Assessment of rock fracture initiation using acoustic emission

It is crucial to understand fracture initiation and propagation in rock as the induced fracture is widely applied in the petroleum industry and rock engineering, and fracture often acts as a precursor to ultimate failure. Due to the relative vast existence of granite and its wide application in tunneling, geothermal systems, and CO2 storage, fracture properties of granite are investigated in this study. Charcoal granite specimens of different sizes and geometries are tested under three- and four-point bending to investigate the effect of these parameters on the dimensions of the fracture process zone measured using acoustic emission (AE) technique. The effects of specimen size, geometry, and loading conditions are found to be more pronounced in the specimens with sizes that are commonly used in the laboratory, while the size effect is predicted to be less significant and eventually negligible as the specimen size increases. It is found that both the fracture process zone length and width increase with the specimen size. In addition, even though the span length is kept the same, the fracture process zone size increases with the increasing specimen depth. Loading condition and specimen geometry also influence the length of the fracture process zone, but have very little effect on its width. Fracture process zone in the post-peak regime is also investigated and found to be approximately constant size. It indicates that the fracture process zone is fully developed at peak load or even prior to it.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste