臺灣博碩士論文加值系統

In this study, four failure excavations were investigated using the finite element method (FEM) with reduced shear strength. Center posts were considered in the finite element model. For comparison, both the elastic and elastoplastic support system were employed. Results showed that as using the elastoplastic support system, the FEM gave more reasonable estimates of stability of the excavations than as using the elastic support system. Effects of the ratio between wall embedded depth to excavation depth (Hp/He), excavation width (B), wall thickness (tw), strut capacity, and normalized undrained shear strength (su/sv’) of soil on stability of excavations in clay were studied. Results showed that when the Hp/He ratio increases, stability of excavations was firstly improved and then remained unchanged with Hp/He. An increase in the excavation width did not influence stability of excavations. The wall bending moment capacity had a more pronounced effect on stability of excavations than the strut capacity. And stability of excavations was clearly affected by su/v’. Finally, a simplified method to estimate the factor of safety and failure mechanisms were proposed for excavations in clay.

Abstract I
Acknowledgement II
Contents III
List of Tables VI
List of Figures VII
List of Symbols XIX
CHAPTER 1 INTRODUCTION 1
1.1 Background 1
1.2 Objectives 2
1.3 Dissertation structure 3
CHAPTER 2 LITERATURE REVIEW 4
2.1 Conventional methods for estimating stability of deep excavations in clay 4
2.2 Finite element method for estimating stability of deep excavations in clay 8
2.3 Comparison between conventional methods and finite element method 13
CHAPTER 3 EVALUATION OF FACTORS OF SAFETY FOR CASE HISTORIES 36
3.1 Introduction 36
3.2 FEM with reduced shear strength 36
3.3 Taipei Rebar Broadway case 37
3.3.1 Overview 37
3.3.2 Finite element model 38
3.3.3 Stability analysis 41
3.4 Taipei Shi-Pai case 46
3.4.1 Overview 46
3.4.2 Stability analysis 47
3.5 Hangzhou case 50
3.5.1 Overview 50
3.5.2 Stability analysis 51
3.6 Nicoll highway case 55
3.6.1 Overview 55
3.6.2 Finite element model 55
3.7 Discussion 59
CHAPTER 4 FACTORS AFFECTING STABILITY OF DEEP EXCAVATIONS IN CLAY 101
4.1 Introduction 101
4.2 Methodology 101
4.2.1 Analysis methods 101
4.2.2 Excavation geometry, construction sequence, and soil profile 102
4.2.3 Finite element model 103
4.3 Excavation geometry 104
4.3.1 Effect of wall embedded depth (Hp) 104
4.3.1.1 He = 10.5 m 104
4.3.1.2 He = 18 m 108
4.3.2 Effect of excavation width (B) 111
4.3.2.1 He = 10.5 m 111
4.3.2.2 He = 18 m 114
4.3.3 Summary 116
4.4 Support system 118
4.4.1 Effect of wall thickness (tw) 118
4.4.1.1 He = 10.5 m 118
4.4.1.2 He = 18 m 120
4.4.2 Effect of strut capacity (Str) 122
4.4.2.1 He = 10.5 m 122
4.4.2.2 He = 18 m 124
4.4.3 Summary 126
4.5 Effect of soil strength (su/v’) 126
4.5.1 He = 10.5 m 126
4.5.2 He = 18 m 128
4.6 Failure mechanisms of deep excavations in clay 129
4.7 Simplified method for estimating stability of deep excavations in clay 132
CHAPTER 5 REDESIGN OF SUPPORT SYSTEM OF CASE HISTORIES 214
5.1 Introduction 214
5.2 Failure mechanisms of case histories 214
5.3 Taipei Rebar Broadway case 215
5.4 Taipei Shi-Pai case 217
5.5 Hangzhou case 218
5.6 Nicoll Highway case 219
5.7 Summary 220
CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 259
6.1 Conclusions 259
6.1.1 Methods for estimating stability of deep excavations in clay 259
6.1.2 Factors affecting stability of deep excavations in clay 260
6.1.3 Failure mechanisms of deep excavations in clay 261
6.2 Recommendations for future work 263
REFERENCES 264
APPENDIX A 269
EFFECT OF WALL EMBEDDED DEPTH 269
APPENDIX B 285
EFFECT OF EXCAVATION WIDTH 285
APPENDIX C 305
EFFECT OF WALL THICKNESS 305
APPENDIX D 329
EFFECT OF STRUT CAPACITY 329

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