The Research On Finite Element Plastic Limit Analysis Method Subjected To Pore Water Pressure

Slope stability analysis is a very important work in the field of geotechnical engineering. The effect of pore water is a key factor of the slope stability. Appraising the current methods of slope stability, the paper puts forward Finite Element Plastic Limit Analysis of the slope stability subjected to pore water pressure. Based on the upper bound and lower bound principles of limit analysis, the mathematical model of slope stability in consideration of pore water is established, by means of finite element technique and mathematical programming technique.In this study, three-node linear triangular finite elements are used to construct both statically admissible stress fields for lower bound analysis and kinematically admissible velocity fields for upper bound analysis. The effects of pore water pressures are considered and incorporated into the finite element formulations. In the lower bound approach, the effective stress of each node are seen as unknown quantity, with the conditions of equilibrium, stress boundary, yielding and stress discontinuity considered, the strength safety coefficient of slope, and the corresponding statically admissible stress field are also obtained. In the upper bound approach, the velocity of each node are seen as unknown quantity, with the conditions of flow rule, velocity discontinuity, velocity boundary, the energy work equation considered, then the strength safety coefficient of slope, and the corresponding kinematically admissible velocity field are obtained. The optimization problem is solved by linear programming technique.Finally taking two classical soil slopes for examples of calculating slope stability, the comparisons among the analytical results of various methods are made .The results show the correctness of the method.