Numerical simulation of ground movement induced by water and sand gushing in subway through fault based on DEM-CFD

Abstract With the rapid development of subway, the ground movement induced by water and sand gushing occurs frequently in the process of tunnel construction. Existing research has not paid significant attention in the influence of sand inflow on the ground settlement and the development process of deep soil after water and sand gushing. Thus, the aims of the present study were: (i) to numerically explore the laws of ground movement, ground loss and the developing process due to water and sand gushing; and (ii) to theoretically explore a prediction formula for the maximum ground settlement after water and sand gushing. The numerical results showed that the surface settlement above the tunnel increased with the increase of mass loss ratio MLR. The development of ground movement can be divided into soil settlement stage induced by seepage, expansion stage of sand loosening region, and trenching stage of ground. The sand inflow first increased slowly, and then sharply, which finally kept stable growth. The growth rate of water inflow increased firstly and then kept it stable state. A simplified theoretical formula is proposed to predict the maximum ground settlement after water and sand gushing by establishing a simplified theoretical model. Moreover, the simulation results were compared with experimental results, and reasonable agreement could be obtained, which could provide a reference significance for the treatment and control of water and sand gushing in subway.