Analysis of the formation mechanism of landslide in Changchong group, Songtao, Guizhou

Guizhou Province is a mountainous region with typical karst topography where the quaternary overburden layer is unevenly distributed, with clayey soil on the shallow surface layer from the front edge to the middle of the slope body and gravelly soil at the rear edge. This geological characteristic, combined with the increase of extreme rainfall and heavy rainfall due to abnormal climate change in recent years, has resulted in a rise of sudden earth landslides in the shallow surface layer after strong rainfall. To investigate this phenomenon, the Changchong Group landslide in Heping Community, Dalu Town, Songtao County, Guizhou Province was studied through field tracking survey, geological drilling, geotechnical testing, and FLAC3D software simulation. The study uses various methods to investigate the shape and geotechnical structure characteristics, and deformation and damage history of the landslide before and after rainfall, in order to analyze the failure process of such landslides and their occurrence mechanism. Results show that: (1) The landslide is a thrust load-caused landslide, and its unique terrain and lithology characteristics provide intrinsic factors for the occurrence of the landslide. (2) Rainfall is the main triggering factor of landslide, and the occurrence process of the landslide can be summarized as follows: a) rear saturated pushing stage, b) transient saturated diffusion and deformation evolution stage, c） front edge overhanging failure stage, and d) overall failure stage. (3) The mechanism of the landslide is mainly due to the combined effect of the changes in permeability induced by precipitation and the slope gravity change, which led to the instability and deformation of the landslide. The study provides insight into the early identification factors of rainfall landslides and provides a theoretical basis for better and faster control and management.