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Various types of discontinuities have great influences on rock stability in underground excavation, as engineering disasters can be triggered by crack growth from flaws. Motivated by this concern, quasi-static biaxial compression tests are conducted on rock-like cement mortar materials. These tests examine the effect of shape, orientation, and interaction of pre-existing defects, representing natural or preconditioning fractures. Mechanical and fracturing characteristics are analyzed using stress-strain response, acoustic emission (AE), digital image correlation (DIC), and synchrotron X-ray computed tomography (CT) techniques. It could be found that the confinement increases the sample peak stress and restricts the development of cracks in intact samples. In hole samples, cracks initiate from the boundary of the hole, and the application of the confining pressure restricts the tensile cracks originating at the roof and floor of the hole to some extent. The hole-flaw interaction changes stress distribution and cracking behaviours. Cracks initiating from intersected flaw tips with a high inclination angle coalesce with the hole, while parallel independent flaws block the propagation of the cracks initiating from the hole boundary. Besides, it is proved that the integrated analysis framework, coupled with acoustic emission information interpretation, is feasible to accurately investigate fracturing characteristics in samples with complex pre-existing defects. The findings would benefit underground civil and resource-related projects.
Ji et al. (Mon,) studied this question.