Progressive failure of brittle rocks with non-isometric flaws: Insights from acousto-optic-mechanical (AOM) data

Uniaxial compression tests combined with nondestructive testing techniques are performed to explore the roles of non-isometric flaws in crack developments in brittle rocks. The acoustic emission (AE) rate-process theory is adopted to analyze fracture-related AE event rate characteristics. The full-field optical method is applied to detect cracking modes. Experimental results show that AE activity is quite active when the matrix microcracking is dominant, while after each macrocracking event, AE activity becomes inactive because of the stress release. Multiphysical data for each tested flaw configuration faithfully confirm the rupture progressivity. The larger the flaw length ratio, the lower the peak stress (also peak axial strain and elastic modulus), as well as the more progressive the cracking process. Moreover, ultimate failure is triggered by the shear fracturing from the relatively long flaw. The short flaw is conditionally involved in ultimate failure when the stress buildup effect dominates. Finally, the fracture mechanism of brittle rocks with non-isometric flaws is revealed.