Investigation of deformation pattern and sliding mode in dip slopes using discrete element method

In the conventional Newmark sliding block method, permanent displacement develops along a single slip surface when a slope is subjected to a seismic motion that exceeds critical acceleration. However, for a slope with geological discontinuities, the Newmark approach could lead to an unsafe assessment that the plastic deformation may occur along the existing weak planes. In this study, the small-scale shaking table tests and the discrete element method were used to understand the dynamic responses of a slope with multiple weak planes under seismic condition. The effect of slope geometry and input motion property were explored. In addition, two types of sliding modes, namely differential and complete, were observed and could be distinguished by using the slope angle as the threshold. Compared to the Newmark approach, the numerical models exhibited greater permanent displacement at the slope crest than the theoretical estimation and the critical acceleration was greatly overestimated in all cases. The comparison indicates that sliding planes develop much more easily along existing discontinuities within the dip slope and can lead to even greater disasters than theoretical estimation by conventional Newmark approach.