原煤受载破坏形式的层理效应研究

Study on bedding effect of failure mode of raw coal under loading

为了研究层理对原煤受载破坏形式的影响,分别对平行层理煤样和垂直层理煤样进行单轴压裂实验和相同围压、不同瓦斯压力下的三轴压裂实验。结果表明:平行层理煤样的抗压强度略小于垂直层理煤样,但后者的峰值应变是前者的2.33倍;随着瓦斯压力增大,垂直层理煤样的峰值应力先增大后减小,变化的幅度为26.62%,平行层理煤样的峰值应力先减小后增大再减小,变化的幅度为35.14%;单轴压裂和三轴压裂时,平行层理煤样的破坏为整体纵向剪切破坏,煤样沿纵向裂开为几大块,垂直层理煤样的破坏为局部横向张拉破坏,煤样上半部分剧烈破坏,下半部分基本保持完整;三轴压裂与单轴压裂相比,垂直层理煤样破裂时保持完整的部分体积约增加73%,平行层理煤样劈裂的角度变化幅度约为42%。

In order to study the influence of bedding on the failure form of raw coal under load,uniaxial fracturing experiments and triaxial fracturing experiments under the same confining pressure and different gas pressures were carried out on parallel bedding coal samples and vertical bedding coal samples.The results show that the compressive strength of parallel bedding coal samples is slightly lower than that of vertical bedding coal samples,but the peak strain of the latter is 2.33 times that of the former.As the gas pressure increases,the peak stress of the vertical bedding coal sample increases first and then decreases,with a change of 26.62%.The peak stress of the parallel bedding coal sample first decreases,then increases and then decreases,the range of change is 35.14%.During uniaxial fracturing and triaxial fracturing,the failure of the parallel bedding coal sample is the overall longitudinal shear failure,and the coal sample splits into several large pieces along the longitudinal direction,the failure of the vertical bedding coal sample is the local transverse tension failure.The upper half of the coal sample was severely damaged,and the lower half remained basically intact.Compared with uniaxial fracturing,the volume of the intact part of the vertical bedding coal sample is increased by about 73%when the vertical bedding coal sample is fractured,and the angle variation range of the parallel bedding coal sample is about 42%.