Information Paper Acceptance Criteria for Performance Test of Soil Nail

Citation preview

Information Paper

Acceptance Criteria for Performance Test of Soil Nail

STRUCTURAL ENGINEERING BRANCH ARCHITECTURAL SERVICES DEPARTMENT March 2013

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 1 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

1.

Introduction

1.1

Purposes of Pull Out Test and Performance Test of Soil Nail ArchSD General Specification for Building (GS) requires both pull-out test and performance test on soil nail construction. The main purpose of pull-out tests is to verify the ultimate bond resistance between soil and grout used in the design. The maximum test load shall be either 90% of the yield load of the steel bar of the test soil nail (Tp)pull-out or the ultimate soil/grout bond load. On the other hand, in order to check the quality of installed soil nails, performance tests are required to be carried out on 6% of the total number of permanent soil nails of the same type grouted in one day. The test load on each soil nail (Tp)performance is 1.5 times the working load as specified in the drawings, or not greater than 80% of the yield stress of the steel bar forming the soil nail. In addition to checking the quality of grout around the soil nail, the performance test intends to check whether the completed soil nail can safely withstand the design loads without any excessive movement and to act as a quality control.

1.2

Existing Acceptance Criteria of Performance Test A soil nail will be considered as failed if before reaching the maximum allowable test load, it is either pulled out or the soil nail head movement has exceeded e f in which



e f  (Tp ) performance eb / Tp

where

(Tpwhere ) performance (Tp ) pull  out (eb ) pull  out

= = =



pull  out

---------- (1)

test load in performance test test load in pull-out test maximum soil nail head movement in pull-out test under test load (Tp ) pull  out

For any one failure of performance test, two additional soil nails shall be selected from the group for further performance tests. If either one of these 2 additional soil nails also fails to reach the test load, the particular group of soil nails shall be considered as not complying with the specified requirements. 1.3

In Equation (1), the allowable movement ef is related to the maximum soil nail head movement in pull-out test (eb)pull-out, However, according to the pull-out test data for the slope stabilization works at Sandy Ridge Cemetery (feature no. 3NW-C/C11,15-19) as shown in Fig. 1, an invalid (eb)pull-out is commonly obtained in the pull-out test. This is because the pull-out displacement will increase disproportionately with a small increase of pull-out force when the pull out force is near the ultimate frictional resistance (i.e. after yielding occurs). The displacement is then kept increasing without increasing the pull-out resistance when the ultimate frictional resistance is reached. This is a common phenomenon for most materials, e.g. steel, when they are subjected to a force larger than the yield strength and proceeds to the plastic range. The pull-out displacement obtained after yielding will over-estimate the allowable movement

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 2 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

ef in the performance test by using Equation (1). Another consideration is whether the displacement measured at pull-out test is similar to that of performance test if they are tested at the same force. It is noted that the soil nail is only partially grouted for the pull-out test (i.e. soil nail grouted to required length, typically 2m in the passive zone) while the installed soil nail in a performance test is grouted to its full length. With the difference in grouted length, the displacement should also be different. Thus, the use of invalid (eb)pull-out and the difference in grouted length between two tests will result in the acceptance criterion being too loose which is evidenced by the past test records that the value of ef was seldom exceeded. The real behaviour of soil nail under pull-out force will therefore be explained and discussed in this paper. Sandy Ridge Cemetery (3NW-C/C11,15-19) Load Displacement Curve of Pull-out Tests

300

250

Load (kN)

200

150

TN1

TN2

TN3

TN4

TN5

TN6

TN7

TN8

TN9

TN10

TN11

TN12

TN13

TN14

TN15

TN16

100

50

0 0

10

20 30 Movement (mm)

40

50

Fig. 1 Load-displacement curve of pull-out tests at slope stabilization works at Sandy Ridge Cemetery (Feature no. 3NW-C/C11, 15-19) 1.4

According to Geoguide 7 – Guide to Soil Nail Design and Construction GEO(2008), there is basically no reliable test to assess the performance of soil nails after their construction, and TDR test cannot be used for acceptance test though can be used for indicative purpose. It is, however, noted that the US, Australia and most other countries in the Europe have specified in their national standards/ specifications requiring a testing to check the quality of completed soil nails, e.g. “Production Nail Test” in BS EN 14490:2010 (BSI 2010), “Proof Test” in Geotechnical Engineering Circular No. 7 – Soil Nail Walls published by the Federal Highway Administration (FHWA) of the US Department of Transportation (FHWA 2003), and “Acceptance Test” in QA Specification R64 Soil Nailing published by Road and Maritime Services of New South Wales Government (RMS 2012). In BS EN 14490, performance test is optional for slopes with negligible risk to property or lifebut is mandatory for other slopes with risk to property or life. Hence, the performance test should be retained in our GS to check whether the completed soil nail can safely withstand the design loads without any excessive movement or long term creep over its service life

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 3 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

and to check the workmanship and the quality of grout around the soil nail. Annex A summarizes the various load tests on soil nails stated in the above national standards/ specifications and all of them require pull-out, performance and creep tests. It is noted that our GS does not include the creep test; but it requires that the deformation in the last 10 minutes should not be larger than 0.05mm which is similar to the creep test requirements. Hence, it is worth to introduce the creep test requirements as a further acceptance criterion for the performance test in our GS in order to ensure that the nail design loads can be safely carried throughout the structure service life. 1.5

With the above background, the purposes of this paper are:i) ii) iii) iv) v) vi)

to briefly discuss the theoretical study of the real behaviour of a soil nail under pull-out force; to study behaviour of a soil nail under pull-out force using numerical method, i.e. “Plaxis” – an elasto-plastic finite element computer program; to compare theoretical studies with actual field test data; to rationalize the acceptance criteria of the performance test; to introduce the creep test requirements during the performance test; and to validate the proposed new acceptance criteria with the data retrieved from previous projects.

2.

Theoretical Study of the Behaviour of Soil Nail under Pull-out Force – HY Wong’s Method

2.1

Dr H.Y. Wong, our ex-SGE/NP, had been consulted, and he drafted a paper entitled A Theoretical Study of the Load Deformation Characteristics of a Soil Nail during Performance Test based on Elastic Theories depicting the behaviour of soil nail during performance test based on elastic theories. In the paper, Dr Wong considered an elementary length of the soil nail with elastic deformation under pull-out force and derived an equation for calculating the maximum soil nail head movement ef that can be allowed in a performance test as follows:-

e f  esteel  f  esoil  f  2(Tp ) performance L d 2 Esteel  (Tp ) performance DGsoil ------- (2) where

(esteel ) f

=

(esoil ) f

=

(Tpwhere ) performance

=

L d Esteel D Gsoil

= = = = =

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

maximum elastic lengthening of the soil nail steel bar that can be allowed under (T p ) performance maximum elastic soil shearing displacement along the grout/soil interface that can be allowed under (T p ) performance maximum tensile pull of 1.5 times working load in a performance test total length of soil nail diameter of soil nail steel bar elastic modulus of steel bar diameter of soil nail grout hole elastic soil shear modulus Page 4 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

In Equation (2), the revised ef is affected not only by the soil nail head movement in the pull-out test but also by other parameters such as D, d, L, Esteel, Gsoil, (Tp)pull-out and (Tp)performance. To compare the new allowable ef, a study has been carried out by adopting Equation (2) on the data retrieved from the previous pull-out and performance tests. Table 1 shows the summary of pull-out and performance tests retrieved from previous ArchSD’s projects, and the results of the study is included in Annex B. 2.2

The results show that the allowable maximum soil nail head movement ef during performance test determined by Equation (2) is smaller than that determined as per the GS by 5 to 50%. This implies that a stricter acceptance criterion will be used when Equation (2) is adopted. Though a stricter but more rational acceptance criterion has been used, only three of the test data out of the 75 performance tests fails, when the revised equation has been applied for soil nails. Table 1 Summary of pull-out and performance tests retrieved from previous ArchSD’s projects Slope Feature No.

Location

3SW-C/C14 3SW-C/F17

Wo Hop Shek Cemetery Wo Hop Shek Cemetery Lady MacLehose Holiday Village Lady MacLehose Holiday Village Tai Mei Tuk Water Sports Center Wo Hop Shek Cemetery

8SW-B/C12 8SW-B/CR11 3SE-D/C111 3SW-C/C24 3NW-C/C11,15-19 12NW-C/C85* 9SE-B/C102* 07SW-C/FR114*

Number of test data retrieved Pull-out Performance 14 15 1 2 3

3

3

5

5 5 16 2 4 4

5 6 14 2 16 5

Sandy Ridge Cemetery Silverstand Beach North Lantau Hospital Central Kwai Chung Park Wo Yi Hop Road Recreation 07SW-C/C117* Ground 2 2 Total 59 75 * denotes that the soil nails were installed with the end grouted in bedrock. For the remaining slope features, the whole soil nails were installed into soil.

2.3

It is, however, noted that in some data of previous pull-out tests, the calculated elastic lengthening of the soil nail steel bar (esteel)pull-out is larger than the maximum soil nail head movement measured in pull-out test (eb)pull-out. The elastic shear displacement along the nail/soil interface becomes negative and hence the elastic shear modulus Gsoil cannot be determined. This phenomenon may be caused by the overgrouting since (esteel)pull-out depends on the bond length (typically 2m) and unbond length of the steel bar. As recommended by Dr Wong in his paper, it can be solved by pulling out the complete bond length at the end of the pull-out test, and this serves to check not only the bond and unbond length but also the diameter of the soil nail grout hole (D).

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 5 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

2.4

In Equation (2), one of the main assumptions is that the soil shear stress at the nail/soil interface along the whole soil nail is constant so that the elastic lengthening of the soil nail steel bar (esteel)f can be assumed to be 2(Tp)performaceL/πd2Esteel during performance tests. However, for soil nails with the end grouted in bedrock, the elastic shear modulus of rock is much larger than that of soil. The soil shear stress distribution is therefore no longer being constant along the soil nail and ef will be wrongly determined according to Equation (2). Dr Wong in his paper concluded that the validity of this theoretical analysis mainly depends on the assumed soil shear stress distribution along the nail/soil interface. This assumption can be verified by measuring the stress distribution along the steel bar during the performance test by installing strain gauges at various locations of the steel bar and, in some cases, completely pull-out soil nail may be required .

2.5

His new method relies on the measurement of pull-out displacement in order to determine Gsoil and D etc. However, as shown in paragraph 1.3 above, an invalid pull-out displacement (eb)pull-out is commonly obtained in pull-out tests. Moreover, it will be discussed in paragraph 3.2 that the pull-out displacement (eb)pull-out in pull-out tests commonly resulted in over-estimation of the allowable movement of performance test. As a result, another simplified method is called for to determine the allowable movement ef and it will be discussed in the later section of this paper.

3.

Theoretical Study of the Behaviour of Soil Nail under Pull-out Force – Hong’s Method

3.1

Hong (2011) and Hong et al (2012) investigated the behaviour of a soil nail under a pull-out force mathematically with comparison of laboratory and field test data. He pointed out that a simple idealized load transfer model introduced by Misra and Chen (2004) can be adopted to define the relationship between the shear stress τ and pull-out displacement u of the nail/soil interface with stiffness factor k as shown in Fig. 2. In the model, the shear stress of the nail/soil interface varies linearly with shear displacement in the elastic zone until the ultimate shear stress of the interface is reached at the critical shear (pull-out) displacement uc. The shear stress then becomes constant with increasing of shear displacement.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 6 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Fig. 2 Load transfer model at the soil-nail interface during pull-out (Source: modified after Hong 2011) 3.2

As yielding is commonly observed in the pull-out test data retrieved from the previous projects, this model can be used to represent the pull-out response in order to further explain why the maximum pull-out displacement obtained from the pull-out tests may not be appropriate for determining the allowable soil nail head movement of the performance test if yielding occurs during the pull-out tests. When yielding occurs, the pull-out displacement keeps increasing at the same ultimate pull-out force and this “maximum” pull-out displacement obtained in the pull-out test will then become meaningless. The use of this “maximum” pull-out displacement in Equation (1) will therefore result in the over-estimation of the allowable movement of performance test as it is expected that the soil nail is loaded within the elastic zone during the performance test.

3.3

Using the idealized load transfer model in Fig. 2, Hong (2011) and Hong et al (2012) further evaluated the pull-out response of a soil nail in the passive zone of a soil nailing system, that is, the behavior of a soil nail section below the potential sliding surface by considering a soil nail element under a pull-out force in a soil mass. The pull-out process is divided into three typical phases: (i) (ii) (iii)

initial pure elastic phase - the nail/soil interface follows a linear elastic stress-displacement relationship; elastic-plastic phase - a transition point presents dividing the elastic and plastic zones; and pure plastic phase.

These three phases of a soil nail in a pull-out process inside a slope passive zone are summarized in Fig. 3.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 7 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Fig. 3 Three transitional phases of a soil nail in a pull-out process inside a slope passive zone (Source: Hong 2011) Following the derivation developed by Misra and Chen (2004) for a pile subjected to an external load, Hong (2011) and Hong et al (2012) established an analytical method for investigating the progressive pull-out behavior of a soil nail in the passive zone on the basis of a simple load transfer model of the nail/soil interface. His verifications indicated that the calculated soil nail pullout resistances are in good agreement with the published test data and his field test. The following equations are their proposed equations governing the relationship between pull-out displacement and pull-out force of a soil nail in different phases. Details of the analytical method can be referred to Hong et al (2012). Pull-out displacement in elastic phase ue x   

P  coshx  ---------- (3) kD sinh l 

Pull-out displacement in elastic-plastic phase 2uc 2 u p l   l p  uc l p tanh  l  l p   uc ---(4) 2 2l 2uc  uc ---------- (5) Pull-out displacement in plastic phase u p  2 where P = pull-out force x = distance from the nail tip l = soil nail length tip in the slope passive zone k = stiffness factor λ = scaling factor = kD EA lp = length of plastic zone uc = critical shear displacement D = diameter of soil nail grout hole



Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 8 of 24



File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

3.4

To compare with the analytical method proposed by Hong (2011), the method is applied for two pull-out test data (TN7 and TN12) for slope stabilization works at Sandy Ridge Cemetery (feature no. 3NW-C/C11,15-19). As the method only considers the soil nail behind the passive zone as shown in Fig. 3, the elastic elongation of steel bar is deducted from the total soil head movement of the above retrieved pull-out tests for the comparison. The critical shear displacement uc and shear stiffness factor k (see Fig. 2) are considered to be 3mm and 150kPa/mm respectively for the retrieved data. The comparison between the data retrieved from pull-out tests and the results obtained by the analytical method indicates that the calculated results fairly match the retrieved data as shown in Fig. 4. Sandy Ridge Cemetery (3NW-C/C11,15-19) Load Displacement Curve of Pull-out Test for TN7 E = 47.9GPa, D = 100mm, l = 2m, uc = 3mm, k = 150kPa/mm

300

250

Load (kN)

200 Pull-out test data

150

100

Analytical method proposed by Hong (2011)

50

0

0

5

10

15 20 Movement (mm)

25

30

35

Sandy Ridge Cemetery (3NW-C/C11,15-19) Load Displacement Curve of Pull-out Test for TN12 E = 47.9GPa, D = 100mm, l = 2m, uc = 3mm, k = 150kPa/mm

300

250

Load (kN)

200 Pull-out test data

150

100 Analytical method proposed by Hong (2011)

50

0 0

2

4

6

8 Movement (mm)

10

12

14

16

Fig. 4 Comparison between the data in Sandy Ridge Cemetery and the analytical method proposed by Hong (2011)

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 9 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

3.5

To examine the effect of different nail lengths on the pull-out response of a soil nail, Hong (2011) plotted the relationships of pull-out force of a soil nail with pull-out displacement for different nail lengths in normalized form. In Fig. 5, normalized pull-out force P/Pc is plotted against the pull-out displacement ratio Up of a soil nail with different nail lengths, where Pc is the critical pull-out force defined by multiplying the shear stress with the contact area between soil and nail (i.e. Pc = -kucπDl) and Up is defined as follows: U p 1

where





1 2 2 w p  w p tanh 1  w p  ---------- (6) 2

  l  l

Dk

4kl 2 and  EA ED

wp  l p l

Fig. 5 Variations of normalized pull-out force with pull-out displacement ratio of a stiff soil nail at different nail lengths (Source: Hong 2012) Instead of normalized curves as shown in Fig. 5, the actual value of pull-out force is plotted against that of pull-out displacement for easy explanation as shown in Fig. 6. From Fig. 6, it is observed that a longer soil nail in the passive zone of a slope can sustain a larger pull-out force compared to a shorter soil nail when the same pull-out displacement is reached.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 10 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

500

E = 57.2GPa, D = 100mm, d = 40mm, uc = 2mm, k = 35kPa/mm

450 400

Pull-out force, P (kN)

350 0.5m

300

1m 2m

250

5m 10m

200

20m

150 100 50 0 0

5

10 15 Pull-out displacement, u (mm)

20

25

Fig. 6 Load-displacement curve of a soil nail at different nail lengths [modified from the normalized curves by Hong (2011)] It is mentioned that the grouted length of soil nails is typically 2m long for pullout tests; but the permanent soil nails are fully grouted for the performance tests. To study the effect on pull-out response of a soil nail during pull-out and performance tests, the load-displacement curve of a fully grouted soil nail (8m grouted length) is determined by the analytical method with the same design parameters in Fig. 4 (E = 47.9GPa, uc = 3mm, k = 150kPa/mm). By comparing with the calculated results of the pull-out test (2m grouted length), Fig. 7 indicates that the soil movement of 8m grouted soil nail is smaller than that of 2m grouted soil nail at the same pull-out force within the elastic phase. This implies that the soil nail movement during performance test is smaller than that during the pull-out test even at the same pull-out force because of longer grouted length. For example, the pull-out displacement is about 4mm for the soil nail with 2m grouted length while the pull-out displacement is about 2mm for the soil nail with 8m grouted length at the same load of 296kN (80% yield stress of 32mm diameter steel bar). Therefore, using the maximum soil nail head movement in the pull-out test to estimate the allowable movement in the performance test is questionable and the acceptance criteria of the performance test should be revised.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 11 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

1200

E = 47.9GPa, D = 100mm, d = 32mm, uc = 3mm, k = 150kPa/mm

Normalized pull-out force, P (kN)

1000

800

600

400

200 Grouted length = 2m Grouted length = 8m 0 0

5

10 15 Pull-out displacement, u (mm)

20

25

Fig. 7 Load-displacement curve of soil nails with different grouted lengths using Hong’s method

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 12 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

4.

Behaviour of Soil Nail under Pull-out Force – Numerical Method

4.1

The above paragraphs concluded that using the maximum soil nail head movement in the pull-out test to estimate the allowable movement in the performance test is questionable, and in this section, the behaviour of a soil nail (especially the effect of the quality of grout) during a typical performance test will be studied. In this study, an elasto-plastic finite element computer program “Plaxis” is adopted to model the load-displacement curve of a pull-out test data (TN7) for slope stabilization works at Sandy Ridge Cemetery (feature no. 3NWC/C11,15-19) and the results are compared with the actual pull-out test data as shown in Fig. 8. In Plaxis, there are two parameters Tmax and R required in modelling of soil nail. Tmax is the maximum frictional resistance that the soil nail interface can sustain, i.e. a failure criterion used to distinguish between elastic and plastic interface behavior. For elastic behavior, only small relative displacement can occur within the interface (between grout body and the soil), and for plastic behavior, large permanent slippage may occur. For R factor, it relates to the interface strength between structural elements (e.g. pile or wall) and the surrounding soil strength (friction angle and cohesion). For real soil-structure interaction, the interface is weaker and more flexible than the associated soil layer, which means that the value of R should be less than 1. The Plaxis User Manual suggests using 2/3 for the R if detailed information is unavailable. It is important to note that both Tmax and R are input data, and the Manual recommends user to calibrate the parameters and compare with the behavior of field testing result. Parameters used in the numerical analysis are hence chosen such that the curve modelled by Plaxis matches with the pull-out test data. As the maximum friction of the pull-out test is considered to be approximately 280kN, the ultimate skin resistance between grout and soil Tmax is assumed to be 120kN/m (equivalent to 318kPa friction between soil and grout) for a 2m grouted soil nail in the model. Fig. 8 shows a good agreement between the actual pull-out test data with those by Plaxis model. The small discrepancies between the actual data and the model may be due to the limitations of the program. For example, the program cannot include the effect of stress release due to hole drilling and exclude the effect of overburden pressure.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 13 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Sandy Ridge Cemetery 3NW-C/C11,15-19) Load Displacement Curve of Pull-out Test for TN7 E = 47.9GPa, l = 2m, uc = 3mm, k = 150kPa/mm

300

Load (kN)

250

200

Pull-out test data

150

Plaxis model

100

Analytical method proposed by Hong (2011)

50

0 0

5

10

15

20 Movement (mm)

25

30

35

40

Fig. 8 Load-displacement curve of pull-out test data at Sandy Ridge Cemetery modelled by Plaxis To further obtain the load-displacement curve of fully grouted soil nail during performance test, the length of the soil nail is increased from 2m to 8m in the model by keeping the same design parameters with Tmax = 120kN/m. The models with different skin resistances Tmax varying from 120kN/m to 10kN/m and corresponding reduction factor R are then performed in order to simulate the fully grouted soil nail with different quality levels as shown in Fig. 9. For example, the soil nail under the curve with Tmax = 30kN/m and R = 0.25 achieves only 25% of the quality for a perfectly grouted soil nail with Tmax = 120kN/m and R = 1.0. Load Displacement Curve by Plaxis (8m grouted length) Perfectly grouted soil nail

1000

900 800 700

Load (kN)

Tmax=120kN/m R=1.0 600

Tmax= 90kN/m R=0.75

Tmax= 60kN/m R=0.50

500

Tmax= 30kN/m R=0.25 400

Tmax= 10kN/m R=0.083 Performance Test (D11)

80% yield stress of steel bar (296kN)

300

Performance Test (E15)

200

0

1.78

0

0.93

100

2

4

6 8 Movement (mm)

10

12

14

Fig. 9 Load-displacement curve with different Tmax simulating the quality level of soil nails modelled by Plaxis

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 14 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

4.2

The shear stress distribution along an 8m soil nail grouted into homogenous soil is also studied by using Plaxis. The results, as shown in Fig. 10, indicate that the distribution for different levels of pull-out force, i.e. the friction may be in the elastic, elastic-plastic or fully plastic, as described in Hong’s model discussed in Section 3.3. When the pull-out force is 200kN, the shear stress varies along the nail length and tends to drop from the nail head and reduces to zero at nearly half of the soil nail (i.e. 4m away from the nail head). When the pull-out force increases to 800kN, the shear stress keeps constant at its ultimate limit near the nail head and then drops to zero at about 6m away from the nail head. These shear stress distributions imply that the pull-out force may be fully resisted by the soil within the first few metres of the nail near the nail head during the performance test in which the test load is generally below 200kN. 400

Pull-out Force, T = 200kN Pull-out Force, T = 800kN

Shear Stress (kN/m 2)

350 300

250 200 150 100

50 0 Pull-out force, T

0

2

4 6 Distance along soil nail (m)

8

10

Fig. 10 Shear stress distribution along an 8m soil nail grouted into homogenous soil obtained by Plaxis As it is expected that the soil near the slope surface is relatively weaker than the soil at nail tip which is tested during the pull-out test, the actual nail movement during performance test should be larger than the nail movement estimated by Plaxis. 4.3

Two performance test data (D11 & E15) retrieved from the same slope feature no. 3NW-C/C11,15-19 are fitted into the curves modelled by Plaxis as shown in Fig. 9. If the soil nails are perfectly grouted and installed completely in the strong soil as in the pull-out test, the movement should be less than 0.5mm under the test force of 120kN. It is found that the test data of performance tests fall within the curve of the soil nail with Tmax = 10kN/m and R = 0.083 as shown in Fig. 9. Theoretically, it may imply that these two soil nails can only achieve 8.3% of the overall quality of an 8m perfectly grouted soil nail. However, as discussed in Section 4.2, the soil near the surface may have sustained all the pull-out force. Since the soil near the slope surface is relatively weaker than the soil at the tip, the actual nail movement during performance test would be larger than the nail movement estimated for the soil at the tip.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 15 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Fig. 11 shows the nail movement estimated by both Plaxis and Hong’s (2011) method when a weaker soil mass surrounding soil nail is assumed (i.e. to reduce the c,  and Tmax in Plaxis and soil stiffness k in Hong’s method). For strong soil at tip, Tmax=120kN/m (equivalent to 318kPa friction between soil and grout) is assumed, whereas the soil at surface, Tmax=40kN/m (equivalent to 106kPa friction) is assumed. Typical range of friction between grout and soil obtained from Armour et al (2000) in FHWA Report- Micropile Design and Construction Guidelines is shown in Table 2 for reference. The actual nail movement during performance test matches with the weak soil model under this low pull-out force. Table 2 Typical range of friction between grout and soil Typical range of grout to ground Soil Description nominal strength (kPa) Silt & Clay (some sand) 35-70 (soft, medium plastic) Silt & Clay (some sand) 50-120 (stiff, dense to very dense) Sand (some silt) 70-145 (fine, loose-medium dense) Sand (some silt, gravel) 90-215 Gravel (some sand) 95-265 (medium-very dense, cemented) (Source: Armour et al 2000) Load Displacement Curve (8m grouted length) 900

By Plaxis (c=17kPa, ø=38˚, Tmax=120kN/m, R=1.0) By Plaxis (c=5kPa, ø=32˚, Tmax=40kN/m, R=1.0) By Hong's formula (uc=2mm, k=160kPa/mm) By Hong's formula (uc=2mm, k=60kPa/mm) Performance Test (D11) Performance Test (E15)

800 700

Load (kN)

600 500 400 300 200 100 0 0

2

4

6

8 Movement (mm)

10

12

14

Fig. 11 Load-displacement curve modelled by both Plaxis and Hong’s (2011) method with weaker soil parameters In addition to above factor, this under-estimation of soil nail quality may be explained by the measurement error of the instruments set up for low displacement range or the quality of grout for the whole length of 8m is not as good as the 2m long in pull-out test and the limitations of the computer program Plaxis as mentioned in Section 4.1. Despite these limitations, the discrepancy is insignificant in the consideration of acceptance criterion for performance tests. Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 16 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

5.

Proposed Revision to Acceptance Criterion of Performance Test

5.1

Dr Wong in his paper has developed a revised analytical equation for the acceptance criteria of the performance test based on the elastic theories, which is a more logical assessment for the current performance test. However, there are still limitations to his equation (especially that his equation relies on the pull-out displacement from the pull-out tests). Therefore, a simple equation will be derived to determine the allowable maximum soil nail head movement ef as the acceptance criterion for performance test, which aims to verify the quality of grout during the installation works. Though such derived equation may not accurately represent the stress distribution along a soil nail, it is more rational than the existing acceptance criteria and hence, can serve as a better quality control of the installed soil nails. Project officer should always pay attention to any sign of abnormalities during the grouting operations, e.g. excessive grouting loss or abnormal grouting durations. The performance test can only act as another quality control of the installed soil nails in addition to good site supervision which is always important for ensuring quality works.

5.2

Proposed new acceptance criterion

5.2.1 The main purpose of the performance test is to check the quality of the installed soil nails, but not to assess the real behaviour of the soil nail, and thus it is recommended that a proposed new acceptance criterion can be adopted similar to the one used for tension piles as in the Code of Practice for Foundations (the “Foundation Code”) issued by Buildings Department (BD 2004). The criterion for the tension pile testing in the Foundation Code is similar to that developed by Davisson (1972). The code defines that a pile is deemed to have failed if the total extension exceeds the allowable total extension calculated by Equation (7) during the loading test. Allowable total extension = where

2WL D   4mm ---------- (7) EA 120

D = least lateral dimension of pile in mm W = design pile capacity under working load L = nett length of pile A = cross sectional area of pile E = Young's modulus of pile

In Equation (7), the allowable total extension consists of elastic deformation of pile and the term of “D/120+4mm”. According to Davisson(1972), the term of “D/120mm” is assumed to be the displacement required to mobilize the toe resistance of the pile and 4mm is assumed to be the further displacement required to reach the ultimate load. It also uses the full length of the pile for elastic deformation ignoring the effect of shaft skin friction. Obviously, this is not the real behaviour of a pile but as an acceptance criterion for ultimate capacity of pile using Davisson method generally accepted in Hong Kong and the US. This “D/120” is generally in line with those required to fully mobilize the skin friction as shown in Fig 12 and 13.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 17 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Figure 12 Relationship of shear resistance with shear displacement at pilesoil interface (Source: modified from Frizzi and Meyer 2000)

Fig 13a Normalized side load transfer for drilled shaft in cohesive soil (Source: O'Neill and Reese 1999)

Fig 13b Normalized side load transfer for drilled shaft in cohesionless soil (Source: O'Neill and Reese 1999)

Similarly, as an acceptance criterion for the performance test of soil nails, it is also assumed that all resistance/ slip occurs at the tip of the soil nail and there is no frictional resistance along the body of the soil nail during the performance test. Again, this is not the real behaviour of a soil nail, and it is used only as the acceptance criterion for the upper bound pull-out displacement of a performance test. In the proposed new acceptance criterion, like the concept of Dr Wong, the equation determining maximum soil nail head movement ef is therefore the sum of maximum elastic elongation of the soil nail (enail)f and maximum elastic soil movement (esoil)f under test load in performance test (Tp)performance. The

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 18 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

following paragraphs will discuss the computation of the terms (enail)f and (esoil)f. 5.2.2 Maximum elastic elongation of the soil nail (enail)f Dr Wong in his paper stated the maximum elastic elongation of soil nail depends on the validity of the assumed soil shear stress distribution along the nail/soil interface. Table 3 shows some typical examples of shear stress distribution along the soil nail. Table 3 Typical examples of shear stress distribution along the soil nail Type

Description

(i)

Shear stress linearly decreases from the soil nail head to zero at the tip.

(ii)

(iii)

(iv)

Shear stress remains constant along the soil nail.

Shear stress profile

(enail)f

(T p ) performance L (Tp)performance

3EA

(T p ) performance L (Tp)performance

Shear stress linearly increases from zero at the soil nail head to the tip.

(Tp)performance

Shear stress only contributes at the soil nail tip.

(Tp)performance

2 EA 2(T p ) performance L 3EA

~

(T p ) performance L EA

where L is the length of soil nail and EA is the rigidity of the soil nail

Similar to the shear stress distribution obtained by Plaxis in Fig. 10, it is considered that either Type (i) or (ii) may be adopted to truly represent the shear stress distribution along the soil nail when the soil is assumed to be homogeneous along the soil nail. However, in real situation it is expected that the soil near the nail head is relatively weaker within the active zone. The location of maximum shear stress developed may shift towards the tip of soil nail when the pull-out force increases. This change of distribution profile may result in the under-estimation of (enail)f and failure in performance test. For the purpose of acceptance of installed soil nails as said earlier, it can be assumed that all pull-out forces are resisted by the tip of the soil nail and there is no frictional resistance along the body of the soil nail, and hence Type (iv) with full elastic elongation of soil nail is adopted in the revised acceptance criterion. Obviously, it is an assumption that is generous for the acceptance criteria of performance test. Apart from the shear stress distribution, the determination of (enail)f depends on the rigidity EA of the soil nail. Dr Wong adopted EA of steel bar to calculate the elastic elongation of the soil nail. However, in the analytical method proposed Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 19 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

by Hong (2011), equivalent EA was adopted and obtained by the following equation:-

EAequivalent  Egrout Agrout  Esteel Asteel  ---------- (8) where

E grout

=

= Esteel where= Agrout Asteel

=

elastic modulus of cement grout elastic modulus of steel bar cross area of cement grout cross area of steel bar

Because of this inconsistency, a study on the effect of EA has been carried out by adopting the revised equation with these two different EA. The results will be presented and discussed in the later section. 5.2.3 Maximum elastic soil shearing displacement along the grout/soil interface (esoil)f In the equation developed by Dr Wong, (esoil)f is calculated by the elastic soil shear modulus Gsoil which is obtained from the results of pull-out test. However, Dr Wong concluded that Gsoil can vary very considerably from site to site as a result of the variation in ground conditions as well as drilling methods and equipment. Even within the same site, the ground conditions and groundwater table condition can also vary from location to location. In addition, the value of Gsoil may not be easily determined without further verification during the pullout test as discussed in the previous section. Similar to the term of “D/120+4mm” in the acceptance criterion for loading test of tension piles, a predetermined value of (esoil)f is therefore proposed to determine the upper bound pull-out displacement of a performance test. As it is expected that the soil nail is loaded mainly within the elastic zone during the performance test, Fig. 2 illustrates that (esoil)f shall be considered to be smaller than the critical shear displacement uc. Luo et al (2000) summarized test results as shown in Fig. 14by Cartier and Gigan (1983), Lim and Tan (1983), Murray et al. (1980), Billam (1972), Chang et al (1977) and Taylor (1948) , and his summary indicated that uc lies between 0.8mm and 5.6mm, where 2.5 – 5.6mm as the most common value. uc varying from 2mm to 8mm was also adopted by Hong (2011) for comparison between his analytical calculations and test data. Furthermore, according to the previous pull-out test data as shown in Annex C, the results indicate that 46 out of 47 estimated uc are less than 5mm. In order to provide an acceptance criterion that is not too stringent and yet serves the purpose of quality control, it is recommended that (esoil)f is assumed to be the value of “D/120+4mm”, i.e. 5mm, in the calculation of the soil nail movement ef during the performance test.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 20 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Fig. 14 Frequency versus critical shear displacement (Source: Luo et al 2000) 5.3

Validation of revised acceptance criterion of the performance test Based on the above studies, the equation determining the allowable maximum soil nail head movement during performance test is proposed as follows:-

e f  enail  f  esoil  f  (Tp ) performance L EA  5mm ---------- (9) A study has been carried out by adopting Equation (9) on the data retrieved from the previous pull-out and performance tests as shown in Table 1. The results are included in Annex D. The results show that none of the performance tests fails when the revised equation is adopted with EA of the steel bar. It is obvious that the allowable soil nail movement ef becomes smaller and a stricter acceptance criterion is attained when the equivalent EA is applied. However, it is found that there are only two of test data out of total 75 performance tests being failed when the equivalent EA is adopted. As the EA of the soil nail is one of the main factors affecting the allowable movement ef of the performance test, further discussion was held in the SE Meeting in December 2012. It was considered that grout may have cracked under tension during the performance test, and therefore it was concluded to adopt a more generous approach that only the steel bar is used. This is in line with the method specified in the Foundation Code for tension pile testing. 5.4

Introduction of creep test requirements As mentioned above, our current GS does not include the creep test; but requires that the deformation in the last 10 minutes should not be larger than 0.05mm which is similar to the creep test requirements as per other national standards/ specifications. On the other hand, creep test to 2 times the working load following other national standards/ specifications has been specified for pull-out tests. According to Geotechnical Engineering Circular No. 7 – Soil Nail Walls published by FHWA, acceptance criteria requires that creep movement between the 1- and 10-minute readings, at maximum test load, must be less than 1 mm. Should the measured creep movement exceed 1mm, the creep movement between the 6- and 60-minute readings must be less than 2 mm at maximum test

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 21 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

load. In order to study the feasibility of introduction of creep test, the previous performance test records as shown in Table 1 have been checked against the creep test requirements of FHWA. As there is no movement record at 1 minute in the previous data, the movement between 0 minute and 10 minutes has been adopted in the study and it is considered that this movement is more conservative. The results in Annex E show that all previous records (except slope 9SE-B/C102 due to no detail movement recorded) can satisfy the acceptance criterion as specified in FHWA. Therefore, it is recommended that the acceptance criterion of creep test as specified in FHWA should be introduced in our GS to ensure that the nail design loads can be safely carried throughout the structure service life. 6.

Conclusion

6.1

Existing acceptance criteria of performance tests using the maximum movement obtained in pull-out tests is considered inappropriate.

6.2

The maximum allowable soil nail head movement is proposed to be revised as follows:

e f  enail  f  esoil  f  (Tp ) performance L EA  5mm 6.3

The revised equation provides a rational acceptance criterion that serves to ensure completed soil nail can safely withstand the design loads without any excessive movement and to check the workmanship and the quality of grout around the soil nail.

6.4

It is recommended that the acceptance criterion of creep test as specified in FHWA should be introduced in our GS to ensure that the nail design loads can be safely carried throughout the structure service life.

7.

Decision of SE Meeting The conclusion and recommendations of Section 6 have been tabled and endorsed in SE Meeting of 6.2.2013.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 22 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Acknowledgment Structural Engineering Branch would like to record thanks to Dr H.Y. WONG, our ex-SGE/NP, for his help in offering valuable comments on the manuscripts. References Armour, T., Groneck, P., Keeley, J. and Sharma S. (2000). Publication No. FHWA-SA-97-070: Micropile Design and Construction Guidelines, Federal Highway Administration, Washington, D.C. Billam, J. (1972). “Some aspects of the behavior of granular materials at high pressure”, Proceedings of the Roscoe Memorial Symposium, Cambridge University, 29-31 March 1971, 70-80. BD (2004). Code of Practice for Foundations, Buildings Department, The Government of the Hong Kong Special Administrative Region. BSI (2010). BS EN 14490:2010: Execution of special geotechnical works – Soil nailing, BSI, London. Cartier, G. and Gigan, J.P. (1983). “Experiments and observations on soil nailing structures”, Proceedings of the 8th European Conference on Soil Mechanics and Foundation Engineering, Helsinki, 23-26 May 1983, 473-476. Chang, J.C., Hannon, J.B. and Forsyth, R.A. (1977). Report No. 640: Pull Resistance and Interaction of Earthwork Reinforcement and Soil, Transportation Research Board Record, California, Dept. of Transportation. Davisson, M.T. (1972), “High Capacity Piles”, Proceedings of Lecture Series on Innovations in Foundation. Construction, American Society of Civil Engineers, ASCE, Illinois Section, Chicago, 22 March 1972, 81-112. FHWA (2003). Geotechnical Engineering Circular No. 7 - Soil Nail Walls, Federal Highway Administration, Washington, D.C. Frizzi, R P and Meyer, M E (2000). “Augercast Piles: South Florida Experience”, Proceedings of Sessions of Geo-Denver 2000, 5-8 August 2000, Denver, Colorado, 382-396. GEO (2008). Geoguide 7 - Guide to Soil Nail Design and Construction, Geotechnical Engineering Office, Civil Engineering and Development Department, The Government of the Hong Kong Special Administrative Region. Hong, C.Y. (2011). Study on the Pullout Resistance of Cement Grouted Soil Nails, Ph.D. Thesis, The Hong Kong Polytechnic University, Hong Kong. Hong, C.Y., Yin J.H., Zhou, W.H., and Pei, H.F.. (2012). “Analytical Study on Progressive Pullout Behavior of a Soil Nail”, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 138(4), 500-507. Luo S.Q., Tan S.A. and Yong K.Y. (2000). “Pull-out Resistance Mechanism of a Soil Nail Reinforcement in Dilative Soils”, Soils and Foundations, 40(1), 47-56. Misra, A., and Chen, C.H. (2004). “Analytical solution for micropile design under tension and compression.” Geotech. Geol. Eng., 22(2), 199-255. Murray, R.T., Inst, H.E., Carder, D.R. and Krawczyk, J.V. (1980). Supplementary Report 583: Pull-out Tests on Reinforcements Embedded in Uniformly Graded and Subject to Vibration, Transport and Road Research Laboratory, Dep. of the Environment, Dept. of Transport, UK.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 23 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

O'Neill, M.W., and Reese, L.C. (1999). Publication No. FHWA-IF-99-025: Drilled Shafts: Construction Procedures and Design Methods, Federal Highway Administration, Washington, D.C. RMS (2012). QA Specification R64 Soil Nailing, Road and Maritime Services (RMS), New South Wales Government. Su, L.J., Chan C.F., Yin, J.H., Shiu, Y.K. and Chiu, S.L. (2008). “Influence of overburden pressure on soil-nail pullout resistance in a compacted fill”, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 134(9), 1339-1347. Taylor, D.W. (1948). Fundamentals of Soil Mechanics, John Wiley & Sons, Inc. Yin, J.H. Zhou, W.H., and Hong C.Y. (2010). “Pullout resistance of a soil nail in a completely decomposed granite soil under different overburden stresses and grouting pressures”, 63rd Canadian Geotechnical conference and 6th Canadian Permafrost Conference, Calgary, Alberta, Canada, 12-16 September 2010. Zhou, W.H., Yin, J.H. and Hong C.Y. (2011). “Finite element modelling of pullout testing on a soil nail in a pullout box under different overburden and grouting pressures”, Canadian Geotechnical Journal, 48(4), 557-567.

Structural Engineering Branch, ArchSD Issue/Revision No. : 1/First Issue Date : March 2013

Page 24 of 24

File code : TestOnSoilNail.doc CTW/MKL/KWK Current Issue Date :March 2013

Annex A Summary of Load Tests on Soil Nail required by National Standards/ Specifications

Standard/ Specification Test type

General Specification for Building 2012 (G.S.) Architectural Services Department (Clause 26.34 - 26.46) Pull-out Test Performance Test

Purpose of test To verify the ultimate bond resistance between soil and grout used in the design.

To check the quality of installed soil nails.

BS EN 14490:2010 (Section 9.3 & Annex C) Production Nail Test

To verify the ultimate soil nail to ground bond resistance used in the design: (1) the bond in the passive zone; (2) the bond in the active zone; (3) the bond along the entire length of the nail.

To demonstrate satisfactory soil nail performance at a load designated by the designer. The test is performed on the entire length of the nail.

Before, during or after production works.

During or on completion of production works.

Prior to construction.

During construction.

Prior to the installation of permanent nails

Production

Sacrificial nails

Production nails

Additional nails to the permanent Permanent nails nails.

Caution should be exercised when testing production nails not to overstress the nail to grout bond or cause damage to corrosion protection. When a structural facing is used the test nail should be debonded within the zone of influence of the facing.

Verification test nails shall have both bonded and unbonded lengths. Along the unbonded length, the nail bar is not grouted. The unbonded length of the test nails shall be at least 1 m (3 ft). The bonded length of the soil nail during verification tests, LBVT, shall be at least 3 m (10 ft) but not longer than a maximum length, LBVTmax, such that the nail load does nor exceed 90 percent of the nail bar tensile allowable load during the verification test.

Production proof test nails shall have both bonded and temporary unbonded lengths. The temporary unbonded length of the test nail shall be at least 1 m (3 ft). The bonded length of the soil nail during proof production tests, LBPT, shall be the least of 3 m (10 ft) and a maximum length, LBPTmax, such that the nail load does nor exceed 90 percent of an allowable value of the nail bar tensile load during the proof production test. The maximum bonded length shall be based on production nail maximum bar grade. Production proof test nails shorter than 4 m (12 ft) in length may be constructed with less than the minimum 3-m (10-ft) bond length.

The nails must have a minimum Provide a minimum debonded bond length of 3m unless zone of 1 metre length of soil nail otherwise shown on the Drawings. immediately behind the facing in Provide a minimum debonded order to prevent influence on the zone of 1 metre length of soil nail test result from the load test immediately behind the facing in reaction system. This debonded order to prevent influence on the length requirement may be waived test result from the load test if the load test reaction system reaction system. This debonded will not exert any pressure on the length requirement may be waived slope surface within a metre radius if the load test reaction system from the circumference of the test will not exert any pressure on the nail drill hole. slope surface within a metre radius from the circumference of the test nail drill hole.

Prior to the installation of After installation of permanent soil nails. permanent soil nails.

Type of nail used

Soil nails subjected to pull- Permanent soil nails Sacrificial out tests shall not form part of the permanent works. (i) Soil nail shall be Do not carry out the If necessary at each grouted over the length as performance test until the different soil layer. specified in the drawings grout has reached a cube or as directed by the SO. strength of 21 MPa. (typically 2m as per Drawing No. C2106/1 in Appendix 4 of G.S. Section 26) (ii) Do not carry out the pull-out test until the grout has reached a cube strength of 21 MPa.

Summary of Soil Nail Testing

QA Specification R64 Soil Nailing Road and Maritime Services, New South Wales Government (Clause 5) Suitability Test Acceptance Test (with creep test) To confirm that the bond strength To act as a measure of quality is achieved and that the control. reinforcement will perform as designed prior to permanent soil nail installation.

Sacrificial Nail Test

When tested

Comments

Geotechnical Engineering Circular No. 7 - Soil Nail Walls The Federal Highway Administration (FHWA), U.S. Department of Transportation (Section 8.5 & Appendix E) Verification Test Proof Test (with creep test) (with creep test) To verify the compliance with To ascertain that the contractor’s pullout capacity and bond construction methods and/or soil strengths used in design and conditions have not changed and resulting from the contractor’s that the production soil nails can installation methods. safely withstand design loads without excessive movement or long-term creep over the service life.

Prior to the application of concrete facing to the exposed ground.

Page 1 of 4

Standard/ Specification Test type Suggested frequency of soil nail load tests

Estimation of maximum test load

General Specification for Building 2012 (G.S.) Architectural Services Department (Clause 26.34 - 26.46) Pull-out Test Performance Test

BS EN 14490:2010 (Section 9.3 & Annex C)

Geotechnical Engineering Circular No. 7 - Soil Nail Walls The Federal Highway Administration (FHWA), U.S. Department of Transportation (Section 8.5 & Appendix E) Sacrificial Nail Test Production Nail Test Verification Test Proof Test (with creep test) (with creep test) The number of pull-out Each group of soil nails of Geotechnical Category 1 Geotechnical Category 1 The number of verification load 5 percent of the production soil tests shall be as shown on the same type and those tests will vary depending on the nails in each nail row or a (negligible risk to (negligible risk to the drawings or as grouted in one day shall be property or life): property or life): size of the project and the number minimum of 1 per row. The instructed by the SO. tested. The number of Optional Optional of major different ground types in Engineer shall determine the performance tests to be which nails will be installed. As a locations and number of proof Geotechnical Category 2 Geotechnical Category 2 GEOGUIDE 7 carried out shall be 6% of minimum, two verification tests tests prior to nail installation in (no abnormal risk to (no abnormal risk to (Cl. 6.3.2) the total number of should be conducted in each soil each row. property or life): property or life): It is common practice to permanent soil nails (in strata that is encountered. 2 %, min. three tests. If no comparable set the number of pullout any case at least one) in experience of soil type, a tests as 2 % of the total the group. minimum of three number of working soil sacrificial nails with at nails subject to a least one sacrificial nail minimum of two. per soil type. Where direct However, designers experience exists then should exercise sacrificial nail tests are engineering judgement to optional. ensure that the number of pullout tests is sufficient Geotechnical Category 3 Geotechnical Category 3 and representative to meet (all other structures not (all other structures not the test objectives. in Category 1 or 2): in Category 1 or 2): A minimum of five 3 %, min. five tests. sacrificial nails with at least two sacrificial nails per soil type.

QA Specification R64 Soil Nailing Road and Maritime Services, New South Wales Government (Clause 5) Suitability Test Acceptance Test (with creep test) Greater of: A total of 3% of permanent nails. - the number specified in the Of these, half must be in the top Drawings, or row, a quarter in the middle row - 1% of the permanent nails but and a quarter in the bottom row. not less than 2.

The maximum test load shall be either 90% of the yield load of the steel bar of the test soil nail (Tp) or the ultimate soil/grout bond load (Tult)unless directed otherwise by the SO.

The value of Ptest shall be based on the value of design bond resistence Td (or working bond Tw), the partial factor γd (normally in the range 1.5 to 2.0) and an appropriate value for the factor ξγ.

Test the soil nails subject to 150% of working load and not Suitability Test to pull-out failure greater than 80% of the ultimate or to 200% of the design working tensile strength of the soil nail bar. load, whichever is lower. Adjust the reinforced bar diameter or strength grade, if necessary, at your cost to ensure that the test load does not exceed 80% of the UTS of the soil nail bar.

Summary of Soil Nail Testing

The test load (Tp) shall be as given by the SO, but in any event it shall be not less than 1.5 times the working load as specified in the drawings, and not greater than 80% of the yield stress of the steel bar forming the soil nail.

The value of Ppr shall be based on either the design bond resistance Td or the working unit bond resistance Tw multiplied by a proof factor k, which normally lies in the range 1.1 to 1.5. The value k should never exceed the esign partial factor γd to minimize the risk of overstressing the soil nail bond, or causing damage to the corrosion protection system.

As a minimum, verification test loading must be carried out to a load defined by the pullout factor of safety times the design allowable pullout capacity. If the factor of safety for pullout is 2.0, then the test load must verify 200 percent of the allowable pullout capacity. Test loads in excess of this minimum, and preferably to failure, are recommended as they provide considerably more information and may lead to more economical drilling installation methods.

150 percent of the Design Test Load (DTL) and not exceed 90 percent of an allowable value of the nail bar tensile load.

Page 2 of 4

Standard/ Specification Test type

General Specification for Building 2012 (G.S.) Architectural Services Department (Clause 26.34 - 26.46) Pull-out Test Performance Test

Load cycles and Load the test nail in load increments stages: from the initial load (Ta) via two intermediate test loads (TDL1 and TDL2) to the maximum test load. TDL1 and TDL2 are the loads that result in the bonded zone tested to the design working bond strength and 2 times the working bond strength respectively. An initial load (Ta) equal to 5% of Tp or TDL1, whichever is smaller shall be applied. All loadings including Ta, TDL1, TDL2 and Tp shall be specified in the drawings or as directed by the SO. During the first two loading cycles, maintain the intermediate loads, TDL1 and TDL2 for 60 minutes for deformation measurement. After the measurement has been completed, the load shall be reduced to Ta and the residual deformation shall be recorded. In the last cycle, the test load shall be increased gradually from Ta straight to maximum test load and then maintained for deformation measurement. The measurement at each of the cycles shall be taken at time intervals of 1, 3, 6, 10, 20, 30, 40, 50 and 60 minutes.

Summary of Soil Nail Testing

BS EN 14490:2010 (Section 9.3 & Annex C)

Geotechnical Engineering Circular No. 7 - Soil Nail Walls QA Specification R64 Soil Nailing The Federal Highway Administration (FHWA), U.S. Department Road and Maritime Services, New South Wales Government of Transportation (Section 8.5 & Appendix E) (Clause 5) Sacrificial Nail Test Production Nail Test Verification Test Proof Test Suitability Test Acceptance Test (with creep test) (with creep test) (with creep test) Apply an initial load (Ta) A minimum of two cycles A single cycle is normally Perform verification tests by Perform proof tests by The rate of load application must The above stages constitute one incrementally loading the proof be in the range of 3 to 5 full cycle of testing. equal to 20% of Tp. Then is recommended with the satisfactory. The minimum incrementally loading the The rate of load application must load the soil nail up to Tp, bond resistance in the first number of load increments verification test nails to failure or test nail to 150 percent of the DTL kN/minute. At each load cycle, is 5. a maximum test load of 200 in accordance with the following hold the load at the peak test load be in the range of 3 to 5 and take measurements of cycle not exceeding Td. percent of the Design Test Load loading schedule. Record the soil for the period of observation as kN/minute. At each load the deformation with the The maximum increment (DTL) in accordance with the nail movements at each load specified in table below. Record increment, hold the load at the test size should be sufficient to load held constant at 2 following loading schedule. increment. the head movement at 1, 2, 3, 5, 6, load for the period of observation define the shape of the minute intervals for at Record the soil nail movements at 10, 20, 30, 50, 60, 90, 120, 150 as specified in table below. least 20 minutes until the load displacement graph each load increment. and 180 minutes. Record the displacement at the deformation in the last 10 and should not normally beginning and the end of the exceed 20% of the minutes is less than observation period. For the creep maximum cycle load. 0.05mm, or for a longer portion of the test, record period as required by the The alignment load (AL) should movements at 1, 2, 3, 5, 6, 10, 20, SO. Reduce the load to Ta be the minimum load required to 30, 50, 60, 90, 120, 150 and 180 and the extension align the testing apparatus and minutes. recorded. Then unload the should not exceed 5 percent of the soil nail as well as that of The alignment load (AL) should DTL. Dial gauges should be set to the bearing plate. be the minimum load required to “zero” after the alignment load has align the testing apparatus and been applied. should not exceed 5 percent of the DTL. Dial gauges should be set to The creep period shall start as “zero” after the alignment load has soon as the maximum test load been applied. Following the (1.50 DTL) is applied and the nail application of the maximum load movement shall be measured and (2.0 DTL), reduce the load to the recorded at 1 minute, 2, 3, 5, 6, alignment load (0.05 DTL and 10 minutes. Where the nail maximum) and record the movement between 1 minute and permanent set. 10 minutes exceeds 1 mm (0.04 in.), maintain the maximum test The creep period shall start as load for an additional 50 minutes soon as the maximum test load and record movements at 20 (1.50 DTL) is applied and the nail minutes, 30, 50, and 60 minutes. movement shall be measured and Maintain all load increments recorded at 1 minute, 2, 3, 5, 6, within 5 percent of the intended and 10 minutes. Where the nail load. movement between 1 minute and 10 minutes exceeds 1 mm (0.04 in.), maintain the maximum test load for an additional 50 minutes and record movements at 20 minutes, 30, 50, and 60 minutes. Maintain all load increments within 5 percent of the intended load.

Page 3 of 4

Standard/ Specification Test type

General Specification for Building 2012 (G.S.) Architectural Services Department (Clause 26.34 - 26.46) Pull-out Test Performance Test

Interpretation of results

The test nail shall be considered to be able to sustain the test load if the difference of nail movements at 6 and 60 minutes does not exceed 2mm or 0.1% of the grouted length of the test nail. In this case, the test shall proceed to the next loading cycle or be terminated if the test nail is subject to Tp. If the deformation in the last 10 minutes is larger than 0.05mm, the load shall be held longer as directed by the SO.

A soil nail shall be considered as failed if before the maximum allowable test load above is reached, (i) It is pulled out, or (ii) The soil nail head movement has exceeded ef in which ef = (Tp)performance [eb/Tp]pull-out And (Tp)performance = Test load in performance test (Tp)pull-out = Test load in pull-out test (eb)pull-out = Maximum soil nail head movement in pull-out test under test load (Tp)pull-out

Action taken in case of noncompliant test result

If the nail fails to sustain the test load TDL1, TDL2 or Tp, terminate the test and record the nail movement against residual load with time. The measurements shall be taken at time intervals of 1, 3, 6, 10 and every 10 minutes thereafter over a period for at least two hours. Where required the measurements shall be continued and at intervals as directed by the SO.

For any one failure of performance test, select two additional soil nails from the group and carry out further performance tests. If either one of these 2 additional soil nails also fails to reach the test load, the particular group of soil nails shall be considered as not complying with the specified requirements.

Summary of Soil Nail Testing

BS EN 14490:2010 (Section 9.3 & Annex C)

Geotechnical Engineering Circular No. 7 - Soil Nail Walls The Federal Highway Administration (FHWA), U.S. Department of Transportation (Section 8.5 & Appendix E) Sacrificial Nail Test Production Nail Test Verification Test Proof Test (with creep test) (with creep test) A sacrificial test result is A production test result is A test nail shall be considered A test nail shall be considered acceptable provided that at acceptable provided that: acceptable when all of the acceptable when all of the the maximum test load Ptest at the maximum proof load following criteria are met: following criteria are met: 1. The total creep movement is 1. The total creep movement is the creep rate is less than 2 Ppr the creep rate is less mm per log cycle of time, than 2 mm per log cycle of less than 2 mm (0.08 in.) between less than 1 mm (0.04 in.) during i.e. (s2−s1)/log(t2/t1) < 2 time, i.e. (s2−s1)/log(t2/t1) the 6- and 60-minute readings and the 10-minute readings or the total the creep rate is linear or creep movement is less than 2 mm mm < 2 mm decreasing throughout the creep (0.08 in.) during the 60-minute where s1 and s2 are the where s1 and s2 are the test load hold period. readings and the creep rate is measured nail measured nail 2. The total measured movement linear or decreasing throughout displacements at time t1 displacements at time t1 and time t2, respectively. and time t2, respectively. at the maximum test load exceeds the creep test load hold period. 80 percent of the theoretical 2. The total measured movement The measured extension at The measured extension at elastic elongation of the test nail at the maximum test load exceeds the head of the nail is not the head of the nail is not unbonded length. 80 percent of the theoretical less than the theoretical less than the theoretical 3. A pullout failure does not occur elastic elongation of the test nail extension of any debonded extension of any debonded at 2.0 DTL under verification unbonded length. length of the test nail Ldb. length of the test nail Ldb. testing and 1.5 DTL test load 3. A pullout failure does not occur under proof testing. Pullout failure at 2.0 DTL under verification is defined as the inability to testing and 1.5 DTL test load further increase the test load while under proof testing. Pullout failure there is continued pullout is defined as the inability to movement of the test nail. Record further increase the test load while the pullout failure load as part of there is continued pullout the test data. movement of the test nail. Record the pullout failure load as part of the test data.

QA Specification R64 Soil Nailing Road and Maritime Services, New South Wales Government (Clause 5) Suitability Test Acceptance Test (with creep test) The suitability test will be The acceptance test will be considered successful if all the considered successful if all of the following are satisfied: following are satisfied: (a) A total creep movement of less (a) A total creep movement of less than 2 mm between the 6 and 60 than 2mm between the 6 and 60 minutes readings is measured minutes readings is measured in during Cycle 4, and Creep Test hold period and (b) A total creep movement of less (b) A total creep movement of less than 1mm between the 60 and 180 than 1mm between the 60 and 180 minutes readings is measured in minutes readings is measured in Cycle 4, and Creep Test hold period and (c) The creep rate is linear or (c) The creep rate is linear or decreasing, when plotted against decreasing, when plotted against the logarithm of time throughout the logarithm of time throughout Cycle 4. Creep Test hold period.

Review soil nail Consult designer for action The Engineer will evaluate the installation method and/or to be taken and approval results of each verification test. consider alternative soil to continue. Installation methods that do not nail length and satisfy the nail testing layout. requirements shall be rejected. The Contractor shall propose alternative methods and install replacement verification test nails. Replacement test nails shall be installed and tested at no additional cost.

Repeat the Suitability Test on a replacement test nail. Any modifications of construction procedures, replacement nails and associated tests must be at your cost.

The Engineer may require the Contractor to replace some or all of the installed production nails between a failed proof test nail and the adjacent passing proof test nail. Alternatively, the Engineer may require the installation and testing of additional proof test nails to verify that adjacent previously installed production nails have sufficient load carrying capacity. Installation and testing of additional proof test nails or installation of additional or modified nails as a result of proof test nail failure(s) will be at no additional cost.

Where a test nail does not meet the acceptance criteria, test an additional 2 soil nails in the vicinity of the non-conforming soil nail. If any soil nail fails an Acceptance Test, abandon the soil nail and completely remove it from the drillhole by a method acceptable to the Principal. Unless otherwise instructed by the Principal, fill the drillhole by grouting. If the failed soil nail cannot be pulled out within 80% of the UTS of the soil nail bar, cutoff the bar flush with the finishing ground and grout the remaining part of the drillhole. Install another soil nail adjacent to the abandoned one for additional test at your cost.

Page 4 of 4

Annex B Results of Using Revised Equation proposed by Dr H. Y. Wong for Past Test Data

Results of Using Revised Equation proposed by Wong (2012) for Past Test Data Feature No.

Nail No.

A6 B5 C2 C12 D7 E13 E27 3SW-C/C14 E36 F29 G7 G32 H11 H22 L4 I7 A2 3SW-C/F17 B8 Row 1-5 8SW-B/C12 Row 1-14 Row 2-10 9 10 8SW-B/CR11 14 16 11 A3 B12 3SE-D/C111 C5 D9 E3 A16 B15 C6 3SW-C/C24 C24A E3 E11 A15 A35 A41 A62 B7 B18 B27 3NW-C/C15~19 B46 B64 B92 c21 D11 E15 F6 B4 12NW-C/C85 D5 A3 A14 A25 A34 B10 B19 B31 D25 9SE-B/C102 C34 C25 C15 C2 E28 E15 D8 E2 D4 A13 07SW-C/FR114 B4 A1 C11 C7 07SW-C/C117 D2 FAIL

Soil stratum soil (m) 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 6 6 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 8 8 8 8 8 5 5

rock (m) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 7 7 7 7 7 4 4

L

d

D

Egrout

Esteel

(Tp)performance

(ef)performance

m 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 9 9

mm 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 32 32 32 32 32 32 32

mm 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

kN/mm2 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30

kN/mm2 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205

kN 140 120 100 100 80 160 160 160 150 80 140 120 140 120 80 110 90 67.5 67.5 80.5 100 100 100 100 54 200 180 180 150 150 90 135 180 135 90 90 100 150 150 120 100 100 120 180 180 120 150 120 100 120 120 100 80.5 80.5 80.5 80.5 84 84 84 84 84 84 84 84 91.5 91.5 84 91.5 80 180 140 180 150 120 80

mm 4.07 1.44 1.29 0.93 1.86 1.38 5.63 3.87 10.79 2.00 4.80 2.38 4.72 3.08 1.02 2.77 1.48 0.28 0.28 0.26 1.50 2.05 1.67 1.93 1.92 2.32 7.53 6.82 2.58 4.03 4.55 9.36 7.27 3.05 2.95 7.85 1.90 2.48 2.32 1.66 0.86 1.16 1.31 1.95 2.08 0.70 1.76 1.78 0.93 1.82 1.86 2.07 0.00 0.79 1.61 1.43 1.55 2.31 0.59 0.34 1.17 0.79 1.80 4.46 2.01 1.93 3.35 0.24 0.26 0.40 0.42 0.52 1.21 1.32 2.34

ef (mm) GS 9.12 7.82 6.51 6.51 5.21 30.22 30.22 48.96 37.03 6.78 31.02 4.83 20.06 13.49 38.58 18.11 14.82 3.16 3.16 3.77 4.69 4.69 4.69 4.69 2.53 16.46 10.92 12.83 9.10 6.96 7.09 17.45 23.27 9.64 11.67 11.67 6.19 28.28 6.24 27.48 6.19 5.74 7.11 7.75 11.06 15.16 9.21 17.03 14.19 15.16 5.14 4.28 9.74 9.74 9.74 9.74 8.52 8.52 8.52 6.29 8.52 8.52 8.52 8.52 11.08 11.08 6.29 11.08 6.49 6.34 9.41 12.10 11.05 7.26 4.84

Wong (2012) 5.72 4.90 4.09 4.09 3.27 26.34 26.34 45.08 33.39 4.84 27.62 N/A 16.67 10.58 36.63 15.44 12.64 1.93 1.93 2.31 2.87 2.87 2.87 2.87 1.55 11.61 6.56 8.46 5.46 N/A 4.36 13.36 17.81 5.55 8.94 8.94 4.37 25.56 N/A 26.27 5.19 4.74 5.90 5.93 9.24 13.95 7.70 15.82 13.18 13.95 2.95 2.46 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 4.72 3.14

denotes test failure

"N/A" denotes that the calculated elastic lengthening of the soil nail steel bar is larger than the maximum soil nail head movement in pull-out test, and therefore e determined.

f

cannot be

Annex C Estimation of Critical Shear Displacement, uc

Estimation of Critical Shear Displacementu c Feature No.

Location

3SW-C/C14

3SW-C/F17 8SW-B/C12

8SW-B/CR11

3SE-D/C111

3SW-C/C24

3NW-C/C11,15-19

12NW-C/C85#

9SE-B/C102#

07SW-C/FR114#

07SW-C/C117#

Nail No.

PT1 PT2 PT3 PT4 PT5 PT6 PT7 Wo Hop Shek Cemetery PT8 PT9 PT10 PT11 PT12 PT13 PT14 Wo Hop Shek Cemetery PT1 T1 Lady MacLehose Holiday T2 Village, Sai Kung, N.T. T3 T4 Lady MacLehose Holiday T5 Village, Sai Kung, N.T. T6 PT1 PT2 Tai Mei Tuk Water Sport PT3 Centre PT4 PT5 PT3 PT4 Wo Hop Shek Cemetery PT5 PT6 PT7 TN1 TN2 TN3 TN4 TN5 TN6 TN7 TN8 Sandy Ridge Cemetery TN9 TN10 TN11 TN12 TN13 TN14 TN15 TN16 PT1 Silverstand Beach PT2 TS1 TS2 North Lantau Hospital TS3 TS4 P1 P2 Central Kwai Chung Park P3 P4 Wo Yi Hop Road Recreation P1 Ground P2

(T p ) pullout at yield kN 127 120.4 123 101.6 127 180.6 123 127 71 115.8 184 184 155.4 115.4 122.2 170.4 170.6 170.4 169.2 169.8 170.1 89.2 184.1 193 202.8 193.2 71.04 132.7 187.33 179.7 174.6 231.9 222.7 165.7 219.2 215.6 208.1 166.9 111.1 220.4 209.7 163.5 216.4 217.7 56.2 164.8 82.7 187.8 241.9 203 203 203 203 296 296 296 296 224.6 214.5

L m 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 15 15 15 15 15 15 15 15 9 9

L unbond m 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 6 6 6 6 6 6 8 8 8 8 8 10 10 10 10 10 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 13 13 13 13 13 13 13 13 7 7

L bond m 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

E steel 2

kN/mm 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205

D mm 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

d mm 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 25 25 25 25 32 32 32 32 32 32

(e b ) pullout at yield mm 5.90 7.35 7.85 4.33 8.16 10.50 11.88 7.13 4.83 6.75 9.54 6.84 8.99 5.86 6.34 6.75 6.74 6.75 6.68 6.73 6.76 5.67 9.43 12.20 10.67 10.27 6.58 9.13 11.50 8.27 9.27 9.72 9.42 7.39 10.47 9.34 8.82 7.84 3.54 10.93 9.87 8.61 9.97 11.08 3.22 5.74 3.73 7.56 9.77 24.59 15.21 20.58 24.56 21.82 19.91 24.03 10.43 12.92 12.35

(e steel ) pullout mm 6.16 5.84 5.97 4.93 6.16 8.76 5.97 6.16 3.45 5.62 8.93 8.93 7.54 5.60 5.93 6.20 6.21 6.20 6.16 6.18 6.19 4.33 8.93 9.36 9.84 9.37 4.31 8.05 11.36 10.90 10.59 8.44 8.10 6.03 7.98 7.85 7.57 6.07 4.04 8.02 7.63 5.95 7.88 7.92 2.05 6.00 3.01 6.83 8.80 26.23 26.23 26.23 26.23 23.34 23.34 23.34 23.34 9.54 9.11

Estimated u c mm -0.26 1.51 1.88 -0.60 2.00 1.74 5.91 0.97 1.38 1.13 0.61 -2.09 1.45 0.26 0.41 0.55 0.53 0.55 0.52 0.55 0.57 1.34 0.50 2.84 0.83 0.90 2.27 1.08 0.14 -2.63 -1.32 1.28 1.32 1.36 2.49 1.49 1.25 1.76 -0.50 2.91 2.23 2.66 2.09 3.16 1.17 -0.26 0.72 0.73 0.97 -1.64 -11.02 -5.65 -1.67 -1.52 -3.43 0.69 -12.91 3.38 3.24

*no yielding is observed from pull-out test data # denotes soil nails with the end grouted in bedrock Summary Table Estimated u c < 0mm 0mm - 1.5mm 1.5mm - 2.5mm 2.5mm - 5mm > 5mm Total

7.00

Estimated uc (mm)

6.00 5.00 4.00 3.00 2.00 1.00 0.00 1

3

5

7

9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 Soil nails installed into soil

Soil nails with the end grouted in bedrock

Soil 7 26 9 4 1 47

Rock 0 2 0 2 0 4

* * * * * * * *

Annex D Results of Using Proposed New Equation for Past Test Data

Results of Using Proposed Equation for Past Test Data Feature No.

Nail No.

A6 B5 C2 C12 D7 E13 E27 3SW-C/C14 E36 F29 G7 G32 H11 H22 L4 I7 A2 3SW-C/F17 B8 Row 1-5 8SW-B/C12 Row 1-14 Row 2-10 9 10 8SW-B/CR11 14 16 11 A3 B12 3SE-D/C111 C5 D9 E3 A16 B15 C6 3SW-C/C24 C24A E3 E11 A15 A35 A41 A62 B7 B18 B27 3NW-C/C15~19 B46 B64 B92 c21 D11 E15 F6 B4 12NW-C/C85 D5 A3 A14 A25 A34 B10 B19 B31 D25 9SE-B/C102 C34 C25 C15 C2 E28 E15 D8 E2 D4 A13 07SW-C/FR114 B4 A1 C11 C7 07SW-C/C117 D2 FAIL

Soil stratum soil (m) 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 6 6 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 8 8 8 8 8 5 5

denotes test failure

rock (m) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 7 7 7 7 7 4 4

L

d

D

Egrout

m 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 9 9

mm 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 32 32 32 32 32 32 32

mm 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

kN/mm 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30

2

Esteel

(Tp)performance

(ef)performance

kN/mm2 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205 205

kN 140 120 100 100 80 160 160 160 150 80 140 120 140 120 80 110 90 67.5 67.5 80.5 100 100 100 100 54 200 180 180 150 150 90 135 180 135 90 90 100 150 150 120 100 100 120 180 180 120 150 120 100 120 120 100 80.5 80.5 80.5 80.5 84 84 84 84 84 84 84 84 91.5 91.5 84 91.5 80 180 140 180 150 120 80

mm 4.07 1.44 1.29 0.93 1.86 1.38 5.63 3.87 10.79 2.00 4.80 2.38 4.72 3.08 1.02 2.77 1.48 0.28 0.28 0.26 1.50 2.05 1.67 1.93 1.92 2.32 7.53 6.82 2.58 4.03 4.55 9.36 7.27 3.05 2.95 7.85 1.90 2.48 2.32 1.66 0.86 1.16 1.31 1.95 2.08 0.70 1.76 1.78 0.93 1.82 1.86 2.07 0.00 0.79 1.61 1.43 1.55 2.31 0.59 0.34 1.17 0.79 1.80 4.46 2.01 1.93 3.35 0.24 0.26 0.40 0.42 0.52 1.21 1.32 2.34

ef (mm) GS 9.12 7.82 6.51 6.51 5.21 30.22 30.22 48.96 37.03 6.78 31.02 4.83 20.06 13.49 38.58 18.11 14.82 3.16 3.16 3.77 4.69 4.69 4.69 4.69 2.53 16.46 10.92 12.83 9.10 6.96 7.09 17.45 23.27 9.64 11.67 11.67 6.19 28.28 6.24 27.48 6.19 5.74 7.11 7.75 11.06 15.16 9.21 17.03 14.19 15.16 5.14 4.28 9.74 9.74 9.74 9.74 8.52 8.52 8.52 6.29 8.52 8.52 8.52 8.52 11.08 11.08 6.29 11.08 6.49 6.34 9.41 12.10 11.05 7.26 4.84

(EA)steel 13.49 12.28 11.07 11.07 9.85 14.70 14.70 14.70 14.10 9.85 13.49 12.28 13.49 12.28 9.85 11.67 10.46 8.28 8.28 8.91 9.85 9.85 9.85 9.85 7.62 17.13 15.92 15.92 14.10 14.10 11.55 14.83 18.10 14.83 11.55 11.55 9.85 12.28 12.28 10.82 9.85 9.85 10.82 13.73 13.73 10.82 12.28 10.82 9.85 10.82 10.82 9.85 17.00 17.00 17.00 17.00 17.52 17.52 17.52 17.52 17.52 17.52 17.52 17.52 18.64 18.64 17.52 18.64 12.28 21.38 17.74 21.38 18.65 11.55 9.37

(EA)equivalent 8.72 8.19 7.66 7.66 7.13 9.25 9.25 9.25 8.99 7.13 8.72 8.19 8.72 8.19 7.13 7.92 7.39 6.43 6.43 6.71 7.13 7.13 7.13 7.13 6.15 10.31 9.78 9.78 8.99 8.99 7.87 9.30 10.74 9.30 7.87 7.87 7.13 8.19 8.19 7.55 7.13 7.13 7.55 8.83 8.83 7.55 8.19 7.55 7.13 7.55 7.55 7.13 8.76 8.76 8.76 8.76 8.92 8.92 8.92 8.92 8.92 8.92 8.92 8.92 9.27 9.27 8.92 9.27 8.19 12.17 10.58 12.17 10.98 7.87 6.91

Annex E Checking the Previous Performance Test Data against the Acceptance Criterion of Creep Test as specified in FHWA

Checking the Previous Performance Test Data against the Acceptance Criterion of Creep Test as specified in FHWA Previous Performance Test Data Feature No.

Nail No.

A6 B5 C2 C12 D7 E13 E27 3SW-C/C14 E36 F29 G7 G32 H11 H22 L4 I7 A2 3SW-C/F17 B8 Row 1-5 8SW-B/C12 Row 1-14 Row 2-10 9 10 8SW-B/CR11 14 16 11 A3 B12 3SE-D/C111 C5 D9 E3 A16 B15 C6 3SW-C/C24 C24A E3 E11 A15 A35 A41 A62 B7 B18 B27 3NW-C/C15~19 B46 B64 B92 c21 D11 E15 F6 B4 12NW-C/C85 D5 A3 A14 A25 A34 B10 B19 B31 D25 *9SE-B/C102 C34 C25 C15 C2 E28 E15 D8 E2 D4 A13 07SW-C/FR114 B4 A1 C11 C7 07SW-C/C117 D2

Nail movement, e (mm) Soil stratum soil (m) 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 6 6 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 8 8 8 8 8 5 5

rock (m) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 7 7 7 7 7 4 4

L m 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 8 8 8 8 8 8 8 8 10 10 10 10 10 12 12 12 12 12 12 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 9 9

*No detail movement record of 9SE-B/C102 can be retrieved.

d mm 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 32 32 32 32 32 32 32

D mm 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

e0 min (1) 3.92 1.44 1.29 0.93 1.78 1.36 5.51 3.86 10.79 1.95 4.78 2.26 4.69 3.07 0.99 2.39 1.41 0.27 0.27 0.25 1.43 1.93 1.40 1.84 1.92 2.31 7.50 6.78 2.58 3.91 4.64 9.34 7.08 3.03 2.95 7.85 1.83 2.45 2.25 1.61 0.85 1.14 1.30 1.89 2.04 0.69 1.69 1.65 0.89 1.74 1.86 2.06 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 0.23 0.39 0.42 0.52 1.20 1.09 2.09

e10 min (2) 4.07 1.44 1.29 0.93 1.86 1.38 5.60 3.86 10.79 1.97 4.80 2.32 4.71 3.08 1.01 2.56 1.45 0.28 0.27 0.26 1.48 2.00 1.66 1.90 1.92 2.32 7.53 6.80 2.58 4.01 4.54 9.34 7.26 3.04 2.95 7.85 1.88 2.48 2.29 1.65 0.85 1.16 1.31 1.94 2.07 0.70 1.75 1.77 0.92 1.82 1.86 2.07 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 0.25 0.40 0.42 0.52 1.20 1.10 2.10

e20 min (3) 4.07 1.44 1.29 0.93 1.86 1.38 5.63 3.87 10.79 2.00 4.80 2.38 4.72 3.08 1.02 2.69 1.48 0.28 0.28 0.26 1.49 2.05 1.67 1.93 1.92 2.32 7.53 6.82 2.58 4.03 4.55 9.36 7.27 3.05 2.95 7.85 1.90 2.48 2.32 1.66 0.87 1.16 1.31 1.95 2.08 0.70 1.76 1.78 0.93 1.82 1.86 2.07 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 0.26 0.40 0.42 0.52 1.21 1.10 2.10

e30 min (4)

e40 min (5)

2.75

2.77

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Acceptance Criteria FHWA (2)-(1) (3)-(2)