Flow channeling in a single fracture induced by shear displacement

The effect on the transport properties of fractures of a relative shear displacement ~u of rough walls with complementary self-affine surfaces has been studied experimentally and numerically. The shear displacement ~u induces an anisotropy of the aperture field with a correlation length scaling as u and significantly larger in the direction perpendicular to ~u. This reflects the appearance of long range channels perpendicular to ~u resulting in a higher effective permeability for flow in the direction perpendicular to the shear. Miscible displacements fronts in such fractures are observed experimentally to display a self affine geometry of characteristic exponent directly related to that of the rough wall surfaces. A simple model based on the channelization of the aperture field allows to reproduces the front geometry when the mean flow is parallel to the channels created by the shear displacement.