With the continuous demand for mineral resources, the construction design and stability of underground rock engineering have been a frontier research topic worldwide. Stability analysis of underground caverns, tunnels, boreholes, and cavities is of critical significance for underground engineering. To investigate the mechanical properties and failure mode of sandstone specimens with prefabricated cavities, experiments were conducted on sandstone samples with the borehole axis parallel to different principal stresses and for varying borehole depths and diameters using a novel true triaxial geophysical apparatus. Computed tomography (CT) was used to analyze the crack development around the borehole wall. The experimental results indicated that the direction of the borehole and the principal stress axis, as well as the borehole depth and size, significantly affected the strength and damage mode of the rock samples. For a given ${\sigma }_3$, with increasing principal stress coefficient $\beta$, the strength of the samples with the borehole axis parallel to the different principal stresses first increased and then decreased, and the maximum strength appeared at $\beta =0.5$. The highest stability of the rock samples appeared when the borehole was parallel to ${\sigma }_1$, and the lowest stability occurred when the borehole was parallel to ${\sigma }_2$ or ${\sigma }_3$. The strength of the sandstone sample decreased as the borehole diameter increased. Four types of typical damaged modes were observed in the CT scan results. Moreover, the intermediate principal stress had a significant effect on the damage-zone distribution around the borehole. This work can help to understand the damage area and failure characteristics of the borehole surrounding rock, also make a significant contribution to support the design of deep rock engineering.

随着矿产资源的不断需求，地下岩石工程的结构设计和稳定性已成为世界范围内的前沿研究课题。地下洞室，隧道，井眼和空腔的稳定性分析对地下工程至关重要。为了研究具有预制空腔的砂岩标本的力学性能和破坏模式，使用新颖的真三轴地球物理仪器对钻孔轴平行于不同主应力并改变钻孔深度和直径的砂岩样品进行了实验。计算机断层扫描（CT）用于分析井壁周围的裂缝发展。实验结果表明，井眼的方向和主应力轴，以及井眼的深度和大小，显着影响了岩石样品的强度和破坏方式。对于给定${\sigma }_3$，随着主应力系数的增加 $\beta$，井眼轴平行于不同主应力的样品强度先增大然后减小，最大强度出现在 $\beta =0。5$。当钻孔平行于井眼时，岩石样品的稳定性最高。${\sigma }_{\mathrm{1个}}$当井眼平行于 ${\sigma }_2$ 要么 ${\sigma }_3$。砂岩样品的强度随着井眼直径的增加而降低。在CT扫描结果中观察到四种类型的典型损坏模式。此外，中间主应力对井眼周围的破坏区域分布有重要影响。这项工作可以帮助了解钻孔围岩的破坏区域和破坏特征，也为支持深部岩石工程的设计做出了重要贡献。