Numerical study of flow anisotropy within a single natural rock discontinuity

The paper investigates the flow anisotropy within a natural joint subjected to mechanical shear. The cubic law is the simplest way to describe fluid flow through rock joints but because of rock wall roughness, deviations from this model have been observed. The Reynolds equation usually gives better results. In this study, micro-scale roughness is taken into account to define a reduced coefficient of permeability. Numerical simulations have been carried out by applying Darcy’s law to the rock joint, described as an equivalent porous medium. The numerical simulations are based on experimental data obtained by Hans (PhD, Grenoble, 2002) from a series of hydromechanical shear tests on a rock joint replica. The numerical results have been compared to the experimental ones, and to the results obtained by applying the Reynolds equation, to assess the relevance of the simulations. For the fracture studied, the approach proposed herein can reproduce relatively well the experimental flow anisotropy, and provides consistent values of flow rates, whereas the Reynolds equation tends to give higher flow rates.