Joint asperity degradation during cyclic shear

Some 30 real rock granite and limestone joints, sawn with a new numerical control technique, were cyclically sheared to measure asperity degradation under normal stresses and displacements consistent with earthquake loading of underground caverns at depths of 50-300 m. Monotonic shearing resistance and normal dilation of the sawn joints was similar to that for large or field scale joints. Asperity degradation under these conditions was found to be a function of work, joint roughness, normal stress and unconfined compressive strength of the joint wall.