Dynamic analyses of high-position long-runout landslide in Shuicheng, Guizhou, China: perspectives from overloading erosion effect

Abstract

On July 23, 2019, a large-scale, high-position landslide was triggered by heavy rainfall at Pingdi Village, Jichang Town, Shuicheng County, Guizhou, China. Based on a field investigation, multi-temporal remote sensing images, and topographic maps, the elevation of the crown of the landslide and the front edge was approximately 1700 m and 1233 m, respectively. The height difference of the landslide was 467 m, and the horizontal distance was approximately 1332 m with a main sliding direction of NE20°. Its volume was up to 1.81 million m3. The landslide buried 21 houses, leading to the death of 51 people. The landslide first exited from the upper part of the steep slope in the Emeishan Formation with a basaltic lithology, which accumulated continuously at the back of a previous residual landslide and triggered the slope instability under the exit. The erosion volume due to the “overloading effect” was up to 1.44 million m3, and the landslide then transferred to a long-runout double-channeled debris flow. The landslide then converted to diffused flow and finally accumulated to the east side of the Jichang reservoir because the terrain was wide and the slope angle decreased gradually. Based on the above investigation, the entire movement process of the Jichang landslide was retrieved using dynamic numerical simulation technology. In contrast to the previous erosion model, the overloading erosion effect was proven, which added loads and drove the deposit below to move downward together.