Simulating dynamic processes and hypermobility mechanisms of the Wenjiagou rock avalanche triggered by the 2008 Wenchuan earthquake using discrete element modelling

The discrete element method is well suited for simulating the cracks and subsequent large displacements of catastrophic landslides or rock avalanches, and is therefore a useful tool for analysing their complicated dynamic processes and hypermobility mechanisms. In this study, particle flow code was used to investigate the dynamic processes and hypermobility mechanisms of the Wenjiagou rock avalanche triggered by the 2008 Wenchuan earthquake. Characterization of the avalanche dynamics was achieved using a model comprising four stages: failure rupture, projectile motion, granular debris flow, and debris mass accumulation. The results show that collision on the valley floor was the main factor causing the fragmentation of the Wenjiagou rock avalanche. The upper and front edge of the landslide body were the most likely to move over a long distance. The results also show that friction was the main source of energy dissipation during the entirety of the avalanche movement. The high gravitational potential energy of the avalanche was the basis of the high mobility. In addition, because of their effects on energy dissipation, the low basal friction coefficient, favourable block movement, and topographical conditions played key roles in the rapid, long-runout Wenjiagou avalanche process.