The bedrock of hydropower stations is susceptible to irreversible failure due to dynamic unloading and loading related to earthquakes, rock bursts or blasting. To ensure operational safety, the damage evolution process of bedrock under cyclic loading must be investigated. Hence, this study investigates the mechanical properties and acoustic emission (AE) characteristics of the bedrock from different positions of the Badantoru hydropower station under different confining pressures. First, the relationship between the dynamic elastic modulus and residual strain is analyzed, and then the brittleness and damage of the rocks are quantitatively characterized. Subsequently, the failure process and crack development of the rocks are revealed from the obtained AE characteristics. The results show that as the applied confining pressure increases, the peak differential stress and fatigue life of the rock specimens increase; whereas, the shear failure angle decreases. Under the same confining pressure, the rocks with a greater number of internal joints and pores (Dam Site I) have a lower bearing capacity under cyclic loading, a greater brittleness after strain softening, and a smaller shear failure angle. With increasing plastic strain, all of the specimens exhibit cyclic softening, and an obvious four-stage fatigue damage evolution can be observed.

中文翻译：

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三轴循环荷载作用下水电站基岩力学特性及声发射特性

水电站的基岩容易因动态卸载和与地震、岩爆或爆破有关的加载而发生不可逆转的破坏。为确保运行安全，必须研究循环荷载作用下基岩的损伤演化过程。因此，本研究调查了不同围压下巴丹托鲁水电站不同位置基岩的力学性能和声发射 (AE) 特性。首先分析动态弹性模量与残余应变之间的关系，然后定量表征岩石的脆性和损伤。随后，从获得的声发射特征揭示岩石的破坏过程和裂缝发展。结果表明，随着外加围压的增加，岩石试样的峰值差应力和疲劳寿命增加；而剪切破坏角减小。在相同围压下，内部节理和孔隙较多的岩石（坝址Ⅰ）在循环荷载作用下承载力较低，应变软化后脆性较大，剪切破坏角较小。随着塑性应变的增加，所有的试样都表现出循环软化，并且可以观察到明显的四阶段疲劳损伤演变。和较小的剪切破坏角。随着塑性应变的增加，所有的试样都表现出循环软化，并且可以观察到明显的四阶段疲劳损伤演变。和较小的剪切破坏角。随着塑性应变的增加，所有的试样都表现出循环软化，并且可以观察到明显的四阶段疲劳损伤演变。