This thesis focuses on the seismic response of piles in liquefiable ground. It describes the design of a three-dimensional, unified plasticity model for large post-liquefaction shear deformation of sand, formulated and implemented for parallel computing. It also presents a three-dimensional, dynamic finite element analysis method for piles in liquefiable ground, developed on the basis of this model,. Employing a combination of case analysis, centrifuge shaking table experiments and numerical simulations using the proposed methods, it demonstrates the seismic response patterns of single piles in liquefiable ground. These include basic force-resistance mode, kinematic and inertial interaction coupling mechanism and major influence factors. It also discusses a beam on the nonlinear Winkler foundation (BNWF) solution and a modified neutral plane solution developed and validated using centrifuge experiments for piles in consolidating and reconsolidating ground. Lastly, it studies axial pile force and settlement during post-earthquake reconsolidation, showing pile axial force to be irrelevant in the reconsolidation process, while settlement is process dependent.
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1 | (24) |
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1 | (2) |
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1.2 Case Histories of Pile Failures in Liquefiable Ground |
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3 | (7) |
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1.2.1 Failure Cases Due to Lateral Effects |
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3 | (5) |
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1.2.2 Failure Cases Due to Vertical Effects |
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8 | (2) |
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10 | (3) |
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1.3.1 Post-liquefaction Shear Deformation Mechanism |
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10 | (1) |
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1.3.2 Constitutive Modelling of Soil Liquefaction |
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11 | (2) |
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1.4 Seismic Response of Piles in Liquefiable Ground |
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13 | (3) |
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1.4.1 Soil-Pile Kinematic Interaction |
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13 | (1) |
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1.4.2 Structure-Pile Inertial Interaction |
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14 | (1) |
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1.4.3 Coupling of Kinematic and Inertial Interactions |
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15 | (1) |
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1.5 Downdrag of Piles in Consolidating Ground |
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16 | (3) |
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1.5.1 Consolidation Induced Dragload and Downdrag Settlement |
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16 | (2) |
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1.5.2 Post-liquefaction Reconsolidation Induced Dragload and Downdrag Settlement |
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18 | (1) |
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1.6 Scope of Dissertation |
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20 | (5) |
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2 A Unified Plasticity Model for Large Post-liquefaction Shear Deformation of Sand and Its Numerical Implementation |
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25 | (30) |
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2.1 Model Formulation in Triaxial Stress Space |
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26 | (5) |
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26 | (1) |
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27 | (1) |
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27 | (1) |
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2.1.4 Plastic Loading and Load Reversal |
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28 | (1) |
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28 | (1) |
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29 | (1) |
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2.1.7 Post-liquefaction Shear Deformation |
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30 | (1) |
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2.2 Multiaxial Generalization |
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31 | (3) |
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2.3 Determination of Model Parameters |
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34 | (1) |
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35 | (5) |
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2.4.1 Numerical Treatment for Zero Effective Stress State |
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35 | (1) |
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2.4.2 Stress Integration Scheme |
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36 | (2) |
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2.4.3 Determination of Projection Point on Maximum Stress Ratio Surface |
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38 | (1) |
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2.4.4 Symmetrisation of the Elastic-Plastic Tangent |
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39 | (1) |
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2.5 Validation of Model Formulation and Implementation |
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40 | (11) |
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2.5.1 Undrained and Drained Triaxial Experiment Simulation |
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40 | (1) |
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2.5.2 Undrained Cyclic Torsional Experiment Simulation |
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41 | (2) |
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2.5.3 VELACS Centrifuge Experiment Simulation |
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43 | (8) |
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51 | (4) |
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51 | (4) |
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3 Analysis of Seismic Single Pile Response in Liquefiable Ground |
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55 | (36) |
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3.1 Centrifuge Test on Single Piles in Liquefiable Ground |
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55 | (2) |
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3.2 3D FEM Method for Simulation of Piles in Liquefiable Ground |
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57 | (5) |
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3.3 Test and Simulation Results |
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62 | (7) |
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3.3.1 LCS, Level Ground with Cap and Superstructure |
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62 | (2) |
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3.3.2 ICS, Inclined Ground with Cap and Superstructure |
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64 | (3) |
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3.3.3 LNN and LNS, Level Ground without Cap, without and with Superstructure |
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67 | (2) |
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3.4 Seismic Response of Single Piles in Liquefiable Ground |
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69 | (18) |
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3.4.1 Major Factors Influencing Pile Responses |
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69 | (6) |
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3.4.2 Role of Inertial and Kinematic Effects |
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75 | (3) |
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3.4.3 Coupling of Inertial and Kinematic Effects |
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78 | (9) |
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87 | (4) |
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88 | (3) |
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4 Dragload and Downdrag Settlement of Single Piles due to Post-liquefaction Reconsolidation |
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91 | (26) |
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4.1 Calculation Method for Dragload and Downdrag Settlement |
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91 | (12) |
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4.1.1 Fundamental Error in Traditional Neutral Plane Solution |
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91 | (1) |
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4.1.2 Beam on Nonlinear Winkler Foundation Solution |
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92 | (7) |
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4.1.3 Modified Neutral Plane Solution |
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99 | (3) |
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4.1.4 Calculation Method for Post-liquefaction Reconsolidation Process |
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102 | (1) |
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103 | (6) |
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4.2.1 Simulation of Single Pile in Consolidating Soil |
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103 | (3) |
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4.2.2 Simulation of Single Pile in Post-liquefaction Reconsolidating Soil |
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106 | (3) |
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4.3 Dragload and Downdrag Settlement During Reconsolidation |
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109 | (5) |
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4.3.1 Liquefiable Ground Without Non-liquefiable Crust |
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110 | (3) |
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4.3.2 Liquefiable Ground with a Non-liquefiable Crust |
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113 | (1) |
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114 | (3) |
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115 | (2) |
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5 Conclusions and Future Work |
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117 | |
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117 | (1) |
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118 | |
The authors research focuses are on geotechnical earthquake engineering, pile foundation, soil liquefaction and constitutive modeling.
Honors Summa cum laude, Ph.D., Beijing 2014 Summa cum laude, Ph.D., Tsinghua University 2014 Outstanding Ph.D. Thesis of Tsinghua University (First Class Award) 2014 Graduate National Scholarship 2012 Scholarship Award for Excellent Doctoral Student, Tsinghua University 2011 National First Class Scholarship (4 times) 2006, 2007, 2008, 2010 Best Paper Award in Geoshanghai 2010 International Conference 2010
Publications
Journal Papers [ 1]Wang R., Zhang J.M., Wang G., 2014. A unified plasticity model for large post-liquefaction shear deformation of sand. Computers and Geotechnics. 59, 54-66. [ 2]Wang R., Zhang J.M., Wang G. Multiaxial Formulation and Numerical Implementation of a Constitutive Model for the Evaluation of Large Liquefaction-induced deformation. China Earthquake Engineering Journal, 2013, 35(1), 91-97. (In Chinese) [ 3]Wang R., Brandenberg S.J., 2013. Beam on nonlinear Winkler foundation and modified neutral plane solution for calculating downdrag settlement. Journal of Geotechnical and Geoenvironmental Engineering. 139 (9), 14331442. [ 4]Zhang G., Wang R., Qian J.Y., Zhang J.M., Qian J.G., 2012. Effect study of cracks on behavior of soil slope under rainfall conditions. Soils and Foundations. 52 (4): 634643. [ 5]Wang R., Zhang J.M., Zhang G. Simplified Analysis Method for Structure-Pile Inertial Interaction in Ground with a Liquefied Top Layer. Rock and Soil Mechanics, 2012, 33(12), 3538-3544. (In Chinese) [ 6]Wang R., Zhang J.M., Zhang G. Centrifuge Shaking Table Test on Single Pile in Lateral Spreading Soil. Engineering Mechanics, 2012, 29(10): 98-105. (In Chinese) [ 7]Wang R., Zhang G., Zhang J.M., 2010. Centrifuge Modelling of Clay Slope with Montmorillonite Weak Layer under Rainfall Conditions. Applied Clay Science. 50, 386-394. [ 8]Zhang G., Qian J.Y., Wang R., Zhang J.M., 2010. Centrifuge model test study of rainfall-induced deformation of cohesive soil slopes. Soils and Foundations. 51 (2). [ 9]Wang R., Zhang G., Zhang J.M., 2010. Centrifuge modeling of rainfall-induced deformation of slopes with weak layers. Chinese Journal of Geotechnical Engineering. 32(10): 1582-1587. (In Chinese)
Conference Papers [ 1]Wang R., Zhang J.M., Zhang G., 2011. Analysis on the Failure of Piles Due to Lateral Spreading. Rock and Soil Mechanics. S1: 501-506. (In Chinese) [ 2]Wang R., Zhang G., Zhang J.M., 2011. Centrifuge Modeling of Rainfall-Induced Layered Soil Slope Failure. Proceedings of the Fifth International Symposium on Deformation Characteristics of Geomaterials, IS SEOUL 2011, September 1~3, 2011, Seoul, Korea, 1070-1073. [ 3]Wang R., Zhang J.M., Zhang G., 2010. Lateral Spreading Ground Displacement Analysis Method in Centrifuge Shaking Table Tests. World Earthquake Engineering. 26S: 225-229. (In Chinese) [ 4]Wang R., Zhang G., Zhang J.M., 2010. Centrifuge Model Tests of Slopes with Weak Layer under Rainfall. ASCE Geotechnical Special Publication No. 202: 159-165 [ 5]Wang R., Zhang G., Zhang J.M., 2010. Centrifuge Model Tests of Slopes with Weak Layer under Rainfall. ASCE Geotechnical Special Publication No. 202: 159-165 [ 6]Chen R. R., Yao Y., Wang R., Zhang J.M., 2014. Three-Dimensional Finite Element Analysis of Underground Structures Dynamic Response in Liquefiable Soil. ASCE Geotechnical Special Publication No. 240: 572-578.
Presentations [ 1]A cyclic model for post-liquefaction deformation and its implementation in OpenSees. The Second International Symposium on Constitutive Modeling of Geomaterials: Advances and New Applications, IS-Model 2012, October 15~16, 2012, Beijing, China. [ 2]Beam on nonlinear Winkler foundation and modified neutral plane solution for calculating downdrag settlement. Presentation for Arup Los Angeles office, February 8, 2012,Los Angeles, California, USA. [ 3]Centrifuge Modeling of Rainfall-Induced Layered Soil Slope Failure. The Fifth International Symposium on Deformation Characteristics of Geomaterials, IS-Seoul 2011, September 1~3, 2011, Seoul, Korea. [ 4]Analysis on the Failure of Piles Due to Lateral Spreading. The 7th National Young Geotechnical Mechanics and Engineering Conference, April 15~18, 2011, Beijing, China. (In Chinese) [ 5]Lateral Spreading Ground Displacement Analysis Method in Centrifuge Shaking Table Tests. The 9th National Conference on Soil Dynamics, December 23~25, 2010, Harbin, China. (In Chinese) [ 6]Centrifuge Model Tests of Slopes with Weak Layer under Rainfall. GeoShanghai International Conference 2010, June 3~5, 2010, Shanghai, China.
