Discrete element simulation of shallow soil landslides with weak interlayer due to the mechanism of unsaturated seepage

Abstract

A hybrid discrete-continuum numerical method was employed to study the shallow red-bed soil landslides that frequently occurred in Southwest China. This study used a clay slope with weak interlayer in Guangxi, China, as a geological model to simulate water infiltration driven by differences in water content in particles. The landslide’s kinematic behavior was performed by the discrete element software MatDEM. Results indicate that the spatial variability of the wetting front is caused by the thickness difference of the soil layer. The water content of the weak interlayer particles increases nonlinearly with time, and the bond between particles decays exponentially with the increase of its water content. In red-bed soil slopes, both higher initial water content and higher recharge boundary water content promote landslide initiation. After triggering the landslide, the soil particles at the foot of the slope and in the weak interlayer move first, and the maximum velocity and kinetic energy of the particles show a trend of first increase and then decrease. During the dynamic process, the sliding body may have an extrusion effect on the underlying soil layer, resulting in a new sliding surface. This study evaluates the effectiveness and potential of this discrete-continuum hybrid numerical approach for revealing the disaster-causing mechanism of rainfall-induced landslides in red-bed areas.