Numerical investigation of large-slope planar failure considering entrainment effects: New insights into the 2009 JWS event

On 5th June 2009, a massive rapid long run-out rock avalanche occurred at the Jiweishan (JWS) area in Chongqing Municipality, China, which claimed 74 lives and injured an additional eight. Previous studies have applied numerical simulation to analyze the post-failure behavior of the JWS rock avalanche over the last decade, but the simulations conducted so far have not fully captured the lateral rock movements, the entrainment of slide mass on weathered blocks at the slope toe, and the subsequent deposition of the debris. This study simulates the planar failure at the initiation of the rock avalanche by three-dimensional (3D) numerical modeling to model the debris movement and deposition of the rock avalanche under the brittle failure of the key block at the front of the slope. The 3D topography and local joint sets are considered in the calculations, with the joint sets cutting the sliding rock mass into irregularly shaped blocks. The shoveling effects are considered to erode the hill ahead of the slope toe to expand the area of influence and match the actual topography. The 3D numerical modeling accurately captured the fundamental characteristics of the rock avalanche, resulting in a post-failure configuration closely resembling what was observed in the field. This method of quantitatively establishing a shoveling model based on field survey results can serve as a reference for the early warning and risk assessment of similar rock avalanche events.