ACOUSTIC EMISSION OF ROCKS UNDER TRIAXIAL COMPRESSION ALONG VARIOUS STRESS PATHS

Acoustic emission of Jinan gabbro and Shangpin granite samples has been observed under triaxial compression along 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 emission rate gradual increased, an abrupt increase of acoustic emission occurred at about several hundred bars prior to rupture. When starting from a high stress state and the confining pressure was decreased (caseB), an abrupt increase of acoustic emission occurred much later, only about 20-30 bars before rupture. The total number of acoustic emission in the fracture process was much less only one-third of that in case A. There were two processes in case B: loading process for differential tensor component of the stress field; unloading process for spherical symmetric tensor componen (hydrostatic). It is possible that the different characteristics of acoustic emission is due to the existence of the unloading process.