Rock mass is often encountered with complicated stress disturbance caused by human-induced engineering loads and the environmental loads. Cyclic or fatigue loading path with fixed loading frequency are widely performed. To date, however, damage and fracture evolution of the pre-flawed rock under variable-frequency multi-level constant amplitude (VFMLCA) cyclic loads was not well understood. In the present study, granite samples containing a circular hole and two fissures were prepared to conduct VFMLCA cyclic loading tests. The fatigue strength, deformation, energy conversion, damage propagation, and crack coalescence were comprehensively investigated. Testing results show that the fatigue strength increases with increasing fissure angle. Rock volumetric strain and the dissipated energy are the maximum for rock with a 50° fissure angle. The dissipated energy increases with decreasing of loading frequency and an exponential relation is revealed between them. In addition, a damage evolution model that can well describe the two-stage and three-stage damage evolution for each cyclic loading level and the entire loading process is proposed and proved. Moreover, three failure modes of single tensile coalescence, double tensile coalescence, and double shear coalescence were revealed from the reconstructed CT images. It is suggested that the double shear coalescence is prone to forming large crack network.

岩体经常遇到人为工程荷载和环境荷载引起的复杂应力扰动。具有固定加载频率的循环或疲劳加载路径被广泛执行。然而，迄今为止，在变频多级恒幅（VFMLCA）循环载荷下预裂隙岩石的损伤和断裂演化尚不清楚。在本研究中，准备了包含一个圆孔和两个裂缝的花岗岩样品进行 VFMLCA 循环加载试验。对疲劳强度、变形、能量转换、损伤扩展和裂纹聚结进行了综合研究。测试结果表明，疲劳强度随着裂隙角度的增加而增加。岩石体积应变和耗散能量对于裂隙角为 50° 的岩石最大。耗散的能量随着加载频率的降低而增加，并且它们之间呈指数关系。此外，提出并证明了一种损伤演化模型，该模型能够很好地描述每个循环加载水平和整个加载过程的两阶段和三阶段损伤演化。此外，从重建的CT图像中揭示了单张拉合并、双张拉合并和双剪切合并三种失效模式。表明双剪聚结容易形成大的裂缝网络。提出并证明了一种能够很好地描述每个循环加载水平和整个加载过程的两阶段和三阶段损伤演化的损伤演化模型。此外，从重建的CT图像中揭示了单张拉合并、双张拉合并和双剪切合并三种失效模式。表明双剪聚结容易形成大的裂缝网络。提出并证明了一种能够很好地描述每个循环加载水平和整个加载过程的两阶段和三阶段损伤演化的损伤演化模型。此外，从重建的CT图像中揭示了单张拉合并、双张拉合并和双剪切合并三种失效模式。表明双剪聚结容易形成大的裂缝网络。