Abstract
In recent years, localized torrential rainfall caused by abnormal weather happens frequently. It triggered numerous sediment disasters as slope failure. During heavy rainfall, it is estimated that degree of saturation increases rapidly in the ground with water flow. It may cause pore air occluding with rapid water flow in some cases. Because natural slope is often unsaturated, it is required to consider effect of pore air pressure. In this study, coupled stress-flow analysis is performed by calculating two-phase flow considered effect of pore air pressure. Failure mechanisms of slope are examined by decreasing effective stress, which is induced by increases of pore water and air pressure. It is discussed on slope stability by the case studies focused land features and rainfall intensity under like these conditions. The calculation results could be divided two prominent failure types. One is resulted from decreasing effective stress caused by rise of ground water level under the condition of gentle slope. And another one is resulted from gravitational sliding caused by increasing soil mass weight with short-time heavy rainfall under the condition of steep slope.
