Dilatancy, or increase in void volume, is typically associated with the inelastic deformation of a relatively intact rock. However, dilatancy associated with frictional sliding in laboratory samples also has been observed. At low normal stresses, dilatancy may be due to the uplift in sliding over asperity contacts. At higher normal stresses, dilatancy appears to result from the initiation and extension of microcracks adjacent to the sliding surface. If the rock is fluid-suturated and dilatancy occurs more rapidly than a pore fluid can diffuse into the newly created void space, the local pore pressure near the sliding surface decreases. This decrease in the pore pressure increases the effective compressive stress (the total compressive stress minus the pore fluid pressure) and inhibits a further frictional slip.

This paper investigates the stability of the quasi-static shearing sliding along a rock porous layer that can result from the coupling between the change in porosity, pore fluid diffusion and dilatancy accompanying the friction sliding.