Drag Forces Applied on Rock Matrix by Fluid Flow through Fracture Network in Rock Mass

Abstract

It is very important to investigate the forces applied on the rock mass by the fluid flow through fractured rock mass, which is one of the issues for analyzing the stability of rock mass. The forces applied on the fissure walls by the fluid flow include the hydrostatic seepage pressure and the dynamic seepage pressure, i.e., the drag force. Based on the cubic law of the single fissure flow, the equations of the drag forces applied on the fissure walls by the single fissure flow are deduced by means of the momentum law of fluid mechanics. The equations are designated for the cases of no-filled fissure, filled fissure and the combined flow of fluid and the fillings, respectively. The equations have important values for analyzing the effect of fluid flow on the behavior of deformation and strength of fractured rock mass, and are the foundation of the interaction mechanism between stress and fluid flow. Based on the equations, the two kinds of forces applied on the fracture wall of fracture network in rock mass are studied, which include the normal hydrostatic seepage pressure and the tangent drag force. The equivalent node force of joint element is deduced under the two-dimensional and three-dimensional conditions. A numerical computation example is also given to indicate the effect of seepage through fracture network on the stress of rock mass.