煤层钻孔卸压技术是防治冲击地压灾害的重要手段。利用自行研制的实时CT扫描真三轴加载试验系统，研究了不同孔径下的巷帮深部钻孔煤体(三向加载状态)和巷帮浅部钻孔煤体(双向加载状态)2种不同应力类型模型的力–应变规律、内部裂纹扩展演化特征，建立了巷帮深、浅部钻孔煤体的峰前裂纹损伤关系，揭示了深部巷道卸压钻孔围岩强度弱化机理。结果表明：相比于未钻孔试样，不同应力类型的煤体试样受应力环境及钻孔孔径影响，随着钻孔的打设和孔径的增大，巷帮深部钻孔煤体试样在峰值应力后，应力跌落现象消失，有利于降低试样能量的突然释放，而巷帮浅部钻孔煤体试样则无法消除应力跌落现象；在内部裂纹扩展上，巷帮深部钻孔煤体试样裂纹发育较少，裂纹呈一定角度发育，而巷帮浅部钻孔煤体试样裂纹均近乎垂直发育，随着钻孔孔径的增加，巷帮深、浅部钻孔煤体试样裂纹数量都有一定程度的增加，但巷帮浅部钻孔煤体试样裂纹产生数量更多，钻孔煤粉封堵情况更明显，钻孔及孔径变化对巷帮浅部钻孔煤体试样影响程度更大。同孔径条件下巷帮浅部钻孔煤体更容易破坏且无法起到卸压减灾效果，进而基于巷帮深、浅部钻孔煤体的差异性，建立了不同孔径下巷帮深、浅部钻孔煤体裂纹损伤变量的函数表达式，揭示了深部巷道卸压钻孔围岩强度弱化机理，提出了深部巷道扩孔卸压理念及方法。

Coal seam drilling pressure relief technology is an important means to prevent and control rock burst disasters. Using the self-developed real-time CT scanning true triaxial loading test system, the force-strain law and internal crack propagation evolution characteristics of two different stress types models, i.e., deep coal body (three-way loading state) and shallow coal body (two-way loading state), under different borehole diameters were studied. The pre-peak crack damage relationship of deep and shallow boreholes in the roadway was established, and the strength weakening mechanism of surrounding rock of pressure relief boreholes in deep roadway was revealed. The results show that compared with the undrilled samples, the coal samples with different stress types are affected by the stress environment and the borehole diameter. With the drilling and the increase of the borehole diameter, the stress drop phenomenon of the deep coal samples in the roadway wall disappears after the peak stress, which is beneficial to reduce the sudden release of the energy of the samples, while the shallow coal samples in the roadway wall cannot eliminate the stress drop phenomenon. In terms of internal crack propagation, the cracks in the deep coal samples of the roadway wall are less developed, and the cracks are developed at a certain angle, while the cracks in the shallow coal samples of the roadway wall are almost vertically developed. With the increase of borehole diameter, the number of cracks in the deep and shallow coal samples of the roadway wall increases to a certain extent, but the number of cracks in the shallow coal samples of the roadway wall is more, and the sealing of the coal powder in the borehole is more obvious. The change of borehole and aperture has a greater impact on the shallow coal samples of the roadway wall. Under the same drilling conditions, the shallow coal body of the roadway wall is more likely to be destroyed and cannot play the effect of pressure relief and disaster reduction. Based on the difference between the deep and shallow drilling coal bodies of the roadway wall, the function expressions of the crack damage variables of the deep and shallow coal bodies of the roadway wall under different drilling apertures are established. The weakening mechanism of surrounding rock strength of deep roadway pressure relief drilling is revealed, and the concept and method of deep roadway reaming and pressure relief are proposed.