Site investigation and long-term monitoring are crucial for planning and designing slope stabilization measures. However, specific in situ topographical and environmental constraints may prevent people and machines from accessing a site, which limits the slope data that can be collected. Therefore, in this case study, monitoring data and numerical analyses with the material point method were used to evaluate the failure surface depth involved in the
Guanghua landslide and to predict its subsequent post-failure behavior. The numerical results indicated that the failure surface developed at a depth of 40–50 m in fractured rock and extended from the upper to the lower slope, causing the slope to settle at the upper section and rise at the lower section. When the sliding masses converged at a valley, the overall movement of the slope along the deep failure surface ceased because of topographical constraints. This numerical result corresponded to the field observations of the Guanghua landslide. The numerical analysis of a high-groundwater-level scenario also revealed that when the groundwater level inside the colluvium layer rises to 7 m below the slope surface, a subsequent landslide in the colluvium layer may occur.
Key Words: material point method, large deformation, failure surface, post-failure behavior