An example of slip instability resulting from displacement-varying strength

A rock cylinder, containing a clay-filled sawcut making an angle of 30?? to the sample axis, was deformed at constant confining and pore pressures and constant remote shortening rate. The sawcut surfaces contained a series of regularly spaced ridges and grooves oriented perpendicular to the direction of shear. The interaction of these grooved surfaces resulted in a sliding strength which varied periodically with displacement. By varying the effective machine stiffness through the use of an electronic feedback circuit, a range of stable and unstable slip behavior was achieved. In this way, we examined fault slip behavior which was dominated by displacement-dependent strength. ?? 1990 Birkha??user Verlag.