This study investigates transient seepage using a two-phase flow scheme in finite difference code,FLAC. The saturation of pore water pressure distribution and the stability of the assumed landslide dams are calculated.The safety factors of the assumed landslide dams are evaluated using the strength reduction technique. The results show that when we increase the saturated permeability of the dam materials, dam failure occurs earlier than those dams with smaller saturated permeability. When the slope angles of the dams are small, the timing of failure is slower than those dams with large slope angles. However, the durations of the failure process of dams with smaller slope angle are shorter than those of dams with larger slope angles. When the peak intensity of rainfall is higher,dams are less stable.
Key Words : Landslide dam, stability, infiltration, unsaturate.