Numerical Simulation of Water and Mud Inrush Processes in Mountain Tunnels Using Coupled Lattice Boltzmann/Discrete Element Methods

Investigating the mechanism of sudden water inrush and mudflow in mountain tunnels is crucial for implementing preventive measures. Tunnel excavation through a fault or fractured zone can easily trigger sudden water inrush or mudflow. In this paper, the coupled lattice Boltzmann method (LBM) and discrete element method (DEM) were employed to reproduce the process of water and mud inrush in mountain tunnels. The failure of tunnel mud burst and water inrush involves a fluid–solid coupling process. A two-dimensional Boltzmann method for fluids and DEM for particles were utilized, with the coupled LBM-DEM boundary adopting the immersed moving boundary method. For simulating the water inrush process, a numerical model was established to replicate the flow of water particles within karst pipelines, featuring dimensions of 7 cm length, 4 cm width, and consisting of 100 particles. Particles are transported through water flow to the outlet of karst pipelines under hydraulic gradient loading. When the hydraulic gradient exceeds 6, the Darcy velocity gradually tends to be constant. As for simulating the mud inrush process, a numerical model was developed with dimensions of 5 cm length and 4 cm height, incorporating 720 randomly generated particles. The results demonstrated the successful reproduction of the evolution process encompassing three consecutive stages of tunnel mud-burst failure: initiation, acceleration, and stabilization. The occurrence of mud inrush disasters is attributed to combined action involving disaster-causing geotechnical materials, groundwater pressure, and tunnel excavation.