Insights into the Transport and Fragmentation Characteristics of Earthquake-Induced Rock Avalanche: Numerical Study

Abstract

The earthquake-induced rock avalanche in the Tangjia Valley was the most notable geological disaster triggered by the Lushan earthquake in 2013. In order to investigate the transport kinematics and depositional mechanism of this catastrophic landslide, a 2D discrete element model was developed and calibrated using field data. The model was then used to analyze the seismic response and mass transport process of a natural slope. The slope response to earthquake was numerically studied focusing on crack initiation, propagation, and coalescence within the rock mass. The mass movement and accumulation process were interpreted in terms of evolution of stress and solid fraction, kinematic behavior, and energy conversion. During the mass transport process, the slope was fragmented progressively due to intense shearing, allowing a basal layer of gradually fining solid particles to be generated with simultaneous occurrence of violent collisions, increase in particle kinematic activities, and the reduction of solid concentration. To further study this deformation process, fragment size distributions and fractal dimensions were described by Weibull distribution and power-law function, respectively. This statistical analysis reveals that dynamic disintegration continuously operates with the increasing runout distance. It is also found that the distribution of the fragment shapes becomes stable as the avalanche loses its momentum and deposition starts in the runout area. The proposed framework for the analysis of rock avalanches can be used to understand the physics of similar geological hazards.