Numerical Investigation of Failure Characteristics and Debris Movement in the Madaling Landslide Using Coupled FDM–DEM

The aim of this study is to investigate the mechanisms and kinematic characteristics of landslides in the southwestern mountainous regions of China. Field surveys and aerial photography were conducted to establish a discrete element method model with calibrated mesomechanical parameters. By considering internal and external triggering factors, a coupled finite difference and discrete element method was used to simulate the deformation, failure mechanism and movement process of slopes as well as to analyse the characteristics of debris movement. The findings revealed that the unique lithological and unfavourable geological structures resulted in an extremely fragmented rock mass, which was the internal cause of landslides. The main external cause was the mining of coal seams beneath the slumped mass, leading to extensive cracks at the trailing edge of the slope and subsequent debris movement. The average velocity of the slumped mass exhibited fluctuation before 3.5 s, followed by a rapid increase at 3.5 s, reaching a maximum speed of approximately 9.5 m/s at 9.8 s. The velocity and displacement of the debris gradually decreased from the bottom to the top in the sliding source area. The maximum displacement of the debris was 1.24 km. The entire landslide process lasted approximately 47 s, with the debris accumulating mostly at the toe of the slope. The research findings provide valuable theoretical support for the prevention and control of geological hazards induced by underground mining activities.