Brittle failure of hard rock poses a serious threat to the stability of surrounding rock in deep underground engineering. In order to study the deformation and failure characteristics of deep buried granite under high confining pressure cyclic loading and unloading, MTS815 electro-hydraulic servo rock test system was used to conduct cyclic loading and unloading tests under confining pressures of 15 MPa, 35 MPa, 45 MPa, and 55 MPa, and the corresponding stress-strain curves and deformation failure characteristic curves were obtained. The experimental results show the follows: (1) under the same confining pressure, the peak strength, crack initiation stress, crack damage stress, and Poisson’s ratio of the specimens under cyclic loading and unloading are larger than those under conventional triaxial loading and unloading, and the unloading elastic modulus is smaller than that, under conventional triaxial compression; (2) the results show that, under different confining pressures, the granite samples show obvious brittle failure characteristics, the elastic modulus and crack initiation stress increase first and then decrease with the confining pressure, the peak strength and crack damage stress of the samples increase linearly with the confining pressure, and Poisson’s ratio increases first and then remains unchanged with the confining pressure; (3) under the two kinds of stress conditions, the macroscopic failure of the samples is mainly shear failure. The deformation and failure law of granite samples revealed in this study has significant reference value for the selection of rock mass mechanical model of surrounding rock stability of underground engineering, the formulation of surrounding rock support countermeasures, and the evolution law of mechanical parameters with damage variables.

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不同围压下深埋花岗岩力学性能的试验研究

在深层地下工程中，坚硬岩石的脆性破坏严重威胁着围岩的稳定性。为了研究深围岩在高围压下的周期性变形和破坏特性，采用MTS815电液伺服岩石试验系统在15 MPa，35 MPa，45围压下进行了周期性的加载与卸载试验。 MPa和55 MPa，并获得了相应的应力应变曲线和变形破坏特性曲线。实验结果表明：（1）在相同的围压下，循环加载和卸载时样品的峰值强度，裂纹萌生应力，裂纹破坏应力和泊松比均大于常规三轴加载和卸载时的值；卸载弹性模量小于常规三轴压缩下的弹性模量。（2）结果表明，在不同围压下，花岗岩试样均表现出明显的脆性破坏特征，其弹性模量和裂纹萌生应力先随围压增大而后减小，其峰值强度和裂缝破坏应力均增大。泊松比与围压成线性关系，泊松比先增大，然后随围压保持不变。（3）在两种应力条件下，试样的宏观破坏主要是剪切破坏。本研究揭示的花岗岩样品变形破坏规律对地下工程围岩稳定性岩体力学模型的选择具有重要的参考价值，