Research On Methods Of Slope Stability Analysis Influenced By Initial Stress

Initial stresses do not receive their deserved consideration in slope stability analysis for a long time. Engineers are used to considering gravity field instead of initial stresses. Initial stresses can not be included in conventional Limit Equilibrium Method (LEM) and recently popular Strength Reduction Method. Although incremental Finite Element Method (FEM) can take initial stresses into account, it only gives a limit load, not a Factor of Safety (FOS). Combining FEM and LEM can give a FOS based on an overload concept, but this definition does not have a straightforward physical meaning. Based on the two numerical methods proposed in this dissertation, both initial stresses and FOS concerned by engineers can be considered.With the help of the concept and experience of engineering geology, research on the relationship between initial stresses and slope stability is done, and an efficient quantitative method (not conceptual analysis only) is also found.The Element Integration Method (EIM) for limit analysis of slope stability is perfected. When considering the influence of a distributed field on the slope stability, EIM has an outstanding advantage. After stability analysis of expansive slopes and slopes under different horizontal tectonic stresses, it is found that the FOS of slopes could decrease dramatically. This agrees with the factual things, and avoids the arbitrariness of inferring strength parameters by results. Taking expansive deformations and horizontal tectonic stresses into consideration, the critical collapse pattern from the same optimization transforms from ordinary deep slide to local shallow slide, which will induce the upside soil mass into another small range of shallow slide. As a result, a larger range of shallow slide comes into being. This agrees well with the traction character of expansive soil slope and the phenomenon of shallow collapse after the excavation of slopes in some hydraulic engineering with high initial stresses.Elastic Compensation Method (ECM) is introduced to geotechnical area. The author modifies the formulation of ECM, particularly in the determination of nominal stress and equivalent stress. By virtue of compiling user subroutines, the procedures of ECM are realized successfully in ABAQUS. In the elastic iterations, statically admissible stress and kinematically admissible velocity can be derived in the same time. Thus limit load or FOS can be attained by limit theorem. ECM can take initial stresses into consideration easily.The research of this dissertation provides an efficient appraisable method for slopes influenced by initial stresses.