Failure mechanism of a high-locality colluvial landslide in Wanzhou County, Chongqing, China

High-locality colluvial landslides primarily occur in the upper zones of failed slopes, which are formed by colluvial deposits. This paper discusses a high-locality colluvial landslide that deformed in 2003 in Wanzhou County, Chongqing. Landslide deformation was evident in October 2017, threatening the life and property safety of 159 people in 58 families. The landslide, called the Shiquan landslide, originated on a 364-m-high hillslope. In this work, the 3-month monitoring data were combined with macro-deformation signs and site topography to analyze the landslide deformation processes; GeoStudio software was used to analyze the failure mechanism and stability of slopes under rainfall and fishpond water leakage with the consideration of unsaturated infiltration. The results indicate that the high-locality colluvial landslide was formed under a favorable geological background, and the height difference between the shear outlet and the trailing edge was approximately 50 m, which provides potential energy conditions for the remote sliding of landslide shear. The deformation characteristics of the landslide are apparent. The deformation of the major controlling cracks on the landslide surface resulted mainly in tensile cracks, and the deformation of the boundaries on both sides of the landslide surface and the deformation controlled by the structure resulted in shear cracks, which are in a creep stage. Rainfall and pond seepage will lead to a decrease in landslide stability, while a large amount of water infiltration at the trailing edge of the landslide will intensify landslide deformation until destabilization. Therefore, the results of this study help provide a more complete hazard picture for studying rainfall-induced high-locality colluvial landslide hazards in mountainous regions.