Reduction of Landslide Shear Resistance by Gravel Fragmentation: Insights from DEM Modelling

The shear resistance of fragmented gravels at the base of landslides plays an important role in landslide dynamics, especially in increasing granular propagation speeds and final runout distances. While many site investigations and theoretical analyses have attempted to explain the intrinsic mechanism of these phenomena, the current paper presents numerical simulations of the mechanical response of fragmented gravels via the Discrete Element Method (DEM) under the drained triaxial compression conditions. It is evident that the non-fragmented gravel mass has relatively large initial void ratio, high peak and residual shear strengths, and large shear contraction and dilation volumetric strains. However, for the fragmented gravels, they behave oppositely. In the analyses, it is clear to see that the peak and residual shear strength, the maximum shear contraction volumetric strains correlate with the fraction of fragmented gravels perfectly by parabolic curves. The current numerical results can qualitatively explain the shear resistance reduction of fragmented gravels during landslides.