Experimental Study on the Nonlinear Shear-Flow Behavior of Granite With a Single Fracture

Abstract

The nonlinear flow behavior of granite with a single fracture at different shear displacements is researched by using the high-precision non-pulse long-time permeability test system. The effects of fracture roughness and confining pressure are studied. Forchheimer’s law and the critical normalized transmissivity can describe fluids’ nonlinear flow behavior under shear displacement. During the shear process, the change process of fluid flow can be divided into two stages, namely the sensitive change stage and the stable change stage, and the hydraulic parameters also change accordingly. The shear displacement is in the sensitive stage of 0–1[Formula: see text]mm, at this point, the nonlinear flow characteristic parameters change significantly, accompanied by a decrease in linear and nonlinear coefficients. The critical Reynolds number decreases with the increasing shear displacement and decreasing confining pressure. The increasing shear displacement and confining pressure decrease the critical hydraulic gradient. The hydraulic aperture of the fractured granite initially increases with the increase of shear displacement. The shear displacement between 1[Formula: see text]mm and 4[Formula: see text]mm is a stable stage, the characteristic parameters of fluid, critical Reynolds number and critical hydraulic gradient tend to be relatively stable and fluctuate in a small range. This is induced by the changes in the hydraulic aperture under the effects of shear displacement and confining pressure, noteworthy the influence of displacement on the hydraulic aperture is greater than that of confining pressure.