煤体结构面分布具有正交的特点。为阐明正交裂隙煤体的围压效应与破坏机理，基于结构面采样与参数标定试验构建正交裂隙煤体模型，采用合成岩体方法开展不同围压条件下正交裂隙煤体的常规三轴压缩试验，提出结构面活化系数的概念，分析围压对正交裂隙煤体破坏特征、强度特性、变形行为与结构面活化的影响，提出并验证结构面活化机制以及围压条件下正交裂隙煤体的破坏机理。研究结果表明:① 正交裂隙煤体的力学性质表现出明显的围压效应。随围压增大，煤体的抗压强度、残余强度、弹性模量增大，抵抗膨胀变形能力增强;力学性质表现出脆延转化;煤块破坏形式由拉伸转为剪切;结构面活化比例降低，结构面对正交裂隙煤体力学性质的影响减弱乃至消失。② 存在围压时结构面活化难度急剧增加，正交裂隙煤体的围压效应在低围压时更为显著。③ 无围压时，正交裂隙煤体发生劈裂破坏，裂隙由结构面活化裂隙和翼裂纹组成;中、低围压时，正交裂隙煤体发生剪切破坏，形成贯穿的倾斜剪切裂隙;高围压时，正交裂隙煤体发生塑性流动破坏。④ 无围压时，结构面控制正交裂隙煤体的破坏;中、低围压时，结构面影响正交裂隙煤体破坏裂隙的形态，但随围压增大影响程度变弱;高围压时，正交裂隙煤体的破坏不受结构面影响。

The distribution of discontinuities in coal mass is characterized by orthogonality.To clarify the confining pressure effect and failure mechanism of coal mass,a numerical model of coal mass containing orthogonal fractures is constructed based on discontinuities sampling campaign and parameters calibration tests.The conven tional triaxial compression tests under different confining pressures are conducted using synthetic rock mass (SRM) approach.The joints activation ratio is put forward.The influences of confining pressure on failure characteristics,strength properties,deformation behavior and joints activation for coal mass are analyzed.The joints activation mechanism and failure mechanism of coal mass under confining pressures are analyzed and verified.The results show that:① the mechanical properties of coal mass containing orthogonal fractures show heavy confining pressure effect.With the increase of confining pressure,the compressive strength,residual strength and elastic modulus are increased,and the ability of resistance to expansion deformation is enhanced.The mechanical behavior transits from brittleness to ductility.The failure form of intact coal transits from tension to shear.The activation ratio of joints is reduced,and the influence of joints on the mechanical properties of coal mass is weakened and even disappears.② The difficulty of joints activation increases sharply when the confining pressure exists and the confining pressure effect is more significant at a low confining pressure.③ When no confining pressure,the coal mass containing orthogonal fractures exhibits splitting failure and the fractures are composed of activated joints and wing fractures.At a low or middle confining pressure,the shear failure occurs with an inclined shear fracture through the coal mass.At a high confining pressure,coal mass ruptures by means of plastic flow.④ When no confining pressure,the failure of coal mass containing orthogonal fractures is controlled by joints.At a low or middle confining pressure,the fracture geometry is influenced by joints,but the influence becomes weak with the increase of confining pressure.At a high confining pressure,the failure is not affected by joints.

1 合成岩体方法

2 正交裂隙煤体模型构建

   2.1 正交裂隙煤体DFN构建

   2.2 正交裂隙煤体SRM模型构建

3 正交裂隙煤体围压效应分析

   3.1 三轴压缩模型与模拟方案

   3.2 围压对煤体破坏特征的影响

   3.3 围压对煤体强度特性的影响

   3.4 围压对煤体变形行为的影响

   3.5 围压对煤体结构面活化的影响

4 正交裂隙煤体破坏机理分析

   4.1 结构面活化与翼裂纹形成机制

   4.2 围压条件下正交裂隙煤体破坏机理

5 结论