Estimation of landslide during heavy rainfall based on FEM-MPM model

Abstract

In 2016, Typhoon No. 10 landed on Hokkaido, Japan and resulted in slope failures near Nissho Pass. The massive precipitation generated serious runoff within the catchment area, which accounted for the slope instability. Besides, the rainfall induced slope instability developed as landslide. However, the traditional slope instability analyses were often finished ignoring the transportation of instable soil. This study conducted soil runout analysis as well as slope instability analysis with a finite element method-material point method (FEM-MPM) model to catch the disaster area. In the slope instability analysis using three-dimensional (3D) FEM model, runoff and infiltration were considered at the same time to evaluate the slope instability during heavy rainfall. Here, the surface flow and subsurface flow were governed by shallow water equation, Richards’s equation and Green-Ampt infiltration capacity model. Then, based on the hydraulic field result, local factor of safety (LFS) distribution and dangerous spots were given by FEM model. Subsequently in the soil runout analysis using two-dimensional (2D) and 3D MPM model, large deformation part after failure and the soil transportation were examined to reveal the amount of soil that is risky to be washed away during heavy rainfall. The simulation results proved the appropriateness of this simulation method to reproduce the slope instability and landslide process during heavy rainfall.