Abstract: Deformation of filled embankment and its stability are common engineering problems of the western mountains area construction. A typical slope of one expressway in Chongqing slides along the weak stratum on the bedrock after stacking fill, under the condition of continuous heavy rain. To study the failure mechanism of the landslide, physical simulation is adopted to study the rainfall influence on slope deformation. We also analyze pore water pressure change with the rainfall time and its relationship with the deformation and failure. The results show that the landslide deformation and failure is due to large amount of stack at trailing edge, changing the slope stress condition greatly. Secondly, the construction changes the original hydrological environment, and continuous heavy rains cause a lot of rain infiltration into the slope. Pore water pressure in the process of the landslide plays a key role. Embankment has a mass of debris and argillaceous, which can be carried to the slide zone with rainwater. And argillaceous of slide is the same. These substances can block the dissipate of groundwater. This phenomenon is the accumulation of slope deformation and pore water pressure. Deformation suddenly increase and pore water pressure decrease. The landslide can divide four phases: rainfall infiltration, slide with full water softening, trailing edge cracks, crack through whole sliding. The final landslide deformation failure mode is creeping-cracking.

Key words: fill embankment, landslide, pore water pressure, deformation, physical model test