Abstract: Taking a certain thick accumulation landslide for example, and based on the theory of unsaturated soil mechanics, this paper uses the finite-element method to calculate and analyze the slope seepage and dynamic stability under the condition of rainfall infiltration and studies the time effect of water movement in the slope mass on the slope stability. The results show that the loose structure of the slope accumulation body, the poor soil strength, the large gradient at the slope front edge and excavation at the slope toe have provided a convenient condition for landslide formation. Under heavy rainfall, the deformation instability firstly occurred near the slope toe, and then pulled the slope rear edge and caused the tensile fissures. The rainwater infiltrated along the slope surface, formed the seepage field in the slope body and weakened the rock-soil mass parameters. Meanwhile, the saturated runoffs formed on the slope surface generated the downward seepage force on the slope front edge, and promoted the slope front edge to slide and triggered the slippage of the hierarchical slopes. In the initial stage of the heavy rainfall, the safety factor of the landslide mass reduced rapidly, which easily caused the landslide. This study reveals that the rainfall infiltration induced the sliding mechanism of the slope with thick accumulation horizon, based on which, the paper recommends to take the measures of water cut-off, drainage and water plugging to drain off the water, and to set the rock-socketed anchor cable anti-slide pile and taking the measures of slope cutting and cleanup earthwork to control the slope. Good effect results have been obtained through the stability calculation.

Key words: unsaturation, weakening, rainfall, accumulation body, mechanism