Numerical Simulation of Water-Sediment Two-Phase Seepage Characteristics and Inrush Mechanism in Rough Rock Fractures

Abstract

The water-sediment two-phase flow in the rough fracture is one of the main causes of water-sediment inrush. In this study, numerical simulation models of the water-sediment two-phase flow in the smooth and rough fractures were established by ANSYS Fluent software based on the seepage theory; the mechanical properties of the water-sediment two-phase flow under different conditions were systematically investigated, and the influence laws of the surface morphology of the fracture on sediment volume concentration, sediment particle size, and sediment particle mass density were analyzed. In addition, the influence laws of the sediment volume concentration, sediment particle size, and sediment particle mass density on the absolute value of the pressure gradient, mean velocity of the fluid, and fluid turbulent kinetic energy were also illustrated from the perspective of sediment particle distribution. Research shows that during the water-sediment flow in the smooth fracture, the absolute value of pressure gradient Gp, the sediment volume concentrationФ, the sediment particle sizeDp, and the sediment mass densityρpare approximately linear, and the linearity ofGpandDpis the lowest; during the water-sediment flow in the smooth fracture, the mean velocityvof the continuous-phase fluid rarely changes withФ,Dp, andρp. However, during the water-sediment flow in the rough fracture,vis greatly affected byФ,Dp, andρp. During the water-sediment flow in the smooth fracture, the fluid turbulent kinetic energy kt decreases with the increase ofρpandФand decreases with the decrease of ρp. During the water-sediment flow in the rough fracture,ktis significantly affected byФ, Dp, andρp, which was manifested in the changes of curve shapes and deviation of the extreme points.