Stability Assessment of Shallow Soil Landslide and Activating Rainfall Threshold

The transient rainfall infiltration and grid-based regional slope-stability (TRIGRS)-Scoops three-dimensional (3D) coupling model combines the influences of rainfall infiltration and 3D topography on slope safety. However, the Scoops 3D model defines the physical and mechanical parameters of underground materials with a uniform or layered method, which cannot describe the variability in the horizontal direction. To address this limitation, a method of creating a 3D distribution file of physical and mechanical parameters for underground materials was proposed. This method was applied to a mountainous area in Chishang Town, China. Based on the TRIGRS-Scoops 3D coupling model, the stability of slopes in the study area was assessed under different rainfall conditions. The dangerous slopes were located where the proportion of unstable grids exceeded 1%. The TRIGRS-Scoops 3D coupling model was repeatedly used to determine the curve of the rainfall threshold for landslide activation. This curve is based on the intensity (I) and duration (D) of rainfall. The results show that the 3D distribution file can effectively reflect the variability of parameters in the horizontal direction. The landslide activating rainfall threshold curves for the 13 dangerous slopes in the study area exhibit a linear relationship between lgI and lgD. This study can reveal slope stability under different rainfall conditions and provide a theoretical basis for landslide warnings.