Based on the kinematic method of limit analysis and the shear strength reduction technique

the equation for expressing the critical limit-equilibrium state is formulated and employed to define the factor of safety and its corresponding critical failure mechanism by mathematical optimization method for a given slope subject to pore-water pressure and seismic load. The presence of pore water and seism can be embodied through work terms in the energy balance equation

and water pressure and seismic inertia force are considered as external forces similar to gravity and surface tractions. 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. Through numerical analyses for several typical examples

the reasonability of the method is verified. Numerical computations are made to examine the influence of pore water pressure and horizontal seismic acceleration coefficient on slope stability.