The conventional method of slope stability analysis based on the concept of limit equilibrium is to calculate a factor of safety for a specified slip surface. However, it is not possible to assure that the failure surface which is decided from the analysis result represents a critical surface which is associated with the minimum factor of safety. Especially for engineers without any basis on a knowledge of geotechnical engineering backgrounds, it will be very difficult to find the critical surface in analyzing the slope stability problem.
Furthermore, we must analyze a slope stability problem due to rainfall because many landslides have been taken place during the wet season in Korea. The usual conventional slope stability analysis only considers the case of perfectly wet or dry condition. However, because a soil is in an unsaturated condition in reality, the conventional slope stability analysis must be extended to incorporate the shear strength of the unsaturated soils. Moreover, we must precisely consider the matric suction variation due to rainfall because the infiltration of rainfall into the slopes can reduce the matric suction, resulting in a decrease in shear strength.
Therefore this paper aims at the development of a slope stability analysis program in consideration of two things in all. First, it adopts an optimization scheme to search for a critical surface. Second, it accommodates consider the shear strength criterion for unsaturated soils. The negative pore water pressure variation is obtained from the analysis result of a commercial finite element program SEEP/W. Then, this paper illustrates the effect of infiltration on the slope stability and it verifies the developed slope stability program in comparison with the results obtained by the commercial program SLOPE/W.
