Slope Stability Analysis Using Direct Search Method Based On 3D FEM And Its Application In Tunnel Excavation

It is very important academic and practical significance to use 3D method directly in the slope stability analysis. Systemic summary to the essential method of 3D slope stability analysis and their problems are presented in this paper. Simultaneously a new method to calculate the safety factor and search critical slip surface based on 3D FEM's stress result is given in this paper too. This method overcome the problems of many supposition conditions in theory and difficulty in searching critical slip surface in 3D limiting equilibrium analysis; It uses the 3D FEM's stress field directly, differs from the practical value of 3D FEM strength reduction method used hypothesized load, and differs from the characteristic of the FEM with limiting equilibrium theory still to need to divide the columniation, and suppose the critical slip surface in advance. In this method, stresses acting along the critical slip surface are computed using 3D FEM analysis, moreover the 3D FEM mesh is used directly as the searching grid. In view of the fact that it is intuitionistic similarity between a FEM mesh and a graph, the mesh may be abstract to a graph, and the optimized thought in dynamic programming may be used to search. This method does not need to suppose the shape and position of 3D critical slip surface, only through the construction of glide pattern, and the searched critical slip surface is a space surface which connects mutually by the grid surface.Through the research of direct search method based on 3D FEM, and its application for the tunnel slope stability analysis, the objectives of this work in this paper are as follows:1. The dynamic programming as well as its application for 3D side slope stability analysis is studied. With the introduction of graph theory concept, one kind of glide pattern of 3D slope is constructed, and the critical slip surface with smallest safety factor is searched with the aid of one auxiliary function including safety factor;2. Using the C++ programming language, the 3D slope stability analysis and the direct search procedure is established, and this method is testified applicably by some contrast analysis, also some influence factor in analysis is discussed;3. Integrated with the different actual situation in tunnel slope, considered its excavation, timbering and rain infiltration, its stability influence and rule is researched used this method, also some processing measure is proposed.