In this study, stress-induced crack paths were observed after DT tests were performed to investigate the relationship between crack paths and crack growth behavior. Crack paths were observed using an EPMA, and the geometry of the crack paths was estimated quantitatively from a fractal analysis and crack length determination process. The fractal dimension and normalized crack path length were lowest for crack paths parallel to plane-3. This was because the geometry of the crack path was smooth when the crack propagated parallel to the plane in which the density of microcracks was high. From the results of the DT tests and crack path analysis, it was shown that the crack density and preferred orientation of the pre-existing microcracks affected the crack growth behavior. The differences between the activation energies of subcritical crack growth in granite were caused by the preferred orientation of the pre-existing microcracks.
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