Abstract In engineering practice, rock masses are often subjected to cyclic loading. Under cyclic loading, the mechanical properties of rocks are significantly different from those under conventional loading conditions. The mechanical behaviour and fatigue of intact rock has been extensively studied. However, the mechanical fatigue properties of rock masses with surface cracks and related damage evolution models are not well understood. In this study, a series of fatigue damage tests were carried out on yellow sandstone specimens; five different pre-existing surface crack angles (0°, 15°, 30°, 45° and 60°) and three different maximum cyclic stress levels (19.1 MPa, 25.6 MPa and 30.3 MPa) were considered. The results showed that with the increase in the number of cycles, Young's modulus gradually stabilized, while the secant modulus decreased non-linearly. The maximum strain and residual strain continuously accumulated. The influence of macro cracks on the damage of rocks was studied through the increase in strain energy. Based on the macro–micro coupling damage, a constitutive model was proposed for the fatigue test. The theoretical results were fitted with the experimental data, showing that the proposed model can effectively describe the fatigue damage characteristics of fractured rock masses. The research results have certain reference value for the long-term stability evaluation in fractured rock mass engineering.

中文翻译：

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单轴循环加载下含预存表面裂纹的黄砂岩疲劳行为及本构模型

摘要 在工程实践中，岩体经常承受循环荷载。在循环加载条件下，岩石的力学性质与常规加载条件下的力学性质有显着差异。完整岩石的力学行为和疲劳已被广泛研究。然而，具有表面裂纹的岩体的机械疲劳特性和相关的损伤演化模型尚不清楚。本研究对黄砂岩试件进行了一系列疲劳损伤试验；考虑了五种不同的预先存在的表面裂纹角度（0°、15°、30°、45° 和 60°）和三种不同的最大循环应力水平（19.1 MPa、25.6 MPa 和 30.3 MPa）。结果表明，随着循环次数的增加，杨氏模量逐渐稳定，而割线模量非线性下降。最大应变和残余应变不断累积。通过应变能的增加，研究宏观裂纹对岩石损伤的影响。基于宏观-微观耦合损伤，提出了疲劳试验的本构模型。理论结果与实验数据吻合，表明该模型能够有效地描述裂隙岩体的疲劳损伤特征。研究成果对裂隙岩体工程的长期稳定性评价具有一定的参考价值。为疲劳试验提出了本构模型。理论结果与实验数据吻合，表明该模型能够有效地描述裂隙岩体的疲劳损伤特征。研究成果对裂隙岩体工程的长期稳定性评价具有一定的参考价值。为疲劳试验提出了本构模型。理论结果与实验数据吻合，表明该模型能够有效地描述裂隙岩体的疲劳损伤特征。研究成果对裂隙岩体工程的长期稳定性评价具有一定的参考价值。