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为探讨瓦斯压力对含瓦斯煤渗透特性的影响,通过含瓦斯煤的三轴剪切试验,获得试件在进行三轴渗流试验时始终处于稳定应力状态的轴向应力和围压的合理取值,在此基础上,以贵州松河煤矿8号煤为剖析对象,利用自主研制的出口压力可调的三轴渗透仪进行了有效应力和温度恒定、不同瓦斯压力条件下的三轴渗流试验。结果表明:当瓦斯压力恒定时,含瓦斯煤试件的抗剪强度随着围压的增加而增加;当有效应力、温度和试件两端压差恒定时,渗透率以指数关系随着间隙气压的增加而下降;当有效应力、温度和间隙气压恒定时,渗透率随着两端压差的增大而减少。试验结果为地面煤层气开发和井下瓦斯抽采提供了有力的技术支撑。
In order to investigate the influence of gas pressure on gas permeability of coal-bearing coal, the reasonable value of axial stress and confining pressure which are always in steady stress during the three-axis seepage test is obtained through the triaxial shear test of gas-bearing coal. On the basis of this, taking No.8 coal of Songhe Coal Mine in Guizhou as the object of analysis, a three-axis seepage test with effective stress and constant temperature under different gas pressures was carried out by using self-developed triaxial permeameter with adjustable outlet pressure. The results show that when the gas pressure is constant, the shear strength of gas coal samples increases with the increase of confining pressure. When the effective stress, temperature and the pressure difference between two ends of the specimen are constant, the permeability increases exponentially with the gap When the effective stress, temperature and gap pressure are constant, the permeability decreases with the increase of pressure drop at both ends. The test results provide strong technical support for the development of coalbed methane and underground gas drainage.