A rigid finite element method for upper bound limit analysis of soil slopes subjected to pore water pressure

An upper bound limit analysis method using rigid finite elements is developed. Rigid finite elements are used to discretize the slope media. Kinematically admissible velocity discontinuities are permitted to occur at all inter element boundaries. The traditional definition of factor of safety is adopted in the present method so that the results from the limit analysis can be directly compared with those from methods of slices. The presence of water can be considered through work terms in the energy work balance equation. To do this effectively, the pore water pressure is considered as an external force, similar to gravity and surface tractions. The proposed method formulates the slope stability problem as a non linear optimization problem with constraints based on the yield criterion, flow rule, boundary conditions, and the energy work balance equation. The optimization problem is solved by a sequential quadratic algorithm.