Naturally fractured rock mass is susceptible to stress disturbance and could result in the stimulation of natural fractures and even serious geological hazards. In this work, multilevel uniaxial fatigue loading experiments were carried out to reveal the fracture and energy evolution of naturally fractured granite using stress-strain descriptions and energy evolution analysis. Results reveal the influence of natural fracture on mechanical properties of granite, regarding the fatigue lifetime, fatigue deformation characteristics, fatigue damage, energy evolution, and fatigue failure pattern. Volumetric and shear processes caused by the sliding and shearing along the natural fracture control the whole failure process. The energy dissipation and release characteristics are strongly impacted by natural fractures. The elastic energy and dissipated energy both decrease with increasing natural fracture volume, growth of the dissipated energy becomes faster for rock near to failure. It is proved that the dissipated energy is mainly used to activate the preexisting natural fractures.

中文翻译：

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多级循环荷载作用下天然断裂花岗岩的动态断裂和能量演化特征

天然裂隙岩体易受应力干扰，并可能导致天然裂隙的激发，甚至造成严重的地质灾害。在这项工作中，进行了多级单轴疲劳载荷实验，以利用应力-应变描述和能量演化分析来揭示天然裂缝花岗岩的断裂和能量演化。结果揭示了天然断裂对花岗岩力学性能的影响，涉及疲劳寿命，疲劳变形特性，疲劳破坏，能量演化和疲劳破坏模式。由沿着自然裂缝的滑动和剪切引起的体积和剪切过程控制着整个破坏过程。天然裂缝严重影响了能量的耗散和释放特性。弹性能和耗散能量都随着自然裂缝体积的增加而减小，对于接近破坏的岩石，耗散能量的增长变得更快。事实证明，耗散的能量主要用于活化天然裂缝。