Numerical modeling of the 2008 Wenchuan earthquake-triggered Niumiangou landslide considering effects of pore-water pressure

Ring-shear experiments are commonly conducted to analyze the kinematic mechanisms of landslides triggered by earthquakes, particularly for landslides impacted by pore-water pressure near the grain-crushing sliding surface. However, pore-water pressure is rarely considered in numerical simulation of the post-failure behavior of earthquake-induced landslides. In this paper, a pore-water pressure model based on the results of ring-shear tests (Cui et al. Landslides 14(3):1-15, 2016) is incorporated into the discontinuous deformation analysis (DDA) for modeling and further understanding the initiation and motion behaviors of the Niumiangou landslide triggered by the 2008 Wenchuan earthquake. The pore-water pressure can be recalculated in each time step before the sliding block is detached from the base in the source area, and the friction coefficient of the sliding surface is simultaneously updated according to the pore-water pressure ratio in the modified DDA. The modified pore-water pressure DDA (PWP-DDA) is validated by means of comparison with the analytical results of the dynamic behaviors of a sliding block on an inclined plane under dynamic acceleration. The simulation results indicate that the pore-water pressure on the sliding surface of the Niumiangou landslide sharply increases within a short period, with small relative displacement of the landslide. Relative to the simulated results from the unmodified DDA, the pore-water pressure calculated by the PWP-DDA promotes higher velocity and longer run-out of the sliding mass. Moreover, the modeling run-out and deposit pattern from the PWP-DDA are in basic agreement with the topography of an actual survey.