原煤力学及渗流特性的层理效应研究

为研究层理对原煤力学及渗流特性的影响，通过实验对比分析平行层理煤样和垂直层理煤样在相同瓦斯压力、不同围压下的三轴压裂力学及渗流特性，同时采集压裂过程的声发射数据并进行分析。结果表明:随着围压增大，平行层理煤样的峰值轴向应力平均增幅为34.5%，远小于垂直层理煤样的平均增幅161.21%；围压为1，3，5 MPa时，垂直层理煤样的压裂时间分别是平行层理煤样的0.68，0.19，2.72倍，层理方向对力学特性的影响随着围压增加呈先减小后增大的趋势；围压相同时，平行层理煤样的声发射幅值随时间增加而增大，垂直层理煤样的声发射幅值随时间增加表现出正弦波变化趋势，且平行层理煤样在压裂过程中的声发射高幅值事件比垂直层理煤样的多；平行层理煤样的渗透率远大于垂直层理煤样的渗透率，且围压越大，初始渗透率越低，说明平行层理方向的孔隙度大于垂直层理方向的孔隙度。

Study on bedding effect of mechanics and seepage characteristics of raw coal

In order to study the influence of bedding on the mechanics and seepage characteristics of raw coal,the triaxial fracturing mechanics and seepage characteristics of parallel bedding and vertical bedding coal samples under the same gas pressure and different confining pressures were compared and analyzed through the experiments,and the acoustic emission (AE) data in the fracturing process were collected at the same time.The results showed that with the increase of confining pressure,the average increase of peak axial stress in parallel bedding coal samples was 34.5%,far less than the average increase of 161.21% in vertical bedding coal samples.The fracturing time of vertical bedding coal samples was 0.68,0.19 and 2.72 times that of parallel bedding coal samples,respectively,and the influence of bedding direction on the mechanical properties decreased first and then increased with the increase of confining pressure.Under the same confining pressure,the AE amplitude of parallel bedding coal samples increased with the increase of time,while that of vertical bedding coal samples presented the change trend of sine wave with the increase of time,and there were more AE high amplitude events during the fracturing process of parallel bedding coal samples than that of vertical bedding coal samples.The permeability of parallel bedding coal samples was much higher than that of vertical bedding coal samples,and the higher the confining pressure,the lower the initial permeability,which indicated that the porosity in the parallel bedding direction was greater than that in the vertical bedding direction.Therefore,the best direction of borehole was the vertical bedding direction when extracting gas in the underground coal mines.