Slope Stability Analysis and Stabilization. New Methods and lnsight Second Edition

Transcription

1 Slope Stability Analysis and Stabilization New Methods and lnsight Second Edition

2 Contents Preface 1 Introduction 1.1 Overview Background Closed-form solutions Engineering judgement Ground mode/ Status quo Ground investigation Design parameters Groundwatet tegime Design methodology Case histories 10 2 Basic slope stability analysis methods 2.1 Introduction Types of stability analyses Defìnition of the factor of safety Slope stability analysis: limit equilibrium method Limit equilibrium formulation of slope stability analysis methods Force equilibrium Moment equilibrium equation Interslice force function Reduction to various methods and discussion Solution of non-linear factor of safety equation Examples of slope stability analysis 38 Xl 1 17 v

3 vi Conre nts 2.3 M iscellaneous considerations o n slope stability analysis Acceptability of the failure surfaces and resufts of the analysis Tension crack Earthqualw Water Saturated density of soil Moment point Use of soilnail/reinforcement Advantages o( soilnailing Failure to converge Location o( the criticai (aih1re surface Three-dimensional analysis Limit analysis method Lower bound approach Upper bound approach Rigid element method Displacements o( the rigid elements Contact stresses between rigid elements Principle o( virtual work Governing equations Genera/ procedure of REM computation Relation between the R EM and the slice-based approach Uses o( design fìgures and tables (or simple problems Finite element method Distinct element method Force displacement law and the law of motion Limitations o( the distinct element method Case studies (or slope stability analysis using PFC Three-dimensional mode/ and distinct element studies of a slope under a patch load Laboratory test on a mode/ slope Three-dimensional distinct numerica/ modelling of slope under /oca/ surcharge 93 3 Location of criticai failure surface, convergence and advanced formulations Difficulties in locating the criticai (ailure sur(ace Generation o( trial failure sur(ace 103

4 C ontents vii 3.3 Global OfJtimization methods Simulated annealing algorithm Genetic algorithms Particle swarm optimization algorithm Simple harmony search algorithm Modified harmony search algorithm Tabu search algorithm Ant colony algorithm Hybrid optimization algorithm Verification of the global minimization algorithms Presence of Dirac function Numerica! studies of the efficiency and effectiveness of various optimization algorithms Sensitivity of global optimization parameters in the performance of the global optimization methods Convexity of critica! failure surface Latera! earth pressure determination (rom slope stability analysis Convergence problem due to iterative solution of FOS Parametric study of convergence Combined impact of optimization and double QR analysis Reasons (or failure to converge Importance o( the methods of analysis Solution o( the inter-slice force function and fundamental investigation into the problem o( convergence Determination o( bounds on FOS and ({x) Numerica! studies and comparisons with classica/ methods of analysis Study of convergence by varying {(x) Validation of maximum extremum principle Variable FOS formulation in LEM Basic formulation for variable FOS formulation Analysis of variable FOS approach Discussion on variable FOS approach Use of internallexternal variables in slope stability analysis and relation of slope stability problem to other geotechnical problems 187

5 viii Concencs Basic methods in (ormulation lnter-slice force function ((x) and thrust line (or horizontal slope problem Boundary forces in LEA Lower bound solution and the maximum extremum {rom limit equilibrium analysis Finite-element methods for slope stability analysis and comparisons with limit equilibrium analysis Comparisons between SRM and LEM Stability analysis (or a simple and homogeneous soil slope using LEM and SRM Stability analysis of a slope with a soft band Local minimum in LEM Effect of water on slope stability analysis Soil nailed slopes by SRM and LEM Distribution of the nail tension force and the critica! slip surface by SRM Stabilization o( slope with piles using SRM Discussion and conclusion Three-dimensional slope stability analysis 5.1 Limitations o( the classica! threedimensionallimit equilibrium methods New formulation for 3D slope stability analysis in Bishop> ]anbu and Morgenstern Price methods by Cheng and Yip Basic formulation with consideration of sliding direction Reduction to 3D Bishop and ]anbu simplified methods Numerica! implementation o( Bishop, ]anbu and MP methods Numerica! examples and verification Comparison between Huang's method and the present methods (or transverse earthquake load Relation o( proposed 3D slope stability method with classica/3d methods Problem of cross-section forcelmoment equilibrium for MP method

6 Contents ix Discussion 0 11 À-'">' (or M P a11alysis Discussion D limit equilibrium stahility (onnulatio Three-dimensionallimit analysis Three-dimensional hearing capacity problem with an inclined slope Failure mechanism o( the patched load acting on the top su-rface o( a slope (D= O m) Work dane rate produced along load length L Work done rate produced at the two end-failure zones of the footing Determining the value of the safety factor Failure mechanism of the patched load acting at an embedded depth {rom the top surface of slope (D> O m) Work done rate produced along footing length L Work done rate produced at two end failures of the burìed load Comparìson of Cheng's method with other analytical solutions Location of generai criticai non-spherical 3D failure surface Three-dimensional NVRBS surfaces Spherical and ellipsoidal surface Selection of sliding surfaces Optimization analysis ofnvrbs surface Case studies in 3D limit equìlibrium global optimization analysis Effect of curvature on FOS Three-dimensional SRM analysis Implementation 6.1 lntroduction FRP nail Dminage Construction difficulties

7 x Contents 7 Routine assessment of feature and design of landslip preventive measures 7.1 lntroduction Geotechnical assessment Desk study Aerial photograph interpretation and ground-truthing Gl and fìeld testing Laboratory testing Man-made features Rainfall records Groundwater regime O Stability assessment o( the existing feature Design o( landslip preventive works Design options (or masonry retaining walls Design options (or fìll slopes Design options (or cut slopes Soil nailing Soil nailing in loose fìll Surfaceand sub-soil drainage Surface erosion contro/ and landscaping Site supervision during implementation Corrosiveness assessment Precautionary measures and other considerations Long-term maintenance Numerical implementation of slope stability analysis methods 8.1 Numerica/ procedures (or simplifìed limit equilibrium methods Numerica! procedures for "rigorous" limit equilibrium methods Spence1 and Morgenstern-Price method ]anbu rigorous method Sarma method Three-dimensional analysis Appendix References lndex