Three-dimensional large deformation modeling of landslides in spatially variable and strain-softening soils subjected to seismic loads

Landslide is a common dynamic large-deformation disaster of mobilized soils, which poses a serious threat to the lives and economic properties of surrounding people. Both the strain-softening effect and spatial variability of soil are reported to have significant impacts on landslide behaviors. This study investigated the coupled effect of strain softening and spatial variability on the occurrence, evolution, and runout behavior of landslides induced by seismic loads, using three-dimensional (3D) large-deformation finite-element method. The results show that both the strain-softening behavior and spatial variability of soil dramatically affect the sliding velocity and runout distance. Their coupled effect further weakens the soil strength, resulting in a larger runout distance. Secondly, the runout distance in the 3D deterministic analysis is always smaller than the minimum value in the corresponding random analysis, which completely differs from the result from the two-dimensional (2D) analysis. This finding indicates that 2D analysis can result in a conservative estimation on the runout distance for spatially variable soils and highlights the advantages of 3D modeling on landslides. Thirdly, a linear formula was proposed to quantify the runout distance based on the horizontal peak acceleration, which can provide some guidelines for the safety design in practical slope engineering.