Statnamic testing of piles in clay 1

STATNAMIC TESTING OF PILES IN CLAY








BY


DUC HANH NGUYEN

A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
DEPARTMENT OF CIVIL AND STRUCTURAL ENGINEERING
UNIVERSITY OF SHEFFIELD
OCTOBER 2005


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A series of pile load tests have been carried out on an instrumented model pile
installed in instrumented clay beds prepared in a 1-g calibration chamber under two
stages of consolidation, i.e. one dimensional and triaxial consolidation. A variety of
loading techniques (Constant Rate of Penetration at different rates, Maintained Load
and Statnamic) have been applied during the model pile tests.

On the basis of these tests, in conjunction with data from previous studies, shear rate
effects in clay, i.e. the enhancement of soil shear resistance under high rates of
shearing are highly non-linear. The available non-linear power laws for rate effects
were applied to the test results to predict the static load-settlement curve from rapid
load pile tests. It was found that these models can give a good prediction of the
ultimate static pile capacity, but they overpredict the settlement at load below the
ultimate value. Following this, an alternative method of deriving the static load-
settlement curve from a rapid load pile test, a non-linear power law incorporating
changing damping parameters, has been proposed. This method was used for the
model pile tests and then it was calibrated for field load tests carried out on a full
size instrumented pile installed in a stiff glacial till.

A simple theoretical method, which was proposed by Randolph & Wroth (1978) to
establish the relationship between the pile load and its settlement for static pile loads,
was modified for static pile load tests and then developed for rapid pile load tests.

The gradual decrease of the pile shaft resistance after its peak value to a residual pile
shaft resistance, which is known as the softening effect, plus the changes of pore
water pressures and the inertial behaviour of the soil around the pile were also

reported and discussed.



iii

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The Author would like to express his deepest gratitude to his supervisors Prof. Bill
Anderson and Dr. Adrian F.L. Hyde for their advice, encouragement and constant
guidance throughout this research programme, and for their valuable time and efforts
in shaping the framework of this thesis. Also, the Author take this opportunity to
thank Prof. Bill Anderson and Dr. Adrian F.L. Hyde for their generosity in helping
me when I had a difficulty in finance at the end of the study.

The Author would like to thank technical staff at the University of Sheffield,
particularly Mr. Paul Osborne and Mr. Mark Foster for their assistance throughout
the experiments.

Special thanks are due to Dr. Michel Brown for his guidance and advice on the
laboratory experimental aspects of this work at the beginning of the research.
Thanks are also due to academic staff in the Geotechnical Engineering Group for
their friendship. Thanks are accorded to my friends for their assistance and sharing

their experience.

The Author would like to express his gratitude to David Lovegrove and his wife, for
their support and encouragement throughout the study. I feel this country is much
more beautiful with their friendship.

Finally, grateful thanks are extended to the Vietnamese government for providing a
full scholarship that enabled the Author to conduct this research.






iv
TABLE OF CONTENTS



Page
ABSTRACT ii
ACKNOWLEDGEMENT iii
TABLE OF CONTENTS iv
LIST OF TABLES ix
LIST OF FIGURES xi
NOTATIONS AND ABBREVIATIONS xxiii

CHAPTER 1 - INTRODUCTION

1.1 Background ……………………………………………………………………1

1.2 Research objectives……………………………………………………………2
1.3 Outline of thesis……………………………………………………………….

2


CHAPTER 2 - LITERATURE REVIEW

2.1 Introduction……………………………………………………………………4
2.2 Static load testing methods…………………………………………………….5
2.2.1 Maintained load test……………………………………………………...5
2.2.2 Constant rate of penetration test………………………………………….6
2.2.3 Osterberg load cell test…………………………………………………...7
2.3 Rate effects…………………………………………………………………….8
2.3.1 Rate effect studies using triaxial tests and torsion tests………………….9
2.3.2 Rate effect studies using direct shear tests……………………………...11
2.3.3 Rate effect studies using penetrometer and shear vane tests…………...13
2.3.4 Rate effect using a model instrumented pile in a clay bed……………...15
2.3.5 Results from field studies……………………………………………….16
2.4 Dynamic pile load tests……………………………………………………….18
2.4.1 The stress wave propagation equation………………………………….19
2.4.2 Pile dynamic resistance…………………………………………………20


v
2.4.3 Static pile capacity……………………………………………………...22
2.4.3.1 Case method of analysis……………………………………..……23
2.4.3.2 Signal matching method…………………………………………..23
2.4.4 Dynamic load test advantages and disadvantages………………………26
2.5 Statnamic load test……………………………………………………………26

2.6 Statnamic data interpretation…………………………………………………28
2.7 Quake values for shaft and toe resistances and the softening effect………….32
2.8 The changes of pore water pressure during pile installation and the subsequent
loading stages…….............……………………………………..…………...37
2.9 Summary……………………………………………………………………...40


CHAPTER 3 - TESTING EQUIPMENT AND PROCEDURES

3.1 Introduction…………………………………………………………………..56
3.2 The calibration chamber……………………………………………………...57
3.3 Boundary effects……………………………………………………………...58
3.4 Bed preparation……………………………………………………………….60
3.4.1 Clay slurry preparation………………………………………………….60
3.4.2 Consolidometer…………………………………………………………61
3.4.3 Clay bed instrumentation……………………………………………….62
3.4.4 1-D consolidation……………………………………………………….63
3.4.5 Triaxial consolidation…………………………………………………..65
3.4.6 Pile installation………………………………………………………….68
3.5 Instrumented model pile……………………………………………………...69
3.5.1 Pile tip component……………………………………………………...69
3.5.2 Pile shaft sleeve component………………………………...…………..71
3.5.3 Actuator - Pile connection………………………………………………72
3.5.4 Pile shaft load cell performance…………………………………...……73
3.6 Servo-hydraulic loading system……………………………………………...73
3.7 Logging and control system………………………………………………….75
3.8 Instrumentation calibration…………………………………………………...76
3.9 Testing procedure…………………………………………………………….78
3.9.1 Constant rate of penetration tests……………………………………….78
3.9.2 Statnamic tests………………………………………………………….79

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3.9.3 Maintained load tests…………………………………………………...80
3.10 Bed dismantling……………………………………………………………..80


CHAPTER 4 - TESTING PROGRAMME

4.1 Introduction…………………………………………………………………101
4.2 Clay bed preparation and transducer locations……………………………..102
4.3 Constant rate of penetration tests (CRP tests)………………………………103
4.4 Statnamic tests (STN tests)………………………………………………….104
4.5 Maintained load tests (ML tests) …...………………………………………105


CHAPTER 5 - BED PROPERTIES

5.1 Introduction…………………………………………………………………114
5.2 Clay bed 1-D consolidation…………………………………………………114
5.3 Clay bed isotropic triaxial consolidation................…………………………117
5.4 Performance of the calibration chamber during the pile load tests…………117
5.5 Bed properties after the testing programme…………………………………119


CHAPTER 6 – PILE TEST DATA AND DISCUSSION

6.1 Introduction…………………………………………………………………139
6.2 Typical results of the pile load tests………………………………………..139
6.3 Pile shaft resistance results and models for the pile shaft resistance………..140

6.3.1 Non-linear models……………………………………………………..141
6.3.2 A new non-linear model for pile shaft rate effects…………………….145
6.3.3 Pile shaft softening effect……………………………………………...150
6.3.4 Repeatability of the static pile shaft resistances……………………….152
6.4 Pile tip resistance results…………………………………………………….153
6.5 Application of the proportional exponent model to the pile total load……...157
6.6 A simple theoretical approach for the load transfer mechanism……………158
6.6.1 Available models for load transfer…………………………………….158


vii
6.6.2 Modifications to the existing models for load transfer for static
pile load tests and a new model for rapid load pile tests….............…...160
6.6.3 Application of the models to static pile load tests.……………………167
6.6.4 Application of the models to rapid load pile tests…..…………………168
6.6.5 Quake value for the pile shaft resistance of a rapid load test………….170
6.7 A comparison between maintained load tests and CRP tests……………….172
6.8 Pore water pressures around the pile during pile load tests…………………173
6.8.1 Pore water pressures during CRP tests at a rate of 0.01mm/s…………174
6.8.1.1 Pore water pressures at the pile shaft……………………………174
6.8.1.2 Pore water pressures around the pile shaft………………………175
6.8.1.3 Pore water pressures at the pile tip………………………………176
6.8.1.4 Pore water pressures below the pile tip………………………….176
6.8.2 Pore water pressures during maintained pile load tests……………….177
6.8.3 Pore water pressure regime during rapid load pile tests………………178
6.8.3.1 Pore water pressures at the pile shaft……………………………178
6.8.3.2 Pore water pressures around the pile shaft………………………178
6.8.3.3 Pore water pressures at the pile tip………………………………179
6.8.3.4 Pore water pressures below of the pile tip……………………….179
6.9 Clay bed inertial behavior…………………………………………………...179

CHAPTER 7 - FIELD LOAD TESTS

7.1 Introduction……………………………………………......................……..254
7.2 Ground conditions………………………......…………..…………………..254
7.3 Pile tests………………….........................…………………………………255
7.4 Prediction of the pile static capacity using the Unloading Point Method…..255
7.5 Application of the analyses to field tests…….....…………………….……..257


CHAPTER 8 - CONCLUSIONS AND RECOMMENDATIONS FOR
FURTHER WORK

8.1 Introduction……………………..........……………………………………..269


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8.2 Main conclusions…………………………………………..………………..269
8.3 Recommendations for further studies…………..…………………………...273


REFERENCES
………………………………………………………………….275

ix
LIST OF TABLES


Table 2.1 Damping parameters in Dayal and Allen study

Table 2.2 Case damping coefficient for different soil types


Table 3.1 Speswhite kaolin properties as supplied by the manufacturers

Table 3.2 Silica sand properties as supplied by the manufacturers

Table 3.3 Silica flour silt properties as supplied by the manufacturers

Table 3.4 Material for one clay bed

Table 3.5 Material properties


Table 4.1 Testing programme for Bed 1

Table 4.2 Testing programme for Bed 2

Table 4.3 Testing programme for Bed 3

Table 4.4 Testing programme for Bed 4

Table 4.5 Testing programme for Bed 5


Table 5.1 Volume of water expelled during 1-D consolidation

Table 5.2 3-D consolidation degrees of Beds 1 to 5

Table 5.3 Undrained shear strengths of Bed 1 determined by hand vane tests

Table 5.4 Undrained shear strengths of Bed 2 determined by hand vane tests

Table 5.5 Undrained shear strengths of Bed 3 determined by hand vane tests

Table 5.6 Undrained shear strengths of Bed 4 determined by hand vane tests

Table 5.7 Undrained shear strengths of Bed 5 determined by hand vane tests

Table 5.8 Moisture contents of Bed 1

Table 5.9 Moisture contents of Bed 2



x
Table 5.10 Moisture contents of Bed 3

Table 5.11 Moisture contents of Bed 4

Table 5.12 Moisture contents of Bed 5

Table 5.13 Shear strengths from undrained triaxial tests


Table 6.1 Static pile shaft resistance of Beds 2 to 5

Table 6.2 Pile tip loads for tests in Bed 1

Table 6.3 Pile tip loads for tests in Bed 2

Table 6.4 Pile tip loads for tests in Bed 3

Table 6.5 Pile tip loads for tests in Bed 4

Table 6.6 The influence of initial effects in the calculation for the pile settlement


Table 7.1 Soil properties from laboratory tests for Grimsby clay

Table 7.2 Grimsby soil description





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LIST OF FIGURES

Figure 2.1 O-Cell

Figure 2.2 Schematic arrangement of a Osterberg test

Figure 2.3 Balderas-Meca’s test apparatus arrangement

Figure 2.4 Damping coefficient, α, versus axial strain for monotonic consolidated
undrained triaxial tests at different rates. (β=0.20; OCR=1)

Figure 2.5 Half steel tube with semi-circular soil sample

Figure 2.6 The shear device for the study of pile-soil interfaces

Figure2.7 Penetrometer and soil container in experimental set-up

Figure 2.8 (a) Schematic of the test arrangement (b) geometry of penetrometer for
side friction tests

Figure 2.9 Undrained peak strength measured from vane tests

Figure 2.10 Slow and quick-penetration tests

Figure 2.11 Shaft resistances and pile movements

Figure 2.12 Wave propagation in a bar produced by an impact load

Figure 2.13 Idealization of a pile as an elastic rod with soil interaction at discrete
nodes

Figure 2.14 Model of downward and upward waves due to soil interaction

Figure 2.15 Smith Model for pile and soil

Figure 2.16 Randolph & Deeks model for pile shaft and soil

Figure 2.17 Randolph & Deeks model for pile tip and soil

Figure 2.18 A typical statnamic loading-time relationship

Figure 2.19 Statnamic device

Figure 2.20 Forces acting on a pile during statnamic loading

Figure 2.21 Unloading point method


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Figure 2.22 Load Settlement response

Figure 2.23 Shaft quake values compared with the pile diameter

Figure 2.24 Ramberg-Osgood model for the relationship of shaft resistance and
displacement

Figure 2.25 Idealised softening behaviour for a pile in clay

Figure 2.26 Chandler & Martins’ test apparatus

Figure 2.27 Strain Path Method to deep penetration in clays

Figure 3.1 Strain distributions during pile installation according to the strain path
method

Figure 3.2 Pumping slurry to the consolidometer

Figure 3.3 The consolidometer

Figure 3.4 Miniature Druck Transducer

Figure 3.5 Transducer arrangement in the calibration chamber

Figure 3.6 Hole arrangement at the bottom plate

Figure 3.7 The accelerometer and its protection

Figure 3.8 1-D consolidation in the laboratory

Figure 3.9 Schematic diagram of 1-D consolidation

Figure 3.10 Loading plate and its o-rings in the laboratory

Figure 3.11 Calibration chamber volume change units

Figure 3.12 Removing the consolidometer after the finish of 1-D consolidation

Figure 3.13 The calibration chamber sand retaining ring and its arrangement

Figure 3.14 The triaxial calibration chamber membrane and drainage sand layer at the

top of the clay bed

Figure 3.15 The calibration chamber top plate and its attached membrane

Figure 3.16 Top plate arrangement during 3-D consolidation

Figure 3.17 Schematic diagram of 3-D consolidation



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Figure 3.18 Using the casing tube and auger to make a hole in the bed for pile
installation

Figure 3.19 Schematic diagram of 3-D consolidation after pile installation

Figure 3.20 Schematic diagram of the instrumented model pile

Figure 3.21 The pile tip load cell

Figure 3.22 The pore water transducer at the pile tip

Figure 3.23 The pile shaft load cell

Figure 3.24 The pore water transducer at the pile shaft

Figure 3.25 Schematic diagram of the connection between the loading system and the
pile for CRP and Statnamic tests

Figure 3.26 The connection between the loading system and the pile for CRP and

Statnamic tests

Figure 3.27 Typical calibration results of a pore water pressure transducer

Figure 3.28 Input loading pulse and actual loading pulse for a statnamic load test

Figure 3.29 Schematic diagram of the connection between the loading system and the
pile for maintained load tests

Figure 3.30 The connection between the loading system and the pile for maintained
load tests

Figure 3.31 The clay bed when the tests had finished

Figure 3.32 Carrying out hand vane tests and taking the samples for triaxial tests


Figure 4.1 Transducer arrangement for Bed 1

Figure 4.2 Transducer arrangement for Bed 2

Figure 4.3 Transducer arrangement for Bed 3

Figure 4.4 Transducer arrangement for Bed 4

Figure 4.5 Transducer arrangement for Bed 5

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Figure 5.1 Bed settlements during 1-D consolidation

Figure 5.2 Pore water pressure distribution during 280 kPa 1-D consolidation of
Bed 1

Figure 5.3 Pore water pressure distribution during 280 kPa 1-D consolidation of
Bed 2

Figure 5.5 Pore water pressure distribution during 280 kPa 1-D consolidation of
Bed 4

Figure 5.6 Pore water pressure distribution during 240 kPa 1-D consolidation of
Bed 5

Figure 5.7 The final transducer locations of Bed 1

Figure 5.8 The final transducer locations of Bed 2

Figure 5.9 The final transducer locations of Bed 3

Figure 5.10 The final transducer locations of Bed 4

Figure 5.11 The final transducer locations of Bed 5

Figure 5.12 Fluctuation of top and side cell pressures during a rapid pile load test

Figure 5.13 Changes of pore pressures in the clay bed due to the drop of the top cell
pressure

Figure 5.14 Changes of pore pressures in the clay bed due to the drop of the top cell
pressure over a period of 200ms


Figure 6.1 Load-settlement curves for a CRP test at a rate of 0.01mm/s
(B2/7/CRP-0.01)

Figure 6.2 Load-settlement curves and pile penetration and velocity with time for a
CRP test at a rate of 200mm/s. (B2/6/CRP-200)

Figure 6.3 Load, settlement, pile velocity, and pile acceleration variation with time
for a statnamic pile load test (B2/9/STN-35)

Figure 6.4 Load – settlement curve and load and settlement variation with time for a
maintained load test (B2/13/MLT)

Figure 6.5 Skin friction load cell values for tests B1/1/CRP-0.01 and B1/2/CRP-100

Figure 6.6 Skin friction load cell values for tests B2/4/CRP-0.01 and B2/7/CRP-100




xv
Figure 6.7 Skin friction load cell values for tests B3/21/CRP-0.01 and
B3/18/CRP-100

Figure 6.8 Skin friction load cell values for tests B4/5/CRP-0.01 and B4/2/CRP-100

Figure 6.9 Skin friction load cell values for tests B5/15/CRP-0.01 and
B5/14/CRP-100

Figure 6.10 Application of Gibson and Coyle’s model for pile load tests in Bed 2
(B1/1/CRP-0.01 and B1/4/STN-15)

Figure 6.11 Application of Randolph and Deeks’ model for pile load tests in Bed 1
(B1/1/CRP-0.01 and B1/4/STN-15)

Figure 6.12 Application of Balderas-Meca’s model for pile load tests in Bed 1
(B1/1/CRP-0.01 and B1/4 /STN-15)

Figure 6.13 Application of Gibson and Coyle’s model for pile load tests in Bed 2
(B2/12/CRP-0.01 and B2/10 /STN-38)

Figure 6.14 Application of Randolph and Deeks’ model for pile load tests in Bed 2
(B2/12/CRP-0.01 and B2/10/STN-38)

Figure 6.15 Application of Balderas-Meca’s model for pile load tests in Bed 2
(B2/12/CRP-0.01 and B2/10/STN-38)

Figure 6.16 Application of Gibson and Coyle’s model for pile load tests on Bed 3
(B3/6/CRP-0.01 and B3/5/CRP-100)

Figure 6.17 Application of Randolph and Deeks’ model for pile load tests in Bed 3
(B3/6/CRP-0.01 and B3/5/CRP-100)

Figure 6.18 Application of Balderas-Meca’s model for pile load tests in Bed 3

(B3/6/CRP-0.01 and B3/5/CRP-100)

Figure 6.19 Application of Gibson and Coyle’s model for pile load tests in Bed 4
(B4/5/CRP-0.01 and B4/2/CRP-100)

Figure 6.20 Application of Randolph and Deeks’ model for pile load tests in Bed 4
(B4/5/CRP-0.01 and B4/2/CRP-100)

Figure 6.21 Application of Balderas-Meca’s model for pile load tests in Bed 4
(B4/5/CRP-0.01 and B4/2/CRP-100)

Figure 6.22 Application of Gibson and Coyle’s model for pile load tests in Bed 5
(B5/15/CRP-0.01 and B5/14/CRP-100)

Figure 6.23 Application of Randolph and Deeks’ model for pile load tests in Bed 5
(B5/15/CRP-0.01 and B5/14/CRP-100)



xvi
Figure 6.24 Application of Balderas-Meca’s model for pile load tests in Bed 5
(B5/15/CRP-0.01 and B5/14/CRP-100)

Figure 6.25 Application of Equation 6.6 for the ultimate pile shaft resistance
(Bed 2)

Figure 6.26 Application of Equation 6.6 for the ultimate pile shaft resistance
(Bed 3)

Figure 6.27 Application of Equation 6.6 for the ultimate pile shaft resistance

(Bed 4)

Figure 6.28 Application of Equation 6.6 for the ultimate pile shaft resistance
(Bed 5)

Figure 6.29 Application of Equation 6.6 for the ultimate pile shaft resistance
(Beds 1 to 5)

Figure 6.30 Application of the proportional exponent soil model for pile load tests in
Bed 1 (B1/1/CRP-0.01 and B1/2/CRP-100)

Figure 6.31 Application of the proportional exponent soil model for pile load tests in
Bed 1 (B1/1/CRP-0.01 and B1/4/STN-15)

Figure 6.32 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/7/CRP-0.01 and B2/3/CRP-50)

Figure 6.33 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/7/CRP-0.01 and B2/4/CRP-100)

Figure 6.34 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/7/CRP-0.01 and B2/5/CRP-150)

Figure 6.35 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/7/CRP-0.01 and B2/6/CRP-200)

Figure 6.36 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/12/CRP-0.01 and B2/8/STN-30)

Figure 6.37 Application of the proportional exponent soil model for pile load tests in

Bed 2 (B2/12/CRP-0.01 and B2/9/STN-35)

Figure 6.38 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/12/CRP-0.01 and B2/10/STN-38)

Figure 6.39 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/12/CRP-0.01 and B2/11/CRP-300)

Figure 6.40 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/20/CRP-0.01 and B2/18/CRP-400)


xvii
Figure 6.41 Application of the proportional exponent soil model for pile load tests in
Bed 2 (B2/20/CRP-0.01 and B2/19/CRP-150)

Figure 6.42 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/1/CRP-0.01, B3/6/CRP-0.01 and B3/3/CRP-25)

Figure 6.43 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/1/CRP-0.01, B3/6/CRP-0.01 and B3/4/CRP-50)

Figure 6.44 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/1/CRP-0.01, B3/6/CRP-0.01 and B3/5/CRP-100)

Figure 6.45 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/6/CRP-0.01 and B3/7/CRP-150)

Figure 6.46 Application of the proportional exponent soil model for pile load tests on
Bed 3 (B3/6/CRP-0.01, B3/15/CRP-0.01 and B3/8/STN-30)

Figure 6.47 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/6/CRP-0.01, B3/15/CRP-0.01 and B3/9/CRP-200)

Figure 6.48 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/6/CRP-0.01, B3/15/CRP-0.01 and B3/10/STN-35)

Figure 6.49 Application of the proportional exponent soil model for pile load tests in
Bed 3(B3/6/CRP-0.01, B3/15/CRP-0.01 and B3/12/CRP-250)

Figure 6.50 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/15/CRP-0.01 and B3/13/STN-38)

Figure 6.51 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/21/CRP-0.01 and B3/16/CRP-300)

Figure 6.52 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/21/CRP-0.01 and B3/17/CRP-200)

Figure 6.53 Application of the proportional exponent soil model for pile load tests in
Bed 3 (B3/21/CRP-0.01 and B3/18/CRP-100)

Figure 6.54 Application of the proportional exponent soil model for pile load tests on
Bed 4 (B4/5/CRP-0.01 and B4/2/CRP-100)

Figure 6.55 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/5/CRP-0.01 and B4/3/CRP-150)

Figure 6.56 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/5/CRP-0.01 and B4/4/CRP-200)

Figure 6.57 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/5/CRP-0.01, B4/8/CRP-0.01 and B4/7/STN-30)


xviii
Figure 6.58 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/10/CRP-0.01 and B4/9/CRP-300)

Figure 6.59 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/10/CRP-0.01 and B4/11/STN-35)

Figure 6.60 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/11/CRP-0.01 and B4/12/CRP-400)

Figure 6.61 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/13/CRP-0.01 and B4/14/CRP-50)

Figure 6.62 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/17/CRP-0.01 and B4/15/CRP-25)

Figure 6.63 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/17/CRP-0.01 and B4/16/CRP-125)

Figure 6.64 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/19/CRP-0.01 and B4/18/CRP-100)

Figure 6.65 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/22/CRP-0.01 and B4/20/CRP-150)

Figure 6.66 Application of the proportional exponent soil model for pile load tests in
Bed 4 (B4/22/CRP-0.01 and B4/26/CRP-50)

Figure 6.67 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/1/CRP-0.01 and B5/2/CRP-100)

Figure 6.68 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/5/CRP-0.01 and B5/4/CRP-75)

Figure 6.69 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/5/CRP-0.01 and B5/7/STN-20)

Figure 6.70 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/13/CRP-0.01, B5/15/CRP-0.01 and B5/14/CRP-100)

Figure 6.71 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/18/CRP-0.01 and B5/17/STN-25)

Figure 6.72 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/20/CRP-0.01 and B5/21/CRP-100)

Figure 6.73 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/24/CRP-0.01 and B5/22/CRP-300)

Figure 6.74 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/24/CRP-0.01 and B5/23/CRP-200)


xix
Figure 6.75 Application of the proportional exponent soil model for pile load tests in

Bed 5 (B5/24/CRP-0.01 and B5/25/CRP-150)

Figure 6.76 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/24/CRP-0.01 and B5/26/STN-30)

Figure 6.77 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/24/CRP-0.01 and B5/27/STN-32)

Figure 6.78 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/30/CRP-0.01 and B5/28/STN-35)

Figure 6.79 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/30/CRP-0.01 and B5/29/STN-34)

Figure 6.80 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/30/CRP-0.01 and B5/31/CRP-125)

Figure 6.81 Application of the proportional exponent soil model for pile load tests in
Bed 5 (B5/30/CRP-0.01 and B5/32/CRP-50)

Figure 6.82 Comparison between the new model and Randolph & Deeks model
(B4/4/CRP-0.01 and B4/5/CRP-200)

Figure 6.83 Comparison between the new model and Randolph & Deeks model
(B4/10/CRP-0.01 and B4/11/STN-35)

Figure 6.84 Post peak softening effects in CRP tests at a penetration rate of 0.01mm/s
(Bed 1)

Figure 6.85 Post peak softening effects in CRP tests at high penetration rates (Bed 1)

Figure 6.86 Post peak softening effects in CRP tests at a penetration rate of 0.01mm/s
(Bed 2)

Figure 6.87 Post peak softening effects in CRP tests at high penetration rates (Bed 2)

Figure 6.88 Post peak softening effects in CRP tests at a penetration rate of 0.01mm/s
(Bed 3)

Figure 6.89 Post peak softening effects in CRP tests at high penetration rates (Bed 3)

Figure 6.90 Post peak softening effects in CRP tests at a penetration rate of 0.01mm/s
(Bed 4)

Figure 6.91 Post peak softening effects in CRP tests at high penetration rates (Bed 4)

Figure 6.92 Post peak softening effects in CRP tests at a penetration rate of 0.01mm/s
(Bed 5)



xx
Figure 6.93 Post peak softening effects in CRP tests at high penetration rates (Bed 5)

Figure 6.94 Pile tip load-settlement curves (B4/5/CRP-0.01 and B4/16/CRP-125)

Figure 6.95 Pile tip load cell and its working mechanism

Figure 6.96 Application of the proportional exponent soil model for the total pile load
(B1/1/CRP-0.01 and B1/4/STN-15)

Figure 6.97 Application of the proportional exponent soil model for the total pile load
(B2/12/CRP-0.01 and B2/9/STN-35)

Figure 6.98 Application of the proportional exponent soil model for the total pile load
(B3/13/CRP-0.01 and B3/17/CRP-200)

Figure 6.99 Application of the proportional exponent soil model for the total pile load
(B4/5/CRP-0.01 and B4/3/CRP-150)

Figure 6.100 Application of the proportional exponent soil model for the total pile
load (B5/13/CRP-0.01 and B5/14/CRP-100)

Figure 6.101 Application of the proportional exponent soil model for the total pile
load (Brown, 2004 data)

Figure 6.102 A simple model for the vertical soil deformation

Figure 6.103 Application of the linear and non-linear models for pile shaft load
transfer mechanism. (B2/1/CRP-0.01)

Figure 6.104 Application of the linear and non-linear models for pile shaft load
transfer mechanism. (B2/7/CRP-0.01)

Figure 6.105 Application of the linear and non-linear models for pile shaft load
transfer mechanism. (B2/6/CRP-200)

Figure 6.106 Application of the non-linear models for pile shaft load transfer
mechanism. (B2/11/CRP-300)

Figure 6.107 Application of the non-linear models for pile shaft load transfer
mechanism. (B4/3/CRP-150)

Figure 6.108 Load-settlement curves for the CRP pile test at the rate of 0.01mm/s and
the maintained pile load test. (B2/12/CRP-0.01 and B2/13/MLT)

Figure 6.109 Load-settlement curves for the maintained pile load tests. (B2/13/MLT
and B2/14/MLT)

Figure 6.110 Load-settlement curves for the CRP pile test at the rate of 0.01mm/s and
the maintained pile load test. (B3/21/CRP-0.01 and B3/22/MLT)



xxi
Figure 6.111 Load-settlement curves for the CRP pile test at the rate of 0.01mm/s and
the maintained pile load test. (B5/34/CRP-0.01 and B5/35/MLT)

Figure 6.112 Changes of pore pressure measured the transducer at the pile shaft
during CRP tests at the rate of 0.01mm/s

Figure 6.113 Changes of pore pressure measured by the transducers around the pile
shaft during CRP tests at the rate of 0.01mm/s

Figure 6.114 Changes of pore pressures measured by the transducer at the pile tip
during CRP tests at the rate of 0.01mm/s

Figure 6.115 Changes of pore pressure measured by the transducers below the
pile tip during CRP tests at the rate of 0.01mm/s

Figure 6.116 Excess pore pressures during a maintained load test (B2/13/MTL)

Figure 6.117 Changes of pore pressure measured by the transducer at the pile shaft
during rapid pile load tests

Figure 6.118 Changes of pore pressure measured by the transducers around the pile
shaft during rapid pile load tests

Figure 6.119 Changes of pore pressure measured by the transducer at the pile tip
during rapid load tests

Figure 6.120 Changes of pore pressure measured by the transducer below the pile
tip during a rapid pile load test

Figure 6.121 Measured clay bed accelerations (B2/9/STN-35)

Figure 6.122 Measured clay bed accelerations (B3/10/STN-35)


Figure 7.1 Borehole record (T.L.P. Ground Investigations). Borehole 1

Figure 7.2 Borehole record (T.L.P. Ground Investigations). Borehole 2

Figure 7.3 Information from SPT, CPT and SCPT at Grimsby

Figure 7.4 Statnamic field test result

Figure 7.5 Constant rate of penetration and maintained load test results

Figure 7.6 Comparison between the Unloading Point Method and static pile load

test results

Figure 7.7 Comparison between the proportional exponent model and static pile
load test results (Equation 7.6)



xxii
Figure 7.8 Comparison between the proportional exponent and proportional
multiplier models (B4/4/CRP-0.01 and B4/5/CRP-200)

Figure 7.9 Comparison between the proportional exponent and proportional
multiplier models (B4/10/CRP-0.01 and B4/11/STN-35)

Figure 7.10 Comparison between the proportional multiplier model and static pile
load test results (Equation 7.8)

Figure 7.11 Comparison between the proportional multiplier model and the
proportional multiplier model

Figure 7.12 The sensitivity of the model to P
STN
Ultimate





xxiii

L
L
I
I
S
S
T
T


O
O
F
F


S
S
Y
Y
M
M
B
B
O
O
L
L
S
S

A
A
N
N
D
D


A
A
B
B
B
B
R
R
E
E
V
V
I
I
A
A
T
T
I
I

O
O
N
N
S
S





A Skempton’s pore pressure coefficient [-]
A
b
Pile tip cross sectional area [m
2
]
A
p
Pile cross sectional area [m
2
]
B Skempton’s pore pressure coefficient [-]
C
b
Dashpot constant in Randolph & Deeks model for a pile tip [kNs/m]
D Pile diameter [m]
E Pile elasticity modulus [kN/m
2
]

F Applied load [kN]
F
a
Pile inertial force [kN]
F
d
Downward force at the pile tip in a dynamic load test or damping
resistance in The Unloading Point Method [kN]
F
d1
Downward travelling force before the interaction with pile shaft
resistance in a dynamic pile test [kN]
F
d2
Downward travelling force after the interaction with pile shaft
resistance in a dynamic pile test [kN]
F
o
Initial downward force in a dynamic pile test [kN]
F
r
Net force at a time of t = 2L/c later than the time of obtaining F
o
in
a dynamic test [kN]
F
s
Static pile resistance in The Unloading Point Method [kN]
F
soil

Total pile load in the Unloading Point Method [kN]
F
STN
Applied load in a statnamic pile test [kN]
Fu Reflected upward force at the pile tip in a dynamic load test [kN]
F
u1
Upward travelling force before the interaction with pile shaft
resistance in a dynamic pile test [kN]
F
u2
Upward travelling force after the interaction with pile shaft
resistance in a dynamic pile test [kN]
F
ur
Return upward force at a time t = 2L/c later than the time at which
the initial downward force was obtained in a dynamic test [kN]
G Soil shear modulus [kN/m
2
]

xxiv
G
i
Initial soil shear modulus at small strain [kN/m
2
]
I
b
Influence coefficient in Randolph and Wroth model to

calculate pile base settlement [-]
I
p
Plasticity index [-]
I
r
Rigidity index of soil [G/c
u
] [-]
J
s
Smith damping factor [s/m]
J
T
Gibson & Coyle damping factor [(s/m)
N
]
K
b
Spring stiffness in Randolph & Deeks model for a pile tip [kN/m]
K
h
Lateral pressure coefficient [-]
K
J
Janbu constant [-]
L Pile length [m]
M Pile mass [tonne]
M
b

Lumped mass in Randolph & Deeks model for a pile tip [tonne]
N Gibson & Coyle damping coefficient [-]
N
b
Pile tip bearing capacity factor [-]
N
w
Wave number [-]
Q
b
Pile tip bearing capacity [kN]
Q
d
Damping component at the pile tip [kN]
Q
u1
, Q
u2
Ultimate pile capacities reached in times of failure t
1
and t
2
[kN]
R
f
Stress-strain curve-fitting constant [-]
R
s
Static resistance [kN]
R

t
Total dynamic resistance [kN]
S
u
Undrained shear strength of clay [kN/m
2
]
S
uo
Undrained shear strength corresponding to the standard
peripheral velocity [kN/m
2
]
T Time for the stress wave to travel from a pile head to its toe
and come back the pile head in a dynamic load test [s]
T
s
Pile shat resistance in a dynamic load test [kN]
V Volume [m
3
]
Z Pile impedance [m/kNs]
a Acceleration [m/s
2
]
c Stress wave velocity in a dynamic pile test or the damping
coefficient in The Unloading Point Method [m/s]
c
u
Undrained shear strength of soil [kN/m

2
]

xxv
c
ub
Undrained shear strength of the soil at the vicinity of a pile tip [kN/m
2
]
j
c
Case damping coefficient [(kNs/m)
2
]
k
f
Final spring stiffness in Ramberg-Osgood model [kN/m]
k
o
Initial spring stiffness in Ramberg-Osgood model [kN/m]
k
1
Dayal & Allen damping constant [-]
m
s
Order of the curve in Ramberg-Osgood model [-]
n Briaud & Garland viscous exponent [-]
n
J
Janbu constant [-]

p
a
Atmosphere pressure [kPa]
p
f
Load corresponding to yield point in Ramberg-Osgood model [kN]
q
d
Dynamic deviator stress in a triaxial test [kN/m
2
]
q
s
Assumed static deviator stress in a triaxial test or pile shaft quake
[kN/m
2
]
q
b
Pile base quake [m]
r Radial distance from a pile [m]
r
m
Radius of the influence zone around a pile shaft [m]
u Pore water pressure or the particle displacement in a dynamic
pile test [kPa]
Δu Excess pore water pressure [kPa]
v Velocity [m/s]
Δv Relative velocity between a pile and the adjacent soil [m/s]
v

d
Downward component of the particle velocity in a dynamic test [m/s]
v
o
Reference velocity [m/s]
v
od
Original net velocity in a dynamic load test [m/s]
v
p
Peripheral velocity of a shear vane test [m/s]
v
po
Standard peripheral velocity of a shear vane test [m/s]
v
s
Assumed static shearing rate [m/s]
v
r
Net velocity at a time of t = 2L/c later than the time of obtaining
v
od
in a dynamic pile test [m/s]
v
u
Upward component of the particle velocity in a dynamic pile test [m/s]
v
x
Temporary maximum velocity in Gibson/GRL method for a dynamic
pile test [m/s]

w Displacement [m]