In this study, the influence of fractures on the mechanical properties and cracking behavior of composite rock mass was investigated by preparing rock-like specimens of composite rock mass with different dip angles of fractures using customized molds. The failure process of the sample was recorded using a camera, and the rock failure process analysis technology was used for quantitative investigation of the mechanical mechanism of crack evolution during the loading process of the sample. Based on the experimental results, the crack propagation and coalescence modes of fractured composite rock mass were analyzed, and the distribution laws of contact force chain and maximum principal stress during initial crack initiation were studied from the microscopic perspective. The results show that with the increase in fracture dip angle, when the fracture is located in hard rock, the peak strength of the specimen decreases first, then increases and then decreases. When the fracture is located in both soft rock and hard rock, the peak strength of the specimen is mainly controlled by the fracture in soft rock. The initial crack mainly occurs at the tip of the soft rock fracture, and then converges with the cracks developed at the end of the hard rock fracture through the interface. The crack propagation type and coalescence mode are affected by the joint action of the fracture dip angle and position. In total, eight crack propagation types and six crack coalescence modes were observed during the failure process. The maximum principal stress concentration area is distributed around the fracture and is “butterfly” type. With the increase in fracture dip angle, the maximum principal stress concentration area gets gradually deflected perpendicular to the fracture direction, and does not pass through the interface of soft and hard rocks. The existence of the interface prevents the transmission of stress to a certain extent.

本研究通过定制模具制备不同裂隙倾角的复合岩体岩体试件，研究裂隙对复合岩体力学性能和开裂行为的影响。利用摄像头记录试件的破坏过程，利用岩石破坏过程分析技术定量研究试件加载过程中裂纹演化的力学机制。基于试验结果，分析了裂隙复合岩体的裂纹扩展和聚结模式，从微观角度研究了初始裂纹萌生过程中接触力链和最大主应力的分布规律。结果表明，随着裂缝倾角的增大，当裂缝位于硬岩中时，试件的峰值强度先减小，然后增大，然后减小。当断裂同时位于软岩和硬岩中时，试件的峰值强度主要受软岩中断裂的控制。初始裂纹主要发生在软岩裂隙尖端，然后通过界面与硬岩裂隙末端发育的裂纹会聚。裂纹扩展类型和合并模式受裂纹倾角和位置的共同作用影响。在失效过程中总共观察到八种裂纹扩展类型和六种裂纹合并模式。最大主应力集中区分布在裂缝周围，呈“蝴蝶”型。随着裂缝倾角的增大，最大主应力集中区逐渐偏转垂直于裂缝方向，且不穿过软硬岩界面。界面的存在在一定程度上阻止了应力的传递。