Static and Seismic Slope Stability Analyses Based on Strength Reduction Method

This study presents the numerical procedure for static and seismic stability analyses of slope based on the shakedown theorem in plasticity7).The stability of slope has been defined as a reduction coefficient in shear strength for the limit state of slope mass.Firstly,the applicability of proposed method to the static slope stability analysis was investigated.The obtained factors of safety were compared with those of the conventional methods.It was clearly shown that the proposed method could evaluate the stability of slope properly.Secondly,the seismic stability of slope was investigated against sine wave accelerations excited at the bedrock of subsoil.The proposed method was shown to estimate the factors of safety by taking account of the effects of frequency in enforced acceleration and vibration properties of slope mass as damping and resonance.The obtained factor of safety for low frequency wave acceleration coincided with that of pseudo-static stability analysis and,on the other hand,the factor of safety approached that of static stability analysis for high frequency wave acceleration.Thirdly,the combined stability method16) which composed of deformation and stability analyses was conducted.The comparison between combined stability and proposed methods in cases of natural slope and embankment was investigated.It was found that the minimum factor of safety for natural slope obtained by the conventional method,however,gave an almost coincident factor of safety by the proposed method.But,the significant difference appeared in case of embankment problem.The possible engineering meaning of time dependent factor of safety obtained by the combined method was clarified.