Dynamic Simulation of Rock Collapse on Reservoir Banks Considering the Fluid-Solid Coupling Process

The instability of reservoir bank rock masses involves issues such as non-linearity, large deformations, and complex stress conditions, which complicate the accurate prediction of their dynamic failure. This study developed an integrated numerical approach based on the Discrete Element Method (DEM), incorporating a fluid force calculation module to simulate the fluid-solid coupling processes during reservoir bank collapse. The proposed method was first validated through particle sedimentation tests and then applied to simulate the failure of the Jianchuandong Unstable Rock Mass (JURM) in the Three Gorges Reservoir Area, China. Contact parameters for the DEM model were calibrated via mechanical tests of samples subjected to dry-wet cycles. The simulation captured the detailed failure process of the JURM, including its kinematic characteristics and energy conversion. Comparative simulation revealed that neglecting fluid forces (drag and buoyancy) not only alters the failure mode but also leads to an overestimation of the maximum kinetic energy by approximately 60%, which could result in overly conservative mitigation measures. This study demonstrated a DEM-based framework for simulating reservoir bank collapse and highlighted the essential contribution of fluid forces, providing a valuable reference for similar engineering applications.