Acoustic emission characteristics of fractured rocks during creep shear

Under a long-term geomechanical loading, creep deformation would occur in fractured rocks, accompanying with acoustic emission(AE). The laws of AE are meaningful to monitor and warning of the rock in stability. In order to look into the AE features of fractured rocks during creep shear, the direct creep shear experiment of fractured rocks induced by compressive shear and Brazilian tension was carried out under constant normal force. AE technology was used to detect the acoustic events during the creep shear. The relationship between AE energy and creep shear displacement at different loading stages is revealed. Meanwhile, the locations of the interlocks and the micro-contact fractures are also identified the laser scanned contour maps of the fractured rock surfaces by the AE events. The experiment shows that there is a signal blank phenomenon of AE events before the instability occurs. Regarding to the fractured rocks induced by Brazilian tension, the peak of AE energy mainly appears at the middle and late stages of the creep shear process, and AE energy reaches local maximum at the early stage of each loading followed with its downward trend;for the fractured rocks induced by compressive shear, AE energy valley appears at the middle stage of the creep shear process, and at each shear loading a small peak of AE energy appears at the middle stage. In addition, AE position detection shows that the micro-contact fractures mainly occur first at the central part of the interlocked surfaces. The initial micro-contact fractures present a directional character that a zonal distribution develops perpendicular to the shear direction at early loading stages. ©, 2015, Academia Sinica. All right reserved.