Numerical Analysis of the Largest Landslide Induced by the Wenchuan Earthquake, May 12, 2008 Using DDA

Abstract

The Daguangbao landslide, with an estimated affected area of about 7.3–10 million m2 and a volume of 750–840 million m3, is the largest landslide induced by the 2008 Wenchuan earthquake. The sliding mass travelled about 4.5 km and blocked the Huangdongzi valley, forming a landslide dam nearly 600 m high. In order to investigate the landslide progression and reproduce the post-failure configuration, the kinematic behavior of sliding mass was simulated by a dynamic discrete numerical analysis method called DDA that has been widely applied for geotechnical engineering problems due to its superiority in modeling the discontinuous material. In this simulation, based on the shape of failure surface and the character of slope topography, the whole slope was divided into three parts: base block, upper sliding mass, and lower sliding mass. Then two sliding masses were divided into the smaller discrete deformable blocks based on pre-existing discontinuities. Corrected real horizontal and vertical ground motion records were applied as volume forces act to the base block. The simulation results of landslide progression, sliding distance, and shape of post-failure were in good agreement with those obtained from post-earthquake investigation, description from the survivors. Therefore, the methodology applied in this paper is able to capture essential characteristics of the landslide and give a post-failure configuration.