Pore pressure stabilization of failure in westerly granite

A series of constant strain rate laboratory experiments have been conducted to examine pore pressure stabilization of failure in Westerly granite. Stabilization is characterized by a gradual increase in axial displacement rate for several hundred seconds prior to failure followed by gradual, inaudible stress drop as the sample fails. In contrast, dynamic failure is characterized by a 20 second or less accelerating axial displacement followed by a sudden audible stress drop. Pore pressure stabilization was observed at ratios of pore pressure to confining pressure, λ, greater than 0.5 or so. The transition between stable and dynamic failure shifted to lower values of λ with increasing effective confining pressure and decreasing strain rate.