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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
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
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 pileshaft 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
6.6.2 Modifications to the existing modelsfor 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
8.2 Main conclusions . .269
8.3 Recommendations for further studies . .273
REFERENCES .275
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effects are ignored. Plus, the soil was assumed to be incompressible and therefore
based on the volume conservation of the soil under the penetration of an indenter, the
velocity functions for soil particles are determined. Once the velocity functions are
determined the soil deformations can be established by integration of the velocity
functions along the streamlines. Likewise, other components of the soil deformation
are determined, such as strain rate and stain paths. To calculate the stresses and pore
water pressures soil models were proposed in which stresses can be calculated once
the strains are determined. The main steps to determine stresses and pore water
pressures are shown in Figure 2.27.
In comparison, the two approaches give a similar pattern of field displacement except
for the zone near the pile shaft (about 10% of the pile radius) and the zone near the
pile tip (few diameters close to the pile tip) (Randolph, 2003).
Chapter 2 Literature review
39
Several projects in which instrumented model piles with the capability of measuring
shaft, tip resistances and pore water pressure were carried out to validate these
theories. Coop and Wroth (1989) used an instrumented model pile, 80 mm in diameter
and 1135 in length, with the capability of measuring pile shaft resistance and pore
water pressures at the pile tip and shaft. Two test-bed sites, one with heavily
overconsolidated clay and one with normally consolidated clay, were chosen for the
experiments. The data showed that pore water pressures were far lower than the cavity
expansion prediction and fluctuated much more widely than the theory predicted.
Bond and Jardine (1991) carried out experiments using instrumented model piles in a
clay where overconsolidation ratio varied from 50 to 20 with depth. Large negative
pore pressures had occurred during pile installation and the cavity theory could not be
applied. In comparison with the strain path method, they concluded that the method
achieved a similar shape of shear strain distribution. However, the strain path method
underpredicted the measured strains. It was suggested that the possible reason for this
was the discrepancy of the roughness between the pile and the soil around it. In the
strain path method there is an assumption of a perfectly smooth boundary between the
pile and the soil. No comparison between the measured and strain path method
prediction of pore water pressures was reported.
Several attempts have been made to measure the pore water pressure changes during
statnamic load tests. However, no theoretical analyses have been used to try to
quantify these changes. Hajduk et al. (2000) published the results of a series of
statnamic load tests which were carried out for two heavily instrumented piles.
However, only the results of pore water pressures for one pile were reported. The pore
water pressures along the piles were measured by four pore water transducers
mounted at different levels (5 m, 10, 15, 20 m from the pile top). The first one was
positioned in overconsolidated clay with an initial pore pressure value of 32 kPa, the
second in soft normally consolidated clay with an initial pore pressure value of 80
kPa, the third in normally consolidated clay with an initial pore pressure value of 135
kPa, and the final in silty sand with an initial pore pressure value of 192 kPa. Six
statnamic tests were carried out on this pile over 2 hours. All pore water transducers
indicated the same trend. Pore pressures dropped during each test (2-10 kPa for the
first transducer, 3-8 kPa for the second, 3-9 for the third, and 4-16 kPa for the final)
Chapter 2 Literature review
40
and then recovered when the tests finished. However, due to six tests being carried in
a two hour period the pore water pressures after one test did not recover to the prior
test value before the next test. Maeda et al. (2000) published the results of a statnamic
test for a cast-in-place concrete pile diameter of 1.2 m and length of 13.4 m with
measurement of pore water pressure at the pile tip which was in gravelly sand. During
the test excess pore water pressure increased simultaneously with applied statnamic
load by up to 80 kPa then dissipated immediately after the test. Conversely, negative
pore water pressures at the pile tip developed during statnamic load tests for steel pipe
piles 216.3mm in diameter, 4.5 m in length which were installed in sand (Ishida et al.
2000).
2.9 Summary
From the literature review, the main points related to this study are as follow:
♦ Theoretical approaches for predicting the pile capacity have advanced significantly.
However, pile load testing methods still play an important role in pile design and for
research purposes.
♦ The development of the statnamic pile testing method shows the innovative and
promising potential of the method. However, further attention needs to be given to the
rate effects and the pore pressure regime around the pile during testing and after a
statnamic test.
♦ A large number of studies have examined rate effects. In general, an exponential
increase of shear capacity with respect to shearing velocity has been proposed.
However, different studies have the relationship in different forms. Attention has
usually been given to rate effect on the ultimate shear strength whereas rate effects on
the shearing resistance prior to failure have received less attention.
♦ The exponent value in the rate effect equation for clays, i.e. damping parameter β,
can be taken as 0.2 as this value has been proposed by several researchers who have
investigated a wide range of clays (reconstituted clay with w = 17%-20%, wP = 17%,
wL = 37% and undisturbed glacial clay at a site near Grimsby, UK with w = 13% -
25%, wP = 12% - 18%, wL = 20 – 36% by Balderas-Meca, 2004; London clay wP =
27, wL = 70, Magnus clay with wP = 17%, wL = 31%, and Forties clay from the North
sea with wP = 20, wL = 38% by Litkouhi and Poskitt, 1980; overconsolidated clay
Chapter 2 Literature review
41
from Heather and Claymore in the NorthSea and Kontich clay, Belgium by Heerema,
1979).
♦ Quake values for pile shaft and base have been studied by several researchers.
Nevertheless, no clear mechanism of quake values for dynamic or statnamic tests has
been reported.
♦ Several models have been proposed to predict the pore water pressures around the
pile during pile installation. Among them, cavity expansion theory and the strain path
method are the most widely used. The cavity theory is easy to apply due to its
simplicity. However, it seems not to provide a good match with the measured data
(Coop & Wroth, 1989; Bond & Jardine 1991). In particular, it fails to predict the
changing of pore water pressure for heavily overconsolidated clays when negative
pore water pressures occur due to shearing. On the other hand, the strain path method
seems to provide a better prediction. However, a sound model for soil with many
parameters are required for the method and due to the difficulty in specifying this
model, the method is less popular.
Chapter 2 Literature review
42
Soil type in bearing
strata
Suggested range
of Jc
Correlation value
of Jc
Sand
Silty sand/sandy silt
Silt
Silty clay/clayey silt
Clay
0.05 – 0.20
0.15 - 0.30
0.20 – 0.45
0.40 – 0.70
0.60 – 1.10
0.05
0.15
0.30
0.55
1.10
Table 2.2 Case damping coefficient for different soil types
(Fleming et al. 1992)
Table 2.1 Damping parameter in Dayal and Allen study
(Dayal and Allen, 1975)
Shear strength
Low velocity High velocity
(kPa) less than152 (mm/s) above 305 (mm/s)
3 0.38 0.93
45.09 0.31 0.75
49.97 0.24 0.66
78.33 0.17 0.38
Damping coefficient (k1)
Chapter 2 Literature Review
43
Figure 2.1 O-Cell Figure 2.2 Schematic arrangement of a
Osterberg test (Osterberg & Pepper, 1984)
Transducer
feedback
amplifier
Load cell
Actuator
LVDT
Electro-
pneumatic
servo
valve
Comparator
Error
amplifier
Command
signal
CDAS
Sample
Error
signal
Pressure
supply
Current
Figure 2.3 Balderas-Meca’s test apparatus arrangement.
(Balderas-Meca, 2004)
Chapter 2 Literature Review
44
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6 7 8
Axial strain %
D
am
pi
ng
c
oe
ffi
ci
en
t α
Figure 2.4 Damping coefficient, α, versus axial strain for monotonic
consolidated undrained triaxial tests at different rates. (β=0.20; OCR=1)
(Balderas-Meca, 2004)
Figure 2.5 Half steel tube with semi-circular soil sample
(Heerema, 1979)
Chapter 2 Literature Review
45
Figure 2.6 The shear device for the study of pile-soil interfaces (Chin, 2004)
Shear
box
Pile on
carriage
A...
Download miễn phí Luận văn Statnamic testing of piles in clay
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
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
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 pileshaft 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
6.6.2 Modifications to the existing modelsfor 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
8.2 Main conclusions . .269
8.3 Recommendations for further studies . .273
REFERENCES .275
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Tóm tắt nội dung:
viscoelastic and inertialeffects are ignored. Plus, the soil was assumed to be incompressible and therefore
based on the volume conservation of the soil under the penetration of an indenter, the
velocity functions for soil particles are determined. Once the velocity functions are
determined the soil deformations can be established by integration of the velocity
functions along the streamlines. Likewise, other components of the soil deformation
are determined, such as strain rate and stain paths. To calculate the stresses and pore
water pressures soil models were proposed in which stresses can be calculated once
the strains are determined. The main steps to determine stresses and pore water
pressures are shown in Figure 2.27.
In comparison, the two approaches give a similar pattern of field displacement except
for the zone near the pile shaft (about 10% of the pile radius) and the zone near the
pile tip (few diameters close to the pile tip) (Randolph, 2003).
Chapter 2 Literature review
39
Several projects in which instrumented model piles with the capability of measuring
shaft, tip resistances and pore water pressure were carried out to validate these
theories. Coop and Wroth (1989) used an instrumented model pile, 80 mm in diameter
and 1135 in length, with the capability of measuring pile shaft resistance and pore
water pressures at the pile tip and shaft. Two test-bed sites, one with heavily
overconsolidated clay and one with normally consolidated clay, were chosen for the
experiments. The data showed that pore water pressures were far lower than the cavity
expansion prediction and fluctuated much more widely than the theory predicted.
Bond and Jardine (1991) carried out experiments using instrumented model piles in a
clay where overconsolidation ratio varied from 50 to 20 with depth. Large negative
pore pressures had occurred during pile installation and the cavity theory could not be
applied. In comparison with the strain path method, they concluded that the method
achieved a similar shape of shear strain distribution. However, the strain path method
underpredicted the measured strains. It was suggested that the possible reason for this
was the discrepancy of the roughness between the pile and the soil around it. In the
strain path method there is an assumption of a perfectly smooth boundary between the
pile and the soil. No comparison between the measured and strain path method
prediction of pore water pressures was reported.
Several attempts have been made to measure the pore water pressure changes during
statnamic load tests. However, no theoretical analyses have been used to try to
quantify these changes. Hajduk et al. (2000) published the results of a series of
statnamic load tests which were carried out for two heavily instrumented piles.
However, only the results of pore water pressures for one pile were reported. The pore
water pressures along the piles were measured by four pore water transducers
mounted at different levels (5 m, 10, 15, 20 m from the pile top). The first one was
positioned in overconsolidated clay with an initial pore pressure value of 32 kPa, the
second in soft normally consolidated clay with an initial pore pressure value of 80
kPa, the third in normally consolidated clay with an initial pore pressure value of 135
kPa, and the final in silty sand with an initial pore pressure value of 192 kPa. Six
statnamic tests were carried out on this pile over 2 hours. All pore water transducers
indicated the same trend. Pore pressures dropped during each test (2-10 kPa for the
first transducer, 3-8 kPa for the second, 3-9 for the third, and 4-16 kPa for the final)
Chapter 2 Literature review
40
and then recovered when the tests finished. However, due to six tests being carried in
a two hour period the pore water pressures after one test did not recover to the prior
test value before the next test. Maeda et al. (2000) published the results of a statnamic
test for a cast-in-place concrete pile diameter of 1.2 m and length of 13.4 m with
measurement of pore water pressure at the pile tip which was in gravelly sand. During
the test excess pore water pressure increased simultaneously with applied statnamic
load by up to 80 kPa then dissipated immediately after the test. Conversely, negative
pore water pressures at the pile tip developed during statnamic load tests for steel pipe
piles 216.3mm in diameter, 4.5 m in length which were installed in sand (Ishida et al.
2000).
2.9 Summary
From the literature review, the main points related to this study are as follow:
♦ Theoretical approaches for predicting the pile capacity have advanced significantly.
However, pile load testing methods still play an important role in pile design and for
research purposes.
♦ The development of the statnamic pile testing method shows the innovative and
promising potential of the method. However, further attention needs to be given to the
rate effects and the pore pressure regime around the pile during testing and after a
statnamic test.
♦ A large number of studies have examined rate effects. In general, an exponential
increase of shear capacity with respect to shearing velocity has been proposed.
However, different studies have the relationship in different forms. Attention has
usually been given to rate effect on the ultimate shear strength whereas rate effects on
the shearing resistance prior to failure have received less attention.
♦ The exponent value in the rate effect equation for clays, i.e. damping parameter β,
can be taken as 0.2 as this value has been proposed by several researchers who have
investigated a wide range of clays (reconstituted clay with w = 17%-20%, wP = 17%,
wL = 37% and undisturbed glacial clay at a site near Grimsby, UK with w = 13% -
25%, wP = 12% - 18%, wL = 20 – 36% by Balderas-Meca, 2004; London clay wP =
27, wL = 70, Magnus clay with wP = 17%, wL = 31%, and Forties clay from the North
sea with wP = 20, wL = 38% by Litkouhi and Poskitt, 1980; overconsolidated clay
Chapter 2 Literature review
41
from Heather and Claymore in the NorthSea and Kontich clay, Belgium by Heerema,
1979).
♦ Quake values for pile shaft and base have been studied by several researchers.
Nevertheless, no clear mechanism of quake values for dynamic or statnamic tests has
been reported.
♦ Several models have been proposed to predict the pore water pressures around the
pile during pile installation. Among them, cavity expansion theory and the strain path
method are the most widely used. The cavity theory is easy to apply due to its
simplicity. However, it seems not to provide a good match with the measured data
(Coop & Wroth, 1989; Bond & Jardine 1991). In particular, it fails to predict the
changing of pore water pressure for heavily overconsolidated clays when negative
pore water pressures occur due to shearing. On the other hand, the strain path method
seems to provide a better prediction. However, a sound model for soil with many
parameters are required for the method and due to the difficulty in specifying this
model, the method is less popular.
Chapter 2 Literature review
42
Soil type in bearing
strata
Suggested range
of Jc
Correlation value
of Jc
Sand
Silty sand/sandy silt
Silt
Silty clay/clayey silt
Clay
0.05 – 0.20
0.15 - 0.30
0.20 – 0.45
0.40 – 0.70
0.60 – 1.10
0.05
0.15
0.30
0.55
1.10
Table 2.2 Case damping coefficient for different soil types
(Fleming et al. 1992)
Table 2.1 Damping parameter in Dayal and Allen study
(Dayal and Allen, 1975)
Shear strength
Low velocity High velocity
(kPa) less than152 (mm/s) above 305 (mm/s)
3 0.38 0.93
45.09 0.31 0.75
49.97 0.24 0.66
78.33 0.17 0.38
Damping coefficient (k1)
Chapter 2 Literature Review
43
Figure 2.1 O-Cell Figure 2.2 Schematic arrangement of a
Osterberg test (Osterberg & Pepper, 1984)
Transducer
feedback
amplifier
Load cell
Actuator
LVDT
Electro-
pneumatic
servo
valve
Comparator
Error
amplifier
Command
signal
CDAS
Sample
Error
signal
Pressure
supply
Current
Figure 2.3 Balderas-Meca’s test apparatus arrangement.
(Balderas-Meca, 2004)
Chapter 2 Literature Review
44
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6 7 8
Axial strain %
D
am
pi
ng
c
oe
ffi
ci
en
t α
Figure 2.4 Damping coefficient, α, versus axial strain for monotonic
consolidated undrained triaxial tests at different rates. (β=0.20; OCR=1)
(Balderas-Meca, 2004)
Figure 2.5 Half steel tube with semi-circular soil sample
(Heerema, 1979)
Chapter 2 Literature Review
45
Figure 2.6 The shear device for the study of pile-soil interfaces (Chin, 2004)
Shear
box
Pile on
carriage
A...