First World Congress of International Consortium on Geo-disaster Reduction (1st ICGdR World Congress)

In recent years, under the influence of extreme climatic conditions, the southeastern coastal regions of China have experienced frequent outbreaks of shallow landslides induced by intense rainfall. On May 17, 2022, and June 16, 2024, two large-scale landslide events occurred in Wuping County, Fujian Province, resulting in severe economic losses and casualties. Nevertheless, the disaster-triggering mechanisms of shallow, rainfall-induced landslides triggered by the combination of toe excavation and rainfall infiltration remain insufficiently understood. Field investigations and tests have demonstrated the presence of a typical “dual structure” in the weathering crust of granite regions, consisting of an upper layer of residual soil and a lower layer of strongly weathered granite, which exhibit markedly different hydrological and engineering geological characteristics. A representative landslide from the June 17 event in Wuping County was selected as the study object. Based on field investigations, field experiments, and engineering geological mapping, the finite element method (FEM) was employed to perform numerical analyses of seepage processes and deformation–failure behavior of both the natural slope and the toe excavation slope. The results indicate that, under the influence of intense rainfall, rapid infiltration of surface water leads to the formation of a saturated zone along the interface between the residual soil and the strongly weathered granite. This increases the internal pore water pressure within the slope, softens the mechanical properties of the soil mass, and reduces its shear strength, which collectively serve as the primary triggers of shallow landslides. Meanwhile, toe excavation creates a free face, increases the downslope driving force, and induces a stress concentration zone near the toe of slope, thereby promoting the development of tensile or shear cracks and significantly reducing the overall slope stability coefficient.

failure mechanism,toe excavation,granite residual soil,heavy rainfall