DEM Simulation of the Bridge Collapse under the Impact of Rock Avalanche: A Case Study of the 2020 Yaoheba Rock Avalanche in Southwest China

Mountainous regions present severe risks, including damage to transportation infrastructure, due to the occurrence of geohazards such as rock avalanches and other types of landslides. Lessons learned from past damaging events are helpful for risk reduction in mountainous regions. In this paper, to study a rock avalanche impact on a bridge, a numerical modeling framework with the aid of the discrete element method (DEM) is developed; the progressive failure process of an expressway bridge that was damaged by a rock avalanche is reproduced, and the failure mechanisms and dynamic behaviors of the bridge under impact are assessed. The Yaxi Expressway bridge that was destroyed by the September 20, 2020, Yaoheba rock avalanche in southwest China is used as an illustrative example. A field investigation is carried out to identify geological conditions, characteristics, and the kinetic failure pattern of the rock avalanche and the bridge. The stereographic projection analyses indicate that this rock avalanche was initiated as a planar slide. A three-dimensional numerical model of the rock avalanche and bridge is developed based on the terrain data acquired. The critical parameters of the numerical model are calibrated based on results obtained from laboratory tests. Finally, the progressive failure process and failure mechanism of the impacted bridge are analyzed based on the constructed numerical model. The comprehensive analysis framework can be applied to similar events involving geohazard-structure interaction.