Numerical evaluation of anisotropic fluid flow in sheared rock fractures

Anisotropic fluid flow in single sheared fractures in granite is investigated numerically under normal stresses up to 90 MPa that are the extended stress conditions of the previous studies. Aperture distributions of the sheared fractures under the normal stresses generated numerically on the basis of direct measurements of contact area suggest anisotropy of connectivity in fracture aperture even under the normal stresses. Numerical simulation of fluid flow using the generated aperture distribution shows not only anisotropy in fracture permeability and that in preferential flow paths, but also the normal stress dependency in the anisotropy of fracture permeability. An investigation on contact ratio reveals the anisotropy and the normal stress dependency in aperture connectivity, which supports the results of flow simulation. These results suggest importance of the flow anisotropy in discrete fractures for investigating three-dimensional flow properties in fractured rocks at a greater depth.