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.

中文翻译：

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双轴压缩下缺陷类岩石材料的力学及断裂特性

地下开挖过程中各种类型的不连续体对岩石稳定性影响很大，缺陷的裂纹扩展可能引发工程灾害。出于这种考虑，对岩石状水泥砂浆材料进行了准静态双轴压缩试验。这些测试检查了代表自然或预处理裂缝的预先存在的缺陷的形状、方向和相互作用的影响。使用应力应变响应、声发射 (AE)、数字图像相关 (DIC) 和同步加速器 X 射线计算机断层扫描 (CT) 技术来分析机械和断裂特性。可以发现，约束增加了样品峰值应力并限制了完整样品中裂纹的发展。在孔样中，裂纹是从孔的边界萌生的，围压的施加在一定程度上限制了孔顶和底板起源的拉伸裂纹。孔与缺陷的相互作用改变了应力分布和开裂行为。从具有高倾角的相交缺陷尖端开始的裂纹与孔合并，而平行的独立缺陷则阻止从孔边界开始的裂纹的扩展。此外，事实证明，集成分析框架与声发射信息解释相结合，可以准确研究具有复杂预存缺陷的样品的破裂特征。这些发现将有利于地下土木和资源相关项目。