| Abstract: | A comparative study on acoustic emission during deformation of two kinds of granites with different structures under triaxial compression was performed using a new acoustic emission recording system with full-waveform record and broad-dynamic range. One is the Inada aplite-granite of homogeneous structure from Japan and the other is the Mayet granite with cemented natural joints from France. For the former granite, acoustic emission events are dispersed randomly and there is no clear clustering along the major fracture. For the latter granite, acoustic emission events are mainly concentrated near the joints. Acoustic emission events occur synchronously with the volumetric dilatation in the former one but far earlier than the volumetric dilatation in the latter one. The two kinds of granites are also clearly different in the frequency spectrum of acoustic emission. The former has a narrower frequency band and a higher frequency component, whereas the latter has a wider frequency band and generally a lower frequency spectrum. In the frequency-energy relation, the number of acoustic emission events in the former shows a well-linear progressive relation from a high-energy level to a low-energy level and it shows an apparent intermittent or nonlinear variation in the middle-high energy interval, with higher proportion of large events for the latter. It indicates that the rock structure has an apparent controlling role in the basic statistical characteristics of acoustic emission events. The cause for such phenomena may be that the different rock structures result in different deformation modes and processes. |
