LightGBM have been greatly improved. The prediction in Figure 6 shows the result of wavelet noise reduction in Figure 5. Compared with Figure 4, the accuracy has been improved to a certain extent, and better results have been achieved.

5 CONCLUSIONS In this paper, according to the hourly flow data of Shuibuya in 2020, LightGBM is used for time series prediction due to the influence of noise in hydrological runoff data. Firstly, wavelet transform is used to de-noise the predicted hourly runoff data. Then, LightGBM is used to predict the shortterm runoff time series. Compared with no wavelet transforming of runoff, the combination of wavelet transform and LightGBM is used for time series prediction, and the effect and accuracy are greatly improved. Using wavelet noise reduction and then using LightGBM for time series prediction can improve the prediction effect. The results prove the effect and significance of this method.

ACKNOWLEDGMENT The research work of this paper is supported by National Natural Science Foundation of China Yalong River Joint Fund Project (U1865202) and National Natural Science Foundation of China Key Project (52039004).

REFERENCES Cui Z.J., Qing X.X., Chai H.X., Yang S.X., Zhu Y., Wang F.F. Real-time rainfall-runoff prediction using light gradient boosting machine coupled with singular spectrum analysis [J]. Journal of Hydrology, 2021, 603: 127124. Fattahi M.H., Talebbeydokhti N., Moradkhani H., Nikooee E. Revealing the chaotic nature of river flow [J]. Iranian Journal of Science and Technology-Transactions of Civil Engineering, 2013, 37(C): 437–456. Gan M., Pan S.Q., Chen Y.P., Cheng C., Pan H.D., Zhu X. Application of the machine learning lightgbm model to the prediction of the water levels of the lower Columbia river [J]. Journal of Marine Science and Engineering, 2021, 9(5): 496. Li G.H., Guan Q.R., Yang H. Noise reduction method of underwater acoustic signals based on CEEMDAN, Effort-To-compress complexity, refined composite multiscale dispersion entropy and wavelet threshold denoising [J]. Entropy, 2019, 21(1): 11. Lu Y., Huang Y.M., Xue W., Zhang G.B. Seismic data processing method based on wavelet transform for de-noising [J]. Cluster Computing-the Journal of Networks Software Tools and Applications, 2019, 22: S6609–S6620. Ren J., Yu Z.P., Gao G.L., Yu G.K., Yu J. A CNN-LSTM-LightGBM based short-term wind power prediction method based on attention mechanism [J]. Energy Reports, 2022, 8: 437–443. Sang Y.F. A review on the applications of wavelet transform in hydrology time series analysis [J]. Atmospheric Research, 2013, 122: 8–15. Wang D., Singh V.P., Shang X.S., Ding H., Wu J.C., Wang L.C., Zou X.Q., Chen Y.F., Chen X., Wang S.C., Wang Z.L. Sample entropy-based adaptive wavelet de-noising approach for meteorologic and hydrologic time series [J]. Journal of Geophysical Research-Atmospheres, 2014, 119(14): 8726–8740. Zhou S.H., Song C.F., Zhang J.J., Chang W.B., Hou W.K., Yang L.C. A hybrid prediction framework for water quality with integrated W-ARIMA-GRU and LightGBM methods [J]. Water, 2022, 14(9): 1322.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on construction monitoring technology of suspended shape up-stiffened steel truss bridge based on incremental launching method Mingcheng He* & Guifen Liu* Hangzhou Transport Development and Guarantee Center, Hangzhou, China

Yang Wang* CCCC Highway Bridges National Engineering Research Centre Co., Ltd., Beijing, China

ABSTRACT: The main bridge of the new Qiantang River Bridge is a catenary type of continuous steel truss bridges with stiffening on the main span of 240m. The main beam is constructed by incremental launching method on both sides and closing in the middle. To make the alignment of the completed bridge and the internal force of the structure meet the design requirements during the incremental launching construction process, and ensure the safety of the main bridge construction process, the main bridge calculation model is established by using Midas civil software, and the internal force displacement index during the construction process is simulated and analyzed in detail. At the same time, the alignment of the construction process is verified theoretically and measured, and the reasonable monitoring point design and deployment are designed for the stress index. The results show that the internal force of the members is reasonable and the structure is safe during the incremental launching construction. 1 INTRODUCTION With the construction of large-scale railway transportation and highway transportation infrastructure in our country, the bridge position resources across the big rivers are becoming more and more scarce. Double-deck bridges can not only save bridge space resources, but also make full use of double-deck bridge decks to improve the overall stiffness of the bridge and meet the requirements of vehicle operation safety and passenger comfort (Zhao 2016). As a new type of steel truss girder bridge, the double-layer rigid suspension-cable-stiffened continuous steel truss bridge is not only beautiful in appearance, but also provides greater vertical rigidity to the structure. Dongguan Dongjiang Bridge (2009) (Wang and Tu et al. 2010), Jinan Passenger Dedicated Line Yellow River Bridge (2016) (Fang and Ding et al. 2016; Hao and Cao 2019; Su 2020), and Chongqing Zengjiayan Jialing River Bridge (2019) (LIU and ZHANG et al. 2020; SU 2017) all adopt this structure. According to factors such as span layout, site topography, traffic conditions, and construction conditions, the construction methods of steel truss bridges mainly include the incremental launching and vertical (horizontal) moving method, the cantilever assembly method, and the floating hoisting method (Chen and Wu et al. 2006; Liang 2021; Zhao and Zhang 2016). Among them, the incremental launching construction method is one of the commonly used methods for erecting steel truss girder. Liu Jian (Liu 2010) took the first link of the ZhengzhouYellow River Highway-Railway Bridge as the engineering background. Through the checking and monitoring of the internal force and stiffness of the main truss member, as well as the elevation and stress of the steel truss girder, the multi-point incremental launching of the main girder steel truss girder was carried out. The whole construction process is monitored, so that after the main truss is closed, the bridge alignment and the stress of the members meet the design requirements. Hua Xugang (Hua and Cao et al. 2019) took the steel truss girder incremental launching construction of the Sanmenxia Yellow River ∗ Corresponding Authors:

230

[email protected], [email protected] and [email protected]

DOI 10.1201/9781003384830-29

Highway-Railway Bridge as the background, and analyzed the transient impact effect caused by the incremental launching start of the structure under the large cantilever condition. The results showed that the incremental launching start has little effect on the vertical support reaction force. Under the combined action of the static wind load, the transient effect of the incremental launching startup increases with the increase of the cantilever span. According to the different construction conditions on both sides of the Xinbaishatuo Yangtze River Bridge on the Chongqing-Guizhou Railway, Wu Zongping (WU 2019) introduced the “partial push and scattered combination method” and analyzed the double cantilever and double-layer 6-track railway steel truss cable-stayed bridge. The erection method ensures that the bridge erection is completed on time. To sum up, there are many cases of technical research on the incremental launching construction of double-layer steel truss girder in China. However, with the emergence of the stiffened continuous beam steel truss bridge, the overall research on the monitoring of its incremental launching construction is still less. And a relatively mature monitoring technology for the incremental launching construction of the stiffened continuous beam steel truss bridge has not been formed.

2 PROJECT SUMMARY 2.1 New qiantang river bridge The new bridge on the Qiantang River is a dual-use public-rail bridge, and the main bridge adopts a catenary-shaped upper-strengthened continuous steel truss bridge. These are shown in Figures 1 and 2. The span of the bridge is arranged as (72+122+4×240+122+72)=1348m (Figure 3), with a double-layer layout. The upper layer is an 8-lane elevated expressway, and the lower layer is a double-track expressway. The upper and lower decks are the overall deck of the plate-truss composite structure of orthotropic steel plates. The bridge deck is connected with the top plate of the chord through the length to realize the common force of the plate girder. The bridge truss is basically a Warren-shaped truss with vertical rods, with a total of 132 internodes, and the standard internode spacing is 10 m. To adapt to the span arrangement of the side span, the length of the seven internodes at the end is adjusted to 12 m. The central distance of the main truss of the steel truss girder is 36.8 m, and the truss height is 12 m.

Figure 1. Caption of a typical figure.

Figure 3.

Figure 2. Overall photo of the main bridge of the new Qiantang River Bridge.

General layout of the main bridge of the Qiantang River New Bridge (unit: m).

231

2.2 Incremental launching method The main girder of the new bridge on the Qiantang River is constructed using the incremental launching method: install the steel truss girder first, push it in place, and then install the rigid stiffening string. The steel beam push-up adopts the two-way push-up construction on both sides of the strait, and closes on the north side of the ZQ5# pier. The rigid stiffening string is transported through the road bridge deck, installed on the road bridge deck, and finally closed span by span. 2.3 Construction monitoring features The single main span of the newly built bridge on the Qiantang River is 240 m long, and the bridge width is 36.8 m. The main girder is a catenary-shaped upper-strengthened continuous steel truss girder structure with a double deck layout. The bridge deck is an orthotropic steel plate with a plate-truss composite structure as a whole. Its structure is complex, the construction is difficult, and the technical content is high. The bolts are used to connect the rods, which has extremely high requirements on the manufacturing accuracy and construction control accuracy of the structural rods. There are many factors affecting the construction control of the incremental launching. The construction monitoring work of bridges is quite different. According to the structural characteristics and construction methods of the bridge, the characteristics of the construction monitoring of this project mainly include the following: (1) (2) (3) (4)

Nearly open-loop control strategy Stress control during construction of steel beams Linear control and reaction force control during the main girder incremental launching process The stability of temporary construction facilities has become one of the key points of monitoring.

3 FINITE ELEMENT SIMULATION The bridge is simulated and calculated by the finite element software Midas Civil. The main chords, webs, transverse links, steel towers, and rigid-connected suspenders are simulated by beam elements. The hinged suspenders are simulated by truss elements, and the steel roof is simulated by plate elements. The whole bridge is divided into 13667 nodes and 34544 elements. 3.1 Stress of main structure The stress envelope diagram of the main truss corresponding to the whole process of incremental launching construction is shown in Figure 4:

Figure 4.

Structural stress envelope diagram of the whole pushing process-Web (unit: MPa).

232

According to the calculation results of the stress envelope of the main truss during the whole pushing process of the first work area, the maximum stress in the pushing process occurs on the vertical web bar at the front end support position in front of the upper pier of the guide beam (maximum cantilever), and the stress is 220.4MPa, which is less than 1.2[σ](Q370qD) = 252MPa, which meets the specification requirements. 3.2 The vertical deformation of the structure During the incremental launching process, before the temporary piers are raised, the main structure has the maximum vertical deformation under the action of its own weight, as shown in Table 1 and Figure 5. Table 1. Summary of the calculation results of the maximum vertical deformation of the front beam end of the upper pier during the incremental launching process.

Figure 5.

Upper pier position

ZQ3

LD2

LD3

ZQ4

LD4

LD5

Max cantilever displacement/mm

–114

–136

–133

–132

–132

–132

Maximum vertical deformation of the structure in front of the upper ZQ3 pier (unit: mm).

3.3 The amount of fallback before connecting For the overall construction plan of pushing both sides to the center, the middle tower at the connection port is 45 m away from the lower mileage side. According to the calculation results, when the two working areas are pushed to this position, the theoretical deflections of the cantilever ends on both sides are different. To ensure the closing angle of the main truss and enable the smooth splicing of each member, the corresponding leveling plan of the closing openings of the two work areas was determined through theoretical calculation. That is, some temporary pier fallback measures were taken to ensure the splicing of the openings. After the steel truss girder is pushed into place, the cumulative vertical deformation on both sides of the closure is shown in Figure 6. The lower deflections of the closure on both sides are 24 mm and 36 mm respectively, and the height difference between the two sides is 12 mm. After calculation, some temporary piers are correspondingly lowered to complete the leveling of the connection ports, as shown in Table 2. According to the above adjustment plan, after the support is completed, the height difference of the connection port is as follows: the upper end of the first work area is 19 mm, the second work area is 31 mm, and the height difference of the connection ports on both sides is within 1 mm, which meets the requirements in theory. If splicing is required, the temporary pier fallback scheme is feasible. 233

Table 2. Corresponding setback of temporary piers for connection operation. Temporary pier number

ZQ4

LD4

Pier 1

Pier 2

Fallback

–25

–50

–60

–30

4 MONITORING DURING CONSTRUCTION 4.1 Monitoring of main beam alignmen Main girder alignment as shown in Figure 6: (1) The bridge deck should be smooth after completion; (2) Main bridge elevation: +20 mm when L≤100 m, L/5000 mm when L>100 m; (3) Bridge deck axis center offset: 10 mm.

Figure 6. Comparative analysis of the actual measured and theoretical elevations of the lower deck after the construction of the main bridge of the Qiantang River New Bridge (unit: m).

4.2 Monitoring of structural stress The deviation between the axial + bending stress value of the main components and the theoretical value in the bridge formation stage is not more than 10%. The truss structure of the main bridge is dense and the vertical and horizontal members are staggered, and the stress of each member in the truss system is complicated. And in incremental launching construction, there is a situation of alternating tension and compression of the same rod. The safety of the main structure during the construction process and the matching and agreement with the theoretical calculation cannot be accurately evaluated if the stress measuring point arrangement is only carried out according to the longitudinal section of the structure. Therefore, in this paper, four selection principles are used as the basis for selecting the stress monitoring object, including the key section members of the structure, the members with relatively unfavorable forces during the incremental launching process, the members with complex forces based on theoretical calculations, and the lateral force characteristics of the structure. The layout of the measuring points and the statistical table are shown in Table 3. Table 3. Statistics of the number of stress sensors at key sections. Order

The section selection

Amount

1 2 3 4 5

The key section corresponds to the stress monitoring of the rod The main girder in the disadvantageous position The rod in the position of large stress and complex stress Stress monitoring according to transverse force characteristics of structure Total

96 56 44 16 212

234

(1) Stress monitoring at key sections corresponds to stress monitoring of members. According to the overall stress characteristics of the main bridge structure in the longitudinal direction of the bridge, select members at key positions such as the mid-span of each span of the main truss, the upper and lower chords on both sides of the main pier, and the web members (A total of 96) for strain monitoring. (2) Stress monitoring of the unfavorable position of the main truss during the incremental launching process. Because the two work areas take the 5# tower to the lower mileage side of 45m as the connection port, and push from both banks to this position respectively, the spacing between temporary piers is 80 m. Therefore, during the incremental launching process, the members (especially the lower chord) that are 35 m away from the closing position of the two work areas (the guide beam is 45 m long) will bear the reaction force of the maximum cantilever state of the temporary pier before each lifting beam is placed on the pier. And the rod at this position is particularly disadvantageous during the pushing process. Therefore, the rods near this position (56 in total) are selected for corresponding stress monitoring. (3) The stress monitoring of the rods with large stress and the rods with complex stress is based on the finite element calculation and analysis of the whole construction process. To evaluate the safety of the main structure during the construction process, the rods with more stress are selected. Corresponding stress monitoring is carried out for the rods with large changes in the force state and the rods (44 pieces) with more complex stress conditions. (4) Stress monitoring according to the lateral force characteristics of the structure. Since the main girders of the bridge are spaced at a distance of 36.8 m, to ensure the overall lateral force safety of the structure and to verify the consistency between the actual force characteristics of the structural beam system and the theoretical calculation results, select stress measuring points laid out on the node beams and the connection system at the inter-node positions of some features. The difference between the measured stress results and the design results is less than 10%, which meets the engineering needs. Due to space limitations, the list is no longer presented here. The stress test results of the main girder and the key section of the stiffening string in the whole construction process show that the measured stress level trend is consistent with the theoretical calculation, and the structural stress state meets the design requirements.

5 CONCLUSION In this paper, taking the Qiantang River new bridge as the engineering background, based on the finite element simulation analysis and field measurement, the monitoring of the incremental launching construction of the catenary upper stiffened steel truss bridge is studied, and the following conclusions are drawn: (1) The new Qiantang River bridge is being jacked up. During construction, the stress of the main truss, the stress of the steel guide beam, and the vertical deformation of the structure all meets the requirements of monitoring and specification. (2) Aiming at the different deflections of the cantilever ends on both sides of the closure in the incremental launching construction, the corresponding drop-back operation plan for some temporary piers was adopted to ensure the closure angle of the main truss and the smooth splicing of the rods to complete the closure of the main bridge. (3) The monitoring of the main girder alignment and structural stress during the construction shows that the overall smoothness of the main girder alignment is good and meets the monitoring requirements. The measured stress level of the main girder and the key sections of the stiffening string during the whole construction process is consistent with the theoretical calculation, and the structural stress is at safe state, meeting monitoring and design requirements. 235

(4) In the construction monitoring of the incremental launching method, in addition to the stress monitoring of the key sections and the locations with high stress or complex forces, to ensure the overall lateral force safety of the structure, it is also necessary to monitor the nodes at the characteristic internode positions. Beams and connection are subjected to stress monitoring.

REFERENCES Chen, H., Wu, J., and Chen, X. 2006. Application of pushing method in bridge engineering. Journal of China & Foreign Highway (03):178–180. Fang, J., Ding, S., Zhang, S., and Liang, C. 2016. Construction techniques for incremental launching of ji’ nan Huanghe river rail-cum-road bridge with Stiffening Chords. Bridge Construction 46(06):112–117. Hao, S., and Cao, M. 2019. Stress analysis of large joints of rigid stiffened continuous steel girder suspension Bridges. Highway 64(03):157–159. Hua, X., Cao, L., Wang, Y., and Chen, Z. 2019. Transient dynamic effect analysis of incremental launching start-up of steel truss girder bridge under long Cantilever state. Bridge Construction 49(04):18–22. Liang, C. 2021. The New Incremental Launching Construction Craftsmanship of Continuous Steel Truss Girder with Three Main Trusses for Both Highway and Railway. Journal of Railway Engineering Society 38(03):41–47. Liu, J. 2010. Research of Construction Monitoring for continuous Steel Truss Girder Cable-stayed Bridge, Zhengzhou University. Liu, J., Zhang, C., Xue, F., Liu, K., and Ou, Y. 2020. Application of BIM technology to design of Zengjiayan Jialingjiang river bridge in Chongqing. World Bridges 48 (02):71–76. Su, J. 2017. Study of steel truss girder erection schemes for Zengjiayan Jialingjiang river bridge in Chongqing. World Bridges 45(02):6–9. Su, L. 2020. Completed bridge test study on mechanical performance of continuous steel truss girder reinforced by stiff suspension cables. Railway Engineering 60(07):1–5. Wang, H., Tu, H., and Li, Y. 2010. Closure techniques for steel truss girder of Dongguan Dongjiang river bridge. Bridge Construction (02):76–79. Wu, Z. 2019. Erection technique for steel truss girder of new Baishatuo Changjiang river bridge on ChongqingGuiyang railway. Bridge Construction 49(03):114–118. Zhao, R., and Zhang, S. 2016. Research status and development trend on incremental launching construction of bridges. China Journal of Highway and Transport 29(02):32–43. Zhao, X. 2016. Study on erection plan of main bridge’s steel truss girder of Jinan yellow river highway and railway shared bridge on Shijiazhuang-Jinan passenger dedicated railway. Railway Engineering (08):10–13.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Influence of central buckle on static and dynamic performance of super-span suspension bridge Fengchao Guo Guang Dong Bay Area Traffic Construction Investment Co., Ltd., Guangzhou, China

Huaimao Yang* CCCC Highway Bridges National Engineering Research Centre Co., Ltd., Beijing, China

Yunhua Zhou Guang Dong Bay Area Traffic Construction Investment Co., Ltd., Guangzhou, China

ABSTRACT: To study the influence of different longitudinal restraint systems on the static and dynamic performance of super-span suspension bridges, this paper took a single-span steel truss girder suspension bridge with a span of 2180m as the research object and established a threedimensional finite element analysis model. The influence of different numbers of central buckles on the static and dynamic performance of the structure was analyzed, and the combined application of central buckles and girder limit damping devices was studied. The results showed that: the central buckle can effectively reduce the girder displacement and the relative displacement between the mid-span cable and the girder under static and dynamic conditions, reduce the longitudinal bending moment at the bottom of the pylon under the earthquake, and improve the anti-symmetric torsional frequency of the structure. The combined application of the central buckle and the girder limit damping device can greatly reduce the internal force of the central buckle under earthquake action, but has little effect on the internal force of the central buckle under static action. 1 INSTRUCTIONS As a structural device of the suspension bridge, the central buckle connects the cable and the girder of the suspension bridge, which can improve the longitudinal stiffness of the suspension bridge, reduce the girder displacement and cumulative displacement, improve the torsional frequency of the suspension bridge, and also have a certain impact on the wind resistance stability. Central buckles include flexible central buckles, rigid central buckles, and new central buckles. Relevant scholars have conducted many studies on the central buckle. The research of Tang (2021) shows that the central buckle can reduce the longitudinal displacement and cumulative displacement of the girder, and increase the torsional stiffness and longitudinal stiffness of the structure. Xu (2010) found that the central buckle improves the anti-symmetric torsional stiffness of the structure and limits the longitudinal drift characteristics of the structure, which can significantly reduce the longitudinal seismic displacement of the girder, but will lead to a significant increase in the seismic stress response of the structure. Yang (2015) found that the vertical displacement of the girder and various internal force responses increased significantly under different central buckle settings, and the bending moment, shear force at the pylon bottom decreased, and the rigid central buckle scheme was the best. The research of Yu (2016) showed that the setting of the central buckle has a great influence on the longitudinal drift characteristics of the suspension bridge, which can effectively reduce the longitudinal displacement of the girder, but greatly increase the stress of the truss on the girder. ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-30

237

Wang (2019) and Song (2021) have shown that the central buckle can significantly improve the overall longitudinal stiffness of the suspension bridge and change the longitudinal floating modal characteristics of the suspension bridge. The central buckle significantly reduces the longitudinal amplitude of the girder and increases the vibration frequency of the girder. This leads to an increase in the cumulative displacement value of the girder. Wan (2020) showed that the central buckle can reduce the longitudinal displacement and moving speed of the girder, and can also improve the durability of the sling. The research of Li (2021) showed that the central buckle improves the longitudinal drift and torsional stiffness of the suspension bridge, changes the relative motion characteristics between the cable and girder, and is beneficial to control the fatigue damage of the short suspension cables of the suspension bridge. Although many scholars have done researches on the central buckle of suspension bridges, there are many researches on the seismic impact of the central buckle, and less studies on the static performance. For suspension bridges with large spans and large load scales, whether the central buckle action is similar to that of conventional medium and small span suspension bridges remains to be further studied. In view of the above problems, a study was carried out on a super-span suspension bridge with a flexible central buckle, and the influence of the central buckle on the structural performance was clarified. 2 ENGINEERING BACKGROUND AND ANALYSIS MODEL The bridge structure scheme adopts the main span of 2180m and the double-layer 16-lane singlespan suspension bridge scheme. The span arrangement is 670m+2180m+710m=3560m, and the cable span ratio is 1:9. The girder of the bridge adopts the form of double-layer steel truss girder with a full width of 45m and a truss height of 13.5m. The pylon adopts a portal frame steel-concrete composite pylon. The overall layout is shown in Figure 1.

Figure 1.

General layout of the bridge.

The analysis model was established by SAP2000 finite element analysis software, and the static and dynamic performance of the structure was analyzed. The analysis model is shown in Figure 2. The girder is modeled with frame elements and plate elements, the pylon, cap and foundation are modeled with frame elements, the cables and suspension cables are modeled with truss elements, and the flexible central buckle is modeled with truss elements with a compression limit of 0. In the simulation, the pile-soil interaction is calculated by the “m” method to calculate the soil spring stiffness. The static load is calculated according to the relevant specifications, and the seismic load adopts the horizontal acceleration time-history curve with a probability of exceeding 4% in 100 years. The seismic time-history curve is shown in Figure 3.

Figure 2.

Finite element analysis model of the main bridge.

238

Figure 3. Time-history curve of horizontal acceleration at E2 level.

3 INFLUENCE OF CENTRAL BUCKLE PARAMETERS ON THE STATIC AND DYNAMIC PERFORMANCE OF THE STRUCTURE To compare and analyze the influence of different central buckle parameters on the static and dynamic performance of the structure, the structural effects of setting 0 ∼ 5 pairs of central buckles are analyzed. Take the central buckle of the half-span unilateral cable surface as the research object, the most lateral central buckle from the mid-span to the far side is named side 1, and the sling number is ①. One pair of central buckles only has side 1 central buckle, and five pairs of central buckles have side 1 ∼side 5 central buckles. The central buckle arrangement and numbering are shown in Figure 4.

Figure 4.

Layout and numbering of the central buckle.

239

3.1 Static effect analysis Figure 5 and Figure 6 show the girder displacement and the relative displacement between cable and girder at mid-span with different numbers of central buckles. It can be seen from the calculation results that setting the central buckle can improve the longitudinal stiffness of the structure and significantly reduce the longitudinal displacement of the girder. The maximum displacement of the girder after setting the central buckle is reduced from 2.52m to about 1.8m, a decrease of 29%. The number of central buckles has little effect on the girder displacement. The central buckle has a significant effect on reducing the relative displacement between the cable and the girder at mid-span. The more the number of central buckles, the more obvious the effect, and the smaller the relative displacement between cable and girder.

Figure 5. The influence of the number of central buckles on the girder displacement.

Figure 6. The effect of the number of central buckles on the relative displacement of the mid-span cable and girder.

It can be seen from Figure 7 and Figure 8 that with the increase of the number of central buckles, the average internal force of the central buckles gradually decreases. When one pair of central buckles is installed, the internal force of the central buckle reaches 10679kN, and the minimum internal force of the five pairs of central buckles is 2174kN. When two and four pairs of central buckles are installed, the internal force is relatively uniform. Due to the large arrangement range of three and five pairs of central buckles, the side No. 2 central buckle is greatly affected by the live load, and the corresponding internal force is also large. With one pair and two pairs of central buckles, the stress amplitudes of the short slings near the mid-span are all larger than those of the scheme without central buckles. The stress amplitudes of short slings near the middle of the central buckle span of three pairs, four pairs and five pairs are quite different. It can be seen that the change of the stress amplitude of the short sling at different positions by the central buckle is different, which has advantages and disadvantages to the change of the stress amplitude of the short sling. 3.2 Earthquake action analysis The analysis of the natural vibration characteristics of suspension bridges is the basis for the analysis of the seismic performance of the structure and the analysis of the wind resistance design. 240

Figure 7.

Central buckle internal force.

Figure 8.

Stress amplitude of short slings in mid-span.

Table 1 shows the effect of different central buckle numbers on the dynamic characteristics of the structure. It can be seen that there is no difference in the first-order transverse bending frequency of the structure with different numbers of central buckles. This indicates that the central buckle of the suspension bridge has little effect on the lateral stiffness of the structure. Setting the central buckle can increase the first-order anti-symmetric vertical bending frequency of the structure, but the number of central buckles has no significant difference in the improvement effect. The central buckle has almost no effect on the first-order symmetrical vertical bending and the first-order symmetrical torsional frequency of the structure, but significantly improves the anti-symmetrical torsional stiffness of the structure. With the increase of the number of central buckles, the firstorder anti-symmetrical torsional frequency gradually increases. Compared with the model without central buckle, the natural vibration frequency is increased by 9.0% when five pairs of central buckles are set, which indicates that setting the central buckle can improve the wind resistance stability of the whole bridge. Table 1. Influence of the number of central buckles on the dynamic characteristics of the structure.

First-order transverse bending frequency /Hz First-order antisymmetric vertical bending frequency /Hz First-order symmetrical vertical bending frequency /Hz First-order symmetric torsional frequency /Hz First-order antisymmetric torsional frequency /Hz

1

2

3

4

5

0.0362

0.0362

0.0362

0.0362

0.0362

0.0362

0.0674

0.0724

0.0725

0.0726

0.0726

0.0726

0.1008

0.1008

0.1008

0.1008

0.1008

0.1010

0.2285

0.2285

0.2285

0.2285

0.2285

0.2286

0.3278

0.3436

0.3503

0.3533

0.3555

0.3573

241

The results of the displacement of the girder and the relative displacement between the cable and the girder in the middle of the span are shown in Figure 9 and Figure 10. It can be seen that the setting of the central buckle also has a significant effect on reducing the girder displacement during earthquake action. With the increase of the number of central buckles, the girder displacement gradually decreases, but the decreasing trend becomes slower, and the maximum can be reduced by 63%. The central buckle increases the connection between the cable and the girder, and has a significant effect on reducing the relative displacement of the cable and the girder in the middle of the span during the earthquake. The greater the number of central buckles, the more obvious the effect, which is similar to the static analysis results.

Figure 9.

Figure 10.

Girder displacement under earthquake action.

Relative displacement of cable and girder in mid-span due to earthquake.

The seismic internal force of the central buckle is shown in Figure 11. With the increase of the number of pairs of central buckles, the seismic internal force of the central buckle gradually decreases. The seismic internal force of one pair of central buckles reaches 32771kN, and the minimum internal force of five pairs of central buckles is 6723kN. The internal force of the central buckle is 3 times larger than that of the static load under the earthquake condition. The internal force of the central buckle should be the focus of attention during the earthquake, and the distribution of the seismic internal force of each central buckle is uneven.

Figure 11.

Central buckle internal force under earthquake action.

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Table 2 shows the influence of different number of central buckles on the internal force of the pylon. It can be seen that the central buckle will reduce the seismic shear force and bending moment at the pylon bottom. When two pairs of central buckles are set, the pylon bottom shear force can be reduced by 18%. The pylon bottom bending moment can be reduced by 29%. When three pairs of central buckles are set, the pylon bottom shear force and bending moment can be reduced by 13% and 24% respectively. Table 2. Influence of the number of central buckles on the internal force of the pylon.

longitudinal shear /kN Longitudinal bending moment/kN·m

0

1

2

3

4

5

81240 6216419

66361 4551080

66425 4645198

70993 4698813

63494 4712547

72993 4606741

3.3 Analysis of combined application of central buckle and girder restraining device The installation of flexible central buckles can reduce the girder displacement and the relative displacement between the cable and the girder, but the maximum static displacement of the girder with the central buckle alone will still exceed 1.7m, resulting in a huge expansion joint size. And the seismic displacement still reaches 0.8m, the earthquake internal force of the central buckle is large. The use of limit stops can effectively limit the girder displacement, and the use of dampers can reduce the girder seismic displacement. Therefore, the combined application of three pairs of central buckles, girder limit stops and viscous dampers is considered. Two limit stops are set at each pylon, and the limit stop limits the maximum displacement of the girder to 1.1m. Four viscous dampers are set at each pylon, and the damping constant is 3000 kN/ (m/s) ξ, the velocity index is 0.1. To compare and analyze the influence of different restraint methods on the static and dynamic performance of the structure, four calculation conditions were selected for comparative analysis. System 1: no restraint at the girder + no central buckle in the middle of the span, System 2: set 3 pairs of flexible central buckles, System 3: Limits and dampers at the girder + no central buckle in the middle of the span, and System 4: Limits and dampers at the girder + 3 pairs of flexible central buckles. Table 3. Calculation results of different systems. Project

System 1

System 2

System 3

System 4

Static

Displacement of girder /m Relative displacement of cable and girder /m Internal force of central buckle /kN Stress amplitude of central buckle /Mpa Stress amplitude of short sling /Mpa Limit force /kN

2.422 1.028 / / 113 /

1.707 0.023 6150 204 146 /

1.103 0.469 / / 111 20764

1.103 0.036 4899 277 147 34864

Dynamic

Displacement of girder /m Relative displacement of cable and girder /m Longitudinal bending moment of pylon /kN·m Internal force of central buckle /kN

1.216 0.883 6216419 /

0.657 0.088 4698813 14426

0.383 0.398 5865267 /

0.291 0.064 4151020 6669

From the analysis in Table 3, it can be seen that the static displacement of the girder is reduced to 1.1 m because of the action of the limit stops that limit the girder displacement. The girder damper can significantly reduce the seismic displacement of the girder, and its capacity is greater than that 243

of the flexible central buckle. When the central buckle and the girder damper are set at the same time, their effects can be superimposed, but it is not a simple linear superposition relationship. The central buckle has the most obvious effect on reducing the relative displacement between the cable and the girder in the mid-span. The girder damper and limit device also have a certain effect on reducing the relative displacement between the cable and the girder, but its effect is far less than that of the central buckle. The central buckle on the mid-span will significantly increase the limit force of the girder. The main reason is that the limit gap of 1.1m is less than the girder displacement caused by the live load + temperature, so the limit stop mainly limits the displacement caused by the live load. Since the live load causes vertical deformation of the cable through half-span loading, which further drives the longitudinal displacement of the girder, the central buckle greatly strengthens the restraint between the cable and girder. The longitudinal deformation trend of the girder is stronger when the half-span is loaded because the restriction of the limit stops and the limit force is larger. The installation of dampers can significantly reduce the internal force of the central buckle under seismic action. Because the damper reduces the displacement of the girder, the displacement of the cable and the girder in the mid-span is reduced, which limits the deformation of the central buckle, thereby reducing the central buckle, the internal force dropped by 54%.

4 CONCLUSION This paper took a 2180m super-span suspension bridge as the research background. Through the analysis of the central buckle set between the cable and the girder in the mid-span, the research on the influence of the central buckle on the static and dynamic performance of the structure was carried out, and the conclusions were as follow: (1) The central buckle can effectively reduce the girder displacement under static and dynamic conditions, and can greatly reduce the relative displacement between the cable and girder under static and dynamic conditions. However, the number of central buckles has little effect on the girder displacement and the relative displacement between the cable and girder. The central buckle can effectively reduce the longitudinal bending moment of the pylon bottom, but the number of central buckles has little effect on the longitudinal bending moment of the pylon bottom. With the increase of the number of central buckles, the central buckle force in both static and seismic conditions showed a decreasing trend, the stress amplitude of some short slings increased, and the stress amplitude of some short slings decreased in the mid-span area. (2) The central buckle can effectively increase the first-order anti-symmetric vertical bending and first-order anti-symmetric torsional frequency of the structure, which is beneficial to the wind resistance stability. (3) The combined application of the central buckle and the limit damping device at the girder can greatly reduce the internal force of the central buckle when the earthquake action, but it has little effect on the internal force of the central buckle under static action. Due to the influence of the longitudinal displacement mechanism of the girder caused by the vertical load, the central buckle will increase the internal force of the limiter.

REFERENCES Li G., Su Q., Gao W., Han W. & Yan C. (2021). Influence of rigid central clamps on dynamic characteristics of suspension bridge and vehicle excitation responses of short suspenders. China Journal of Highway and Transport: 34(04):174–186. Song X., Huang G. & Sun Z. (2021). Assessment and design of mitigation of longitude displacement of suspension bridges. Highway Engineering: 46(04):104–109.

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Tang M., Li S., Tang Q. & Li C. (2021). Influence of central buckle on static and dynamic characteristics of long-span space cable suspension bridge. Journal of China & Foreign Highway: 41(02):129–134. Wan T. & Li S. (2020). Longitudinal displacement characteristics and longitudinal supporting requirements for long-span railway suspension bridge. Bridge Construction: 50(04):29–35. Wang L., Sun Z. & Cui J. (2019). Effects of central buckle on end displacement of suspension bridges under vehicle excitation. Journal of Hunan University (Natural Sciences): 46(03):18–24. Xu X. & Qiang S. (2010). Influence of central buckle on dynamic behavior and seismic response of long-span suspension bridge. Journal of the China Railway Society: 32(04):84–91. Yang H., Zhong T. & Xia H. (2005). Study on effect and mechanism of central buckle on seismic responses of long span suspension bridge. Journal of the China Railway Society: 37(5):7. Yu E. & Li J. (2016). Influence of central buckle on seismic response of long-span suspension bridges. Structural Engineers: 32(01):112–118.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Passive cooling measures—the thermosyphon embankment techniques of roads on plateau permafrost Ziyi Wang*, Tianyi Ye & Yuhang Chen Chang’an University, Shaanxi, China

ABSTRACT: Permafrost is a kind of frozen ground widely distributed in a cold region. It is sensitive to temperature and can melt and refreeze according to the heat it absorbs. Thus, permafrost always relates to engineering problems like thaw settlement and frost heaving. To maintain the stability of the embankment, thermosyphon is widely used to maintain the frozen state of the permafrost. Thermosyphon can cool the embankment of width under 10m effectively. However, it perhaps fails to support the cooling work for the broad-width road from 24.5m to 45m. Two kinds of improvement methods are discussed in this paper, which are the combination method and thermosyphon selfimprovement. The combination method combines thermosyphons with other cooling techniques like crushed-rock revetment and insulation boards. Meanwhile, self-improvement refers to changes to the structure of the thermosyphon evaporator. The actual cooling ability of different methods is compared in the paper, providing that the combination of thermosyphon, crushed-rock revetment and insulation are relatively mature and full of hope for further study. Additionally, the effect of global warming and the law of crack generation have also been reviewed in the essay.

1 GENERAL INTRODUCTIONS In cold regions (high latitude or high altitude), the water in the soil can exist in a frozen state. Some ground has this kind of frozen layer only for several months, called seasonally frozen ground, while the other type is permafrost (Meixue et al. 2010). Permafrost is frozen ground with a temperature of less than or equal to 0-degree centigrade for at least two years, distributed in high latitude and highaltitude areas (Dobinski 2011). Natural permafrost is solid and hard. However, when constructing a road in the plateau area, heat conserved by the building process and the road itself can increase the temperature of the permafrost. Subsequently, the asphalt pavement can inhibit the heat transferred from the permafrost, leading to the degradation of the underground permafrost (Luo et al. 2021). Mutually, the thaw consolidation of permafrost can cause the construction settlement above it. Thus, various scientific methods have been invented to prevent the degradation of permafrost. According to Long & Zarling (2013), methods to treat the permafrost engineering problem can be divided into “Active” and “Passive” cooling techniques. The active cooling technique uses an electric chiller to absorb the heat outside the permafrost (Evans 2015). “Passive technique” is a traditional solution to transfer the heat out of the permafrost with no power or mechanical assistance (Long & Zarling 2013). As a piece of effective passive cooling equipment, thermosyphon is widely used in plateau permafrost areas, e.g., Qinghai-Tibet Road (Song et al. 2013). It has been shown to cool the narrow road (width below 10m) effectively. However, researchers have found new problems after utilizing them in wider roads or railway embankments (e.g., leading to the road’s longitudinal cracks), which demand higher cooling efficiency (Lai et al. 2009). This problem shows that engineers need to find a method to improve the thermosyphon embankment to enable it to ∗ Corresponding Author:

246

[email protected]

DOI 10.1201/9781003384830-31

serve every situation. To compare the previous improvements on thermosyphon to suggest further study, this paper will review the improvement of the thermosyphon embankment on the plateau and compare different methods finding that the combination method using thermosyphon, crushed rock revetment, and insulation may be the most appropriate to conduct further investigation. It will first review the initial thermosyphon on narrow roads and then focus on different improvements to optimize its cooling ability. 2 ENGINEERING PROBLEMS ROSE IN PERMAFROST CONSTRUCTION Permafrost is sensitive to temperature changes. The heat generated in the construction process can affect its temperature balance. Furthermore, asphalt pavement can absorb more heat than the natural ground, accelerating the melt of permafrost under the pavement, and causing thaw settlement (Wei et al. 2009). Subsequently, since the embankments can usually be built near the slope with a longer downward-side slope, the longer slop with the larger surface can accumulate more heat, triggering the unbalanced heat distribution in the embankment and affecting its stability. Additionally, embankments built on slopes can suffer from the shade-sunny effect (Song et al. 2013), which means that one side slope is direct to the sun and traps radiation (sunny slope) while the shaded slope acts conversely. Thus, there will be a significant temperature difference between the slopes of the road, breaking the stability of the embankment. To maintain the frozen state of permafrost, a thermosyphon is employed to absorb heat from the embankment. 3 THE EFFICIENT COOLING EFFECT OF THERMOSYPHON 3.1 Thermosyphon working principle Thermosyphon, a two-phase closed tube (TPCT), is a sealed tube half inserted underground which works in winter. The underground part is called the evaporator, which can absorb heat in the permafrost by gasifying the fluid in the tube, accumulating cold energy for the permafrost. In winter, the gas will later rise into the condenser (the part on the ground), condensing into fluid because of the low temperature outside. The liquid will stream back to the evaporator under gravity and start a new circulation that decreases the underground temperature. However, in summer, since the temperature on the ground is high that it cannot liquefy the gas in the condenser, the gas will remain in the condenser, and TPCTs stop working (Long & Zarling 2013). Fortunately, based on the cold energy accumulated in winter, the embankment can still be freezing even without summer circulation. 3.2 Thermosyphon performance on the narrow and wide road The TPCT embankment has been found to cool the permafrost efficiently to maintain the natural state of the permafrost after construction. However, it can only cool the circular area around it with a limited radius (Figure 1). The limited cooling range can trigger uneven heat distribution, causing the road’s deformation. To expand the cooling area of TPCTs, researchers have proposed various adjusting methods for their implementation. In the study of YunLong Xuesong & Zhongjie (2012), the authors assert the installation standard of the TPCT that the ratio of the side slop of TPCT embankments should be between 1:1.5-1:2.0, with a buried depth of 3.0-3.5m underground and longitudinal intervals of 3.0-3.6m. Furthermore, Li and Lina (2014) investigate different types of TPCT (straight type TPCT, oblique inserting type TPCT, L-type TPCT), pointing out that the oblique inserting type can be most effective considering its cooling area and internal working processes. Thus, TPCT embankment has become a vital solution for construction in places like Trans-Alaska Pipeline System, Qinghai–Tibet Railway (QTR), the Qinghai–Tibet Highway (QTH), and Qinghai–Tibet Power Transmission Line (Luo et al. 2021). Although different inserting methods and careful design are made in TPCTs installation, problems still arise when there are demands for the high-standard road. The initial method failed to 247

Figure 1. The working principle of thermosyphon (Long & Zarling 2013).

maintain the frozen state of the permafrost when applying this technique from the highway (width less than or equal to 10m) to the expressway (wide from 24.5 to 45m). An important reason is that as the road becomes wider, it can conserve more heat with a more extensive range, making the heat-transferring work more difficult. However, the cooling ability of the original TPCT is limited, which finally threatens the road’s stability, causing deformation (Ma et al. 2017). This deformation can further develop into longitudinal cracks. Thus, an increasing quantity of research is being carried out to satisfy the need for improvements in the broad road (width > 20m). 3.3 Influencing factor on embankment stability Yu, Zhang, Lai, Liu, Qi, and Yao (2017) and Chang, Qihao, Yanhui & Lei (2018) investigate roads on plateau permafrost and find out the developing time of longitudinal cracks with some influence factors which contribute to the future monitoring method and elements for the road stability. Another problem that has arisen in the permafrost area is global warming. It has been pointed out by Meixue, Nelson, Shiklomanov, Donglin, and Guoning that the temperature of the Tibetan plateau started to climb in the mid-1950s and is predicted to keep on rising in the future. Therefore, a new, improved method based on the initial TPCTs is required to enhance their own cooling ability or to combine TPCTs with other passive cooling methods and maintain the stability of the whole road.

4 COMBINATION OF VARIOUS COOLING TECHNIQUES 4.1 Other cooling techniques In addition to TPCTs (Figure 2), thermal barriers (Figure 3) and crushed rock layers (Figure 4) are also widely used methods used in road construction on permafrost. Thermal barriers, also called insulation, are materials with low heat conductivity. It is often installed under but near the surface, soil to weaken the heat gain from the road surface (Long & Zarling 2013). Correspondingly, crushed stone can also fill in layers of the road. Crushed stone, for example, cobbles, is a highly porous material used to fill layers of the embankment. Figure 5 shows that the air in the crushed stone comes from two parts: air from the permafrost under the crushed stone layer (henceforth P) and 248

air from the outside environment (henceforth O). At the original time, P lies under O. In winter, when the external environment is much colder than the permafrost, P is much warmer and lighter than O. Therefore, P with rises from the bottom of the crushed stone layer to the top while O falls to replace it, forming a circulation in the layer. Since the outside is freezing, the top warm and light air will flow away through the pores of the crushed stone and allow the outside colder air in. The circulation will restart. Conversely, in summer, the outside is much hotter than the permafrost, which means the top air O turns to be hotter and lighter now. Therefore, as Figure 6 shows, the circulation is suspended, preventing the outside hotter air from entering (Guodong et al. 2007).

Figure 2. A general view of the cooling range of thermosyphons with the annotation by the present author (YunLong Xuesong & Zhongjie 2012).

Figure 3.

Embankment with insulation boards (Yan et al. 2020).

Figure 4.

Crushed-rock layer (Yan et al. 2020).

249

Figure 5. The heat flux in the crushed-rock layer in winter (Based on Guodong et al. 2007).

Figure 6. The heat flux in the crushed-rock layer in winter (Based on Guodong et al. 2007).

4.2 Combination methods In Lai, Guo, & Dong’s (2009) study, it is argued that combining TPCT, crushed-rock revetment, and insulation together could solve the longitudinal cracking problem. They demonstrated that this new design for wide embankment is helpful with experiments in the laboratory, the cross-section of which is shown in Figure 7. Ma, Luo, Gao, Sun, Li, & Lan (2022) have further validated this design with 20 years of field experiment on a low-graded road of 26m width on the Qinghai-Tibet Plateau. Although it has been proved that this compound embankment can eliminate the cracks in a low-graded highway of 26m, its performance on expressways with widths of 28 to 42m and more strict requirements remains unknown. A further issue is that this method uses three cooling techniques, which means that it can cost a lot for construction, health monitoring, and repair. However, the research of Ma et al. (2022) is supported by national groups like the National Nature Science Foundation of China. It can therefore plausibly be regarded as reliable and be reliable and full of space for further study.

Figure 7. Test model with L-shaped thermosyphon, insulation and crushed rock revetment (unit cm).

250

Luo et al. (2021) and Pei, Zhang, Yan, Lai, Lu, & Dai (2022) highlighted another design of composing an embankment with an L-shaped TPCT and insulation board. The two research are studied in the Qinghai-Tibet plateau (QTP). The project of Luo et al. (2021) was conducted on an experimental expressway located between the QTR (34◦ 49 N, 92◦ 54 E) and QTH (K3056 + 500), whereas Pei et al. (2022) investigated the Gonghe-Yushu Highway. Two section views of the projects are shown in Figures 8 and 9. The researchers argue that this combination method can adequately cool the core and shade slope (the side slope that is back to the sunlight). However, problems of embankment deformation and longitudinal cracks still exist. Consequently, Pei et al. (2022) further comment that adding other cooling techniques could be helpful for these remaining problems.

Figure 8. 2021).

Composed embankment structure with insulation and L-shaped thermosyphon (TPCT) (Luo et al.

Figure 9. The cooling system’s schematic structure in the Gonghe-Yushu Highway’s experimental section (Pei et al. 2022).

According to Mei, Chen, Wang, Hou, Zhao, Zhang, Dang, & Gao 2021, crushed-rock revetments focus on eliminating the heat conserved in the embankment, while thermosyphons can transfer the heat outside actively. It is argued that crushed-rock revetment has a weaker cooling ability than 251

TPCT when operating separately. However, Mei et al. (2021) suggested that coupling these two techniques can produce “a whole greater than the sum of the parts”. Thus, they pointed out a combination embankment using crushed-rock revetment and thermosyphons, as shown in Figure 10, demonstrating that this method can reduce the deformation of the embankment. They monitored the permafrost under construction from 2006 to 2018. Before the measurements (crushed-rock revetment and TPCT) were applied, the permafrost continued melting because of climate warming. Subsequently, crushed-rock revetment and thermosyphon resisted the problem effectively. However, it is reported by Mei et al. (2021) that the amount of permafrost under the embankment started to decrease between 2016 to 2018, which can affect the health of the road embankment. Since there is a lack of relevant information for researchers, the reason for the decrease remains unknown. Even though no embankment deformation had occurred, researchers pointed out the potential risks and advised that embankment deformation contour measures should be prepared in advance. Constructing an embankment using crushed-rock revetment Subsequently is still considered more reasonable than building it with insulation and thermosyphons. The reason is that under the 12 years of monitoring, the experimental road has not generated cracks or failure, and the hidden danger of cracks can be eliminated with adjustment.

Figure 10. A composed embankment with crushed-rock revetment and thermosyphons (Mei et al. 2021).

The study of Yan, Zhang Lai, Pei, Luo, Yu, & Yang (2020) compared four combination methods, each of which includes three passive techniques. The four models are: (1) The embankment combined with inclined TPCT and insulation (shown in Figure 11); (2) The embankment combined with inclined TPCT, insulation and crushed-rock revetment (shown in Figure 12); (3) The embankment combined with L-shaped TPCT and insulation (shown in Figure 13); (4) The embankment

Figure 11. The embankment combined with inclined TPCT and insulation (Unit: m) (Based on Yan et al. 2020).

252

combined with L-shaped TPCT, insulation and crushed-rock revetment (shown in Figure 14). After testing their performance in the laboratory, it is shown that the fourth method—combination of Lshaped TPCT, insulation and crushed-rock revetment, has the best cooling ability, which is similar to the research conclusion of Lai, Guo, & Dong in 2009, as stated previously.

Figure 12. The embankment combined with inclined TPCT, insulation and crushed-rock revetment (Unit: m) (Based on Yan et al. 2020).

Figure 13. The embankment combined with L-shaped TPCT and insulation (Unit: m) (Based on Yan et al. 2020).

Figure 14. The embankment combined with L-shaped TPCT, insulation and crushed-rock revetment (Unit: m) (Based on Yan et al. 2020).

253

5 THERMOSYPHON EMBANKMENT IMPROVEMENTS Apart from the combined method that adds other passive techniques to “help” TPCTs, it is also argued to be appropriate to improve the thermosyphon itself. Chang et al. (2018) affirmed the original oblique installation way of the thermosyphon. Subsequently. They pointed out that installing TPCTs straight and inclined in turns along the side of the road could significantly decrease the longitudinal cracks’ generation. The road model they use is shown in Figure 15.

Figure 15. 2018).

Inclined-vertical Subsequently embankment structure of expressway (Unit: m) (Chang et al.,

Improving the traditional shape is another state-of-art way of thermosyphon improvement. The Original thermosyphon is designed in a tube shape with an above-the-ground side (condenser) and an underground side (evaporator). Since the evaporator is created to be straight and tube-like, it only cools the circular area within a limited radius around the tube. When the width of roads climbs to 20m (expressway), the effective cooling area of two-sided TPCTs along the road cannot cover the core of the roads; the deformation and longitudinal cracks, therefore, arise (Ma et al. 2017). As noted above, the main reason for uneven cooling in the road embankment is the limited cooling ability of TPCTs. Thus, Kukkapalli and Kim studied the branched TPCT, which changed the original straight evaporator into a branched one. They first showed the single-branchedY-shaped evaporator (Figure 16) in 2019, followed by a more precise improvement of more branches and determination of the exact angle between different branches and different shaped branches (Y and T shape) (Figure 17). It is reported that the more branches there are in an evaporator, the better cooling effect it will gain. Additionally, they have also determined the optimum spaces between different branched TPCTs. However, these new TPCTs have not been tested with field experiments.

Figure 16. Y-shaped branched TPCT (Kukkapalli & Kim 2019).

254

Figure 17. Y and T-shaped branched TPCT (Kukkapalli & Kim 2021).

6 CONCLUSION Cooling techniques like TPCT, crushed-rock layer, and insulation are invented to maintain the frozen state of permafrost and prevent road deformation. TPCT can cool the narrow embankment effectively with the proper installation method. However, its cooling ability can be insufficient when encountering wide embankments like an expressway. For this reason, other cooling methods are utilized simultaneously. There are various types of embankments with more than one cooling technique. However, all the composed embankment designs listed above can have their shortcomings. The embankment design of Lai et al. (2009) and Ma et al. (2022) have not been tested in expressways and can be expensive to implement. However, the design is likely valuable to investigate further since it successfully eliminated cracks in the low-graded highway of 26m. Additionally, the later investigation of Ma et al. (2022) is supported by national groups, which makes their findings more convincing. Unfortunately, Luo et al. (2021) and Pei et al. (2022) found cracks in their experimental expressway section with thermosyphon and insulation, meaning that this design still needs some improvement. Mei et al. (2021) also demonstrated an effective embankment with crushed-rock revetment and TPCT. However, it is predicted in 2018 that the deformation may occur in the future. In the study by Yan et al. (2020), they compared four kinds of combination methods in the laboratory: inclined TPCT and insulation, inclined TPCT, insulation and crushed-rock revetment, L-shaped TPCT and insulation, L-shaped TPCT, insulation, and crushed-rock revetment. Among these, the last one is similar to the design of Lai et al. (2009) and Ma et al. (2022), and the research advocated that the last method is more suitable than the other three. Considering the investigation on thermosyphon self-improvement, Kukkapalli and Kim (2019) have made progress in determining the space between thermosyphons and the exact appropriate branch numbers. However, their work may still need to be tested in field experiments. To conclude, there is a lack of a perfect answer for the engineering problems in wide embankments like an expressway. However, the combination method of thermosyphon, crushed rock revetment and insulation can be seen as more suitable for further application on expressways, since it has been tested in field experiments for several decades and has demonstrated to be successful in the low-graded highway of 26m on plateau permafrost. Further investigation may keep on monitoring its performance in the expressway. As mentioned in the first section, global warming threats can significantly affect the health of embankments on plateau permafrost. It is clear that investigating an effective and general method is vital and urgent.

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REFERENCES Chang, Y., Qihao, Y., Yanhui, Y. & Lei, G. 2018, “Formation mechanism of longitudinal cracks in expressway embankments with inclined TPCTs in warm and ice-rich permafrost regions”, AppliedThermal Engineering, vol. 133, pp. 21–32. Dobinski, W. 2011, “Permafrost”, Earth-science reviews, vol. 108, no. 3–4, pp. 158–169. Evans, S.A. “Solar-Driven Active Hydronic Cooling System for Permafrost Preservation”, Cold Regions Engineering 2015, pp. 276–286. Guodong, C., Yuanming, L., Zhizhong, S. & Fan, J. 2007, “The “thermal semi-conductor” effect of crushed rocks”, Permafrost and Periglacial Processes, vol. 18, no. 2, pp. 151–160. Available at: https://chn.oversea. cnki.net/kcms/detail/detail.aspx?FileName=LJGC201204040&DbName=CJFQ2012 https://www.researchgate.net/publication/309680646_A_Review_on_Permafrost_Geotechnics_Foundation_ Design_And_New_Trends Kukkapalli, V. & Kim, S. 2019, “Roadway embankment stabilization on permafrost using thermosyphons with Y-shaped evaporators”, IOP Conference Series: Materials Science and Engineering, vol. 507, no. 1, pp. 12017 Kukkapalli, V.K., Kim, J. & Kim, S. 2021, “Optimum design of thermosyphon evaporators for roadway embankment stabilization in the arctic regions”, Journal of Mechanical Science and Technology, vol. 35, no. 10, pp. 4757–4764. Lai, Y., Guo, H. & Dong, Y. 2009, “Laboratory investigation on the cooling effect of the embankment with L-shaped thermosyphon and crushed-rock revetment in permafrost regions”, Cold Regions Science and Technology, vol. 58, no. 3, pp. 143–150. Li, J and Lina, Z., 2014. “Study on the relationship between the hot rod position and hot rod effect”, Forest Engineering, Vol. 30, No. 1, pp.117–119. Available at: https://kns.cnki.net/kcms/detail/detail.aspx? FileName=SSGC201401030&DbName=CJFQ2014 Long, E.L. and Zarling, J.P., 2013. Passive techniques for ground temperature control. In Esch, DC (ed.) Thermal Analysis, Construction and Monitoring Methods for Frozen Ground. Reston, USA: ASCE, pp. 77–165. Luo, X., Yu, Q., Ma, Q., You, Y., Wang, J. & Wang, S. 2021, “Evaluation on the stability of expressway embankment combined with L-shaped thermosyphons and insulation boards in warm and ice-rich permafrost regions”, Transportation Geotechnics, vol. 30, pp. 100633. Ma, Q., Luo, X., Gao, J., Sun, W., Li, Y. & Lan, T. 2022, “Numerical evaluation for cooling performance of a composite measure on expressway embankment with shady and sunny slopes in permafrost regions”, Energy (Oxford), vol. 244, pp. 123194. Ma, T., Tang, T., Huang, X., Ding, X., Zhang, Y. & Zhang, D. 2017, “Thermal stability investigation of wide embankment with asphalt pavement for Qinghai-Tibet expressway based on finite element method”, Applied Thermal Engineering, vol. 115, pp. 874–884. Mei, Q., Chen, J., Wang, J., Hou, X., Zhao, J., Zhang, S., Dang, H. & Gao, J. 2021, “Strengthening effect of crushed rock revetment and thermosyphons in a traditional embankment in permafrost regions under a warming climate”, Advances in Climate Change Research, vol. 12, no. 1, pp. 66–75. Meixue, Y., Nelson, F.E., Shiklomanov, N.I., Donglin, G. & Guoning, W. 2010, “Permafrost degradation and its environmental effects on the Tibetan Plateau; A review of recent research”, Earth-science Reviews, vol. 103, no. 1–2, pp. 31–44. Pei, W., Zhang, M., Yan, Z., Lai, Y., Lu, J. & Dai, Y. 2022, “Thermal control performance of the embankment with L-shaped thermosyphons and insulations along the Gonghe-Yushu Highway”, Cold Regions Science and Technology, vol. 194, pp. 103428. Sheshpari, M. and Khalilzad, S., 2016, “A review on permafrost geotechnics, foundation design and new trends”, International Journal of Research in Engineering and Science. Vol. 4, pp. 59–71. Song, Y., Jin, L. & Zhang, J. 2013, “In-situ study on cooling characteristics of two-phase closed thermosyphon embankment of Qinghai–Tibet road in permafrost regions”, Cold Regions Science and Technology, vol. 93, pp. 12–19. Wansheng, P., Mingyi, Z., Yuanming, L., Long, J. & Harbor, J. 2014, “Thermal stability analysis of crushedrock embankments on a slope in permafrost regions”, Cold Regions Science and Technology, vol. 106–107, pp. 175–182. Wei, M., Guodong, C. & Qingbai, W. 2009, “Construction on permafrost foundations; Lessons learned from the Qinghai-Tibet Railroad”, Cold Regions Science and Technology, vol. 59, no. 1, pp. 3–11.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on compaction quality monitoring technology of the embankment based on continuous compaction indices Yuanlong Song Honghu Flood Storage Area Engineering Administration, Hubei, China

Mingpeng Li∗ School of Civil Engineering, Wuhan University, Wuhan, China

ABSTRACT: In this paper, taking the test section of the embankment of the flood storage project in the east subsection of Honghu Lake as an example, the relationship between the vibration acceleration signal of the vibratory roller and the compaction degree measured in the field is analyzed and studied, and the real-time compaction measurement method applicable to the embankment is obtained. Compared with the data on compaction degree detected by the conventional method, it is found that the VCV value in the continuous compaction index has a good correlation with the conventional compaction degree, while the CMV value has no correlation with the conventional compaction degree. In addition, when the moisture content of the filler exceeds the optimal moisture content by a large amount, the VCV value exhibits certain volatility, and the correlation decreases. 1 INTRODUCTION The flood storage area in the east subsection of Honghu Lake is an important part of the overall flood control in the middle and lower reaches of the Yangtze River, serving as an imperative engineering facility to transfer excess flood water and guarantee the flood control safety of the Jingjiang River embankment. The flood storage project in the flood storage and detention area in the east subsection of Honghu Lake is required to build a new 26.774-kilometer embankment, which adopts the earth embankment type. Since the foundation of the embankment is a multi-layer structure (III), with Q42 silty clay in the upper part and silty clay as well as silty loam in the lower part, the silty clay is buried at a shallow depth so that there is a problem of settlement and deformation, indicating that the engineering geological conditions are poor. Therefore, the embankment should be compacted in layers when filling to ensure the quality of the rolling compaction construction. According to the existing construction specifications, the filling and rolling quality of the earth embankment is mainly controlled by the rolling parameters during the construction process and the compaction degree or dry density of the samples tested in the wake of the rolling. However, the existing detection and management methods have the problem of limited data volume and data accuracy, and it is difficult to eliminate the problem of point and surface due to human factors, posing difficulty in comprehensively and truly reflecting the uniformity of filling and compaction. In the mid-1980s, foreign countries embarked on developing compaction instruments (Adam and Kopf 2000; Mitchell et al. 2009; Noshe and Kitano, 2002). The Swedish compactor method installs the acceleration sensor on the vibratory roller, derives the fundamental frequency of the vibration signal and its second harmonic component, and then uses the percentage of the latter to the former (CMV value) to characterize the compaction situation. In the 1990s, the hydropower department in China introduced and imitated the Swedish compactor, and tried to apply it to some dams, but it was not popularized, which may be related to the lack of good correlation between the evaluation index of the compactor and the routine inspection index. Xu Guanghui’s scientific research team ∗ Corresponding Author:

258

[email protected]

DOI 10.1201/9781003384830-32

(Duan 2012; Xu 2005; Xu and Luo 2015) independently proposed a dynamic method of continuous compaction control in 1998 based on elastic-plastic theory and vibration theory, drawing on the idea of continuous testing of compactors. In 2008, Southwest Jiaotong University, Harbin Institute of Technology, and China Railway Research Institute jointly undertook the scientific research task of “Research on High-speed Railway Continuous Compaction Inspection Control Technology and Equipment” by the Ministry of Railways (Tian 2015; Xu 2005), and further improved this set of technology with regard to theoretical systems, testing equipment, and engineering applications. The continuous compaction index VCV value was proposed, and nearly 1,000 sets of comparative tests and engineering applications were carried out in several railway projects. At present, the above-mentioned continuous compaction indices are more used in the transportation field (Zhang 2005; Zhao 2016), but less applied in water conservancy projects. Moreover, due to the limitations of soil types, improvement is further required for the existing compaction evaluation methods before they can be promoted in water conservancy or other industries. To this end, the applicability of the continuous compaction index in water conservancy projects needs to be further tested. Although there are many types of compaction detection indices, they are generally based on certain theoretical assumptions, which are difficult to be satisfied in practical engineering. In order to study the applicability of the continuous compaction index in water conservancy projects, this paper will select the Wulin section of the embankment for experimental research to verify the correlation between detection indices of the compaction degree (CMV and VCV values) and the compaction degree detected by the conventional method. The influence of parameters such as moisture content of fillers on compaction indices is studied, so as to provide a research basis and reference experience for promoting the development of continuous compaction control technology and contributing to the wider application of this technology in water conservancy projects. 2 CONTINUOUS COMPACTION INDICES CMV AND VCV 2.1 Harmonic ratio method and CMV The harmonic ratio method uses the distortion degree of the dynamic (vibration) response signal of the roller to evaluate the compaction degree, which is actually a signal analysis method. The principle of this method is as follows: when the fillers of the filling body are relatively loose, the measured dynamic signal is basically the sinusoidal signal excited by the vibratory roller, and there is only the fundamental frequency component in the frequency; as the number of rolling passes increases, the fillers are gradually compact, its physical and mechanical properties are also reinforced, and the reaction to the rolling wheel is also strengthened, which makes the waveform shape of the measured signal distorted. In addition to the fundamental frequency signal, there are signals of other frequency components in the frequency, in which harmonic components are the main influencing factors, regardless of other components. There is a certain relationship between the distortion degree and the compaction degree of the filled body, from which the compaction quality can be evaluated. This method deals with the vibratory roller’s response signal from the angle of signal form processing, and its index is a dimensionless relative value. The specific expression of compaction detection value (CMV) is: CMV = C

A1 A0

where A0 is the amplitude of the fundamental frequency signal, A1 is the amplitude of the first harmonic component, and C is a constant, usually taking 300. 2.2 Dynamic vibration compaction method and VCV The dynamic vibration compaction method is based on the principle of mechanical balance to obtain the resistance Fs of the filling body, based on which the compaction degree of the filling body is 259

evaluated. In fact, the resistance of the filling structure is the reaction of the filling structure to the rolling machine, which can characterize the ability of the filling structure to resist deformation. The expressions of response acceleration and the resistance of the vibration excitation system in the process of roadbed vibration compaction are as follows: F(u) = Psin(ωt) + Mg − M ü where P is the amplitude of the exciting force, ω is the angular velocity of the eccentric block, M is the mass of the vibrating wheel, and ü is the acceleration of the vibrating wheel. The above formula is a transient expression, which can be regarded as a vector expression, suitable for theoretical analysis. Multiple parameters are needed to determine the solution, and it cannot be solved by measuring the acceleration. According to the expression of the resistance force of the excitation system, when the vibratory roller is rolling on the same rolling track, the difference between the resistance of the subgrade structure in two adjacent passes (the (n+1)-th pass and the n-th pass) is: Fn+1 (u) − Fn (u) = M (ün − ün+1 ) It can be seen that there is a linear relationship between the resistance of the subgrade filling and the acceleration of the vibratory roller. Therefore, the dynamic response (acceleration, etc.) of the vibrating wheel of the roller is the best way to identify the resistance of the roadbed, which eliminates the need for complicated calculations. At the same time, detailed parameters related to the roller are not required, only certain vibration parameters and stable performance are required. Taking the acceleration response as the continuous compaction control index, the resistance index VCV is: VCV = Psin(ωt) + Mg − M ηf (ü, ω) which is VCV ∼ F(u) ∼ ü where f (ü, ω) is a function or time series related to acceleration and vibration frequency of the vibration wheel, and η is a comprehensive correction function, serving as a dynamic quantity. For a rolling machine with stable performance, when the vibration parameters are constant, the VCV value of the rolling body can be calculated by continuously collecting the acceleration of the vibration wheel. The VCV index is actually a relative concept. In practical applications, it is not necessary to solve the absolute value of the index, while it is needed to establish the relationship between the VCV index and the detection index in conventional indices through the on-site calibration test, thereby realizing the indirect evaluation of the rolling quality.

3 ROLLING EXPERIMENT OF THE EMBANKMENT 3.1 Experimental design The foundation in the Wulin section (0+000∼0+200) of the embankment selected in this test area is a multi-layer structure (III), with Q42 silty clay in the upper part and silty clay as well as silty loam in the lower part, and the silty clay is buried at shallow depth so that there is a problem of settlement and deformation, indicating that the engineering geological conditions are poor. The filling is constructed in layers from low to high. According to the rolling test report and the design technical requirements, the thickness of the soil is generally controlled at about 40cm, and the width of the fill is not less than 50cm over the design edge. A 22t road roller is used for segmented rolling, the driving speed is 1.0–1.5 km/h, and the number of compaction times is 6–8 times according to the test report. The basic parameters of this roller are as follows: 260

Table 1. Parameters of the vibratory roller. Work quality

Kg

22000

Static line load Amplitude Vibration frequency Exciting force Maximum walking speed

N/cm mm Hz KN km/h

506 2.0 28 380 10.5

For the sake of studying the correlation between detection indices (CMV and VCV values) for the compaction degree and the compaction degree detected by the conventional method, we installed the sensor SC100 on the road roller to collect the acceleration signal, with the acquisition frequency of 1000Hz, and the acceleration signal feature is analyzed to get the CMV and VCV values. In order to study the influence of parameters such as moisture content of fillers on the compaction index, we conducted experimental comparative studies on two fillers with different moisture contents. According to the field conditions, the embankment in the Wulin section is selected as the test section. The test section is about 100m long and 12m wide, and the rolling method is carried out in the light stacking method of 6-wheel tracks in 3 areas. After the rolling is completed, 2 to 3 points at each wheel track should be selected for conventional compaction testing, and compared with the theoretical analysis results. 3.2 Correlation analysis of compaction detection indices 3.2.1 Comparative analysis of VCV value and conventional method to detect compaction value Since the acceleration data at different positions in each pass is changing, after eliminating the interference data in the non-test areas at both ends, the acceleration signal is filtered and calculated to obtain the change curve of the VCV value during the rolling process, as shown in Figure 1.

Figure 1.

Change curve of VCV value during the rolling process.

The average value of the compaction data in the rolling area is taken as the representative value of the compaction degree of this pass, and the change curve of the compaction degree with the number of rolling passes is drawn, as shown in Figure 2. It can be seen from the plotted curve that with the increase in the number of rolling passes, the compaction degree shows an upward trend, but after a certain number of rolling passes, the compaction degree will no longer increase, and may even have a slight downward trend. At this time, it suggests that the filler has reached a 261

stable compaction state, and if the rolling is continued, the physical structure of the filler will be destroyed due to overpressure.

Figure 2.

Change curve of CVC value with the number of rolling passes.

In order to check the correlation between the VCV value and the conventional compaction degree, representative points on the change curves of compaction in different wheel track areas corresponding to the number of rolling passes were selected for detection by the conventional method. The detected compaction values and the corresponding VCV value are plotted into a graph in the order from low to high, as shown in Figure 3. From the corresponding relationship curve between the two, it can be seen that the VCV value and the compaction value detected by the conventional method are basically linearly correlated, showing that the two are well correlated.

Figure 3. Correlation curve between VCV value and the value of compaction degree detected by the conventional method.

3.2.2 Comparative analysis of CMV value and conventional method to detect compaction value After calculating and analyzing the frequency of the acceleration signal at different positions of each pass, the CMV value during the rolling process is obtained, and the average value of the CMV value in the rolling area is taken as the representative CMV value of this pass, and the change curve of CMV value with the number of rolling passes is plotted as shown in Figure 4. It can be seen from the plotted curve that with the increase in the number of rolling passes, the CMV value shows a downward trend, contradicting the fact that the compaction degree increases. The detected compaction value and the corresponding CMV value are drawn into a graph in order from low to high, as shown in Figure 5. From the corresponding relationship between the 262

Figure 4.

Change curve of CMV value with the number of rolling passes.

two, it can be seen that there is no correlation between the CMV value and the compaction value detected by the conventional method.

Figure 5.

Scatter plot of CMV value and the value of compaction detected by the conventional method.

Figures 6 and 7 show the waveform and spectrum map of the vibration signal during the third and fifth passes of the compaction separately. It can be observed from the spectrum map of the vibration signal during the second and third rolling passes that there are other frequency components in addition to the first harmonic, and the intensity difference of the harmonics is relatively large, showing the characteristics of nonlinear vibration. It can be noted from the spectrum map of the vibration signals during the fourth and seventh rolling passes that, except for the first harmonic, other frequency components are very small, and the CMV value becomes 0 or very small. Theoretically, when the stiffness of the soil becomes very large, the vibration wheel of the roller will bounce. At this time, CMV tends to be 0, and the compaction effect cannot be assessed. 3.3 Influence of the moisture content of fillers on the compaction index VCV For the compaction of general clay soil, the most important factor is to control the moisture content, which is the decisive factor for the compaction effect. In the experiment, it was found that the high moisture content of the filler in this area is a common phenomenon, which is inseparable from the local weather conditions. For this reason, we repeated the experimental scheme when the moisture content of the filler was too large, in an attempt to verify the correlation between the VCV value and the compaction value detected by the conventional method when the moisture content was too large. 263

Figure 6. Waveform and spectrum map of the vibration signal during the third pass of compaction.

Figure 7. Waveform diagram and spectrum map of vibration signal during the fifth pass of the compaction process.

Figure 8 shows the compaction values detected by the conventional method and the corresponding VCV values plotted as scatter plots in order from low to high, and it can be seen from the scatter plots of the correlation between the two that there is a linear correlation between the VCV values and the compaction values detected by the conventional method, but it is not too obvious.

Figure 8. Scatter plot corresponding to the VCV value of compaction index and the compaction test value of the conventional method.

In view of the problem that the linear correlation is not obvious, the moisture content of the filling body before and after rolling was analyzed, and it was found that the moisture content was between 24% and 28%, which was much higher than the optimal moisture content of clay. Due to the over-pressured soil produced by the high moisture content filler under the repeated action 264

of external force, the dispersibility of the soil is increased, the free water in the channels between the aggregates is increased, and the structural strength of the soil is reduced. Therefore, it is very important to control the moisture content of fillers in rolling construction, which should be given attention, and the natural moisture content test of fillers must be carried out before paving. 4 CONCLUSION In this paper, taking the test section of the embankment of the flood storage project in the east subsection of Honghu Lake as an example, the research on the quality monitoring technology of rolling operation is carried out, and the main conclusions are drawn as follows: 1) Compared with the compaction degree data detected by the conventional method, it is found that the VCV value of the continuous compaction index has a good correlation with the conventional compaction degree, while the CMV value has no correlation with the conventional compaction degree. The rolling process of the embankment can be controlled by the VCV value. 2) For the case where the filler is cohesive soil, when the moisture content exceeds the optimal moisture content by a large amount, the resistance to deformation of the filler is relatively low, and the VCV value exhibits a certain fluctuation. Therefore, special attention should be paid to the distribution of moisture content when establishing the relationship between VCV value and compaction degree. ACKNOWLEDGMENTS This work was financially supported by the Key scientific research projects of water conservancy in Hubei Province (project No. HBSLKY202013). REFERENCES Adam, D. and Kopf, E. (2000). Theoretical Analysis of Dynamically Loaded Soils. European Workshop Compaction of Soils and Granular Materials, 3–16. Duan, L.Q. (2012). Research on Continuous Compaction Quality Control Technology of Rock-filled Embankment [D]. Southwest Jiaotong University. Feng, L.C. (2008). Discussion on common control indicators for compaction quality testing of passenger dedicated line bases [J]. Chongqing Architecture, 53(2): 23–26. Mitchell, M.R., Link, R.E. and Facas, N.W. (2009). Position reporting error of intelligent compaction and continuous compaction control roller-measured soil properties [J]. Journal of Testing & Evaluation, 38(1):13–18. Noshe, Y. and Kitano, M. (2002). Development of A New Type of Single Drum Vibratory Roller. Proc. 14-Th International Conference of the International Society for Terrain—Vehicle Systems, Vicksburg, MS USA October, 20∼24. Tian, L.F. (2015). Research on the Evaluation Method of Continuous Compaction Quality of Roadbed [D]. Southwest Jiaotong University. Xu, G.H. and Luo, Z.H. (2015). A review of the development of continuous compaction control technology [J]. Road Construction Machinery and Construction Mechanization, 32(28): 33–38. Xu, G.H. (2005). Dynamic Monitoring Technology of Subgrade System Formation Process [D]. Southwest Jiaotong University. Xu, Q., Chang G.K. and Gallivan V.L. (2012). Development of a systematic method for intelligent compaction data analysis and management [J]. Construction & Building Materials, 37:470–480. Zhao, X.P. (2016). Research on Intelligent Compaction Control Technology of Roadbed [D]. Chang’an University. Zhao, G.J. and Guo, P. (2006). Correlation analysis of highway subgrade compaction detection methods [J]. Journal of Xi’an University of Science and Technology, 02(4): 14–18. Zhang, D.P. (2005). Program Design and Research of IntelligentVibratory Roller Control System [D]. Chang’an University.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Design and practice of deformation monitoring of seawall during construction Hai Zhao* & Linsong Yang* CISPDR Corporation, Wuhan, China

ABSTRACT: Deformation monitoring of soft foundation seawall during construction is an important part of engineering construction. Reasonable design and layout of seawall monitoring equipment, acquisition of monitoring data of seawall’s displacement, pore water pressure, and groundwater level, and understanding of the relationship between seawall deformation characteristics and construction process, meteorology, tide, and dike foundation geology can provide a reference for the foundation treatment process, project construction organization design, etc. At the same time, the settlement of the seawall foundation is preliminarily predicted and analyzed, which provides the basis for maintenance during operation.

1 INTRODUCTION The West Dike project around the island is an important infrastructure for the construction of the Hengqin new area. The seawall engineering grade is Grade I, and the standard of tide prevention is the design of a 100-year return period. The standard of tide prevention for dike-crossing buildings is designed once in 100 years and checked once in 200 years. The main building level is Grade 1, and the secondary building level is Grade 3. The project is constructed on the original natural beach and the shoreline of the inland river port fishery waters, most of which are in the range of soft foundation and low-lying water areas. The foundation treatment and monitoring during the construction period are important links for the smooth implementation of the project. Through monitoring during the construction period, we can reveal the real situation of the main body of the building and the construction area in different construction stages, so as to evaluate the stability and safety of the building [Gu 2021], and then guide the construction and operation management.

2 MONITORING CONTENT The main contents of seawall engineering monitoring include settlement monitoring, horizontal displacement monitoring, pore water pressure monitoring, groundwater level monitoring, horizontal displacement monitoring of deep soil, layered settlement monitoring of soil, and observation of sea tide state and coastal tide level during engineering monitoring. The monitoring items, equipment, and installation elevation of the West Dike project around the island (lower section) are shown in Table 1 [Yin 2019].

∗ Corresponding Authors:

266

[email protected] and [email protected]

DOI 10.1201/9781003384830-33

Table 1. Table of design features and installation features of the equipment. Installation Elevation

Feedback position Range

Serial number

Items

Equipment

1

Surface subsidence

Benchmark

2 3

Internal settlement Layered settlement

Settlement plate Settlement ring

4

Surface horizontal displacement

Plane observation pier

5

Inclinometer tube

−30.0

3.7 ∼ −30.0

6

Internal horizontal displacement Pore water pressure

Osmometer

−20.0

−2.0 ∼ −20.0

7

Groundwater level

Piezometric tube

−1.0

3.7 ∼ −1.0

Surface

−1.0 −30.0

≤ −1.0 1 ∼ −32 Surface

Unit: m

Explain Observe according to the requirements of the national first-class level. Common point layout with inclinometer tube Unified construction and measurement with the construction control network Groundwater level One osmometer is buried every 4 ∼ 6m Near the osmometer

3 SECTION LAYOUT The dike type of the West Dike around the island (lower section) is designed according to the type of compound slope seawall with the platform. The top elevation of the dike is 4.5 ∼ 4.7 m, and the elevation of the wave dissipation platform outside the dike is 2.5 ∼ 2.7 m.

Figure 1.

Monitoring project layout.

267

The monitoring equipment is arranged according to the cross-section of the seawall, and a monitoring section is generally set up at about 200 m. Due to the influence of site and construction conditions, the head and tail sections of this section (K4 + 568 ∼ K4 + 870, K6 + 450 ∼ K6 + 725) are not equipped. A total of 9 monitoring sections are arranged between K4 + 870 ∼ K6 + 450. According to the principle of reasonable and efficiency increase [Hao 1999], two types of monitoring sections are arranged, as shown in Figure 1. Because the seaward side is the main functional part of the seawall, it bears the direct impact of waves and tides, and its deformation and damage are likely to be greater. Therefore, benchmarks, inclinometer tubes, and settlement rings are arranged on the outer side of the top of the seawall (besides the wave wall or guardrail) and on the wave-absorbing platform of each section. In order to understand the change of pore water pressure, underground water level, and settlement at a certain elevation of seawall, osmometer, piezometer, and settlement plate are respectively arranged. These three kinds of monitoring devices are arranged in groups at the wave dissipation platform of Type ① monitoring section, the center of the dike top, and the foot of the slope inside the dike (land side).

4 INSTALLATION AND COLLECTION 4.1 Installation of main monitoring equipment 4.1.1 Metal structure settlement plate monitoring point The settlement plate of seawall shall be buried before the medium and coarse sand is dumped. The pipe orifice shall be taken over as per 1.0 m along with the filling progress of the seawall body. When the concrete is laid at the bottom of the protection well of the seawall, it shall be connected with the settlement plate φ100 mm PVC casing isolation. 4.1.2 Inclinometer tube, layered settlement magnetic ring The inclinometer pipe shall be buried after the completion of medium-coarse sand dumping. UPVC pipe is used for the inclinometer. The length of a single inclinometer pipe is 3m. Adopt drilling methods for construction. The upper and lower bottom covers of the inclinometer tube and the joint are sealed and connected, and the clamping groove corresponds to the main direction of measurement (A: vertical seawall. B: parallel seawall), manually tamped within 50 cm around the inclinometer. The inclinometer tube is used as the settlement pipe in the layered settlement monitoring point. Before the inclinometer pipe is buried, the settlement magnetic ring is sheathed at the corresponding position of the inclinometer tube, and the elastic sheet is bound with a matching paper rope. The settlement magnetic ring is pasted on the outer wall of the inclinometer tube with ordinary transparent tape. The tape and paper rope lose their function soon after encountering water, and the elastic sheet is expanded and inserted into the soil, so the settlement magnetic ring moves with the soil movement. The position of the settlement magnetic ring at the deepest part of the hole bottom of the inclinometer pipe is about 20 ∼ 30 cm away from the bottom of the inclinometer pipe. When the inclinometer pipe is lengthened, one settlement magnetic ring is installed every 3 m interval. The settlement distance of the magnetic ring downward should not be less than 1.5 m, and the distance between the top magnetic ring and the embankment surface should not be more than 1.5 m. 4.1.3 Installation of osmometer Before embedding and installing the pore osmometer, its permeable parts shall be immersed in water for more than 2 hours to eliminate the bubbles in the permeable stone. The reference value of the osmometer is read after immersion. The pore osmometer of the dike foundation is buried after the construction of inserting the drainage board. The length of the connecting cable is reserved for 1.5 m above the ground after the completion of the project. The data cables of the monitoring 268

points of the seaside and the dike are exported to the ground and placed in the observation well. The data cables of the monitoring points on the land side are bundled on the piezometric tube [Li 2000]. 4.1.4 Burying and installation of piezometric tube The seepage pressure is monitored at the pore pressure monitoring point near the dike. The piezometer consists of a permeable section and conduit. The outside of the permeable section is wrapped with non-woven geotextile, which can prevent soil particles from entering. The bottom elevation of the monitoring point is −1.0 m. After the installation and sealing of the piezometric tube, a sensitivity test is carried out. 4.2 Benchmark value and monitoring frequency The deformation monitoring datum value is generally based on the initial value (the observation value in the original state before the object is not loaded), or the first value is taken as the benchmark value (independent observation twice, taking the average value as the reference value), or taking a measurement value as the reference value (after the instrument passes the debugging and the measurement value is stable) [Zhang 2005]. The monitoring frequency is determined according to the damage degree of building deformation, deformation rate, and construction requirements. The determination method and monitoring frequency of each monitoring data reference value of seawall are shown in Table 2. Table 2. Determination method of monitoring equipment reference value and observation frequency. Serial number

Equipment

Reference value

Observation frequency

1

Benchmark

The average value of twice, take the average value

2

Settlement plate

First observation value (initial value)

3

Settling ring

Average of two observations

4

Plane observation pier

Independent observation twice, take the average value

5

Inclinometer tube

Position of the bottom of the inclinometer tube (initial value)

6

Osmometer

7

Piezometric tube

When the instrument is in the state of full water saturation, the measured value before embedding is taken as the reference value. Formal observation shall be started more than 24 hours after burying Continuous observation after the completion of embedding, take the average value.

Construction period: 1 ∼ 7 times/week, operation period: 1 ∼ 2 weeks observation. Construction period: 1 ∼ 7 times/week, operation period: 1 ∼ 2 weeks observation. Construction period: 1 ∼ 4 times/week, operation period: 1 ∼ 2 weeks observation. Construction period: 1 ∼ 4 times/week, operation period: 1 ∼ 2 weeks observation. Construction period: 1 ∼ 7 times/week, operation period: 1 ∼ 2 weeks observation. Construction period: 1 ∼ 7 times/week, operation period: 1 ∼ 2 weeks observation.

Simultaneous observation with an osmometer

The observation frequency can be adjusted according to the change in the measured value, the progress of the project construction process, and the construction intensity. Intensive observation is required for engineering construction intensity increase, typhoons, spring tide, and heavy rainfall. 269

Intensive observation is required when there is pumping and drainage, filling, and soil sampling construction near the measuring point, which may affect the operating environment or stress condition of the building. When the monitoring value changes abnormally, approaches, or exceeds the warning value, the observation shall be intensified. 5 DEFORMATION ANALYSIS At the beginning of the construction of the monitoring project of the West Dike around the island (lower section), the monitoring items in the construction period began to enter the site, and the settlement plate settlement of the foundation was first monitored. With the progress of the project, the data monitoring of internal horizontal displacement, layered settlement, seepage, seepage pressure, and other data were successively carried out. It took 32 months to obtain a large number of monitoring data during the construction period. It provides sufficient support for engineering construction and understanding the deformation mechanism of the seawall. 5.1 Settlement analysis of settlement plate Settlement plates are set at the seaside, embankment, and land side of pile No. K6 + 450. The bottom elevation of the settlement plate is −1.0 m. The initial value observation was started in October 2013. The last observation in April 2016 showed that the filling height of the high sea, middle and land sides were 0.8 m, 1.8 m, 0.8 m to 2.7 m, 3.51 m, and 1.8 m respectively. The seaside reached the design height in June 2015, and the middle part of the dike reached the design height in May 2014. On the land side, it was filled to the design height in January 2014. The settlement process chart is shown in Figure 2. The initial settlement of seawall soft foundation treatment is very obvious. In late October 2013, the maximum settlement rate was 43 mm/d. After mid-February 2014, the soft foundation treatment was initially completed, and the land side was filled to the design elevation. The settlement rate decreased from about 7 mm/d to 3 mm/d, and most of them were 1∼2 mm/d. After that, when the dike body and seaside were filled to the design elevation, the settlement rate increased slightly in the short term (20 ∼ 60 days), about 4 mm/d, and then gradually decreased to about 1 mm/d. After the hardening construction of the embankment surface and wave dissipation platform, the settlement rate increased significantly from July to August 2015, about 4 mm/d, and then gradually decreased to about 1 mm/d.

Figure 2. Line Diagram of Load-Time-Settlement Process at Monitoring Point of subsiding (Settlement Plate) of Pile K6 + 450.

270

5.2 Settlement analysis of settlement ring There are 20 layered settlement monitoring points and 240 settlement magnetic rings in 10 monitoring sections of the West Dike around the island (lower section). The cumulative settlement displacement is between -43 mm and 1002 mm, and the average cumulative settlement is 368 mm. The settlement change of the settlement magnetic rings is related to the geological conditions (coastal distance) of each monitoring section, the difference in pile load, the difference in construction technology and construction progress control, and the consolidation degree of each layered soil. Too fast and too large changes in the groundwater level of the dike foundation are also the influencing factor. For example, the river at the K4+870 monitoring section was originally flooded into the sea, and the initial elevation of the West Dike was lower, so the filling load was the largest. The groundwater level was directly facing the sea, which was greatly affected by the tide and changed rapidly. The seepage pressure and seepage velocity inside the dike foundation changed obviously. It has a significant influence on the settlement of the layered soil of the embankment foundation. Up to the last observation, the average accumulated settlement of 24 settlement magnetic rings in two-layered settlement monitoring points at this section is 597 mm, which is the monitoring section of 20 layered settlement monitoring sections of the West Dike foundation with the largest average accumulated settlement of settlement magnetic rings. The results show that the subsidence of the magnetic ring tends to slow down at the end of this period. The load time settlement process line of monitoring points of layered settlement displacement (settlement ring) is shown in Figure 3.

Figure 3. Line diagram of the load-time-settlement process of layered settlement displacement monitoring point in K4+870.

5.3 Analysis of internal horizontal displacement The A+ direction of the horizontal displacement monitoring point inside the inclinometer tube is consistent with the direction of the vertical dike pointing to the seaside. The maximum accumulated horizontal displacement of different elevation positions in each monitoring point hole is −140.45 mm ∼ 108.59 mm, and the maximum cumulative horizontal displacement is −140.45 mm at the 1.0 m elevation of the monitoring point hole at the seaside of section K4 + 870. The maximum horizontal displacement rate is 7.49 mm/d, which appears at the elevation of −10.5 m in the K5 + 450 seaside hole (observed from October 13 to 15, 2015). The direction B+ is parallel to the dike body and points to the direction of small mileage. The maximum cumulative horizontal displacement of different elevation positions in each monitoring point hole 271

is −74.76 mm ∼ 80.04 mm, and the maximum cumulative horizontal displacement is 80.04 mm at 1.0 m elevation in the monitoring point hole of section K5 + 850. The maximum horizontal displacement rate is 5.47 mm/d, which appears at the elevation of 2.5 m in the middle hole of K6 + 050 dike (observed from April 13 to 22, 2015). During the construction period, the horizontal displacement of the deep soil mass of the embankment foundation is mainly manifested as the lateral sliding deformation under the load variation caused by the embankment filling loading. The peak value of the displacement rate change is closely related to the strength of the loading construction. With the construction loading progress, the embankment foundation load increases continuously. Within the scope of the embankment foundation bearing capacity, the soil mass of the embankment foundation has plastic deformation. The lateral displacement shows the increasing horizontal displacement rate, and there are 6 points with cumulative displacement reaching or exceeding 100 mm. The larger horizontal displacement rate appears in the process of embankment loading construction. The land side of the K4 + 870 section is a large area of water, and its connection with the open sea is small, and part of the time period is completely separated. Under the action of tide, the rise or fall of the land side water area seriously lags behind the tide fluctuation state. The change of the land side water level is quite different from that of other sections, and the foundations of both sides of the embankment are similar, and the ground elevation has no significant difference.

Figure 4. The displacement-depth curve of the vertical seawall (A) at the monitoring point of internal horizontal displacement (inclinometer) of pile number K4+870.

272

Figure 4.

Continued.

The maximum lateral displacement of the deep foundation is −452.4 mm, which is the largest horizontal displacement of the deep foundation, as shown in Figure 4. The lateral displacement of the middle section inside the monitoring point of the inclinometer tube basically presents a “C” or “S” symmetrical structure, and there is no abnormal single point protruding. The lateral displacement of each elevation position of the surface soft foundation is a plastic change within the bearing capacity of the foundation. However, the horizontal displacement of the top part of the inclinometer pipe mouth is affected by the interference of the dike top construction, such as uneven rolling on both sides of the measuring point, and repair after construction damage. For the lateral displacement of the top section of the inclinometer pipe, retest and discrimination shall be carried out in the observation work in combination with the patrol situation. 5.4 Analysis of underground water level The five monitoring sections of the West Dike (lower section) around the island are buried with boreholes according to the seaside, middle part, and land side of the dike foundation. There are 15 underground water level monitoring points for pipe installation. After the water injection test, the sensitivity of the piezometers is good. A total of 150 observations have been made since the piezometer was buried until 3 months after the completion of the project. After the underground water level monitoring points of the West Dike are arranged and buried, by May 2016, the cumulative variation of the groundwater level at the monitoring points of the dike foundation will be in the range of between −139.00 cm and 57.30 cm. During the construction period, the change rate is between −57.39 cm/d and 29.15 cm/d. The last observation results of the monitoring points show that the overall variation of groundwater level in the West Dike foundation 273

is between −86.00 cm and 47.00 cm, and the change rate is gradually slowing down from −3.58 cm/d to 2.04 cm/d. Figure 5 is the process line diagram of load-time-groundwater level change at the pile number K6 + 050. The real-time and uninterrupted change of tide level in front of the dike directly affects the groundwater level of the dike foundation. Before the formal monitoring, the whole tide water level and the response of the measuring points were observed. The response observation data showed that the response of different monitoring points to the sea level was quite different, the seepage line of the dike body lagged behind the influence of the tide level change in front of the dike, and the influence of the tide level in front of the dike on the dike body gradually weakened from the waterside slope to the back waterside slope. The rapid short-term change of the groundwater level of the dike foundation is closely related to the sand blowing (filling) loading construction in the core of the dike during the construction period, the heavy rainfall caused by the strong convective weather in the coastal area, and pumping and draining the accumulated water in the construction area.

Figure 5. Line diagram of the load-time-tide-change process of groundwater level at monitoring point of pile number K6+050 dike foundation.

5.5 Analysis of pore water pressure The main purpose of monitoring the pore water pressure of the dike foundation during the construction period of the West Dike around the island is to observe the variation of the pore water pressure curve and the pore pressure ratio at different depths by means of the pore osmometer embedded in different depths, calculate the consolidation degree of the embankment foundation soil layer, analyze the foundation strength growth and guide the reasonable control of the construction progress. 15 monitoring points are arranged at 5 ① type monitoring sections of the West Dike (lower section) around the island according to the location of the seaside, the middle part of the dike, and the land side. At each point, 5 sets of pore osmometers are arranged at different elevation positions in the deep layer of the dike foundation, with a total of 75 pore osmometers. From March 2014 to May 2016, there were 150 observations. The cumulative variation range of pore seepage pressure is −49.96 KPa ∼ 12.31 KPa. Through the observation of the response of seepage pressure of dike foundation to the whole tide level, we can master the general range of the response of seepage pressure of dike foundation to tide level, and monitor the seepage pressure of dike foundation under roughly the same tide fluctuation state and similar tide level, so as to weaken its influence as much as possible. When the measured value of seepage pressure changes abnormally, it can be used to judge the treatment effect of soft foundation and soil consolidation state, and to warn and guide the construction strength and interval time of embankment body loading. 274

The real-time tidal level, tidal state, and real-time groundwater level of dike foundation are also observed and recorded during the stage observation of pore seepage pressure of dike foundation, which provides valuable data for the correlation study of seepage pressure tide groundwater level of seawall during the construction period. As shown in Figure 6, the response hydrograph of tide time pore water pressure groundwater level at monitoring point of pile No. K6 + 450 (in the dike) on May 3, 2014 is shown.

Figure 6. Response hydrograph of tide level-time-pore water pressure-groundwater level at monitoring point of pile number K6+450.

After the construction of inserting drainage board, the soil pore water is drained out, the soil gradually consolidates, the soil settlement of the embankment foundation is faster, the stress intensity of the embankment foundation is improved, and the pore seepage pressure dissipates quickly. After the construction of the embankment in stages, the pore seepage pressure increases rapidly and then dissipates gradually. With the continuous filling during the construction period, the overall observation data also show that the gradual dissipation of pore seepage pressure is a general trend, and the change rate of seepage pressure tends to gradually slow down, as shown in Figure 7, load time pore water pressure response process line of monitoring point at pile No. K4 + 870 (middle dike). The influence factors of the large change of the measured pore pressure of the dike foundation in a short time also include the heavy precipitation under adverse weather conditions, the large

Figure 7. Load-Time-Pore Water Pressure Response Process Line of Monitoring Point at Pile K4+870 (in the dike).

275

change of the groundwater level formed by the accumulation and drainage of surface water in the construction area, and other construction near the monitoring point will also cause the abnormal change of the seepage pressure of the dike foundation. Fully considering and screening all kinds of influencing factors, the seepage pressure variation law of the dike foundation during the construction period is analyzed to avoid the change of stress structure at different elevation positions of the dike foundation due to the rapid loading rate, which causes the instantaneous increase of seepage pressure of dike foundation, which forms scouring on the dike body or foundation and causes slope instability. 6 PREDICTION OF SETTLEMENT DEFORMATION OF SEAWALL The monitoring time of the construction period of the West Dike around the island (lower section) is from the beginning of the project to 3 months after the completion of the project. At the end of the monitoring project in the construction period, the effective quantity of various monitoring changes normally, and the settlement monitoring data tend to converge. In order to evaluate the settlement of the seawall after the completion of monitoring during the construction period, the later settlement is predicted according to the existing observation data. The quadratic exponential smoothing model is used to predict the settlement [Song, 2019]. The prediction process is carried out by taking the monitoring of the settlement plate at the monitoring point of K6 + 450 (the top of the embankment) as an example. From October 2013 to April 2016, a total of 205 observations were made, and the time interval of each observation was from 1 to 7 days in advance. For the convenience of time series analysis, the observation data is counted as monthly settlement, and some data series with more than 3 days from the monthly statistical time point are converted to the accumulated settlement at the time point according to the settlement rate of this period. Table 3. K6+450 (Seawall center) secondary exponential smoothing calculation table of plate settlement data. Weight coefficient

Period 13.09 13.10 13.11 13.12 14.01 14.02 14.03 14.04 14.05 14.06 14.07 14.08 14.09 14.10 14.11 14.12 15.01 15.02 15.03 15.04

M.S.Q (mm)

M.S.R (mm/M)

368.0 368.0 439.0 104.0 351.0 223.5 90.3 71.4 85.4 120.3 90.3 63.8 50.4 36.4 24.5 31.3 17.6 15.3 30.6 52.5

11.9 14.2 3.4 11.3 7.2 2.9 2.3 2.8 4.0 2.9 2.1 1.7 1.2 0.8 1.0 0.6 0.5 1.0 1.7

0.6

S1

S2

a1

b1

368.0 368.0 410.6 226.6 301.3 254.6 156.0 105.2 93.3 109.5 98.0 77.5 61.3 46.4 33.2 32.0 23.4 18.5 25.8 41.8

368.0 368.0 393.6 293.4 298.1 272.0 202.4 144.1 113.6 111.2 103.3 87.8 71.9 56.6 42.6 36.3 28.5 22.5 24.5 34.9

368.0 368.0 427.6 159.9 304.4 237.2 109.6 66.4 73.0 107.9 92.7 67.2 50.6 36.1 23.9 27.8 18.3 14.5 27.1 48.7

0.0 0.0 25.6 −100.2 4.7 −26.1 −69.6 −58.3 −30.5 −2.5 −7.9 −15.5 −15.9 −15.3 −14.0 −6.3 −7.7 −6.0 1.9 10.4

Forecast (mm) 368.0 368.0 453.2 59.7 309.1 211.0 40.0 8.1 42.6 105.4 84.8 51.7 34.7 20.8 9.9 21.5 10.6 8.5 29.0

Error (mm) 0.0 71.0 −349.2 291.3 −85.7 −120.7 31.4 77.4 77.7 −15.1 −21.0 −1.3 1.7 3.6 21.4 −3.9 4.7 22.1 23.5 (continued)

276

Table 3. Continued. Weight coefficient

Period 15.05 15.06 15.07 15.08 15.09 15.10 15.11 15.12 16.01 16.02 16.03 16.04 16.05

M.S.Q (mm) 17.9 39.3 52.3 102.3 41.7 27.2 29.1 24.4 17.0 19.2 14.8 13.0

0.6

M.S.R (mm/M) 0.6 1.3 1.7 3.3 1.4 0.9 1.0 0.8 0.5 0.7 0.5 0.4

S1

S2

a1

b1

27.4 34.5 45.2 79.4 56.8 39.0 33.1 27.9 21.3 20.1 16.9 14.6

30.4 32.9 40.3 63.8 59.6 47.2 38.8 32.2 25.7 22.3 19.1 16.4

24.5 36.2 50.1 95.1 54.0 30.8 27.4 23.5 17.0 17.8 14.7 12.8

−4.5 2.5 7.4 23.5 −4.2 −12.3 −8.5 −6.5 −6.5 −3.4 −3.3 −2.7

Forecast (mm)

Error (mm)

59.1 20.0 38.6 57.5 118.6 49.8 18.5 18.9 17.0 10.5 14.4 11.5 10.1

−41.2 19.3 13.7 44.7 −77.0 −22.6 10.7 5.5 0.0 8.8 0.3 1.5

It can be seen from Table 3 that the greater the monthly settlement deformation rate changes, the greater the prediction error for the next period of the month. The correlation between the prediction error and the settlement change is shown in Figure 8. In August 2015, there was a large amount of abnormal settlement deformation. After October 2015, the settlement deformation rate tends to be stable, and the predicted quality is good. The predicted settlement of 16.05 is 10.1 mm.

Figure 8.

Forecast error and monthly settlement variation chart.

7 CONCLUSIONS During the construction period, the settlement, horizontal displacement change, seepage pressure, and groundwater level change of the seawall foundation and internal soil layers are closely related to the increase of load and the control of surcharge construction progress. The settlement distribution of the dike foundation is consistent with the actual filling height of each embankment section. The hysteresis response of seepage pressure and groundwater level affected by tide has a certain delay and gradually weakened. The change process line of each effect quantity accords with the general change law in the process of increasing load after the treatment of coastal soft soil foundation. 277

REFERENCES Guina, Sun Song, Zhang Deyou. Analysis on the necessity of embankment safety monitoring [J]. Jiangsu Water Conservancy, 2021(3): 59–61. Hao Changjiang. My opinion on the safety monitoring design of the main canal project in the middle route of the South-to-North water transfer project [J]. People Changjiang, 1999, 30(8): 26–28. Li Gang, Xu Weijun, Ma Shui-shan, Liao Yong-long. Safety monitoring of vertical seepage control project of Jingnan Changjiang Main Dike [J]. Journal of Yangtze River Scientific Research Institute, 2000, 17(Supp.): 25–27. Song Zhichao, Chen Hanxin, Wen Zongyong. Innovation and development of engineering survey technology in Great Country [M]. Beijing: China Construction Industry Press, 2019. Yin Zhengyu, Tsering Zhuo Ma, Zhou Binshan, Bu Lei, Dan Zengluo, Duan Dan. Current situation and the prospect of total monitoring of the pangduo water conservancy project in tibet [J]. ChinaWater Conservancy, 2019(14): 42–44. Zhang Zhenglu et al. Engineering surveying [M]. Wuhan: Wuhan University Press, 2005.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Crack control of hydraulic dam mass concrete pouring based on image feature Xiaogang Li∗ China Northwest Water Conservancy & Hydropower Engineering Consulting Co., Ltd., Xi’an, China

ABSTRACT: The traditional crack control method of mass concrete pouring mostly uses the digital image analysis method to calculate the geometric parameters of cracks, which can not extract the topological structure characteristics of cracks, resulting in low accuracy of geometric parameters calculation results and reducing the compressive strength of the crack structure. Based on this, the image feature technology is introduced, and a new method of pouring crack control is proposed. The crack width parameters and the degree of structural damage are obtained by using the image feature technology and the binary processing of the pouring crack image. The surface repair method is used to repair and control the pouring crack. In the experiment, the compressive strength of the crack surface structure of mass concrete pouring is verified, and the experimental results show that the compressive strength of the crack surface structure is significantly improved by using the proposed method to control the concrete pouring crack.

1 INTRODUCTION Mass concrete, as the most frequently used building material in the construction of hydraulic dams, has a greater impact on the quality of hydraulic dam construction. Mass concrete is different from ordinary concrete in the hydration heat of cement, the heat dissipation rate of the concrete surface, and the degree of internal and external thermal expansion and contraction (Wang 2022). Mass concrete is prone to different types of cracks in hydraulic dam construction, mainly temperature cracks and subsidence cracks (Li 2021). Once cracks appear in the mass concrete, it will lead to different degrees of diseases in the hydraulic dam, including the decline of the dam impermeability, the reduction of the dam structural strength, the dam settlement, etc. In serious cases, the dam foundation may collapse, and there are greater safety risks and hidden dangers (Liu 2021). Scientific and reasonable crack control method for mass concrete pouring is very important (Chang 2020). However, there are still some shortcomings in the practical application of the traditional concrete pouring crack control methods. It is mainly reflected in the low accuracy of the image acquisition of concrete cracks, and the lack of detailed analysis of the causes and characteristics of cracks, which can not provide strong support for crack control (Wang 2021). Image feature processing technology can improve the above problems by detecting and extracting crack features, obtaining concrete crack types and geometric feature parameters, and generating corresponding crack control schemes (Zhou 2021). Based on this, this paper introduces the image feature processing technology and designs a new crack control method for mass concrete pouring, which contributes to the overall improvement of the safety and reliability of the hydraulic dam operation.

∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-34

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2 STUDY ON A CRACK CONTROL METHOD OF MASS CONCRETE POURING 2.1 Geometric parameters extraction of pouring cracks based on image feature In the crack control method of hydraulic dam mass concrete pouring designed in this paper, firstly, the noise of concrete surface structure pouring crack image is filtered and preprocessed by using image feature processing technology. Identify the pouring cracks, and then extract the geometric parameters of the cracks to provide a basic guarantee for the subsequent pouring crack control (Li 2020). Based on the principle of imaging transformation, the camera imaging model of mass concrete pouring crack is established, as shown in Figure 1.

Figure 1.

Camera imaging model of mass concrete pouring crack.

As shown in Figure 1, in the model, the abscissa represents the optical axis of the mass concrete pouring crack, and the ordinate represents the camera projection center of the pouring crack. Through the function of perspective projection change of the model, the pouring crack image is collected (Hou 2020). The image feature processing technology is used to filter out the redundant noise interference information in the image, enhance the illumination uniformity of the crack image, realize the binarization of the pouring crack image, and ensure the integrity of the mass concrete crack information (Wang 2019). On this basis, the method of image feature thinning processing is used to retain the basic outline of the crack image, simplify the structure of the image, and extract the topological structure features of the pouring crack. The width of the crack is calculated according to the topological structure of the pouring crack, and the formula is: r=

Q × L f

h=r × N

(1) (2)

Where r represents the pixel size of the pouring crack image; h represents the crack width of mass concrete; Q represents the pixel size of the pouring crack image after image feature processing; f represents the focal length of a lens in a camera imaging model; L represents the real distance between the camera imaging model lens and the pouring crack; N represents the number of width pixels of the crack image. Through calculation, the crack width parameters of the mass concrete pouring are obtained, and the damage degree of concrete surface cracks is determined. 2.2 Control of pouring cracks by surface repair method After the geometric parameters of the hydraulic dam mass concrete pouring crack are extracted, the damage degree of the surface structure of the pouring crack is obtained. On this basis, the surface repair method is used to repair and control the pouring cracks. 280

Firstly, the surface of the crack part of the mass concrete of the hydraulic dam is chiseled into a groove shape. Set the groove specification as 20mm * 200mm, use high-pressure water to wash the excess impurities in the groove, mix the cement mortar, and add waterproofing agent with a concentration of 1% ∼ 2% into the cement mortar to improve the anti-seepage effect of the cement mortar. Brush 2-3 layers of cement mortar on the surface of the groove, and control the thickness of the mortar within the range of 10 mm to 20 mm to form a rigid waterproof layer. A layer of 2.5mm thick cement paste shall be plastered on the surface of the waterproof layer. After the cement paste is solidified, it shall be watered and covered for curing. The surface of the mass concrete pouring crack is covered with a plastic film, and a template is arranged to carry out top pressure firm treatment so as to enhance the bonding effect between the mortar and the concrete pouring crack. Epoxy mastic shall be applied to the surface of the part where the width of the pouring crack is less than 0.01 m. The epoxy mastic shall be dried by the high temperature of the blowtorch, and then the excess part of the crack surface shall be removed with a wire brush. Glass fiber cloth shall be pasted at the uneven positions where the pouring cracks are repaired, and a layer of putty shall be applied to fill the cracks in the mass concrete pouring of the hydraulic dam. Through the surface repair method to control the pouring cracks, on the one hand, the surface structure of the cracks can be repaired, on the other hand, the stability and bearing capacity of the concrete crack structure can be improved.

3 EXPERIMENTAL ANALYSIS 3.1 Preparation for the experiment To sum up, this paper uses image feature processing technology to design the whole process of the crack control method for mass concrete pouring cracks of the hydraulic dam. On this basis, in order to further make an objective analysis of the feasibility of the control method designed above, the following experiments are carried out. The S hydraulic dam project in a certain area is selected as the research object. Among the hydraulic dams, the earth-rock dams account for about 75%, and the low dams with a height of fewer than 30 m account for about 72%. The hydraulic dam site is located 22 km upstream of the hydropower station. The overall project is located in relatively open terrain, and the geological conditions are granite with a hard texture. The S hydraulic dam is a mass concrete gravity dam, with an overall dam length of 2014 m, a dam foundation bottom width of 108 m, a top width of 35 m, an elevation of about 190 m, an average water level of 160 m, and a maximum discharge of 100,000 cubic meters per second. The earthwork excavation volume of the S hydraulic dam project is about 108 million cubic meters, and the mass concrete pouring volume is about 26.5 million cubic meters. The hydraulic dam project was completed in 2015, and the surface structure and strength of the mass concrete were inspected at regular intervals. In the latest quality inspection, it was found that the dam concrete had different degrees of pouring cracks, which seriously reduced the reliability and safety of the dam operation. Therefore, the control method of the mass concrete pouring cracks based on image features designed in this paper is applied to the S hydraulic dam project to control the pouring cracks.

3.2 Analysis of results To verify the effectiveness of the crack control method of mass concrete pouring designed in this paper more intuitively, the experimental method of comparative analysis is used. The control method of mass concrete pouring cracks based on image features designed in this paper is compared with the digital image control method of concrete structure surface cracks proposed in reference and the closed-loop control method of concrete shrinkage cracks designed in reference. Randomly select 6 groups of mass concrete pouring cracks and number them, which are numbered as JZLF01, JZLF02, JZLF 03, JZLF 04, JZ LF 05, and JZ LF 06. Calculate the compressive strength of each 281

group of pouring cracks, and the formula is: Pc = Fc /S

(3)

Where Pc is the compressive strength of the surface structure of the pouring crack; Fc is the maximum load when the pouring crack is damaged; S is the area of the compression part of the pouring crack. Finite element analysis software is used to analyze the depth of pouring cracks, and the calculation results of crack depth and compressive strength are drawn into a table, as shown in Table 1. Table 1. Crack depth and compressive strength of mass concrete. No.

Crack depth

Compressive strength

JZLF01 JZLF02 JZLF03 JZLF04 JZLF05 JZLF06

The depth is up to 2.4m, and there is a closing trend below 2.4m. The depth is up to 2.2m, and there is a closing trend below 2.2m. Depth up to 1.5m The depth reaches 2.3m, and there is a closing trend below 2.3m. When the depth is below 0.6m, there is a trend of closure. When the depth is below 0.4m, there is a trend of closure.

204 MPa 198 MPa 212 MPa 248 MPa 267 MPa 288 MPa

As shown in Table 1, after obtaining the crack depth, closure tendency, and compressive strength of mass concrete, the pouring cracks are repaired. A crack monitoring line is embedded in the mass concrete to monitor the change in the pouring cracks of the internal structure and the external structure of the concrete in real time. On this basis, the MATLAB analysis software is used to determine the change of compressive strength of the surface structure of each group of pouring cracks after the application of the three concrete pouring crack control methods, and the results are shown in Figure 2.

Figure 2.

Comparison results of compressive strength of concrete pouring crack.

According to the comparison results of compressive strength of mass concrete pouring cracks in Figure 2, among the three pouring crack control methods, after the application of the image 282

feature-based pouring crack control method designed in this paper, the compressive strength of the surface structure of each group of concrete pouring cracks has been significantly improved, which is above 350MPa. The advantages are obvious, and the effect of crack repair and control is better.

4 CONCLUSION To sum up, as an important part of water conservancy projects and hydraulic construction projects in China, hydraulic dams have higher requirements for the quality and intensity of their construction. In order to improve the defects of a traditional crack control method for the mass concrete pouring of hydraulic dam, a new crack control method is designed by introducing image feature technology. Through the research of this paper, the stability and impermeability of the hydraulic dam structure are effectively improved, the number of cracks on the surface of mass concrete is reduced, and the durability of the hydraulic dam is optimized.

REFERENCES Chang J. (2020). Numerical simulation of temperature field of raft foundation mass concrete construction [J]. Construction Mechanization, 41(11): 44–48. Hou Y., Chen Y.H. & Gu X.Y. et al. (2020). Intelligent recognition of asphalt pavement targets and cracks based on convolutional self-encoding [J]. Chinese Journal of Highways, 33(10): 288–303. Li Z.Q. (2021). The main factors and treatment techniques for the formation of building concrete cracks [J]. Sichuan Cement, 11: 31–32. Liu Y.F., Fan J.S. & Nie J.G. et al. (2021). Research review and the prospect of digital image recognition of structural surface cracks [J]. Chinese Journal of Civil Engineering, 54(06): 79–98. Li L., Wei W.J. & Yan F.K. (2020). Analysis of control measures for irregular cracks in dam mass concrete [J]. Anhui Architecture, 27(09): 250–251. Wang J. & Kong X.Z. (2022). Experimental study on the effect of raw materials on the autogenous volume deformation of hydraulic dam concrete [J]. Cement, 5: 1–5. Wang C., Jia H. & Zhang S.R. et al. (2021). Image-based quantitative and efficient identification of concrete surface cracks [J]. Journal of Hydroelectric Power, 40(03): 134–144. Wang B.X., Wang Z. & Zhang Y.F. et al. (2019). Concrete surface crack detection algorithm based on image high-dimensional feature compression mapping [J]. Journal of Beijing Institute of Technology, 39(04): 343–351. Zhou X., Xia W.J. & Wang J. et al. (2021). Key technologies for closed-loop control of concrete shrinkage cracks in Taihu tunnel structures [J]. Concrete, (02): 151–156.

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Smart city construction and resource sustainability

Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Research on key technologies of intelligent site management platform Nana Liu, Geng Chen∗ & Yingjia Wang Chongqing College of Architecture and Technology, Chongqing, China

ABSTRACT: In recent years, China is striving to develop intelligent manufacturing industries while the construction field also witnesses the transformation from the traditional mode to the intelligent one which is characterized by green building, new building industrialization, and building industry informatization. For construction units, an intelligent and unified management mode is the main development direction, which calls for an intelligent site. An intelligent site management platform integrates intelligence, unification, automation, and big data into one, which has been widely promoted in construction sites. Intelligent site management platforms are widely used. In addition to the function of intelligent personnel management and attendance, it has made significant improvements in unmanned monitoring, safety early warning, transportation, and data processing. As a new construction site management mode in the construction industry, the intelligent site management platform has been applied to the actual operation of construction sites, which not only improves the efficiency of construction and the management system but also significantly upgrades the level of civilized construction.

1 GENERAL INSTRUCTIONS 1.1 Research overview With the progress of science and technology and the transformation of the construction industry development, construction project management has entered the era of big data. Modernized, intelligent management has become an important part of the construction process, conforming to the ideology of “civilized construction, green building” in our country. Yet construction management is faced with serious challenges in both facilities management and personnel management, They all need to be standardized and efficient (Ou 2017). To better implement the management system in the construction site and improve the efficiency of construction management, the intelligent, unified, advanced, and data-oriented intelligent construction management platform will replace the former manual management instead. This paper takes big data analysis as the background of the intelligent site management platform. According to the information management of the construction site and the implementation of realtime monitoring, the data processed on-site are predicted, and the corresponding management measures are implemented. The implementation of the intelligent site management platform is the product of the combination of the Internet of things and the construction industry, and it is an important means to realize civilized construction and green development of civilized cities. 1.2 Research background The construction industry is the pillar of our national economy, which has played an important role in promoting our national economic growth and social comprehensive development. While ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-35

287

the traditional construction mode is mostly in the form of manual construction and management, the construction site is often faced with many uncontrollable factors, such as the low production efficiency in construction caused by the lack of management experience, densely staffed construction site, low production efficiency, frequent accidents, the difficulty in managing the personnel, the backward communication form, and unresponsive report to the superior in real-time. All these disadvantages directly affect the development of the construction industry and can’t keep pace with the times. There is no positive correlation between social demand and the backward construction mode, which affects the sustainable development of the construction industry (Qiao 2020). At the same time, it also increases the cost input of the industry. Based on the above problems, the management mode of construction needs to be adjusted in time and modern technology should be used to improve production efficiency. At present, a growing number of construction units are beginning to adopt a more intelligent, unified digital management platform. With the widespread application of Internet technology, intelligent construction site management platform has begun to mature and be used by more construction companies, which can effectively realize real-time and effective project management.

1.3 Research status In the era of big data, the development of all industries is more standardized and efficient. However, it is still difficult for the construction industry to develop by using modern technology. The integration of big data and the construction industry as well as the change of thinking mode depends on the management. Some data of the construction industry cannot be reflected by big data technology, resulting in the ineffective application of big data in the construction industry with no advantages being displayed. The data in the construction industry even cannot be collected (Jiao 2018). The reason is that the current analysis technology and software do not have a reasonable classification of big data, causing invalid data processing. However, as time advances, many construction companies begin to strengthen the utilization rate of data analysis to improve work efficiency. At present, the most widely used intelligent construction site management platform, integrating big data, the Internet of Things, and various digital devices, is put into operation to optimize the construction site management process, collect, upload, save, and analyze the data collected on the construction site, and finally realize that each data has a basis and prediction. The goals of efficient operation of the management process, efficient completion of construction work, and efficient development of the construction industry are achieved (Huang 2021).

2 DATA ANALYSIS TECHNOLOGY BASED ON-SITE MANAGEMENT PLATFORM 2.1 Intelligent site management data platform The intelligent site data management platform stores, collects, organizes, and analyzes the data collected on the site through digital and information construction, and displays the obtained data on the intelligent map to clearly show the data of the building structure. During the analysis and classification of the data, the data can also be displayed in the form of tree charts, pie charts, and line charts, which can accurately reflect the problems on the construction site. The intelligent site management platform breaks the current situation of data fragmentation and inadequate supervision and can realize unified supervision of personnel, mechanical equipment, and the construction process. Based on hierarchical management of personnel, real-time control of equipment authority, adjustment of construction progress, the establishment of the inspection system, and standardized scoring system, the scientific nature of construction process management is improved, and the site safety risks can be identified by algorithms to achieve real-time alarming, strengthen accident warning, and improve the safety of site construction and production (Xie 2018). 288

Figure 1.

Intelligent site management system composition.

2.2 Research on data acquisition and storage technology According to the existing data collection equipment, such as tower crane black box, surveillance camera, environmental monitoring instrument, one-card card reader, and other equipment, the data collected at the target site is uploaded to the corresponding software, and the technical personnel passes the data collection standard to screen the data (Zhao 2020). Different data collection standards should be established according to the functional embodiment and requirements of hardware devices, as well as the data types required by the equipment. For one card-swiping machine and other equipment, military encryption is used to protect the user’s privacy in the system management process.

Figure 2.

Intelligent site management system operation process.

289

The collected data will be uploaded to the cloud database, analyzed by the algorithm form of the database, and finally returned to the management platform for storage (Chen 2018). Data storage is mainly for data security, confidentiality, and data storage time standards on the management platform. This study investigates the storage of data, such as the methods, paths, and devices for storage. 2.3 Information data acquisition equipment requirements Intelligent site management platform adopts different data collection equipment for different forms of data collection and different work characteristics, mainly to ensure the accuracy and efficiency of data collection. (1) The internal structure of the data acquisition equipment is mainly composed of a data receiver, data processor, and data output device. Most of them are in the form of sensors, analog multiplexing switches, AD converters, or computers. (2) Given that the collected data is clearly visible, the filter of the data acquisition equipment should be a low-pass one. In general, the corner frequency of the filter should be set as 1/2 of the Nyquist frequency. In addition, bandwidth design and order should also be considered when the filter is designed from the perspective of frequency. The equipment system, with the characteristics of low cost, high reliability, and small size, should be embedded to tailor the data in software and hardware and can be applied to different complex environments with its great adaptability for site management. (3) Since most of the data acquisition equipment is placed in the outdoor environment, the waterproofing, compressive resistance and overpressure ability of the data acquisition equipment should also be taken into account to cope with different conditions on the construction site. 2.4 Data storage software requirements Due to the differences in data collection standards formulated by data collection devices, sometimes structured, semi-structured, or unstructured data may appear in the collected data. In such cases, the data storage platform needs to support both structured and unstructured storage and retrieval functions. Semi-structured and structured data can be stored in relational databases. The common way to store semi-structured data is to use the MySQL database. Using the master-slave replication mechanism of MySQL can effectively reduce the downtime of devices or servers, which promotes future data storage nodes. Unstructured data is mainly stored in the form of files, usually with the help of third-party platforms, such as cloud platforms and file servers. Third-party platforms, such as Hikvision AICloud cloud, can store image data. Data storage software has high requirements on CPU, memory, and hard disk, and the system algorithm needs to be transformed according to the different types of data requirements.

3 DATA ANALYSIS PROCESS There are many types of data collected from construction sites, including video data, large machinery and equipment data, environmental data, and labor data. 3.1 Environmental monitoring data The building site is mostly outdoors, thus facing a variety of unexpected conditions, such as changes in the weather, which might affect the progress of construction. And the noise and dust at the construction site will also affect the surrounding environment, so monitoring of the environment is necessary for the construction process. An intelligent site management platform in different parts of the site of the installed equipment can collect the humidity, temperature, noise, PM 2.5, and air 290

quality. After the data is collected, classified, and transferred to the database, the database will use its powerful analysis function to analyze and integrate the data and then return the data back to the platform, the BI big data map, to verify the environmental conditions at that time. After comparing the data transferred to the platform with relevant national and local environmental standards, we can judge whether the environment is appropriate for outdoor work. If not, the alarm system will be triggered to convey the alarm information to the APP in the hands of each person in charge so as to adjust the following construction work.

3.2 Video surveillance data Video monitoring is a widely used management equipment in construction sites. Video monitoring can not only effectively manage construction equipment, materials, and personnel, but also ensure the safety and confidentiality of construction sites. The intelligent site management platform is used to monitor the video data collected by the monitoring equipment through different user devices, such as mobile phone apps and computer users. The data is uploaded to the platform and regularly saved under a specific transformation mode. By means of video monitoring, the construction situation of the site can be monitored in real time, and the video data collected by the equipment can be analyzed to predict the working status of the construction site.

3.3 Site inspection data Site inspection is generally divided into two types, the on-site one and the online one. On-site inspection refers to the inspection personnel entering the construction site to conduct on-site inspection, while online inspection uses the Internet to conduct online monitoring through the film and television data and environmental data received by the platform. Compared with on-site inspection, online inspection is more controllable, less restricted by time and place, and can work more efficiently. The use of mobile apps and client improves the convenience and reliability of inspection. When inspection researchers found the problems in a construction site through a small application program, they would issue the online corrective instruction, and the platform would stay at home after receiving the instruction to reschedule the construction work. The whole inspection process, the inflows and outflows of background data, and the sorting and storage make construction more convenient.

4 ADVANTAGES OF INTELLIGENT SITE MANAGEMENT SYSTEM (1) (2) (3) (4)

Scientific management to reduce costs Strong security and high real-time performance Facilitate the supervision of personnel and equipment Reliable data collection and analysis

5 CONCLUSION Combining with the Internet of Things and big data and based on the traditional site management method, the intelligent site management platform is quite efficient. Construction site management may encounter many problems in development but is an inevitable trend. The construction companies will adopt the integrated platform for project management and with so many advantages, the intelligent site management platform will be more widely used in the future. 291

REFERENCES Chen Wenyun (2018). A Smart Construction Site Safety Management Platform System Architecture, CN108446866A[P]. 2018. Guo Haodong (2018). Research and application of intelligent site management cloud platform in the construction industry [J]. China Science and Technology Investment, 2018, 000(029): 38. Huang Jiancheng, Xu Kun, Dong Zhanbo (2021). Research and implementation of intelligent site management platform system architecture [J]. Construction Economics, 2021, 42(11): 6. Ou Manli, Cao Weijun (2017). Research and application of intelligent site management cloud platform in the construction industry [J]. Enterprise Science and Technology Development, 2017(8): 3. Qiao Xin, Chang Fei (2020). A Smart Construction Site Management Platform. CN111080260A [P]. 2020. Shevevey (2018). Research on Application of intelligent site management platform [J]. Architectural Engineering Technology and Design, 2018. Zhao Yonghong (2020). Application analysis of smart site management platform in construction engineering [J]. Building Materials Technology and Application, 2020(5): 3.

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Optimization of building design and contribution to sustainable development Yiran Wang* The High School Affiliated to Renmin University of China, China

ABSTRACT: Optimum design of engineering structure refers to the best design method for certain indicators of the building structure (such as weight, cost, stiffness) under the condition of meeting various specifications or certain specific requirements. Among all the available options and practices, the best method should be selected according to a certain objective. The traditional building structure is to first give or assume a design plan and practice based on experience and judgment and use the engineering mechanics method to carry out structural analysis to check whether the requirements of bearing capacity, stiffness, stability, size, etc. specified in the code are met. If it meets the requirements, it is usable. Or an available program can be obtained by comparing a few programs and methods. Structural optimization design is to find the optimal solution among many, even infinite, available plans to practice, that is, the plan and practice with the most economical materials, the lowest cost, or the best certain indicators. The such engineering structure design is developed from analysis and verification to synthesis and optimization, which has a great practical significance in improving the economic benefits and function of engineering structures. Synthesis and optimization are essentially optimal designs of the building structure.

1 INTRODUCTION Architecture is the art or science of building or formation or construction resulting from or as if from a conscious act. “The practice of architecture is to meet the needs of practicality and expression.” (Rohloff, M 2005) Therefore, it serves utilitarian and aesthetic purposes (Rohloff, M 2005). Architecture is everywhere, and architecture in different regions has different meanings, including environment, history, art, and daily lifestyle. In certain areas, architecture can even reflect the local natural environment and social relations. Usually, a good building needs to satisfy several requirements, including its suitability for human use in general, its adaptability to specific human activities, the stability, durability, and safety of the building structure, and even the transmission of experiences and ideas through its form (Rohloff, M 2005). Geometric design refers to the size and arrangement of visible features of the road (Wong KD 2013). The design includes pavement width, horizontal and vertical alignment, ramping, intersections, and other features that can significantly affect road network operations, safety, and capacity (Parvin, K 2021). The geometric design is an interesting trend that focuses on the simple aesthetic of mixing certain shapes, lines, and curves for creative effects. Based on practical mathematical principles, geometric designs can be created with formulaic precision or through simulation, which is commonly used to create diverse patterns, abstract backgrounds, and fabulous visualization effects. ∗ Corresponding Author: [email protected]

DOI 10.1201/9781003384830-36

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Geometry is nothing but visible numbers. It is the first representation of numbers, long before the shorthand symbols 1, 2, and 3 were created for them. Early geometers revealed the relationships between numbers by looking at how geometric shapes related to each other. Since numbers had profound meaning, so did the meaningful patterns that emerged from them. Based on geometry, we can create different beautiful patterns. Geometry is the branch of mathematics that studies the size, shape, position, angle, and dimensions of things. Geometry includes two-dimensional shapes: points, lines, and planes, and three-dimensional shapes: spheres, and cubes (Ahmad, T 2016; Tushar, Q 2021). Geometry has many applications. Everything around us has certain shapes, volumes, surface areas, positions, and other physical properties, all of which are related to geometry (Evins, R 2013; Kazimieras Zavadskas, E 2019; Sherif 2019). Architecture is a major application of geometry. In the construction of a building and to maximize the use of the building, the structure of its components is a determining factor for safety. Geometric design also applies the knowledge of geometry to create the most perfect works in a limited area. Any design scheme of a building structure can be represented by many given parameters and some design variables which vary with the changes in the scheme. The dimensional direction composed of these design variables can be represented by a point in the dimensional space, which is called the “design point” (Bajjou, M. S 2017; Yeo, D 2015). Design specifications state that conditions or other constraints that must be met are called “constraints” to optimize the design. A design point that satisfies all “constraints” is called a “usable design” (Bank, L. C 2010; Zhou, Z 2021). Those design points that represent all available designs form a sub-city of the dimensional space, called the “available city” (also known as the feasible region) (Ogunmakinde, O. E 2022). The criteria for evaluating the pros and cons of the scheme (such as structural weight, cost, etc.) are functions of design variables, which are called “objective functions”. The structural optimization design is to use some mechanical and mathematical methods to search for the optimal point of the minimum (or maximum) objective function in the available domain, that is, the optimal design scheme (Damtoft, J. S 2008; Kim, J. T 2018). Optimization, also known as mathematical programming, is a collection of mathematical principles and methods used to solve quantitative problems in many disciplines, including physics, biology, engineering, economics, and business (Ekeocha, R. J 2019). Optimization problems usually have three basic elements: a single numerical quantity, or objective function, which is to be maximized or minimized; a collection of variables; a set of constraints that restrict the values a variable can take (Ekeocha, R. J 2019). Within this broad framework, optimization problems can have different mathematical properties. The simple problem in linear programming is finding the maximum or minimum value of a simple function under certain constraints (Ekeocha, R. J 2019). As a result, optimization can be used to find minimal cost, maximal profit, minimal error, optimal design, optimal management, and variational principles (Arora, J 2004). Thus, this essay is going to combine optimization with a geometric design to find the solution to building design and contribution to sustainable development. With the help of optimization, we can find the best combination of thickness, electricity, heating, total consumption, and so on.

2 METHODOLOGY 2.1 Dynamic programming (linear/nonlinear programming) Dynamic programming is a technique for breaking a problem into subproblems and saving the results for future use. And it is mainly an optimization of ordinary recursion. Dynamic programming can be used to optimize recursive solutions when they repeatedly call the same inputs. The idea of dynamic optimization is to simply store the results of subproblems so that we don’t have to recalculate them later when needed, reducing the time complexity from exponential to a polynomial

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(Felzenszwalb, P. F 2010). As a result, it ensures that optimal solutions can be found in the case of optimal solutions. This programming technique has many advantages, including that it is very easy to understand and implement, it only solves subproblems when needed, and it is easy to debug. But sometimes, the call stack takes up more memory when the recursive techniques are used. And sometimes stack overflow conditions occur when the recursion is too deep. Therefore, when the memory footprint is too high, the overall performance deteriorates. In mathematics, linear programming is a method of optimizing operations with certain constraints. The primary goal of linear programming is to maximize or minimize numerical values (Murota, K 2020). Linear programming consists of linear functions that are constrained in the form of linear equations or inequalities and are considered to be an important technique for finding the best use of resources (Murota, K 2020). And it’s a kind of important optimization problem, which helps to find a feasible region and optimization solutions to get the highest or lowest value of the function (Murota, K 2020). Linear programming is widely used in mathematics and other fields, such as economics, business, telecommunications, and manufacturing (Murota, K 2020). The linear programming problem has two basic parts. First, it must have an objective function that describes the primary purpose of the formation to maximize some returns or to minimize some. Second, it is a constant set with a system of equalities or inequalities which describes the condition or constraints of the restriction under which optimization is to be accomplished. While linear programming models work well in many cases, some problems cannot be modeled accurately if they do not include nonlinear components. Nonlinear problems arise when goals or constraints cannot be expressed as linear functions without sacrificing some fundamental nonlinear characteristics of real-world systems (Gill, P. E 2005). An optimization problem is nonlinear if the objective function f(x) or any of the inequality constraints ci (x) ≤ 0, i = 1, 2, …, m, or equality constraints dj (x) = 0, j = 1, 2, …, n, are nonlinear functions of the vector of variables x (Gill, P. E 2005). 2.2 Convex optimization (general continuous form) Convex optimization refers to the optimization method in which the objective function is a convex function under the optimization requirements of minimization (maximization), and the feasible region set formed by the constraints is a convex set. With the ability to sequentially query external data sources, online convex optimization has emerged as a method to obtain optimal solutions to convex functions and has gained widespread popularity for its scalability in large-scale optimization. For convex optimization problems, there are many algorithms including the most used gradient descent method, Newton method, quasi-Newton method, etc., all of which are guaranteed to converge to the global minimum point. In some optimization problems, the number of constraints is limited, but the number of variables will explode with the increase of the size of the problem, so all variables cannot be explicitly expressed in the model. When this type of programming is solved by the simplex method, the basic variable is only related to the number of constraints, and only one new non-basic variable enters the basis in each iteration. Therefore, in the whole solution process, the column generation algorithm finds the non-basic variable that can be entered into the basis by solving the sub-problem. And the non-basic variable is not explicitly written in the model, which can be regarded as generating a variable. Each variable is equivalent to a column, so this method is called a column generation algorithm. If there is no non-basic variable that can be entered into the basis, the reduced cost of all non-basic variables satisfies the conditions of the optimal solution. In other words, the optimal solution to linear programming has been found, even if many variables are not written out in the model. The normal form of the mathematical optimization problem is as follows. Minimize f(x) Subject to fi (x) ≤ bi , i = 1, . . . , m.

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The vector x = (x1 …, xn ) is the optimization variable of the problem, the function f0 : Rn → R is the objective function; the functions fi : Rn → R, i = 1, …, m, are the inequality constraint function and the constants b1 , …bm are the limits or bounds for the constraints. Vector x is called optimal or the solution of the problem above; if it has the smallest objective value among all vectors that satisfy the constraints, for any z with f1 (z) ≤ b1 , fm (z) ≤ bm , we have f0 (z) ≥ f0 (x ). To solve the optimization problem, we use the notation as follows minimize f0 (x) subject to fi (x) ≤ 0, i = 1, . . . , m hi (x) = 0, i = 1, . . . , p to describe the problem of finding an x that minimizes f0 (x) among all x that satisfy the conditions fi (x) ≤ 0, i = 1, …, m, and hi (x) = 0, i = 1, …, p. We call x ∈ Rn the optimization variable and the function f0 : Rn → R the objective function or cost function. The inequalities fi (x) ≤ 0 are called inequality constraints, and the corresponding functions fi : Rn → R are called the inequality constraint functions. The equations hi (x) = 0 are called the equality constraints, and the functions hi : Rn → R are the equality constraint functions. If there are no constraints (i.e., m = p = 0), we say the problem above is unconstrained.

3 EXPERIMENTS AND NUMERICAL RESULTS To solve the multi-objective optimization problem, hyperparameter optimization was designed to include multiple variables including the orientation, window-to-window ratio, thickness, electricity, hearting, colling, and total consumption as a comprehensive objective function to evaluate. Hyperparameter space was discretized to solve the optimization problem by using numerical algorithms. The hyperparameter space and the corresponding total consumptions were shown in Table 1 and the optimal solution was obtained by the minimum of the objective function.

Table 1. Hyperparameter input space consists of orientation, window to wall ratio, insulation thickness, electricity: facility, district heating: facility, district colling: facility, ventilation, glazing, and total consumption.

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Figure 1. Correlation coefficient matrix of multiple input variables including orientation, window to wall ratio, insulation thickness, electricity facility, discrete heating facility, district cooling facility, and total consumption.

4 CONCLUSIONS The optimization technique we developed involves long-term decision-making at multiple levels including technical and ecological development, which can be exacerbated by the rise of distributed multi-energy systems, including new energy systems which have broad real-world applications in building design. Reasonable architectural design is a key part of making use of the outdoor microenvironment of the building to improve the indoor microenvironment of the building. When it comes to real-world applications, the influence of a wide range of climatic conditions and specific environmental climatic characteristics of the building itself is important to be used such as external airflow, rainwater, and lighting to create good conditions for the buildings so that people can reduce the reliance on the building equipment. In the rapid development of urbanization in my country, the proportion of building energy consumption is increasing, and the contradiction between energy and development has become increasingly prominent. Based on realizing its intelligent and comfortable goals, green buildings have aroused widespread concern about their large operating energy consumption, and green building energy-saving research has become an important direction of energy-saving research. The operating energy consumption of building equipment accounts for about 60% of the total energy consumption and has become the main energy consumption object of intelligent buildings. In this paper, the equipment operation control in green buildings is taken as the research object with the combination of the engineering practice to study the energy saving of equipment operation. There are several potential research directions for future work. The discrete optimization problem could be improved to a continuous objective function with both quantitative and qualitative variables. This will improve the smoothness and continuity of the objective function. In addition, more applicable factors could be taken into consideration in the design of the multiple objective-integrated models. 297

REFERENCES Ahmad, T., Thaheem, M.J. & Anwar, A. (2016). Developing a green-building design approach by selective use of systems and techniques. Architectural Engineering and Design Management, 12(1), 29–50. Arora, J. (2004). Introduction to Optimum Design. Elsevier. Bajjou, M.S., Chafi, A., Ennadi, A. & El Hammoumi, M. (2017). The practical relationships between lean construction tools and sustainable development: A literature review. Journal of Engineering Science & Technology Review, 10(4). Bank, L.C., McCarthy, M., Thompson, B.P. & Menassa, C.C. (2010, December). Integrating BIM with System Dynamics as a Decision-making Framework for Sustainable Building Design and Operation. In Proceedings of the First International Conference on Sustainable Urbanization (ICSU) (pp. 15–17). Damtoft, J.S., Lukasik, J., Herfort, D., Sorrentino, D. & Gartner, E.M. (2008). Sustainable development and climate change initiatives. Cement and Concrete Research, 38(2), 115–127. Ekeocha, R.J. (2019). Optimization of systems. International Journal of Sciences, 8(03), 118–125. Evins, R. (2013). A review of computational optimization methods applied to sustainable building design. Renewable and Sustainable Energy Reviews, 22, 230–245. Felzenszwalb, P.F. & Zabih, R. (2010). Dynamic programming and graph algorithms in computer vision. IEEE transactions on pattern analysis and machine intelligence, 33(4), 721–740. Gill, P.E., Murray, W. & Saunders, M.A. (2005). SNOPT: An SQP Algorithm for Large-scale Constrained Optimization. SIAM Review, 47(1), 99–131. Goubran, Sherif, and Carmela Cucuzzella. “Integrating the sustainable development goals in building projects.” Journal of Sustainability Research 1.e190010 (2019): 1–43. Kazimieras Zavadskas, E., Antucheviciene, J. & Kar, S. (2019). Multi-objective and multi-attribute optimization for sustainable development decision aiding. Sustainability, 11(11), 3069. Kim, J.T. & Yu, C.W.F. (2018). Sustainable development and requirements for energy efficiency in buildings– the korean perspectives. Indoor and Built Environment, 27(6), 734–751. Murota, K. (2020). Linear programming. In Computer Vision: A Reference Guide (pp. 1–7). Cham: Springer International Publishing. Ogunmakinde, O.E., Egbelakin, T. & Sher, W. (2022). Contributions of the circular economy to the UN sustainable development goals through sustainable construction. Resources, Conservation and Recycling, 178, 106023. Parvin, K., Lipu, M.H., Hannan, M.A., Abdullah, M.A., Jern, K.P., Begum, R.A. & Dong, Z.Y. (2021). Intelligent Controllers and Optimization Algorithms for Building Energy Management Towards Achieving Sustainable Development: Challenges and Prospects. IEEE Access, 9, 41577–41602. Rohloff, M. (2005). Enterprise Architecture-framework and Methodology for the Design of Architectures in the Large. ECIS 2005 Proceedings, 113. Tushar, Q., Bhuiyan, M.A., Zhang, G. & Maqsood, T. (2021). An integrated approach of BIM-enabled LCA and energy simulation: The optimized solution towards sustainable development. Journal of Cleaner Production, 289, 125622. Wong K.D. & Fan Q. Building Information Modelling (BIM) for Sustainable Building Design. Facilities. 2013 Feb 22. Yeo, D. & Potra, F.A. (2015). Sustainable design of reinforced concrete structures through CO2 emission optimization. J. Struct. Eng, 141(3), B4014002. Zhou, Z., Alcalá, J. & Yepes, V. (2021). Optimized application of sustainable development strategy in international engineering project management. Mathematics, 9(14), 1633.

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Reconstruction technology of residential ecological architecture in China Zhuang nationality Cong Lu∗ , Nenglang Huang & Haocheng Luo College of Architecture and Civil Engineering, Nanning University, Nanning City of Guangxi Province, China

ABSTRACT: With higher living standards, the requirements of Chinese rural residents for highquality life are also stipulated. Yet the traditional residential houses are restricted by their old style, not only in the contradiction between the appearance and safety of the building material and people’s cultural needs but also in the gap between practicality and people’s demands for modern life. Since ancient times, China has been inhabited by many ethnic groups, including Guangxi Province in the southwest of China, where the Zhuang people reside. They still preserve the rich cultural symbols of Zhuang rural traditional dwellings in the form of conventional dwellings. Under the background of rural revitalization, Guangxi Zhuang dwellings for ecological landscape renovation is an important content of new rural image construction. In this paper, the development of ecological architecture and the compatibility of Chinese Zhuang traditional folk houses is summarized, the transformation technology from the perspective of design and construction is analyzed, and the new rural construction and ecological architecture in rural residential reconstruction ideas are provided for reference.

1 INTRODUCTIONS The improvement of living standards and the growth of urban construction have made people focus more on architectural design under ecological principles. The ecological harmony perspective refers to the good integration of environmental protection, economic practicality, modern technology used in the design, and a natural ecological balance environment to minimize the pollution of the environment around the building, prolong the service life of the building, and unify the ecology, environmental protection, and natural balance development, allowing people to harmonize with the environment. Green design and ecological strategy are the inevitable choices for social development, human progress, and architectural design under the background of an energy shortage. Many scholars are exploring the organic transformation of traditional buildings to make the traditional residential buildings obtain the renovation scheme combined with the local ecological climate and regional characteristics. Traditional dwellings are the product of the Chinese traditional culture and history, the spiritual sustenance of the Chinese people since ancient times, and the witness to the glorious years. They should not be allowed to die out naturally, but should properly transform and implant new functions to survive. As one of the ethnic minorities in China, the Zhuang nationality has rich materials in history, culture, and architectural inheritance. With the implementation of China’s rural revitalization strategy, the ecological transformation of the traditional Zhuang nationality dwellings is the only way to improve the living environment of the ethnic minority settlements and continuously improve the rural style.

∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-37

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2 ECOLOGICAL ARCHITECTURES AND THE STYLE AND CHARACTERISTICS OF CHINESE ZHUANG NATIONALITY FOLK DWELLINGS 2.1 Concept of ecological architecture Ecological architecture should emphasize and handle the connection between people, architecture, and nature from the design and production stages (He 2021). It should not only create a pleasant space for human activities, such as healthy temperature, humidity, clean air, suitable light, and sound environment, and flexible and open space with high practicality but also blend with the surrounding natural environment and reduce the influence on it as far as possible. This implies that ecological architecture requires less demand for nature and causes fewer adverse effects on nature (Jiang 2017). The primary characteristic of ecological architecture is the less use of natural resources, including land conservation, reducing use, reusing, recycling, and replacing renewable resources. Besides, the ecological architecture can reduce emissions and ensures proper disposal of hazardous waste (including solid waste, sewage, and harmful gas), and reduce light pollution and sound pollution (Zhou 2021). Starting from the perspective of architectural design, the following key issues should be paid attention to in the design. (1) The focus should be on the full and efficient use of solar energy and other renewable energy. The natural ventilation and natural lighting and shading need to get more attention in the design. The multi-dimensional greening methods can be used to improve the living internal climate; (2) The long-term use function and flexibility of space should be the other focus and the use of large-span light structure should be considered; (3) The recycling of water in construction use, garbage classification, treatment, and construction waste recycling and reuse need to be strengthened. Obviously, the whole life cycle of ecological architecture to maintain its harmony with the natural ecology and the need for sustainable building calls for a combination of professional ability, such as structure, equipment, gardens, building physics, and building materials. Since the architect plays a leading role at the beginning of ecological architecture design, they must put forward and integrate the concept of ecology from the whole conception requirements. From the perspective of construction, the impact of the construction process on the building’s internal environment and external natural environment should be taken into consideration in the construction of ecological architecture or landscape renovation. The damage to the natural resources and environment should be reduced by using green building materials, green construction technology, and an efficient and reasonable construction management scheme. 2.2 Characteristics of Zhuang nationality folk dwellings in China Modern residential buildings are generally brick or reinforced concrete structures. The comfortableness depends mainly on the equipment, energy, and resources but is less related to the climate, culture, and regional characteristics. The most obvious feature of modern architecture is not the brand-new architectural technology, not the new types of architecture, but the disrespect for nature, the neglect of the terrain, soil covering, water flow, sunshine, air, and so on. Modern architecture not only has some significant improvements but also brings destruction and incoordination to nature. China is a developing country, and most parts of China, especially most parts of the west, are still in a backward and poor state. In particular, small and medium-sized towns are characterized by small-scale production and centralized decentralization, and they still retain considerable traditional economic models, technical methods, and traditional craftsmen. Such objective elements need to be reckoned with to improve the affordability of the region and the applicable objects during the design. And on the basis of the overall applicability principle, various design strategies should be adopted for diverse regions and different architectural forms. The extreme dependence on the regional economy, the marginality of culture, and the lack of regional identity can easily be caused by the absence of effective guidance. With brick walls, leveling or small green tile, aluminum alloy 300

windows, and ceramic tile veneer being the characteristics of the new rural architecture, the old houses can’t meet people’s living requirements. And the natural ecological environment like painting and stiff modern architecture also makes the building and environment appear incompatible with no beauty because of its simple building form. Guangxi is located in southwest China, along the ancient Baiyue land, and has a unique natural environment, which is mountainous with a wide karst landform coverage and a rich natural resource endowment. Guangxi has a long history of ethnic culture and forms a unique residential community under the integration of a unique environment. Guangxi’s traditional local architecture has rich ethnic and regional cultural characteristics and various architectural characteristics. The traditional architectural forms, structures, and materials are organically integrated, coordinated, and unified with the characteristics of geography, climate, architecture, and environment. And it is one of the representative areas of ecological residential communities in southwest China. In particular, Guangxi is characterized by Zhuang nationality gathering and has the integrated ecological and cultural characteristics of the southwest mountain area, Baiyue culture, and karst landform. From the perspective of ecological architecture, it is advisable to explore the sustainable architectural approach of the new Zhuang residential buildings to meet China’s rural revitalization strategy, inherit and carry forward the excellent architectural culture of the Zhuang nationality in China, improve the rural living environment, and shape a new rural style of inherited civilization, Gui style and Zhuang charm, ecological livability, harmony, and beauty.

3 RECONSTRUCTION TECHNOLOGY OF RESIDENTIAL ECOLOGICAL ARCHITECTURE IN CHINA ZHUANG NATIONALITY 3.1 Principles of ecological architecture style reconstruction The rural housing reconstruction and construction follow the principle of ethnic groups before zoning. To be specific, the areas with particularly strong ethnic characteristics and relatively high ethnic minorities should be determined according to the local ethnic characteristics. And the transformation and construction should be determined according to the style in other areas and follow the following principles. (1) The focus should be on inheriting and highlighting the national cultural characteristics. Guangxi Zhuang nationality has colorful ethnic culture and a long history and culture, with prominent architectural culture characteristics and rich connotations. The reconstruction of residential houses in the region should carry on the national culture on the basis of rationally using the form of traditional architectural components, inheriting the context, and highlighting the cultural characteristics. (2) The measures to local conditions should be adjusted to reflect regional characteristics. Guangxi Zhuang features distinctive geographical traits, with many terrain and landform types and typical karst landforms. The building materials are rich and diverse regions own various farmhouse architectural features. Rural housing design and construction are basically in accordance with nature, reflecting regional characteristics. (3) The principle to be followed is to keep pace with the times and reflect the characteristics of the times. The reconstruction design and construction of residential houses in Guangxi Zhuang nationality should conform to the development of the modern era, meet the use functions of modern dwellings, pay attention to the application of new materials and new technologies, meet the requirements of energy conservation and environmental protection, and reflect the functional needs of modern life functions and the style nowadays. 3.2 Ecological architecture landscape renovation technology The landscape renovation technology of ecological architecture mainly starts from the three dimensions of design, construction, and usage. This paper specifically analyzes the implementation ideas 301

of the ecological architecture landscape renovation technology represented by the roof, wall, doors, and windows. (1) Roof energy-saving renovation. In renovating traditional dwellings, the energy-saving renovation of the roof will gradually develop in the direction of green ecological energy conservation. Energy-saving renovation of the building roof can have many functions. Firstly, it can alleviate the greenhouse effect, improve air quality, and increase air humidity. Secondly, it can reduce the temperature of the building’s top floor to reduce the loss of electricity. Thirdly, the filter layer and soil used in greening can use the construction waste to reduce the cost and achieve the purpose of rational allocation of resources. In addition, the green design of the building also takes into account the planting of agricultural products on the roof, which can play the role of protecting the roof to prolong the life of the roof (Wang 2016). Green roofs can be classified as simple green roofs and green roof gardens. (2) Energy-saving transformation of the wall. For heat insulation in summer and winter heat insulation measures, the building wall insulation measures both on the wall body and outside the wall. The use of high-quality thermal insulation measures in buildings can extend the service life of the main body of the building, but also can play the energy-saving effect and economic benefits of building projects. (3) Energy-saving renovation of doors and windows. The heat loss caused by the windows accounts for a large amount of heat loss in buildings (Xian 2018), so energy-efficient windows are necessary. The energy-saving outer window can be selected to effectively reduce the heat transfer coefficient and improve the air tightness of the internal space of the building. To ensure heat insulation and ventilation and to reduce the heat loss of heat to the indoor space effectively, the window material should be the one with good heat insulation, and the glass of the window should be double one with good heat insulation performance.

3.3 Case Analysis This part talks about the characteristic of energy consumption of residential ecological buildings in Guangxi. (1) Case Introduction As a southwest border area of Southwest China and the gathering place of Zhuang people, Guangxi in China is a subtropical monsoon climate area with a high annual temperature, the extremes of which could be up to 33.7–42.5◦ C, warm climate, and abundant rain. It is one of the most abundant precipitation areas in China, with annual precipitation of more than 1000 mm. Higher humidity and rich forest resources in the Guangxi region are in line with the moisture and beast proof and flood geographical adaptability characteristics of the stilt-type building. The construction is hollow at the bottom, supporting the weight of the upper layer with a pile-type structure, and the upper layer resides, and the lower layer stores or raises poultry. Hence, the stilt-type building of Guangxi is quite typical among those buildings in the whole country. The Zhuang stilt-style architectures are simple in structure. The roof is mostly green and gray, and the building is natural in color with the roof hanging always. The main elements of the exterior shape are wooden buckets, tile slopes, roofs, eaves, wooden doors, and railings, boasting especially the characteristics and pattern of Zhuang architectural brocade (as shown in Figure 1). When the traditional dwelling landscape is renovated, the modern building materials and construction techniques are combined to enhance the modern practicality of dwellings and meet the requirements of all kinds of design standards. For part of the main structure material using aluminum, the ethnic characteristics are retained, making it from the facade form and internal space function to achieve harmony and unity, as shown in Figure 2. 302

Figure 1. A prototype of traditional residential houses and details in the Zhuang nationality region, China (northern Guangxi, Guangxi).

Figure 2. Transformation of traditional residential and details style in China Zhuang Nationality (northern Guangxi, Guangxi).

(2) Data Analysis For the purpose of further analyzing and evaluating the effect of ecological energy-saving transformation of traditional residential buildings, a representative ecological residential building was selected for data observation and collection. The hot box method was used for data collection, and the heat transfer coefficient K of the temperature envelope on the inner and outer surfaces of the envelope was calculated by the formulas as follows. K=



Kn /n

Kn = Qn /[A1 • (Ti − Te )]

(1)

(2)

Qn is the heat transfer per unit test time, A1 is the opening area of the hot box, Kn is the heat transfer coefficient value per unit test time, Ti is the indoor temperature, Te is the outdoor temperature, and n is the test times. Through observation and calculation, the change of heat transfer coefficient in the middle of July in the summer of a certain year is obtained, as shown in Figure 3. 303

Figure 3.

Change curve of heat transfer coefficient of an ecological residence.

4 CONCLUSION With the continuous improvement of China’s urbanization level, the traditional dwellings in ethnic minority areas are gradually abandoned along with the migration of residents. With the promotion of the rural revitalization strategy, China’s new countryside has also gained new vitality. On the premise of maximizing the retention of traditional culture and regional cultural characteristics in northern Guangxi, the transformation of traditional residential style is renewed with new vigor from the perspective of ecological harmony. The design ideas and techniques of ecological architectural landscape renovation of traditional dwellings in Zhuang nationality of China from various aspects such as ecological environment, building materials, symbolic design, and functional optimization are also discussed in this paper. It provides more materials and inspiration for enriching the cultural research and functional-based transformation practice of traditional dwellings in minority areas of China.

ACKNOWLEDGMENTS The author’s thanks go to the financial support from the 2022 Guangxi’s middle-aged teachers’ basic ability improvement project: Research on the Parametric Design and Fabrication of Guangxi Minority Buildings based on Three-Dimensional Reconstruction.

REFERENCES He J.T. New and old in building renovation [J]. Architecture and Culture, 2021 (04): 11. DOI:10.19875/j.cnki.jzywh.2021.04.001. Jiang W.L. Research on the new practice path of building reconstruction [J]. Jiangxi Building Materials, 2017 (18): 269 + 271. Wang S.H. Application of green and ecological energy-saving technology in building reconstruction [J]. Residential Housing and Real Estate, 2016 (36): 79. Xian X.L., Wang J.T. Application of suitable ecological energy saving technology in the reconstruction design of existing buildings [J]. Journal of Qingdao University of Technology, 2018, 39 (03): 70–73. Zhou W.J. Exploring the building reconstruction design in urban renewal in China [J]. Real Estate World, 2021 (01): 43–45.

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Advancements in super cool roofs Dongdong Tian* School of Architecture and Urban Planning, Nanjing University, Nanjing, Jiangsu Province, China

ABSTRACT: Super cool roofs have high solar reflectance (ρ ≥ 0.95) and thermal emissivity (ε ≥ 0.95), having great advantages in increasing indoor comfort in summer. In recent years, the use of super cool roofs has become a hot topic and attracted the attention of many scholars. This paper reviews the effects of super cool roofs on radiative cooling potential and indoor comfort. The results show that the use of super cool roofs is limited by geography and climate and the net cooling power can be up to 150 W/m2 in dry and rainless areas. Super cool roofs will play an important role in alleviating the intensity of urban heat islands and saving energy. 1 INTRODUCTION Since the beginning of summer in 2022, there was frequent high-temperature weather in many parts of the world. The energy consumption of the roof accounts for 5%∼10% of the total energy consumption of the building (the more floors, the lower the percentage), and it accounts for more than 40% of the energy consumption of the top floor (Gao 2017, Rawat & Singh 2022). How to prevent the heat from entering the room from the roof and improve the thermal comfort in summer has always been a concern of scientists and engineers. One solution is to use super cool roofs. In this paper, a roof with solar reflectance greater than or equal to 0.95 and thermal emissivity greater than or equal to 0.95 is defined as a super cool roof (Sinsel 2021). The technology behind the super cool roofs is radiative sky cooling, hereafter referred to as radiative cooling. Radiative cooling is the process by which a sky-facing surface uses atmospheric windows (Diatezua 1996), with a wavelength between 8 and 13µm to emit radiation into outer space (the temperature of the outer space is 3 K), thereby reducing its own temperature. The radiative energy radiated by objects on the earth’s surface with a wavelength of 8–13µm can pass through the atmospheric window to outer space directly without significant absorption. In this paper, the application of super cool roofs is reviewed. The main research objective is the radiative cooling potential of super cool roofs and the effect of super cool roofs on indoor thermal comfort.

2 SUPER COOL ROOF 2.1 Radiative cooling potential of the super cool roof To study the radiative cooling potential of super cool roofs, Gentle et al. used spectrally selective materials to create a super cool roof with a solar reflectance of 0.97 and a thermal emissivity of 0.96, which was measured in an outdoor experiment in Sydney. Super cool roofs have higher reflectivity to sunlight than commercial cool roofs and regular roofs, as shown in Figure 1. The results showed that the temperature of the outer surface of the super cool roof was consistently lower than the ambient and commercial cool roof temperature without excluding the effects of convection. Under direct sunlight of 1060 W/m2 , the temperature of the outer surface of the super cool roof remains ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-38

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2◦ C below the air temperature. Although such super cool roofs can be produced on a large scale, further design refinements are still in urgent demand to avoid light pollution (Gentle & Smith 2015).

Figure 1. Cool roof properties: (a) Schematic of commercial cool roof and super cool roof; (b) A comparison of surface temperatures on a clear summer day of commercial cool roof and super cool roof (Gentle & Smith 2015).

The potential benefits of super cool roofs were quantified by Baniassadi et al., who used EnergyPlus to calculate surface temperatures and heat fluxes from the super cool roofs in eight typical US cities (Albuquerque, Atlanta, Chicago, Houston, Lost Angeles, Miami, Philadelphia, and Phoenix) with typical climates. The results showed that in all eight cities selected, the surface temperature of the super cool roofs was always lower than the air temperature and the annual benefit of a super cool roof was twice as high as that of a white roof. For areas with hot summers and high electricity costs, a super cool roof is recommended by the authors (Baniassadi 2019). Figure 2 summarizes the radiative cooling potential of the recent super cool roofs experiments in different regions (Chen 2021a; Chen 2021b; Cheng 2021; Feng, Chunzao 2021; Feng, Jie 2021; Gentle& Smith 2015; Lu 2016; Mandal 2018; Sinsel 2021; Tso 2017; Wang, Tong 2021; Wang, Xin 2020; Zhou 2019). Table 1 gives information on the radiative cooling potential of super cool roofs. It can be seen from the table that for dry and low-rainfall areas (such as Yinchuan and Alice Springs), the net cooling power of super cool roofs can reach 150 W/m2 , which is a good radiative cooling effect. For hot and humid areas (such as Hong Kong), however, daytime radiative cooling is not achieved. 2.2 Cooling energy saving of super cool roofs Several specialists have studied the use of super cool roofs in the U.S. Fang et al. compared super cool roofs with conventional cool roofs and normal roofs. They used the glass-polymer super cool roof mentioned by Zhai (Zhai 2017) to conduct experiments in three typical climate cities in the US to validate the roof heat transfer model. It was found that using a conventional cool roof still transferred 8.5-128.2 kWh/m2 per year from the outside to the inside while using a super cool roof 306

Figure 2.

Super cool roofs experiments on temperature drop and radiant cooling potential in different regions.

Table 1. Radiative cooling potential of the super cool roof. Reference, year

Spectral property

Testing conditions

Cooling performance

(Gentle&Smith 2015)

ρ ∼ 0.97; ε ∼ 0.96

T ∼2◦ C

subtropical monsoon

(Lu 2016)

ρ ∼ 0.97

(Lu 2016)

ρ ∼ 0.97

T ∼2.3◦ C; Pnet ∼20.1 W/m2 T ∼0.1◦ C;

subtropical monsoon tropical monsoon

(Tso 2017)

ρ ∼ 0.97

none

subtropical

(Mandal 2018)

ρ ∼ 0.98; ε ∼ 0.97

T ∼6◦ C

tropical oceanic

(Mandal 2018)

ρ ∼ 0.98; ε ∼ 0.97

Pnet ∼96 W/m2

tropical oceanic

(Mandal 2018) (Zhou 2019)

ρ ∼ 0.98; ε ∼ 0.97 ε ∼ 0.95

T ∼3◦ C

tropical monsoon

(Wang, Xin 2020)

ρ ∼ 0.97; ε ∼ 0.96

G∼1060 W/m2 ; Sydney (Experiment) Shanghai (Simulation) Bangkok (Simulation) Hong Kong (Experiment) G∼890 W/m2 ; Phoenix (Experiment) G∼750 W/m2 ; Phoenix (Experiment) Chattogram (Experiment) New York (Experiment) G∼1000 W/m2 ; Shanghai (Experiment)

T ∼11◦ C; Pnet ∼120 W/m2 T ∼6◦ C; Pnet ∼61 W/m2

temperate continental subtropical monsoon

climate

(continued)

307

Table 1. Continued. Reference, year

Spectral property

Testing conditions

Cooling performance

(Sinsel 2021)

(Wang, Tong 2021)

ρ ∼ 0.95; ε ∼ 0.98

(Feng, Chunzao 2021) (Feng, Jie 2021) (Chen 2021)

ρ ∼ 0.96; ε ∼ 0.96

G∼941 W/m2 ; New York (Simulation) G∼950W/m2 ; Hong Kong (Simulation) G∼930 W/m2 ; Shanghai (Experiment) G∼800 W/m2 ; Yinchuan (Experiment) Alice Springs (Experiment) Lanzhou (Simulation) G∼803 W/m2 (Experiment)

T ∼6.95◦ C

(Chen 2021)

ρ ∼ 0.96; ε ∼ 0.97 ρ ∼ 0.95

(Cheng 2021)

ρ ∼ 0.96; ε ∼ 0.97 ρ ∼ 0.96; ε ∼ 0.97 ρ ∼ 0.95; ε ∼ 0.96

climate

T ∼2.6◦ C

temperate continental subtropical

T ∼5.5◦ C; Pnet ∼85 W/m2

subtropical monsoon

T ∼7◦ C; Pnet ∼150 W/m2

temperate continental

T∼11.5◦ C; Pnet ∼153.3 W/m2 Pnet ∼71.9 W/m2

desert

T ∼8.1◦ C; Pnet ∼89.6 W/m2

temperate continental temperate monsoon continental

Note: G is the solar irradiation intensity.

removed 137.6–268.7 kWh/m2 per year from the inside to the outside environment. Compared to a normal roof, a super cool roof saves 113.0-143.9 kWh/m2 per year (Fang 2019). Baniassadi et al. used the porous polymer-coated super cool material (the solar reflectance > 0.96 and the thermal emissivity > 0.97) mentioned in Mandal’s (2018) paper on building roof to perform whole-building energy simulations on a selection of typical residential and commercial buildings in eight US cities. It was found that the surface temperature of the super cool roof was always lower than the air temperature and that the super cool roof was able to reduce the energy consumption of commercial buildings by 4–19% and residential buildings by 28%. The cold energy savings and thermal energy compensation of a super cool roof are twice that of a typical white roof (the solar reflectance being 0.7 and the thermal emissivity being 0.9) (Baniassadi 2019). Li et al. produced a super cool material by de-wooding and densification (Figure 3a) and found that the surface temperature of this material was consistently lower than the air temperature throughout the day (Figure 3b), with an average temperature drop of more than 9◦ C at night and more than 4◦ C at midday (11:00-14:00) and a net radiative cooling power of 16 W/m2 and 63 W/m2 during the day and night respectively. They then used EnergyPlus to simulate the energy savings from the use of the material on the facades and roofs of midrise apartments in 16 typical US cities with typical climates. The simulations reckoned the heat balance between the interior and exterior.

Figure 3. A radiative cooling structural material (a) Cooling wood (b) Cooling power and temperature (difference) (Li 2019).

308

It was found that houses using the material were able to save 20-60% of energy, with Phoenix having the highest potential for cool energy savings in a hot and dry climate. The authors predicted the energy savings potential of mid-rise buildings in all cities in the U.S. and the results showed that the hot, dry southwest has the highest energy savings potential (∼40 MJ/m2 ) (Li 2019). 3 CONCLUSION Super cool roofs have only begun to be put into wide use in recent years with advances in materials technology. Super cool roofs have played a significant role in improving indoor comfort and saving energy. The use of cool roofs is strictly influenced by climate and location. The net cooling power of the super cool roof can reach 150 W/m2 in dry and low-rainfall areas. Super cool roofs will play an important role in alleviating the intensity of urban heat islands and saving energy. REFERENCES Baniassadi, A., Sailor, D.J. & Ban-Weiss, G.A. (2019). Potential Energy and Climate Benefits of Super-cool Materials as a Rooftop Strategy. Urban Climate. 29, 100495. Chen, J., Lu, L. & Gong, Q. (2021a). A new study on passive radiative sky cooling resource maps of China. Energy Conversion and Management. 237, 114132. Chen, J., Lu, L., Gong, Q., et al. (2021b). Techno-economic and environmental performance assessment of radiative sky cooling-based super-cool roof applications in China. Energy Conversion and Management. 245, 114621. Cheng, Z., Han, H., Wang, F., et al. (2021). Efficient radiative cooling coating with biomimetic human skin wrinkle structure. Nano Energy. 89, 106377. Diatezua, D.M., Thiry, P.A., Dereux, A., et al. (1996). Silicon oxynitride multilayers as spectrally selective material for passive radiative cooling applications. Solar Energy Materials and Solar Cells. 40(3), 253–259. Fang, H., Zhao, D., Yuan, J., et al. (2019). Performance evaluation of a metamaterial-based new cool roof using improved roof thermal transfer value model. Applied Energy. 248, 589–599. Feng, C., Yang, P., Liu, H., et al. (2021). Bilayer porous polymer for efficient passive building cooling. Nano Energy. 85, 105971. Feng, J., Khan, A., Doan, Q.-V., et al. (2021). The heat mitigation potential and climatic impact of super-cool broadband radiative coolers on a city scale. Cell Reports Physical Science. 2(7), 100485. Gao, Y., Shi, D., Levinson, R., et al. (2017). Thermal performance and energy savings of white and sedum-tray garden roof: A Case Study in a Chongqing Office Building. Energy and Buildings. 156, 343–359. Gentle, A.R. & Smith, G.B. (2015). A subambient open roof surface under the mid-summer sun. Advanced Science. 2(9), 1500119. Li, T., Zhai, Y., He, S., et al. (2019). A radiative cooling structural material. Science. 364(6442), 760–763. Lu, X., Xu, P., Wang, H., et al. (2016). Cooling potential and applications prospects of passive radiative cooling in buildings: The current state-of-the-art. Renewable and Sustainable Energy Reviews. 65, 1079–1097. Mandal, J., Fu, Y., Overvig, A.C., et al. (2018). Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling. Science. 362(6412), 315–319. Rawat, M. & Singh, R.N. (2022). A study on the comparative review of cool roof thermal performance in various regions. Energy and Built Environment. 3(3), 327–347. Sinsel, T., Simon, H., Broadbent, A.M., et al. (2021). Modeling the outdoor cooling impact of highly radiative “super cool” materials applied on roofs. Urban Climate. 38, 100898. Tso, C.Y., Chan, K.C. & Chao, C.Y.H. (2017). A field investigation of passive radiative cooling under Hong Kong’s climate. Renewable Energy. 106, 52–61. Wang, T., Wu, Y., Shi, L., et al. (2021). A structural polymer for highly efficient all-day passive radiative cooling. Nature Communications. 12(1), 365. Wang, X., Liu, X., Li, Z., et al. (2020). Scalable flexible hybrid membranes with photonic structures for daytime radiative cooling. Advanced Functional Materials. 30(5), 1907562. Zhai, Y., Ma, Y., David, S.N., et al. (2017). Scalable-manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling. Science. 355(6329), 1062–1066. Zhou, L., Song, H., Liang, J., et al. (2019). A polydimethylsiloxane-coated metal structure for all-day radiative cooling. Nature Sustainability. 2(8),718–724.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Visual analysis of flood control and drainage texts based on CiteSpace Siyi Peng School of Water Conservancy and Environmental Engineering, Zhejiang Institute of Water Resources and Hydropower, Hangzhou, China

Dongfeng Li∗ The Key Laboratory for Technology in Rural Water Management of Zhejiang Province, Zhejiang University of Water Resources and Electric Power, Hangzhou, China

Shiming Liu, Yifan Zhu & Bin Cheng School of Water Conservancy and Environmental Engineering, Zhejiang Institute of Water Resources and Hydropower, Hangzhou, China

ABSTRACT: Due to the impact of human activities, climate change, and other factors, global warming continues to intensify, and floods have increasingly become the focus of international attention, and have also had different degrees of impact on the ecological environment. There are more and more studies on flood control and drainage, but there is a lack of systematic literature review and insufficient understanding of the evolution characteristics and development trends of the hot spots in the research field. This paper takes the core database web of science as the research object and uses the Bibliometrics software CiteSpace 6.1.r3 to carry out visual analysis from the number of documents, author groups, publishing institutions, high-frequency keywords, emergence, etc., which aims to find the research frontiers in the field of flood control and drainage, and summarize the evolution laws and development trends of flood control and drainage and water environment research. The results show that the impact of human activities and climate change on floods and their restoration, flood simulation and control technology, risk assessment, and ecological water conservancy construction projects has always been the research hot spots. 1 INTRODUCTION In recent years, extreme weather occurs frequently and the climate is unusually severe in China. Flood control and drainage have gradually become hot topics in the water conservancy industry. Many research institutions have been involved in this topic, especially in combination with water environment governance and ecological restoration. Based on the data analysis function of CiteSpace, this paper conducts visual analysis from the perspectives of literature circulation, author groups, publishing institutions, high-frequency keyword emergence, summarizes the research hotspots in flood control and drainage and water environment, and grasps the research direction in this field. 2 RESEARCH METHOD 2.1 Data sources The data is selected from the core data set of the Web of Science. The core database of Web of Science was selected as the data sample of foreign literature, and the matching search and analysis ∗ Corresponding Author:

310

[email protected]

DOI 10.1201/9781003384830-39

were carried out with the theme “flood control and drainage” or “water environment”. After the systematic search, matching, and elimination of repetitive literature, this study finally screened 950 relevant literature, distributed from 1995 to 2022, and exported the effective pieces of literature in Refworks format. 2.2 Analytical method In terms of research methods, one is to use CiteSpace software to conduct literature analysis, import the literature of the web of science into the software, conduct keyword co-occurrence, cluster analysis, and research author analysis through CiteSpace software. The corresponding knowledge map is obtained. CiteSpace version 6.1.r3 is adopted (Wang, Wang & Wu 2019). The second is to use Excel to carry out the statistics and chart drawing of the number of documents issued, analyze the characteristics of documents issued in different periods according to the changing trend shown in the chart, and reveal the research process of flood control and drainage. 3 RESULTS AND ANALYSIS 3.1 Study the time sequence analysis of the number of documents issued Research on flood control and drainage has been on the rise since 1995. According to the number of issued documents and the changes in time (See Figure 1), flood control and drainage research can be roughly divided into four stages: From 1995 to 2006, the research on flood control and drainage was very few, mainly because the human understanding of flood control and drainage function was still weak; the period from 2007 to 2012 is the development period. In the process of rapid urbanization in China, there are problems such as a mismatch of urban basic functions, among which the urban flood problem is very serious and brooks no delay (Huang, Hu, Hu, Zhang & Yang 2022); 2013-2019 is a high-speed growth period, and the number of documents issued in 2019 reached the peak. On September 25, 2019, the United Nations Intergovernmental Panel on climate change (IPCC) adopted the special report on oceans and the cryosphere in climate change, which shows that human activities have caused unprecedented and lasting changes to the oceans and the cryosphere. The melting of glaciers and ice sheets will lead to sea level rise. The 2019 China climate change ocean blue book also shows that the frequency of extreme events along the coast will increase, and the flood once in a hundred years will become once a year; the period from 2020 to 2022 is a period of fluctuation and stability, and the number of domestic and foreign documents has entered a stable growth. After nearly 25 years of development, international flood control and drainage research are still in the development stage. Under the background of increasing global environmental change, flood control and drainage research have unique significance for global

Figure 1. Annual document volume.

311

ecological stability and have received more and more attention (Zhao, Di, Wang, Pan, Fu & Li 2021). 3.2 Research team analysis CiteSpace was used to analyze the foreign teams in the field of wetland restoration, and the author’s cooperation map (See Figure 2) was obtained. The map has 338 nodes and 258 connections, and the network density is 0.0045. The color of the node circle indicates the change in the author’s posting time. The brighter the color is, the closer the author’s posting time will be to the present. The larger the node is, the more the author’s posting amount will be. The darker the color of the connecting lines, the closer the cooperation between the authors will be. From the author’s arrangement table (See Table 1), it can be seen that the scholar with the largest number of articles is Kim J, and the occurrence frequency is 8 times; Wang Q, Smith J, Li Y, Scholz M appeared 7 times. The scholars with a high volume of articles are mainly from China.

Figure 2. Author node diagram.

3.3 Analysis of issuing organization To explore the main institutional forces of flood control and drainage research at home and abroad, CiteSpace is used to visually analyze the document issuing institutions. Each node in the visual map represents a mechanism, and the size of the node represents the number of documents it sends. The nodes with the red outer circle in the map are high and middle heart nodes (centrality > 0.1), which play the role of a link between nodes. It can be seen from the node map of the issuing organization (See Figure 3) that there are 541 nodes and 559 connections in the map of the issuing organization at home and abroad, and the network density is 0.0038. Chinese Acad SCI has the largest number of articles, with 35 articles published. It is the leading institution in the field of flood control and drainage research. From the list of issuing institutions, it can be seen that Tongji University, Colorado State University, Hohai University, Tsinghua University, and other institutions have issued more than 10 documents, which constitute the main force of flood control and drainage research. 3.4 Research hotspot and trend analysis 3.4.1 Cluster analysis of core keywords Keywords analysis can reflect the frontiers and hotspots of research topics during the research period. With the help of CiteSpace, high-frequency keywords in the literature during the research 312

Figure 3.

Organization node diagram.

period can be extracted, and further clustering and emergence analysis of keywords can be carried out. Cluster analysis can reveal the relationship between keywords and the Timeline view, reflect the main research contents during the research period, and reveal the formation and development of various knowledge in the research field to a certain extent. The emergence of keywords refers to the rapid increase in the frequency of keywords in a certain period, which reflects the research hotspot or new research trend in this period, and explores the evolution trend of the current research hotspot in flood control and drainage. According to the keyword cluster analysis of flood control and drainage research literature at home and abroad (See Figure 4), the basic directions of flood control, drainage, and water environment research mainly include 1) flood risk pattern recognition. 2) urban drainage system design. 3) ecological water conservancy project construction. 4) acid mineral water discharge and methane discharge. 5) alluvial plain and serpentine mountain genesis. The deterioration of the ecological environment and the bad global climate are important causes for the frequent occurrence of natural disasters in recent years. Especially with the economic development and the expansion of the world population, the forest area has been greatly reduced, and the vegetation has been seriously damaged, resulting in climate deterioration and frequent floods. Therefore, protecting the ecological environment and building ecological water conservancy have become long-term and arduous tasks for flood control and disaster reduction (Li, Chen & Fan 2005).

3.4.2 High-frequency keywords distribution analysis From the distribution of high-frequency keywords and the analysis of the top 18 high-frequency keywords (See Table 1), the research on flood control, drainage, and water environment covers many types of rivers and lakes, with emphasis on urban drainage system management and flood dynamic simulation, acid mine water prevention and treatment, the impact of rainfall-runoff on River water level and low impact development mode. In the aspect of dynamic simulation, according to the existing flood control and drainage projects recommended by the regional water conservancy comprehensive planning, the one-dimensional unsteady flow mathematical model of the river network is adopted to establish a water conservancy calculation model and calculate the implementation effect of the scheme, which can effectively relieve the flood control and drainage pressure of the block, and is the forefront of the flood control and drainage field (Hu, Li, Zheng & Jin 2022). 313

Figure 4.

Keywords: settlement map.

Table 1. Top 18 keyword arrangement. Keyword arrangement: Top18 1 2 3 4 5 6 7 8 9

82 72 61 59 53 51 39 33 29

0 0 0 0 0 0 0 0 0

2004 2003 1991 1996 2010 2005 2007 2000 2011

management climate change model water impact system runoff water quality urbanization

10 11 12 13 14 15 16 17 18

29 25 24 23 23 22 22 21 20

0 0 0 0 0 0 0 0 0

2004 2015 2004 1997 1994 2011 1991 1999 2004

drainage simulation catchment storavator management drainage system performance risk flow water management

3.4.3 Burst analysis of high-frequency keywords From the distribution of high-frequency keywords in different periods and the emergence of keywords (See Figure 5), the depth and breadth of research content in all aspects are increasing over time, and new research hotspots are emerging. Before 2005, there were no high-frequency keywords and keyword outbursts. From 2005 to 2009, the keywords “transportation”, “soil”, “evolution”, “variability” and “vegetation” were very prominent. The theoretical research on runoff migration, plant community succession, soil composition, and water flow variability is the main content. From 2010 to 2017, the management of runoff and sediment impact in paddy fields began to be widely studied. From 2018 to 2022, the most prominent keywords in this phase include “water management”, “real-time control” and “drainage system”. With the introduction of hydrodynamic principles, flood dynamic simulation, optimal configuration and formation of the water network, flood risk assessment and other technologies have been continuously improved. At the same time, more research has been conducted on the drainage system and low-impact development mode of the sponge city. 314

Figure 5. Top 30 Keywords with the strongest citation bursts.

4 CONCLUSION With the help of CiteSpace software, this paper conducts a metrological analysis of the documents in the field of flood control and drainage at home and abroad from 1995 to 2022, and draws the following conclusions from the number of documents issued by domestic and foreign authors, issuing teams, issuing agencies, keyword cluster analysis and evolution trend analysis: (1) The number of documents issued by flood control and drainage research at home and abroad generally shows an increasing trend, and the number of documents issued after 2019 is significantly increased. (2) Foreign wetland restoration research institutions include Chinese Acad SCI, Tongji University, Colorado State University, Hohai University, Tsinghua University, and other institutions, which are the backbone of flood control and drainage research. In addition, Chinese Acad SCI has the largest number of documents and is the leading institution for flood control and drainage and water environment research. (3) The research on flood control and drainage has mainly experienced three stages. Before 2009, it belonged to the preliminary exploration stage for water environment treatment. From 2010 to 2017, it entered the research stage focusing on hydrodynamic flow and dredging. From 2018 to 2022, this is the model-building research stage for coping with climate change and human activities. (4) In the past decade, the research on the impact of human activities and climate change on floods and their restoration, flood dynamic simulation technology and risk assessment, drainage system of sponge city, and ecological water conservancy construction project have been hot topics. Under the background of the increasingly severe global environmental change, the local flood discharge capacity of the flood control and drainage pattern is poor, the contradiction with urban functions and ecological water storage is prominent, and the super standard flood response measures are fuzzy (Liu, Zhou, Zhong & Fang 2020). 315

ACKNOWLEDGMENTS This research was supported by the Funds Key Laboratory for Technology in Rural Water Management of Zhejiang Province (ZJWEU-RWM-202101), the Joint Funds of the Zhejiang Provincial Natural Science Foundation of China (No. LZJWZ22C030001 No. LZJWZ22E090004), the Funds of Water Resources of Science and Technology of Zhejiang Provincial Water Resources Department, China (No.RB2115, No.RC2040), the National Key Research and Development Program of China(No.2016YFC0402502), and the National Natural Science Foundation of China (51979249).

REFERENCES Hu Shiyuan, Li Hongxian, Zheng Furong, Jin Kai. Research on optimization of flood control and drainage pattern in Zhijiang area under the background of future urban practice area construction [J]. Water Conservancy Planning and Design, 2022 (06): 25–27. Huang Qiang, Hu Junjie, Hu Chuanwei, Zhang Wendong, Yang Gongqi. Study on the establishment of urban flood control and drainage system under the concept of resilient city [J]. Anhui Architecture, 2022, 29 (01): 87+114. Doi:10.16330/j.cnki.1007–7359. 2022.01.039. Li Daming, Chen Haizhou, Fan Yu. Development and current situation of flood control and disaster reduction at home and abroad [J]. China Rural Water Conservancy and Hydropower, 2005 (09): 33–37. Liu Shuguang, Zhou Zhengzheng, Zhong Guihui, Fang Qi. Construction of flood control and drainage system in the process of urbanization [J]. Science, 2020, 72 (05): 32–36+4. Wang chuanlei, Wang Jingjuan, Wu Juanhua. Knowledge map, stage characteristics, and evolution trend of logistics finance research [J]. Journal of Chongqing Industrial and Commercial University (Social Science Edition), 2019, 36 (03): 38–46. Zhao Xiyue, di Suchuang, Wang Junwen, pan Xingyao, Fu Chaochen, LiYongkun. Evolution and optimization of flood control and drainage pattern in central Beijing [J]. China Flood Control and Drought Relief, 2021, 31 (03): 26–31+35.

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Energy saving test and analysis of rural traditional residence in cold region of China Chen Lin Shandong University of Art & Design, Jinan, China

Xiaotong Peng*, Shuai Zhou & Dingyu Chen University of Jinan, Jinan, China

ABSTRACT: Energy dissipation has been studied as a subject light in the fields of construction. This study is an effort to solve the problems of high energy consumption and low thermal comfort of traditional rural residences in the Shandong province of China. A typical rural residence was selected and tested for analyzing and evaluating the thermal behavior and energy consumption of the building envelope. The results indicate that the tested residence has ultra-high energy consumption and low thermal comfort because of poor thermal performance and excessive shape coefficient. An energy-saving modification for exiting residences is proposed through theoretical analysis and design. Implementation of a modification scheme to rural residences could meet the energy saving standard of 65% and decrease the energy consumption of traditional rural residences by 70%.

1 INTRODUCTION The development of energy-saving buildings has been widely concerned and highly recognized all over the world. To reduce building energy consumption, the energy saving regulation EnEV2009 (Wan 2015) was promulgated in German. Green building evaluation systems such as LEED (Ugur 2017), BREEAM (Li 2012), and CASBEE (Hayashi 2020) were formulated respectively by the United States, Britain, Canada, and Japan. Accordingly, design standards of 75% for residential buildings were implemented in many regions of China. Research on rural residential building energy-saving technology was constantly conducted by domestic and foreign scholars. Chedwal Rajesh (Rajesh 2015) carried out a study for energysaving reformation on the envelope structure, heating, ventilation, and air conditioning of three traditional Indian buildings. The study performed by Chwieduk (Chwieduk 2017) for traditional dwellings in Polish presented that adding a sunshine room can greatly improve the solar energy utilization rate. Junting Sun (Sun 2018) performed energy-saving transformation in three aspects: layout optimization, the envelope structure, and renewable energy utilization for a typical rural traditional residence in Runcheng, Shanxi Province. Based on simulation analysis on energysaving transformation and variable parameter analysis on heat preservation practices, an economic energy-saving reformation scheme was conducted by Shiyong Zhao (Zhao 2015). In summary, a series of regional research on energy conservation in rural residential buildings were carried out by previous scholars. However, there is little measured or simulated research on traditional rural buildings in Shandong Province. The study aims to analyze and evaluate the thermal behavior and energy consumption of the building envelope. Based on that, an energy-saving scheme for existing buildings was proposed. ∗ Corresponding Author:

[email protected]

DOI 10.1201/9781003384830-40

317

2 EXPERIMENTS ON THE RESIDENCE 2.1 Case study description Based on the layout, height, structure type, construction, and the location and size of doors and windows, a typical traditional residential building which is built in 1998 with a wing room of 10.5m2 and a main room of 33m2 in Changqing, Jinan was selected to test and evaluate its energysaving performance. The floor plan of the residence is shown in Figure 1. Heating consumption is the main factor of energy consumption in Jinan which belongs to the cold area (Lv 2021).

Figure 1.

Floor plan of residence.

The test period was from 28th January to 4th February and 20th February to 27th February. Measure points were set on the windows, doors, roof, and chimney staying away from the outside wall. Each measuring point included one indoor heat flow sensor and two temperature sensors indoor and outdoor. The temperature, heat flow, humidity, and PMV-PPD (Cheung 2017) of tested rooms were collected by temperature and humidity meter, temperature heat flow inspector, and thermal comfort level meter. 2.2 Data analysis The steady-state data on February 24th in room B was selected for analysis in Figure 2. The room temperature and surface temperature inside the wall were 17∼21◦ C. The room temperature fluctuated greatly and was 1–2◦ C higher than the surface temperature inside the wall. The surface temperature outside the wall and room temperature both increased in the daytime and fell at night, but the variation of the former lagged behind the latter. It indicates that the wall has heat storage and capacity for temperature self-adjustment to some extent.

3 BUILDING ENERGY DISSIPATION ANALYSIS The building energy efficiency is mainly affected by the body shape coefficient, heat transfer coefficient of the envelope, and area ratio of the window to the wall. Based on test data, the energy saving evaluation index and building heat consumption index are calculated. The measured heat transfer coefficient should be corrected by the three-dimensional 318

Figure 2.

Reads of the southern wall and indoor and outdoor temperature of Room B.

heat transfer and solar radiation based on the standard, and the correction coefficients of the north wall were the same as the north walls. The envelope thermal performance is evaluated by the building heat consumption coefficients. As is shown inTable 1, in terms of total heat consumption, the roof has the most heat consumption, and the heat consumption of the wall accounts for 40% of the total heat consumption. In terms of heat consumption in one square meter, the door has the most heat consumption in one square meter, followed by the outer window and then the roof. It indicates that the wall, roof, doors, and windows are the main parts of energy dissipation and energy-saving transformation. The comprehensive evaluation was made based on the building heat consumption coefficient and thermal comfort coefficient. As is shown in Table 2, the heat consumption indexes of two measured rooms are up to 10 times the limit of the energy saving standard of 75%. It is concluded that the measured residential building has ultra-high energy consumption. Table 1. Room B palisade structure heat consumption.

Items Roof Exterior wall

The door External window Total

East South West North South North

Area (m2 )

Heat consumption per unit area (W)

Percentage of heat consumption per unit area

Percentage of total heat consumption

33.12 16.10 16.10 17.83 23.28 3.95 3.42 1.92 148.84

58.75 27.56 26.99 26.42 25.90 114.23 58.85 65.77 416.54

14.10 6.62 6.48 6.34 6.22 27.42 14.13 15.79 100

40.65 10.27 9.08 9.85 8.71 9.41 4.21 2.64 100

Table 2. Building heat consumption index. Heat consumption per unit building (W/m2 ) Index

Room A

Room B

Enclosure structure heat consumption per unit floor area Air permeation heat consumption per unit floor area Internal heat gain per unit area Building heat consumption index The standard limit of 65% energy conservation for residential buildings The standard limit of 75% energy conservation for residential buildings

268.70 1.24 3.80 266.14

154.85 0.97 3.80 152.02

319

14.1 12.8

4 ENERGY-SAVING SCHEME Based on the various design elements such as room layout, space arrangement, and envelope structure, an energy-saving scheme was proposed for existing residential buildings. As is shown in Figure 3, the roof is equipped with an XPS external insulation layer. Thermal insulation measures are performed at the overhanging eaves to prevent local condensation phenomena inside. The XPS external insulation layers are used for the external wall. The existing external window has remained, and the polyurethane-filled bridge aluminum windows and double hollow Low-e coated glass insulation window (6Low-e + 12Air + 6Low-e) are adopted. The outer door is replaced by the thermal insulation door with the same structure.

Figure 3.

The caption of a typical figure.

As is shown in Table 3, the building heat consumption is calculated based on the theoretical heat transfer coefficient. The heat transfer coefficient of the exterior walls was reduced by more than 75%. The heat transfer coefficient of the roof was reduced by more than 90%. The heat transfer coefficients of the doors and windows were reduced by more than 50%. Except for the shape coefficient, all indexes met the energy saving standard of 65%. The heat consumption coefficients were reduced by 77.3% after transformation. Table 3. Analysis of energy-saving transformation and transformation. Room B’s original plan Index

Roof

Wall

Heat transfer (W/(m2 ·K) Heat consumption per unit area Building heat consumption (W/m2 ) Energy saving 65% Energy saving 75%

4.69 40.64

2.01 6.40 26.72 62.31 152.02 No No No No

No No

Window

320

Room B transformation scheme

Door

Roof

Wall

6.40 114.23

0.35 4.38

0.39 5.46

No No

Yes No

Window

2.2 30.79 34.31 Yes Yes No Yes

Door 2.2 32.43 Yes Yes

5 CONCLUSION The present study was carried out in the rural traditional residence of Jinan which belongs to the cold region of China. The study conducted the on-site energy-saving detection and analyzed comfort degree and energy-saving evaluation index. Accordingly, the energy-saving transformation scheme for the existing traditional residential buildings is formulated. The study concludes that there is ultra-high energy consumption performance of the measured building and a large potential for existing building envelope renovation. The key conclusions are as follows: (1) The measured building meets neither the current energy-saving standard of 75% nor 65%. The main factors are the large building shape coefficient and poor thermal performance of external wall and roof, which accounts for more than 70% of the total. (2) The energy-saving transformation scheme of existing residential buildings was carried out with the goal of energy saving at a standard of 65%. After transformation, the energy consumption of room B was reduced by 77.3%. The energy-saving technology of rural residences is in the initial stage. The results of the study can be utilized for the energy-saving research of rural systems.

ACKNOWLEDGMENTS The work was sponsored by the Natural Science Foundation of Shandong Province (ZR2019MEE009), the Ministry of Education University-Industry Collaborative Education Program (201802276002; 201902204001; 201902204002), and the Science and Technology Project of Housing and Urban-Rural Development of Shandong Province (2020-K2-3). The writers gratefully acknowledge all the support provided.

REFERENCES Cheung, T. (2019) Analysis of the accuracy of PMV-PPD model using the ASHRAE global thermal comfort database II [J]. Building and Environment. 153, 205–217. Chwieduk, D. Towards modern options of energy conservation in buildings[J]. Renewable Energy, 2017, 101(2): 1194–1200. Hayashi, T. (2020). CASBEE-Wellness Office: An objective measure of the building potential for a healthily built environment [J]. Japan Architectural Review. 4(1), 233–240. Li, C. & Zhou, X.B. (2012). Comparison between the green building evaluation standard of China and BREEAM of the UK. Green Building. 42(10), 60–66. Lv, K. L. (2021). Investigation of existing circumstances and revision of zoning variables on building climate zoning. Journal of Building Energy Efficiency. 49(11), 96–99. Rajesh, C. & Jyotirmay, M. (2015). Energy saving potential through energy conservation building code and advanced energy efficiency measures in hotel buildings of Jaipur city. Energy and Buildings. 92(1), 282–295. Sun, J. & Sun, T. (2018). Ecological energy-saving transformation strategy of traditional houses in Runcheng Town, Shanxi. Building Energy Efficiency. 9, 95–98. Ugur, L. & Leblebici, N. An examination of the LEED green building certification system in terms of construction costs [J]. Renewable & Sustainable Energy Reviews, 2017, 81. Wan, W. (2015). The German energy certificate certification system and its enlightenment to my country’s low carbon supervision. Journal of Guizhou University (Social Science Edition). 4, 115–125. Zhao, S.Y. & Hao,Y.H. (2015). Energy consumption status and energy saving retrofit scheme of rural residential buildings in northern China areas. Journal of Building Energy Efficiency. 2, 114-117+123. Building Energy Efficiency.

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Frontiers in Civil and Hydraulic Engineering – Mohamed A. Ismail and Hazem Samih Mohamed (Eds) © 2023 The Authors, ISBN 978-1-032-47155-6

Discussion on the application of green and low-carbon concept in large-scale complex buildings Yan Yu University of Glasgow, Glasgow, Scotland, UK

ABSTRACT: At present, energy and resources are increasingly depleted, and environmental problems are becoming more and more serious. Sustainable development has become an inevitable choice for all countries in the world. The idea of sustainable development has entered all fields of life, and the construction industry has also set off a research upsurge of “greening” of buildings. Largescale complex buildings are the image of a city, an important place for people’s public activities, and are closely related to social management. The purpose of this paper is to study the application of green and low-carbon concepts in large-scale complex buildings. This paper firstly summarizes the basic connotation of the low-carbon green concept based on the overview of the low-carbon economy and green economy. Based on the ideas of proposing, analyzing, and solving problems, this paper analyzes and studies the green energy-saving renovation strategies of large-scale complex buildings. The effects of a green and low-carbon environment on the indoor temperature of largescale complex buildings are verified by experiments. Experiments have shown that after the green and low-carbon transformation, the temperature difference can reach 5◦ C compared with the high floor before the transformation, and the scores of experts have reached 3 or more. The long-term use performance score has reached 4 points, which is excellent for long-term use.

1 INTRODUCTION People use more than 50% of the raw materials obtained from nature to build most of their buildings, and these buildings consume up to 50% of the world’s energy in manufacturing and use. Including air pollution, fire pollution, electrical pollution, etc., construction waste accounts for 34% of the total waste generated by human activities. It can be seen that whether it is energy, material power, or pollution, buildings are the key to solving sustainable problems (Cheng 2019). The construction industry, which uses the most natural materials, must take the road of sustainable development, and the knowledge and science of greenhouses have emerged as time requires. Related research and practice have become an important part of solving environmental problems (Cove 2019). In the discussion on the application of green and low-carbon concepts in large-scale complex buildings, many scholars have studied it and achieved good results. For example, Zhang J took EU countries as an example to analyze the development of green renovation technology in depth and believed that for the original building, windows and roofs should be regarded as the most important adjustment objects which will help to control the cost (He 2021). He S studied the business cases of energy-saving renovation of existing commercial buildings and compiled a business report on the green renovation cases of existing commercial buildings in the United States from multiple aspects. With the renovation of commercial buildings, the market share of green renovation of existing commercial buildings will increase rapidly (Li 2020). Based on the ideas of proposing, analyzing, and solving problems, this paper analyzes and studies the green energy-saving renovation strategies of large-scale complex buildings. Then, the analytic ∗ Corresponding Author:

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[email protected]

DOI 10.1201/9781003384830-41

hierarchy process is used to determine the weight coefficient of green and low carbon evaluation of large-scale comprehensive buildings, making the evaluation system complete. The effects of a green and low-carbon environment on the indoor temperature of large-scale complex buildings are verified by experiments. 2 DISCUSSION ON THE APPLICATION OF GREEN AND LOW-CARBON CONCEPTS IN LARGE-SCALE COMPLEX BUILDINGS 2.1 Development of green building technology All along, my country’s traditional buildings have been paying attention to green energy saving since ancient times, and there are great differences according to the characteristics of energy utilization and other factors. For example, among the seven schools, the characteristics of the Cantonese school, Beijing school, and Sichuan school are more typical. Although the genres are different, in the architectural design, the most consideration is still the local precipitation, sunshine, and other climatic conditions. Compared with the closed northern buildings, the Cantonese-style house has a more open view. In addition, a valve was also unscrewed, and its function is mainly reflected in two aspects. One is to facilitate air circulation and heat dissipation, and the other is to connect the bones of the building together, which can shield it from wind and rain (Li 2020). The biggest feature of Beijing-style courtyard houses is that the courtyards are arranged according to the northsouth axis. Beijing is relatively dry in spring, and there is a lot of wind and sand. Based on this climatic environment, Beijing’s residents attach great importance to the function of the building against cold, wind, and sand. Therefore, thick brick walls are often built around the periphery, and the roof and house walls are also very thick to prevent cold, wind, and sand. The stilted building of the Sichuan style is a popular architectural style in Sichuan, Yunnan, and other places. This architectural style has certain national characteristics. 2.2 Expert evaluation algorithm In this paper, the design questionnaire is discussed based on the application of the green and lowcarbon concept in large-scale complex buildings studied in this paper, and relevant professional experts are consulted on relevant issues, making statistics of expert opinions. Reflecting the convergence of expert opinions, the calculation formula of the coordination coefficient is as follows:  12 nj−1 dj2 ω= (1)    N 2 k 3 − k − N Ni=1 Ti Among them, N is the total number of experts,k is the number of factors to be evaluated, Ti represents the same rank index, and dj is the difference between the rank of the j index and its average score. The value of ω is between 0 and 1. The larger the value of ω is, the better the degree of coordination of the opinions of experts will be. In other words, the opinions of experts are more consistent. However, fluctuations in the range of 0.5 in actual research can indicate that the error is well controlled and the degree of coordination of expert opinions is high. The x2 test is carried out on the value of ω. When P