Changes in acoustic event properties with progressive fracture damage

Laboratory results from uniaxial compression tests performed on pink Lac du Bonnet granite samples indicate that a number of stages in the progressive failure process of rock can be identified through the combined analysis of strain gauge and acoustic emission (AE) data. Testing focused on identifying the crack initiation (σci) and crack damage (σcd) stress thresholds, two key components in the brittle fracture process. Results from this testing also showed that the properties of the acoustic events are markedly different throughout loading most notably before and after crack initiation. This proved valuable in substantiating observations made using strain gauge data. This paper explores the use of acoustic emissions and the interpretation of the acoustic event properties in identifying the different stages of crack development