Slope instability due to rainfall and earthquake

This paper discusses the coincident effects of rainfall and earthquake on the slope stability. A numerical program for the analysis of the slope instability due to rainfall has been already developed. The program unites a finite element program for the infiltration analysis and a Rigid-Body-Spring-Model (RBSM) program for the slope stability analysis. The numerical results for a model slope show that the reduction of the shear strength of the slope surface soil due to rain infiltration causes the reduction of the safety factor of the slope. When the slope suffers from both rainfall and earthquake, its safety factor will decrease more and it must become more unstable. The effect of seismicity is taken into account by applying the additional horizontal seismic force in RBSM as the pseudo-static limit equilibrium procedure of the slope stability analysis. The calculation results show that the slope suffering from the rain infiltration becomes more unstable when the additional seismic force acts. The greater magnitude of the seismic intensity strongly reduces the safety factor of the model slope.