Direct shear tests of granite discontinuities filled with sandy gouges

Abstract

The ultimate shear strength of dry sandy gouges infilling artificial and flat discontinuities in sound and fine grained granite were studied by using a direct shear equipment. The results obtained concluded that the ultimate shear strength of the filled discontinuities was always lower than that of the unfilled discontinuity and they influenced the traditional plots shear strength vs. thickness which in our case show two branches: an upper one, presenting the decrease of the shear strength with the increase of thickness; and a lower one reproducing the increase of shear strength with thickness (rolling friction may control this behaviour).