Acoustic emission of rocks under triaxial compression with various stress paths

Abstract

Acoustic emission of Jinan gabbro and Changpin granite was measured under triaxial compression over various stress paths (confining pressure up to 1.3 kb). When the maximum principal stress was increased until the rock sample failed (case A), the average acoustic emmision rate gradually increased. An abrupt increase in acoustic emission rate occurred several hundred bars prior to rupture. When the confining pressure was decreased while at a high differential stress (case B), an abrupt increase of acoustic emission occurred much later, only 20–30 bars before rupture. The total number of acoustic emission events in the fracture process in case B was much less than that in case A. There were two stress processes in case B: loading process for devitoric components of stress field: unloading process for hydrostatic components of the stress field. It is possible that the different feature of acoustic emission in various loading modes is due to the existence of the unloading process.