Roadway excavation changes the original equilibrium stress state of the rock mass, resulting in the loading and unloading of the surrounding rock near the free surface. After the excavation, the tangential stress increases and the radial stress decreases, which mainly cause deformation and collapse of the roadway. In order to study the strength characteristics of the surrounding rock after the excavation, one effective way is to carry out triaxial compression tests on small surrounding rock samples. Therefore, this paper focuses on the triaxial compression mechanical propertiesof thick-walled cylinder granites with an electrohydraulic, servo-controlled rock mechanics testing system (MTS-815). It studies how different pore sizes and confining pressures affect the triaxial compressive strength (TCS), deformation, and failure modes of granite samples. The results are as follows: (1) Under triaxial compression, the stress-strain curves have no obvious yield stage, and the peak TCS increases with the confining pressure (σ₃). When σ₃ is low, there is little difference in the TCS between the complete specimen and the thick-walled cylinders. When σ₃ reaches 30 MPa∼40 MPa, the TCS of samples with apertures of 15 mm and 20 mm are obviously lower. The σ₃ has an obvious influence on the elastic modulus of thick-walled cylinder granites. (2) Shearing and splitting are the main failure modes under triaxial compression. When σ₃ is low, shear failure appears. As σ₃ reaches 30 MPa∼40 MPa, split failure occurs. The area of the fracture surface increases with σ₃. (3) As σ₃ grows, the influence parameter (m) of the three-dimensional Hoek-Brown criterion increases. Under the same σ₃, the value of m presents a decreasing trend from the outer wall to the inner wall, which means the bearing capacity keeps getting lower and lower. As a result, the inner wall is most likely to be damaged. The theoretical analysis results agree well with the tests.

中文翻译：

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三轴压缩下不同孔径厚壁圆柱花岗岩的力学性能和破坏模式

巷道开挖改变了岩体的原始平衡应力状态，从而导致在自由表面附近对围岩进行加载和卸载。开挖后，切向应力增大，径向应力减小，这主要是造成巷道变形和坍塌的原因。为了研究开挖后围岩的强度特性，一种有效的方法是对较小的围岩样品进行三轴压缩试验。因此，本文重点研究了采用电液伺服控制岩石力学测试系统（MTS-815）的厚壁圆柱花岗岩的三轴压缩力学性能。它研究了不同的孔径和围压如何影响花岗岩样品的三轴抗压强度（TCS），变形和破坏模式。σ ₃）。当σ ₃是低，有在完成试样和厚壁汽缸之间的TCS几乎没有差别。当σ _3个达到30 MPa~40兆帕，样品的TCS为15mm的孔和20mm明显降低。所述σ ₃对厚壁圆筒花岗岩的弹性模量有明显的影响。（2）剪切和分裂是三轴压缩下的主要破坏方式。当σ ₃低时，剪切破坏出现。作为σ _3个达到30 MPa~40兆帕，发生分裂的失败。与断裂面的面积增加σ ₃。（3）σ ₃增长，三维Hoek-Brown准则的影响参数（m）增加。在相同的σ ₃，的值米礼物从外壁与内壁有减少的趋势，这意味着承载能力不断越来越低。结果，最有可能损坏内壁。理论分析结果与试验结果吻合良好。