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Preloading effects on dynamic sand behavior by resonant column tests [Elektronische Ressource] / vorgelegt von Lidong Bai

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237 pages
Preloading Effects on Dynamic Sand Behavior by Resonant Column Tests vorgelegt von Master of Science Lidong Bai aus Guizhou, China von der Fakultät VI - Planen Bauen Umwelt der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktor der Ingenieurwissenschaften (Dr.-Ing.) genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr.-Ing. Y. Petryna Berichter: Prof. S. Savidis Dr.-Ing. C. Vrettos Tag der wissenschaftlichen Aussprache: 13. Dezember 2010 Berlin 2011 D83 To My Wife, Wei Wei for her support and understanding My father, Zuoguang Bai for his encouragement My mother, Jianv Jia for her endurance and love My brothers, Liling Bai and Hai Bai for their support, understanding and looking after parents ACKNOWLEDGMENTS I would like to thank my supervisor, Professor Dr.-Ing. Stavros A. Savidis, the dean of Faculty VI of Technical University of Berlin (TU Berlin), for his guidance, training, patience, and friendship, his research and work attitude greatly impresses me. I owe him my deepest respect and appreciation. I also would like to thank Dr.-Ing. Frank Rackwitz for his assistance, comments, friendship, and arranging a lot of work for my testing in the laboratory. Special appreciation is given to my second supervisor, Professor Dr.-Ing.
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Preloading Effects on Dynamic Sand Behavior by
Resonant Column Tests

vorgelegt von
Master of Science
Lidong Bai
aus Guizhou, China

von der Fakultät VI - Planen Bauen Umwelt
der Technischen Universität Berlin
zur Erlangung des akademischen Grades

Doktor der Ingenieurwissenschaften
(Dr.-Ing.)

genehmigte Dissertation
Promotionsausschuss:
Vorsitzender: Prof. Dr.-Ing. Y. Petryna
Berichter: Prof. S. Savidis Dr.-Ing. C. Vrettos

Tag der wissenschaftlichen Aussprache: 13. Dezember 2010

Berlin 2011
D83


To



My Wife, Wei Wei
for her support and understanding

My father, Zuoguang Bai
for his encouragement

My mother, Jianv Jia
for her endurance and love

My brothers, Liling Bai and Hai Bai
for their support, understanding and looking after parents


ACKNOWLEDGMENTS


I would like to thank my supervisor, Professor Dr.-Ing. Stavros A. Savidis, the dean
of Faculty VI of Technical University of Berlin (TU Berlin), for his guidance, training,
patience, and friendship, his research and work attitude greatly impresses me. I owe
him my deepest respect and appreciation. I also would like to thank Dr.-Ing. Frank
Rackwitz for his assistance, comments, friendship, and arranging a lot of work for my
testing in the laboratory. Special appreciation is given to my second supervisor,
Professor Dr.-Ing. Christos Vrettos from Technical University of Kaiserslautern for
his constructive suggestions to improve this thesis, sincere acknowledgments also are
extended to Professor Y. Petryna, the chairman of the academic degree commission
for his encouragement. I am also greatly indebted to Professor Wei Xiang of China
University of Geosciences (Wuhan) for his encouragement during my study at TU
Berlin.

The financial support of my study abroad was provided by China Scholarship Council
(CSC) and TU Berlin which is gratefully acknowledged.

Special words of appreciation go to laboratory technicians Mr. Harald Lorenz, Mr.
Harald Podeswa, Mr. Boguslav Grzedzinski for their assistance in instrument
modification and some additional tests. Great appreciation also goes to Mr. Jerry
Sutton from GDS Instruments Limited for his valuable suggestions to install the
testing system. I also thank diplom students Ms. Asja Kühn, Ms. Juliane Stopper, and
Mr. Viet Hung Le for their assistance in the laboratory at the beginning of my study at
TU Berlin. Many thanks are extended to Mr. Dipl.-Ing. Winfried Schepers and Mr.
Dipl.-Ing. Ralf Glasenapp, Mr. Dipl.-Ing. Ercan Tasan, and other colleagues and
friends for their support and good times.

Special thanks are extended to the staffs of Education Section of China Embassy in
Germany, particularly to Minister-counselor Dr. Feng Jiang and his wife for their
great help, solicitude, friendship and encouragement.

Finally, I extend my deepest gratitude to my father, Zuoguang Bai, my mother, Jianv
Jia, my younger brothers, Liling Bai and Hai Bai and their wifes, for their love,
constant encouragement and belief in me. My endless words of gratitude go to my
beloved wife Wei Wei for her support, understanding, and sacrifice; without her I can
not make my doctoral dream come true.
1
ABSTRACT

Dynamic behavior of Berlin sand and the preloading effects on shear modulus and
damping properties of sand were investigated by resonant column tests in this study,
in addition, a new reliable calibration method for the Stokoe resonant column
apparatus is also presented. The influences of confining pressure, void ratio, water
content, sampling method, stress history, confinement duration and others on dynamic
properties of Berlin sand were examined by resonant column tests. An empirical
equation was proposed to predict the small-strain shear modulus, and two em
models were proposed to simulate the nonlinear modulus and damping properties of
Berlin sand, a brief comparison of small-strain shear modulus by resonant column and
bender element tests is addressed as well.

In this study, the author initially introduced the preloading concept to investigate
vibration history effects on dynamic sand behavior, which is quite different from the
prestraining concept conventionally employed in previous investigations. For the
preloading concept, the previous vibration applied to specimen is employed by the
non-resonant vibration mode of stress-controlled shear by resonant column apparatus.
With this concept the number of loading cycles can be enlarged to a range from one to
any desired number. By contrast the prestraining concept cannot investigate low
number of cycles due to the necessary several hundreds of cycles to determine the
resonant frequency. In addition, the use of the preloading concept can also ensure
constant preloading stress during the previbration is applied to the tested specimen at
the same vibration frequency and input drive voltage. The prestraining concept may
introduce less precision of the calculation of prestraining amplitude if the set vibration
frequency and input drive voltage are not adjusted during previbration. That is due to
variation of the resonant vibration frequency and other parameters, if the stiffness of
tested specimen varies with number of cycles, and therefore the set vibration
frequency is not the resonant frequency of the vibration system any more.

The effects of many factors which may influence the preloading effects on the
dynamic behavior of sand were fully explored in this study. One of the most important
findings is that the shear modulus or stiffness of sand decreases with number of cycles
if it does not exceed a threshold number and increases when the number of cycles
exceeds this threshold. A theoretical interpretation of the reduction of stiffness of sand
subjected to preloading was proposed herein.

Key Words: Berlin sand, shear modulus, damping ratio, resonant column test, number
of cycles, preloading frequency, unloading, reloading, water content
II


LISTS OF CONTENTS



CHAPTER 1 INTRODUCTION ...................................................................................1
1.1 Background......................................................................................................1
1.2 Objectives ........................................................................................................2
1.3 Organization.....................................................................................................3

CHAPTER 2 LITERATURE REVIEW.........................................................................4
2.1 Introduction4
2.2 Factors Influence Small-strain Shear Modulus................................................8
2.2.1 Void Ratio .............................................................................................8
2.2.2 Confining Pressure................................................................................9
2.2.3 Stress Ratio .........................................................................................12
2.2.4 Grain Characteristics...........................................................................16
2.2.5 Degree of Saturation17
2.2.6 Frequency of Loading.........................................................................18
2.2.7 Duration of Confinement ....................................................................19
2.2.8 Prestraining21
2.3 Factors Influence Nonlinear Dynamic Soil Properties ..................................24
2.3.1 Confining Pressure..............................................................................24
2.3.2 Frequency of Loading26
2.3.3 Stress Ratio .........................................................................................27
2.3.4 Number of loading cycles ...................................................................28
2.3.5 Prestraining30
2.4 Summary........................................................................................................33

CHAPTER 3 TESTING EQUIPMENT AND CALIBRATION..................................34
3.1 Introduction....................................................................................................34
3.2 Detail of Resonant Column Apparatus ..........................................................35
3.2.1 Procedure of Resonant Column Test...................................................36
3.2.2 Drive system .......................................................................................37
3.2.3 Rotation Monitoring............................................................................38
3.2.4 Confining Chamber and Cell Pressure................................................39
3.3 Resonant Column Test ...................................................................................40
3.3.1 Shear Modulus ....................................................................................40
III
3.3.2 Damping Ratio....................................................................................42
3.3.3 Shearing Strain44
3.4 Torsional Shear Test.......................................................................................47
3.5 Bender Element Test ......................................................................................48
3.6 Calibration of Drive System for Resonant Column Test ...............................51
3.6.1 Theory Background.............................................................................52
3.6.2 Calibration Bars and Weights..............................................................53
3.6.3 Testing Results ....................................................................................56
3.6.4 Mass Polar Moment of Inertia of Drive System .................................60
3.6.5 Discussion...........................................................................................61
3.6.6 Correction Procedure ..........................................................................63
3.7 Calibration of Torque for Torsional Shear Test..............................................66
3.7.1 Theory Background.............................................................................66
3.7.2 Effect of Torsional Stiffness................................................................67
3.7.3 Effect of Input Voltage........................................................................69
3.7.4 Proposed Procedure ............................................................................70
3.8 Summary........................................................................................................72

CHAPTER 4 MATERIALS AND TESTING PROCEDURES...................................73
4.1 Introduction....................................................................................................73
4.2 Properties of Testing Sands73
4.3 Specimen Preparation ....................................................................................75
4.3.1 Tamping Method.................................................................................76
4.3.2 Raining Method ..................................................................................79
4.3.3 Dimension Measurement ....................................................................79
4.3.4 Deviation in Dimension Measurement ...............................................80
4.4 Testing System Installation ............................................................................83
4.5 Testing Procedures .........................................................................................86
4.5.1 Confining Pressure..............................................................................86
4.5.2 Specimen Density ...............................................................................87
4.5.3 Water Content......................................................................................87
4.5.4 Shearing Strain Amplitude..................................................................88
4.5.5 Number of Preloading Cycles.............................................................88
4.5.6 Preloading Stress and Frequency ........................................................88
4.5.7 Pressure Release Effects .....................................................................89
4.5.8 Accumulated Axial Strain ...................................................................90
4.5.9 Bender Element Test ...........................................................................91
4.6 Summary........................................................................................................91

IV
CHAPTER 5 DYNAMIC PROPERTIES OF BERLIN SAND ..................................92
5.1 Introduction....................................................................................................92
5.2 Small-strain Shear Modulus...........................................................................92
5.2.1 Effect of Void Ratio ............................................................................93
5.2.2 Effect of Confining Pressure...............................................................95
5.2.3 Empirical Equation .............................................................................96
5.2.4 Effect of stress history.........................................................................99
5.2.5 Effect of Confinement Duration .......................................................101
5.2.6 Effect of Water Content ....................................................................102
5.2.7 Effect of Sampling Technique...........................................................104
5.3 Nonlinearity in Shear Modulus105
5.3.1 Effect of Confining Pressure.............................................................105
5.3.2 Effect of Void Ratio ..........................................................................110
5.3.3 Empirical Modeling115
5.4 Damping Properties .....................................................................................120
5.4.1 Effect of Void Ratio120
5.4.2 Effect of Confining Pressure125
5.4.3 Effect of Water Content ....................................................................127
5.5 Comparison of G by RC and BE Tests....................................................128 max
5.6 Summary......................................................................................................132

CHAPTER 6 PRELOADING EFFECTS ON DYNAMIC PROPERTIES OF SAND
....................................................................................................................................133
6.1 Introduction..................................................................................................133
6.2 Void Ratio during Testing ............................................................................133
6.2.1 Empirical Expression........................................................................134
6.2.2 Variation of Void Ratio with Number of Cycles ...............................138
6.3 Small-strain Shear Modulus Correction.......................................................139
6.4 Small-strain Shear Modulus.........................................................................144
6.4.1 Effect of Number of Cycles ..............................................................145
6.4.2 Effect of Preloading Frequency ........................................................146
6.4.3 Effect of Preloading Ratio.................................................................149
6.4.4 Effect of Void Ratio ..........................................................................152
6.4.5 Effect of Confining Pressure.............................................................153
6.4.6 Effect of Reloading ...........................................................................155
6.4.7 Effect of Unloading162
6.4.8 Effect of Water Content ....................................................................170
6.4.9 Miscellaneous Effects .......................................................................176
6.5 Nonlinear Dynamic Properties.....................................................................183
V
6.5.1 Effect of Preloading Frequency ........................................................183
6.5.2 Effect of Number of Cycles ..............................................................186
6.5.3 Effect of Reloading ...........................................................................187
6.5.4 Effect of Unloading188
6.5.5 Effect of Water Content ....................................................................191
6.5.6 Effect of Prestraining ........................................................................192
6.6 Theoretical Interpretation.............................................................................194
6.7 Summary......................................................................................................199

CHAPTER 7 CONCLUSIONS AND OUTLOOK....................................................200
7.1 Conclusions..................................................................................................200
7.1.1 Calibration.........................................................................................200
7.1.2 Dynamic Properties of Berlin Sand ..................................................200
7.1.3 Effects of Preloading on Dynamic Properties of Sand .....................201
7.2 Outlook ........................................................................................................203

BIBLIOGRAPHY......................................................................................................205

APPENDIX................................................................................................................213




















VI
LISTS OF FIGURES

Figure 2.1 Normalized modulus and damping curves with different zones of
cyclic shearing strain amplitude for soil (slightly modified from Vucetic
1994) ..............................................................................................................6
Figure 2.2 Relationship between volumetric cyclic threshold shearing strain
and modulus reduction and damping curves (Vucetic and Dobry 1991;
Vucetic 1994) .................................................................................................7
Figure 2.3 Variation of cyclic threshold shearing strain with plasticity index
from cyclic triaxial tests (from Vucetic 1994) ...............................................8
Figure 2.4 Relation between shear modulus with mean confining pressure
(Alarcon-Guzman, Chameau et al. 1989) ....................................................10
Figure 2.5 Increment of small-strain shear modulus with Stress Ratio (after
Chien and Oh 2002).....................................................................................15
Figure 2.6 Relation between parameter B and mean grain size D for clean 50
sands (after Iwasaki and Tatsuoka 1977) .....................................................16
Figure 2.7 Variation of small-strain shear modulus with degree of saturation
for Glacier Way silt (after Wu, Gray et al. 1984).........................................17
Figure 2.8 Variation of Normalized small-strain shear modulus with degree of
saturation for Glacier Way silt (after Wu, Gray et al. 1984)........................18
Figure 2.9 Variation of shear modulus and vertical strain with time for dry sand
at constant confining pressure (after Afifi and Woods 1971) ......................21
Figure 2.10 Variation in Shear Modulus and Vertical Strain with Time for Dry
Sand at Constant Confining Pressure (after Afifi and Woods 1971) ...........21
Figure 2.11 Variation of small-strain shear modulus with number of cycles at
various cyclic shear strain amplitude for hollow dry sand specimen
(Drnevich, Hall et al. 1967) .........................................................................22
Figure 2.12 Development of small-strain shear modulus with number of cycles
at various prestraining amplitude for fine sand (after Wichtmann and
Triantafyllidis 2004) ....................................................................................23
Figure 2.13 Development of small-strain shear modulus with number of cycles
at various prestraining amplitude for medium sand (after Wichtmann and
Triantafyllidis 2004)24
Figure 2.14 Variation of shear modulus with shearing strain amplitude for
Berlin sand under various confining pressures ............................................25
Figure 2.15 Effect of confining pressure on normalized shear modulus
reduction curve for sand (after Ishibashi 1992) ...........................................26
Figure 2.16 Effect of confining pressure on damping curve for silty sand (after
VII
Darendeli 2001) ...........................................................................................26
Figure 2.17 Effects of number of cycles on the location of shear modulus
curves for clean dry sand (after Hardin and Drnevich 1972).......................28
Figure 2.18 Effects of number of cycles on the location of damping curves for
clean dry sand (after Hardin and Drnevich 1972)........................................29
Figure 2.19 Effects of number of cycles on shear modulus and damping ratio
for dry sand (Li and Cai 1999).....................................................................29
Figure 2.20 Effect of number of cycles on shear modulus reduction curves
(after Drnevich and Richart 1970) ...............................................................30
Figure 2.21 Effect of prestraining on damping ratio of Ottawa sand at various
confining pressures (data from Drnevich and Richart 1970)) .....................31
Figure 2.22 Modulus and damping curves before and after 1,200,000 cycles of
vibration (after Li and Yang 1998)32
Figure 2.23 ping curves (1) shear modulus, and (2) damping
6ratio, for fine dry sand before and after 3×10 cycles of loading (after
Wichtmann and Triantafyllidis 2004) ..........................................................33
Figure 3. 1 Arrangement of the testing components of resonant column
apparatus and bender element testing instrument ........................................35
Figure 3. 2 Arrangement of main components of resonant column apparatus
and bender element testing instrument ........................................................36
Figure 3. 3 Sketch map of the configuration of the resonant column testing unit
......................................................................................................................37
Figure 3. 4 Photographs for drive system of resonant column apparatus.........38
Figure 3. 5 Sketch map for drive excitation modes for drive system ...............38
Figure 3. 6 Accelerometer and counter balance on the drive system (top view)39
Figure 3. 7 Up and bottom parts of confining chamber used in this study.......40
Figure 3. 8 Typical frequency response curve obtained from resonant column
test................................................................................................................43
Figure 3. 9 Typical free vibration decaying curve for measurement of material
damping ratio from resonant column test ....................................................44
Figure 3. 10 Diagram of the concept for torsional strain in a fixed-free cylinder
specimen ......................................................................................................45
Figure 3. 11 Concept of shear modulus and material damping ratio in torsional
shear test.......................................................................................................48
Figure 3. 12 An example of bender element insert made by GDS used in this
study.............................................................................................................49
Figure 3. 13 Configuration of bender element (left: dimension, right: inside
VIII