CENTRIFUGE AND NUMERICAL MODELLING OF THE SEISMIC RESPONSE OF PILE GROUPS IN SOFT CLAYS ZHANG LEI NATIONAL UNVERSITY OF SINGAPORE 2014 CENTRIFUGE AND NUMERICAL MODELLING OF THE SEISMIC RESPONSE OF PILE GROUPS IN SOFT CLAYS ZHANG LEI (M. Eng., SDU; B. Eng., CQU) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING NATIONAL UNVERSITY OF SINGAPORE 2014 Declaration DECLARATION I hereby declare that this thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. Zhang Lei 25 July 2014 Acknowledgements ACKNOWLEDGEMENTS It is my great pleasure to express my sincere and profound gratitude to my supervisors, Asst. Prof. Goh Siang Huat and Prof. Lee Fook Hou, for their invaluable and thorough guidance and constant support throughout this research. Their crucial advice, analytical and methodical way of working, and generous encouragement has made it possible to accomplish this research work. I have learned a lot from the discussions with Asst. Prof. Goh Siang Huat and Prof. Lee Fook Hou going over every detail of both the centrifuge test and numerical simulation. Besides, the assistances provided by Asst. Prof. Goh Siang Huat and Prof. Lee Fook Hou are also appreciated. I am extremely grateful to Dr. Banerjee Subhadeep for his generous help to give me necessary training and suggestion on the seismic centrifuge test. Dr. Banerjee Subhadeep’s help on the numerical simulation work is also greatly appreciated. Dr. Zhao Ben’s, Dr. Liu Yong’s and Dr. Yi Jiang Tao’s suggestions on the numerical simulation work and Dr. Ma Kang’s suggestions on the seismic centrifuge test are greatly appreciated. I am also very grateful to the staffs of the Geotechnical Centrifuge Laboratory at the National University of Singapore for their assistance throughout the study. Mr. Tan Lay Heng, Mr. Wong Chew Yuen and Dr. Shen Rui Fu had helped me a lot in the operation of centrifuge machine and for the improvement of experimental set-up. Mdm. Jamilah Bte Mohd, Mr. Foo Hee Acknowledgements Ann, Mr. John Choy and Mr. Loo Leong Huat also provided necessary assistance related to the experimental instrumentation components. Special thanks are given to Dr. Tang Chong, Dr. Saw Ay Lee, Dr. Ho Jia Hui, Dr. Li Yu Ping, Mr. Yang Yu, Dr. Chen Jian, Dr. Sun Jie, Dr. Xiao Hua Wen, Dr. Ye Fei Jian, Dr. Yeo Chong Hun, Dr. Tran Huu Huyen Tran, Dr. Lu Yi Tan and other my fellow graduate students in the Center for Soft Ground Engineering for the friendship and encouragement. I would also like to acknowledge NUS for providing all necessary financial and academic support throughout this study. Table of Contents TABLE OF CONTENTS TABLE OF CONTENTS ···········································································I SUMMARY ······················································································VI LIST OF TABLES ···············································································VIII LIST OF FIGURES ················································································IX LIST OF SYMBOLS ·········································································XXVII CHAPTER INTRODUCTION ································································1 1.1 Earthquake Effects on Pile Foundations in Soft Soil ······························1 1.2 Far-field Earthquake Risks in Singapore ············································3 1.3 Motivation and Objectives of This Research ········································4 1.3.1 Limitations of Conventional Seismic Design Practice ···························4 1.3.2 Previous Work by Banerjee (2009), Zhao (2013) and Others at the National University of Singapore······························································6 1.3.3 Objectives and Scope of the Present Research ····································8 1.4 Outline of This Thesis ·································································10 CHAPTER LITERATURE REVIEW ····················································18 2.1 Dynamic Soil-pile Interaction under Seismic Loading ··························18 2.1.1 Dynamic Field Tests ·······························································18 2.1.2 1-g Shaking Table Test ····························································24 I Table of Contents 2.1.3 Centrifuge Test ·····································································27 2.1.4 Simplified Analytical Methods ···················································31 2.1.5 Numerical Simulations Using FEM, FDM and BEM ··························35 2.2 Pile Group Effect ·······································································41 2.3 Concluding Remarks ··································································46 CHAPTER CENTRIFUGE TEST SET-UP AND SPECIMEN PREPARATION ································································58 3.1 Introduction ·············································································58 3.2 Principles of Geotechnical Centrifuge Modeling ·································58 3.3 Shake Table ·············································································60 3.3.1 Laminar Box ········································································60 3.3.2 Shaking Apparatus ·································································61 3.4 Transducers ·············································································62 3.5 Pile-raft System ·········································································63 3.6 Sample Preparation ····································································64 3.6.1 Preparation of Clay Slurry·························································64 3.6.2 Consolidation of Clay Slurry······················································65 3.7 Input Earthquake Motions ···························································66 CHAPTER CENTRIFUGE TEST RESULTS AND DISCUSSION·············77 4.1 Soil State after 50-g Consolidation Phase ··········································79 4.2 Pore Pressure Response due to the Applied Ground Motions ·················81 4.3 Free-field Acceleration Response of Pure Kaolin Clay Beds ···················82 4.4 Raft Acceleration Response ··························································86 4.4.1 Influence of Pile-raft Configuration ··············································86 4.4.2 Influence of Ground Motion Intensity ···········································90 4.4.3 Influence of Added Masses on the Raft··········································92 II Appendix B Typical Measured Acceleration and Bending Moment Time Histories 500 Bending moment (kNm) Bending moment (kNm) 500 250 0 10 15 20 25 -250 -500 250 0 15 20 25 -250 -500 Time (s) 10 Time (s) (a) Outer pile (b) Inner pile Figure B.46 Measured bending moment time histories at uppermost strain gauge for 4×3 hollow pile group sample with added mass-1, subjected to shortduration medium ground motion (2.425 m below pile head, Test 31) 500 Bending moment (kNm) Bending moment (kNm) 500 250 0 10 15 20 25 -250 -500 250 0 (a) Outer pile 10 15 20 25 -250 -500 Time (s) Time (s) (b) Inner pile Figure B.47 Measured bending moment time histories at uppermost strain gauge for 4×3 hollow pile group sample with added mass-2, subjected to shortduration medium ground motion (2.425 m below pile head, Test 32) 350 Appendix B Typical Measured Acceleration and Bending Moment Time Histories 500 Bending moment (kNm) Bending moment (kNm) 500 250 0 10 15 20 25 -250 -500 250 0 (a) Outer pile 10 15 20 25 -250 -500 Time (s) Time (s) (b) Inner pile Figure B.48 Measured bending moment time histories at uppermost strain gauge for 4×3 hollow pile group sample with added mass-3, subjected to shortduration medium ground motion (2.425 m below pile head, Test33) 351 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter APPENDIX C LIST OF NUMERICAL SIMULATIONS FOR THE PARAMETRIC STUDIES IN CHAPTER Table C.1 List of numerical simulations performed for the parametric studies with short-duration ground motions M A 0.1345 ρsoil (g/cm3) 2.7 0.9 2060 Hsoil (m) 16.2 729 0.0562 2.7 0.9 2060 16.2 729 0.0135 2.7 0.9 1030 16.2 15 729 0.0135 2.7 0.9 2060 16.2 15 729 0.0135 2.7 0.9 4120 16.2 15 30 1919 0.0562 2.7 0.9 2060 16.2 15 30 6086 0.0562 2.7 0.9 2060 16.2 15 30 729 0.1345 2.7 0.9 1030 16.2 15 30 729 0.1345 2.7 0.9 2060 16.2 10 15 30 729 0.1345 2.7 0.9 4120 16.2 11 15 30 729 0.0562 2.7 0.9 1030 16.2 12 15 30 729 0.0562 2.7 0.9 2060 16.2 13 15 30 729 0.0562 2.7 0.9 4120 16.2 14 15 30 729 0.0135 2.7 0.9 2060 16.2 15 15 70 1919 0.1345 2.7 0.9 2060 16.2 16 15 70 1919 0.0562 2.7 0.9 2060 16.2 17 15 70 6086 0.1345 2.7 0.9 2060 16.2 18 15 70 6086 0.0562 2.7 0.9 2060 16.2 19 15 70 729 0.1345 2.7 0.9 1030 16.2 20 15 70 729 0.1345 2.7 0.9 2060 16.2 21 15 70 729 0.1345 2.7 0.9 4120 16.2 22 15 70 729 0.0562 2.7 0.9 1030 16.2 23 15 70 729 0.0562 2.7 0.9 2060 16.2 24 15 70 729 0.0562 2.7 0.9 4120 16.2 25 15 70 729 0.0135 2.7 0.9 2060 16.2 26 15 210 1919 0.0562 2.7 0.9 2060 16.2 27 15 210 6086 0.0562 2.7 0.9 2060 16.2 28 15 210 729 0.1345 2.7 0.8 2060 16.2 29 15 210 729 0.0562 2.7 0.9 2060 16.2 30 15 210 729 0.0135 2.7 0.9 2060 16.2 31 15 70 1919 0.0135 2.7 0.9 2060 16.2 No. lp (m) Ep (GPa) 15 mstr (tonne) 729 15 15 PBA (g) 352 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 32 15 729 0.0135 2.7 0.8 2060 16.2 33 15 729 0.0135 2.7 1.2 2060 16.2 34 15 30 729 0.0562 2.7 0.8 2060 16.2 35 15 30 729 0.0562 2.7 1.2 2060 16.2 36 15 70 729 0.1345 2.7 0.8 2060 16.2 37 15 70 729 0.1345 2.7 1.2 2060 16.2 38 15 70 729 0.0562 2.7 0.8 2060 16.2 39 15 70 729 0.0562 2.7 1.2 2060 16.2 40 15 729 0.0135 1.76 0.9 2060 16.2 41 15 729 0.0135 7.85 0.9 2060 16.2 42 15 30 729 0.0562 1.76 0.9 2060 16.2 43 15 30 729 0.0562 7.85 0.9 2060 16.2 44 15 70 729 0.1345 1.76 0.9 2060 16.2 45 15 70 729 0.1345 7.85 0.9 2060 16.2 46 15 70 729 0.0562 1.76 0.9 2060 16.2 47 15 70 729 0.0562 7.85 0.9 2060 16.2 48 20 729 0.1345 2.7 0.9 2060 21.2 49 20 729 0.0562 2.7 0.9 2060 21.2 50 20 729 0.0135 2.7 0.9 1030 21.2 51 20 729 0.0135 2.7 0.9 2060 21.2 52 20 729 0.0135 2.7 0.9 4120 21.2 53 20 30 729 0.1345 2.7 0.9 2060 21.2 54 20 30 729 0.0562 2.7 0.9 2060 21.2 55 20 30 729 0.0135 2.7 0.9 2060 21.2 56 20 70 729 0.1345 2.7 0.9 2060 21.2 57 20 70 729 0.0562 2.7 0.9 1030 21.2 58 20 70 729 0.0562 2.7 0.9 2060 21.2 59 20 70 729 0.0562 2.7 0.9 4120 21.2 60 20 70 729 0.0135 2.7 0.9 2060 21.2 61 20 70 729 0.1345 2.7 0.9 1030 21.2 62 20 70 729 0.1345 2.7 0.9 4120 21.2 63 20 210 729 0.1345 2.7 0.9 2060 21.2 64 20 210 729 0.0562 2.7 0.9 2060 21.2 65 20 210 729 0.0135 2.7 0.9 2060 21.2 66 20 30 1919 0.1345 2.7 0.9 2060 21.2 67 20 30 1919 0.0562 2.7 0.9 2060 21.2 68 20 30 6086 0.1345 2.7 0.9 2060 21.2 69 20 30 6086 0.0562 2.7 0.9 2060 21.2 70 20 70 1919 0.1345 2.7 0.9 2060 21.2 71 20 70 1919 0.0562 2.7 0.9 2060 21.2 72 20 70 6086 0.1345 2.7 0.9 2060 21.2 73 20 70 6086 0.0562 2.7 0.9 2060 21.2 74 20 210 1919 0.1345 2.7 0.9 2060 21.2 75 20 210 1919 0.0562 2.7 0.9 2060 21.2 353 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 76 20 210 6086 0.1345 2.7 0.9 2060 21.2 77 20 210 6086 0.0562 2.7 0.9 2060 21.2 78 20 729 0.0135 1.6 0.9 2060 21.2 79 20 729 0.0135 7.85 0.9 2060 21.2 80 20 30 729 0.0562 1.6 0.9 2060 21.2 81 20 30 729 0.0562 7.85 0.9 2060 21.2 82 20 70 729 0.1345 1.6 0.9 2060 21.2 83 20 70 729 0.1345 7.85 0.9 2060 21.2 84 20 70 729 0.0562 1.6 0.9 2060 21.2 85 20 70 729 0.0562 7.85 0.9 2060 21.2 86 20 729 0.0135 2.7 0.8 2060 21.2 87 20 729 0.0135 2.7 1.2 2060 21.2 88 20 30 729 0.0562 2.7 0.8 2060 21.2 89 20 30 729 0.0562 2.7 1.2 2060 21.2 90 20 70 729 0.1345 2.7 0.8 2060 21.2 91 20 70 729 0.1345 2.7 1.2 2060 21.2 92 20 70 729 0.0562 2.7 0.8 2060 21.2 93 20 70 729 0.0562 2.7 1.2 2060 21.2 94 25 729 0.1345 2.7 0.9 2060 26.2 95 25 729 0.0562 2.7 0.9 2060 26.2 96 25 729 0.0135 2.7 0.9 1030 26.2 97 25 729 0.0135 2.7 0.9 2060 26.2 98 25 729 0.0135 2.7 0.9 4120 26.2 99 25 30 729 0.1345 2.7 0.9 2060 26.2 100 25 30 729 0.0562 2.7 0.9 2060 26.2 101 25 30 729 0.0135 2.7 0.9 2060 26.2 102 25 70 1919 0.1345 2.7 0.9 2060 26.2 103 25 70 1919 0.0562 2.7 0.9 2060 26.2 104 25 70 6086 0.1345 2.7 0.9 2060 26.2 105 25 70 6086 0.0562 2.7 0.9 2060 26.2 106 25 70 729 0.1345 2.7 0.9 1030 26.2 107 25 70 729 0.1345 2.7 0.9 2060 26.2 108 25 70 729 0.1345 2.7 0.9 4120 26.2 109 25 70 729 0.0562 2.7 0.9 1030 26.2 110 25 70 729 0.0562 2.7 0.9 2060 26.2 111 25 70 729 0.0562 2.7 0.9 4120 26.2 112 25 70 729 0.0135 2.7 0.9 2060 26.2 113 25 210 729 0.1345 2.7 0.9 2060 26.2 114 25 210 729 0.0562 2.7 0.9 2060 26.2 115 25 210 729 0.0135 2.7 0.9 2060 26.2 116 25 30 1919 0.1345 2.7 0.9 2060 26.2 117 25 30 1919 0.0562 2.7 0.9 2060 26.2 118 25 30 6086 0.1345 2.7 0.9 2060 26.2 119 25 30 6086 0.0562 2.7 0.9 2060 26.2 354 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 120 25 210 1919 0.1345 2.7 0.9 2060 26.2 121 25 210 1919 0.0562 2.7 0.9 2060 26.2 122 25 210 6086 0.1345 2.7 0.9 2060 26.2 123 25 210 6086 0.0562 2.7 0.9 2060 26.2 124 25 729 0.0135 1.76 0.9 2060 26.2 125 25 729 0.0135 7.85 0.9 2060 26.2 126 25 30 729 0.0562 1.76 0.9 2060 26.2 127 25 30 729 0.0562 7.85 0.9 2060 26.2 128 25 70 729 0.1345 1.76 0.9 2060 26.2 129 25 70 729 0.1345 7.85 0.9 2060 26.2 130 25 70 729 0.0562 1.76 0.9 2060 26.2 131 25 70 729 0.0562 7.85 0.9 2060 26.2 132 25 729 0.0135 2.7 0.8 2060 26.2 133 25 729 0.0135 2.7 1.2 2060 26.2 134 25 30 729 0.0562 2.7 0.8 2060 26.2 135 25 30 729 0.0562 2.7 1.2 2060 26.2 136 25 70 729 0.1345 2.7 0.8 2060 26.2 137 25 70 729 0.0562 2.7 0.8 2060 26.2 138 25 70 729 0.1345 2.7 1.2 2060 26.2 139 25 70 729 0.0562 2.7 1.2 2060 26.2 140 35 729 0.1345 2.7 0.9 2060 36.2 141 35 729 0.0562 2.7 0.9 2060 36.2 142 35 729 0.0135 2.7 0.9 1030 36.2 143 35 729 0.0135 2.7 0.9 2060 36.2 144 35 729 0.0135 2.7 0.9 4120 36.2 145 35 30 1919 0.1345 2.7 0.9 2060 36.2 146 35 30 6086 0.1345 2.7 0.9 2060 36.2 147 35 30 729 0.1345 2.7 0.9 2060 36.2 148 35 30 729 0.0562 2.7 0.9 1030 36.2 149 35 30 729 0.0562 2.7 0.9 2060 36.2 150 35 30 729 0.0562 2.7 0.9 4120 36.2 151 35 30 729 0.0135 2.7 0.9 2060 36.2 152 35 70 1919 0.1345 2.7 0.9 2060 36.2 153 35 70 1919 0.0562 2.7 0.9 2060 36.2 154 35 70 6086 0.1345 2.7 0.9 2060 36.2 155 35 70 6086 0.0562 2.7 0.9 2060 36.2 156 35 70 729 0.1345 2.7 0.9 1030 36.2 157 35 70 729 0.1345 2.7 0.9 2060 36.2 158 35 70 729 0.1345 2.7 0.9 4120 36.2 159 35 70 729 0.0562 2.7 0.9 1030 36.2 160 35 70 729 0.0562 2.7 0.9 2060 36.2 161 35 70 729 0.0562 2.7 0.9 4120 36.2 162 35 70 729 0.0135 2.7 0.9 2060 36.2 163 35 210 729 0.1345 2.7 0.9 2060 36.2 355 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 164 35 210 729 0.0562 2.7 0.9 2060 36.2 165 35 210 729 0.0135 2.7 0.9 2060 36.2 166 35 729 0.0135 1.76 0.9 2060 36.2 167 35 729 0.0135 7.85 0.9 2060 36.2 168 35 30 729 0.0562 1.76 0.9 2060 36.2 169 35 30 729 0.0562 7.85 0.9 2060 36.2 170 35 70 729 0.1345 1.76 0.9 2060 36.2 171 35 70 729 0.1345 7.85 0.9 2060 36.2 172 35 70 729 0.0562 1.76 0.9 2060 36.2 173 35 70 729 0.0562 7.85 0.9 2060 36.2 174 35 729 0.0135 2.7 0.8 2060 36.2 175 35 729 0.0135 2.7 1.2 2060 36.2 176 35 30 729 0.0562 2.7 0.8 2060 36.2 177 35 30 729 0.0562 2.7 1.2 2060 36.2 178 35 70 729 0.1345 2.7 0.8 2060 36.2 179 35 70 729 0.1345 2.7 1.2 2060 36.2 180 35 70 729 0.0562 2.7 0.8 2060 36.2 181 35 70 729 0.0562 2.7 1.2 2060 36.2 182 35 70 1919 0.0135 2.7 0.9 2060 36.2 183 35 70 6086 0.0135 2.7 0.9 2060 36.2 184 35 70 6086 0.1345 2.7 0.9 2060 36.2 185 35 30 1919 0.0562 2.7 0.9 2060 36.2 186 35 30 6086 0.0562 2.7 0.9 2060 36.2 187 35 210 1919 0.1345 2.7 0.9 2060 36.2 188 35 210 1919 0.0562 2.7 0.9 2060 36.2 189 35 210 6086 0.1345 2.7 0.9 2060 36.2 190 35 210 6086 0.0562 2.7 0.9 2060 36.2 191 15 729 0.1345 2.7 0.9 2060 36.2 192 15 729 0.1345 2.7 0.9 1030 36.2 193 15 729 0.1345 2.7 0.9 4120 36.2 194 15 729 0.1345 1.76 0.9 2060 36.2 195 15 729 0.1345 7.85 0.9 2060 36.2 196 15 729 0.0562 2.7 0.9 2060 36.2 197 15 729 0.0135 2.7 0.9 2060 36.2 198 15 30 1919 0.1345 2.7 0.9 2060 36.2 199 15 30 1919 0.1345 2.7 0.9 1030 36.2 200 15 30 1919 0.1345 2.7 0.9 4120 36.2 201 15 30 1919 0.1345 1.76 0.9 2060 36.2 202 15 30 1919 0.1345 7.85 0.9 2060 36.2 203 15 30 1919 0.0562 2.7 0.9 2060 36.2 204 15 30 6086 0.1345 2.7 0.9 2060 36.2 205 15 30 6086 0.0562 2.7 0.9 2060 36.2 206 15 30 729 0.1345 2.7 0.9 2060 36.2 207 15 30 729 0.1345 1.76 0.9 2060 36.2 356 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 208 15 30 729 0.1345 7.85 0.9 2060 36.2 209 15 30 729 0.0562 2.7 0.9 2060 36.2 210 15 30 729 0.0562 2.7 0.9 1030 36.2 211 15 30 729 0.0562 2.7 0.9 4120 36.2 212 15 30 729 0.0562 1.76 0.9 2060 36.2 213 15 30 729 0.0562 7.85 0.9 2060 36.2 214 15 30 729 0.0135 2.7 0.9 2060 36.2 215 15 70 1919 0.1345 2.7 0.9 2060 36.2 216 15 70 1919 0.0562 2.7 0.9 2060 36.2 217 15 70 1919 0.0562 1.76 0.9 2060 36.2 218 15 70 1919 0.0562 7.85 0.9 2060 36.2 219 15 70 6086 0.1345 2.7 0.9 2060 36.2 220 15 70 6086 0.0562 2.7 0.9 2060 36.2 221 15 70 729 0.1345 2.7 0.9 2060 36.2 222 15 70 729 0.1345 1.76 0.9 2060 36.2 223 15 70 729 0.1345 7.85 0.9 2060 36.2 224 15 70 729 0.0562 2.7 0.9 2060 36.2 225 15 70 729 0.0562 2.7 0.9 1030 36.2 226 15 70 729 0.0562 2.7 0.9 4120 36.2 227 15 70 729 0.0562 1.76 0.9 2060 36.2 228 15 70 729 0.0562 7.85 0.9 2060 36.2 229 15 70 729 0.0135 2.7 0.9 2060 36.2 230 15 210 1919 0.1345 2.7 0.9 2060 36.2 231 15 210 1919 0.0562 2.7 0.9 2060 36.2 232 15 210 6086 0.1345 2.7 0.9 2060 36.2 233 15 210 6086 0.0562 2.7 0.9 2060 36.2 234 15 210 729 0.1345 2.7 0.9 2060 36.2 235 15 210 729 0.1345 1.76 0.9 2060 36.2 236 15 210 729 0.1345 7.85 0.9 2060 36.2 237 15 210 729 0.0562 2.7 0.9 2060 36.2 238 15 210 729 0.0562 1.76 0.9 2060 36.2 239 15 210 729 0.0562 7.85 0.9 2060 36.2 240 15 210 729 0.0135 2.7 0.9 2060 36.2 241 15 729 0.0562 2.7 0.8 2060 36.2 242 15 729 0.0562 2.7 1.2 2060 36.2 243 15 30 729 0.1345 2.7 0.9 1030 36.2 244 15 30 729 0.1345 2.7 0.9 4120 36.2 245 15 30 729 0.1345 2.7 0.8 2060 36.2 246 15 30 729 0.1345 2.7 1.2 2060 36.2 247 15 30 729 0.0562 2.7 0.8 2060 36.2 248 15 30 729 0.0562 2.7 1.2 2060 36.2 249 15 70 729 0.1345 2.7 0.9 1030 36.2 250 15 70 729 0.1345 2.7 0.9 4120 36.2 251 15 70 729 0.1345 2.7 0.8 2060 36.2 357 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 252 15 70 729 0.1345 2.7 1.2 2060 36.2 253 15 70 729 0.0562 2.7 0.8 2060 36.2 254 15 70 729 0.0562 2.7 1.2 2060 36.2 255 15 210 729 0.1345 2.7 0.9 1030 36.2 256 15 210 729 0.1345 2.7 0.9 4120 36.2 257 15 210 729 0.0562 2.7 0.9 1030 36.2 258 15 210 729 0.0562 2.7 0.9 4120 36.2 259 15 210 729 0.1345 2.7 0.8 2060 36.2 260 15 210 729 0.1345 2.7 1.2 2060 36.2 261 15 210 729 0.0562 2.7 0.8 2060 36.2 262 15 210 729 0.0562 2.7 1.2 2060 36.2 263 25 729 0.1345 2.7 0.9 2060 36.2 264 25 729 0.0562 2.7 0.9 2060 36.2 265 25 729 0.0562 2.7 0.9 1030 36.2 266 25 729 0.0562 2.7 0.9 4120 36.2 267 25 729 0.0562 1.76 0.9 2060 36.2 268 25 729 0.0562 7.85 0.9 2060 36.2 269 25 729 0.0562 2.7 0.8 2060 36.2 270 25 729 0.0562 2.7 1.2 2060 36.2 271 25 729 0.0135 2.7 0.9 2060 36.2 272 25 30 1919 0.1345 2.7 0.9 2060 36.2 273 25 30 1919 0.0562 2.7 0.9 2060 36.2 274 25 30 1919 0.0562 1.76 0.9 1030 36.2 275 25 30 6086 0.1345 2.7 0.9 2060 36.2 276 25 30 6086 0.0562 2.7 0.9 2060 36.2 277 25 30 6086 0.0562 7.85 0.9 4120 36.2 278 25 30 729 0.1345 2.7 0.9 2060 36.2 279 25 30 729 0.1345 2.7 0.8 2060 36.2 280 25 30 729 0.1345 2.7 1.2 2060 36.2 281 25 30 729 0.1345 2.7 0.9 1030 36.2 282 25 30 729 0.1345 2.7 0.9 4120 36.2 283 25 30 729 0.1345 1.76 0.9 2060 36.2 284 25 30 729 0.1345 7.85 0.9 2060 36.2 285 25 30 729 0.0562 2.7 0.9 2060 36.2 286 25 30 729 0.0562 2.7 0.9 1030 36.2 287 25 30 729 0.0562 2.7 0.9 4120 36.2 288 25 30 729 0.0562 1.76 0.9 2060 36.2 289 25 30 729 0.0562 7.85 0.9 2060 36.2 290 25 30 729 0.0562 2.7 0.8 2060 36.2 291 25 30 729 0.0562 2.7 1.2 2060 36.2 292 25 30 729 0.0135 2.7 0.9 2060 36.2 293 25 70 729 0.1345 2.7 0.9 1030 36.2 294 25 70 729 0.1345 2.7 0.9 4120 36.2 295 25 70 729 0.0562 2.7 0.9 1030 36.2 358 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 296 25 70 729 0.0562 2.7 0.9 4120 36.2 297 25 210 729 0.0562 2.7 0.9 1030 36.2 298 25 210 729 0.0562 2.7 0.9 4120 36.2 299 25 70 1919 0.1345 2.7 0.9 2060 36.2 300 25 70 1919 0.0562 2.7 0.9 2060 36.2 301 25 70 6086 0.0562 2.7 0.9 2060 36.2 302 25 70 729 0.1345 2.7 0.9 2060 36.2 303 25 70 729 0.1345 1.76 0.9 2060 36.2 304 25 70 729 0.1345 7.85 0.9 2060 36.2 305 25 70 729 0.0562 2.7 0.9 2060 36.2 306 25 70 729 0.0562 1.76 0.9 2060 36.2 307 25 70 729 0.0562 7.85 0.9 2060 36.2 308 25 70 729 0.0135 2.7 0.9 2060 36.2 309 25 210 729 0.1345 2.7 0.9 2060 36.2 310 25 210 729 0.1345 1.76 0.9 2060 36.2 311 25 210 729 0.1345 7.85 0.9 2060 36.2 312 25 210 729 0.0562 2.7 0.9 2060 36.2 313 25 210 729 0.0562 1.76 0.9 2060 36.2 314 25 210 729 0.0562 7.85 0.9 2060 36.2 315 25 210 729 0.0135 2.7 0.9 2060 36.2 316 25 70 6086 0.1345 2.7 0.9 2060 36.2 317 25 210 1919 0.1345 2.7 0.9 2060 36.2 318 25 210 1919 0.0562 2.7 0.9 2060 36.2 319 25 210 6086 0.0562 2.7 0.9 2060 36.2 320 25 210 729 0.1345 2.7 0.9 1030 36.2 321 25 210 729 0.1345 2.7 0.9 4120 36.2 322 25 70 729 0.1345 2.7 0.8 2060 36.2 323 25 70 729 0.1345 2.7 1.2 2060 36.2 324 25 70 729 0.0562 2.7 0.8 2060 36.2 325 25 70 729 0.0562 2.7 1.2 2060 36.2 326 25 210 6086 0.1345 2.7 0.9 2060 36.2 327 25 210 729 0.1345 2.7 0.8 2060 36.2 328 25 210 729 0.1345 2.7 1.2 2060 36.2 329 25 210 729 0.0562 2.7 0.8 2060 36.2 330 25 210 729 0.0562 2.7 1.2 2060 36.2 359 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter Table C.2 List of numerical simulations performed for the parametric studies with long-duration ground motions No. Ep (GPa) mstr (tonne) PBA (g) ρsoil (g/cm3) M A 334 0.1576 2.7 0.9 2060 334 0.0615 2.7 0.9 2060 334 0.0112 2.7 0.9 1030 334 0.0112 2.7 0.9 2060 5 334 0.0112 2.7 0.8 2060 334 0.0112 2.7 1.2 2060 334 0.0112 2.7 0.9 4120 334 0.0112 1.76 0.9 2060 334 0.0112 7.85 0.9 2060 10 30 334 0.1576 2.7 0.9 2060 11 30 334 0.0615 2.7 0.9 1030 12 30 334 0.0615 2.7 0.9 2060 13 30 334 0.0615 2.7 0.9 4120 14 30 334 0.0615 1.76 0.9 2060 15 30 334 0.0615 7.85 0.9 2060 16 30 334 0.0615 2.7 0.8 2060 17 30 334 0.0615 2.7 1.2 2060 18 30 334 0.0112 2.7 0.9 2060 19 70 334 0.1576 2.7 0.9 1030 20 70 334 0.1576 2.7 0.9 4120 21 70 334 0.1576 2.7 0.9 2060 22 70 334 0.0615 2.7 0.9 2060 23 70 334 0.0112 2.7 0.9 2060 24 70 334 0.1576 2.7 0.8 2060 25 70 334 0.1576 2.7 1.2 2060 26 70 334 0.0615 2.7 0.9 1030 27 70 334 0.0615 2.7 0.9 4120 28 70 334 0.0615 2.7 0.8 2060 29 70 334 0.0615 2.7 1.2 2060 30 210 334 0.1576 2.7 0.9 2060 31 210 334 0.0615 2.7 0.9 2060 32 210 334 0.0112 2.7 0.9 2060 33 906 0.0615 2.7 0.9 2060 34 2906 0.0615 2.7 0.9 2060 35 30 906 0.0615 2.7 0.9 2060 36 30 2906 0.0615 2.7 0.9 2060 37 70 906 0.1576 2.7 0.9 2060 38 70 906 0.0615 2.7 0.9 2060 39 70 2906 0.0615 2.7 0.9 2060 40 70 334 0.1576 1.76 0.9 2060 41 70 334 0.1576 7.85 0.9 2060 42 70 334 0.0615 1.76 0.9 2060 360 Appendix C List of Numerical Simulations for the Parametric Studies in Chapter 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 70 210 70 70 30 30 70 70 70 210 30 30 30 30 30 30 30 30 210 210 210 210 210 210 210 210 210 210 210 210 210 210 334 906 906 2906 906 906 2906 2906 2906 2906 334 334 906 2906 334 334 334 334 906 2906 334 334 334 334 334 334 334 334 334 334 334 334 0.0615 0.1576 0.0112 0.1576 0.1576 0.1576 0.0615 0.0615 0.0112 0.1576 0.1576 0.1576 0.1576 0.1576 0.1576 0.1576 0.1576 0.1576 0.0615 0.0615 0.1576 0.1576 0.1576 0.1576 0.1576 0.1576 0.0615 0.0615 0.0615 0.0615 0.0615 0.0615 361 7.85 2.7 2.7 2.7 7.85 1.76 1.76 7.85 2.7 2.7 1.76 7.85 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 1.76 7.85 2.7 2.7 2.7 2.7 1.76 7.85 2.7 2.7 2.7 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.8 1.2 0.9 0.9 0.9 0.9 0.9 0.9 0.8 1.2 0.9 0.9 0.9 0.9 0.8 1.2 0.9 2060 2060 2060 2060 1030 4120 1030 4120 2060 2060 2060 2060 2060 2060 1030 2060 2060 4120 2060 2060 1030 2060 2060 2060 2060 4120 1030 2060 2060 2060 2060 4120 Appendix D Typical Computed Lateral Displacements at Raft Top and Sample Base APPENDIX D TYPICAL COMPUTED LATERAL DISPLACEMENTS AT RAFT TOP AND SAMPLE BASE As shown below, a few plots showing the lateral displacements computed from the FEM study are presented below, which can be used to facilitate judgment on whether gapping/slippage could occur during the shaking events. 0.25 Base 0.15 0.05 -0.05 45 90 135 180 -0.15 -0.25 Displacement (m) Displacement (m) 0.25 Raft 0.15 0.05 -0.05 45 90 135 -0.15 Time (s) -0.25 Figure D.1 Computed displacement time histories at base and raft top for 4×3 solid aluminum pile group subjected to long-duration small ground motion Time (s) 362 180 Appendix D Typical Computed Lateral Displacements at Raft Top and Sample Base 0.25 Base 0.15 Displacement (m) Displacement (m) 0.25 0.05 -0.05 45 90 135 180 -0.15 Raft 0.15 0.05 -0.05 45 90 135 -0.15 -0.25 Time (s) Time (s) -0.25 Figure D.2 Computed displacement time histories at base and raft top for 4×3 solid aluminum pile group subjected to long-duration medium ground motion Displacement (m) 0.25 Base 0.15 0.05 -0.05 50 100 150 -0.15 Raft 0.15 0.05 -0.05 50 100 150 -0.15 Time (s) -0.25 Time (s) -0.25 Figure D.3 Computed displacement time histories at base and raft top for 4×3 solid aluminum pile group subjected to long-duration large ground motion 0.25 Raft Base 0.15 Displacement (m) Displacement (m) 0.25 0.05 -0.05 10 15 20 25 -0.15 -0.25 Time (s) Figure D.4 Computed displacement time histories at base and raft top for 4×3 solid aluminum pile group subjected to short-duration small ground motion 363 180 Appendix D Typical Computed Lateral Displacements at Raft Top and Sample Base 0.25 Raft Base Displacement (m) 0.15 0.05 -0.05 10 15 20 25 -0.15 -0.25 Time (s) Figure D.5 Computed displacement time histories at base and raft top for 4×3 solid aluminum pile group subjected to short-duration medium ground motion Raft Base Displacement (m) 0.25 0.15 0.05 -0.05 10 15 20 25 -0.15 -0.25 Time (s) Figure D.6 Computed displacement time histories at base and raft top for 4×3 solid aluminum pile group subjected to short-duration large ground motion The computed displacement time histories at base and raft (equivalent to the pile head) for 4×3 solid aluminum pile group subjected to long- and shortduration small, medium and large ground motions are presented in Figures D.1-6. As can be seen, the relative motions between base and raft increase with the earthquake intensity. For the small long- and short-duration ground motions excited, the relative motions between base and raft are very small, with values of about 2% and 13% respectively; the slippage or gapping likely does not occur between the pile and soil interface. On the other hand, for the 364 Appendix D Typical Computed Lateral Displacements at Raft Top and Sample Base large long- and short-duration ground motions excited, the corresponding relative motion between the pile head and tip are about 34% and 30% respectively; hence, the slippage or gapping may potentially occur between the pile and soil interface for the large imposed ground motion. Hence, the current modelling technique which neglects the possible gapping and slippage between pile and soil interface may need further validation when the excited ground motions are of relatively much larger amplitudes. 365 [...]... instrumentation for single pile and pile group centrifuge seismic test in sand and clay (after Wilson et al., 1998) 55 IX List of Figures Figure 2.8 Layout and instrumentation for a single pile centrifuge seismic test in sand (after Wilson et al., 2000) 55 Figure 2.9 Schematic diagram of the centrifuge model for studying liquefactioninduced lateral spread effects on a single pile embedded in a two-layer... studying the influence of different pile spacings (D =pile diameter) 283 Figure 6.51 Maximum bending moment profiles for 2× sparse pile groups with 1 different pile spacings (E=70 GPa, structural mass=27 tonne per pile) 284 Figure 6.52 Influence of pile spacing on the maximum pile bending moment (D =pile diameter) 285 Figure 6.53 Influence of structural mass on the normalized... user-defined subroutine of the hyperbolic-hysteretic soil model proposed by Banerjee (2009) for soft clays The numerical simulations provided reasonably good predictions for the maximum pile bending moments along the piles as well as the acceleration response at both the free-field ground surface and the raft top The numerical simulations were then extended to perform a series of parametric studies to investigate... studies to investigate the influence of factors such as thickness of the soft soil layer, soil shear modulus, soil friction angle, pile flexural rigidity, pile length, pile material density, bedrock acceleration intensity and mass of superstructure The finite element simulations of the parametric studies were carried out for a 5× pile group in a pure clay bed subjected to a series of far5 field short-duration... mounted on the centrifuge platform The accelerations at selected locations within the model, as well as the bending strains at various depths along the piles, were measured during the simulated earthquake events A series of three-dimensional finite element simulations were carried out to back-analyze selected centrifuge tests using the general purpose finite element program ABAQUS These analyses incorporate... modulus on maximum pile bending moment with short-duration ground motion 273 Figure 6.35 Predicted (Eq 6.23) and FE computed results showing the influence of the slope of critical state line on maximum pile bending moment with short-duration ground motion 273 Figure 6.36 Predicted (Eq 6.23) and FE computed results showing the influence of pile density on maximum pile bending moment with... 6.23) and FE computed results showing the influence of thickness of soft soil layer on maximum pile bending moment with shortduration ground motion 274 Figure 6.38 Predicted (Eq 6.24) and FE computed results showing the influence of pile length on peak raft acceleration with short-duration ground motion 275 Figure 6.39 Predicted (Eq 6.24) and FE computed results showing the influence... previous work carried out at the National University of Singapore by Banerjee (2009) Banerjee studied the seismic response of kaolin clay beds subjected to short-duration far-field ground motions of about 25 secs, with and without an embedded single pile raft system In this study, the pile foundations are extended to include small to medium size pile groups In addition to the short-duration far-field... SUMMARY The behavior of pile foundations under earthquake loading is an important factor affecting the performance of structures Observations from past earthquakes have shown that piles in firm soils generally perform well, while those installed in soft or liquefiable soils are more susceptible to problems arising from ground amplification or excessive soil movements This study is a continuation of the. .. results showing the influence of structural mass on maximum pile bending moment with short-duration ground motion 272 Figure 6.33 Predicted (Eq 6.23) and FE computed results showing the influence of peak base acceleration on maximum pile bending moment with shortduration ground motion 272 Figure 6.34 Predicted (Eq 6.23) and FE computed results showing the influence of small-strain shear . CENTRIFUGE AND NUMERICAL MODELLING OF THE SEISMIC RESPONSE OF PILE GROUPS IN SOFT CLAYS ZHANG LEI NATIONAL UNVERSITY OF SINGAPORE 2014 CENTRIFUGE AND NUMERICAL. NUMERICAL MODELLING OF THE SEISMIC RESPONSE OF PILE GROUPS IN SOFT CLAYS ZHANG LEI (M. Eng., SDU; B. Eng., CQU) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF. Prof. Goh Siang Huat and Prof. Lee Fook Hou going over every detail of both the centrifuge test and numerical simulation. Besides, the assistances provided by Asst. Prof. Goh Siang Huat and