Multiphysics Simulation of the Catastrophic Process of Water and Mud Inrush in a Karst Tunnel: A Case Study of Tunnel, Western China

This paper investigated the mechanism and dynamic process of a significant water and mud inrush disaster that occurred in the Baiyunshan Tunnel, which crosses a karst fault zone. By integrating multi-source data including geological exploration and geophysical surveys, a three-dimensional geological model characterizing the cave–conduit–tunnel system was developed. A numerical approach coupling the Phase-Field and Particle-Tracking Methods was employed, successfully reconstructing the entire disaster process involving the transport of water-air-mud three-phase flow. Simulation results demonstrated that the dynamic viscosity of the mudflow predominantly controls the dynamic characteristics of the particle, such as transport distance and mudflow velocity. Parameter sensitivity analysis revealed quantitative relationships between key mudflow parameters (transport distance, velocity, and drag force) and the Reynolds number, identifying an exponential decay of drag force with increasing Reynolds number in high-viscosity mudflows. This study establishes a comprehensive methodology from geological identification to numerical simulation, providing a theoretical basis and technical support for precise risk assessment and the design of preventive measures for tunnel water and mud inrush disasters.