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为了研究渗透率随有效应力的变化特征,利用含瓦斯煤热–流–固耦合三轴伺服渗流装置,在外部应力不变、降低进口气体压力,外部应力、进气口压力同步降低2种实验条件下,观测了赵各庄煤矿9号煤层样品的应变和气相(氦气)渗透率,研究有效应力对煤样变形和渗透性的影响。实验结果显示,随着有效应力升高,煤样的收缩应变加剧,有效应力为5.2~6.5 MPa,收缩体积应变与有效应力之间符合线性关系,有效应力大于6.5 MPa或小于5.2 MPa,应力–应变曲线发生偏折,部分煤样出现扩容现象;气体渗流速度随进口气体压力的降低而降低;升高或降低有效应力,煤样渗透率均随着进口气体压力的降低而增大。由此可见研究有效应力变化条件下的渗透率变化特征,应适当考虑气体滑脱效应的影响。
In order to study the changing characteristics of permeability with effective stress, two kinds of experiments were carried out by using gas-coal-thermal-fluid-solid coupling three-axis servo oil seepage device to keep the external stress unchanged and reduce the gas pressure, external stress and inlet pressure simultaneously The strain and gas (helium) permeability of No.9 coal seam in Zhaoguzhuang Coal Mine were observed to study the effect of effective stress on the deformation and permeability of coal sample. The experimental results show that with the increase of effective stress, the shrinkage strain of coal sample aggravates. The effective stress is 5.2-6.5 MPa. The linear relationship between shrinkage volume strain and effective stress is obtained. The effective stress is greater than 6.5 MPa or less than 5.2 MPa. The stress- The strain curve is deflected, some of the coal samples appear dilatancy phenomenon; the gas seepage velocity decreases with the decrease of the inlet gas pressure; the effective stress is increased or decreased, and the coal sample permeability increases with the decrease of the inlet gas pressure. It can be seen from the study of changes in permeability under the conditions of effective stress changes should take due consideration of the effect of gas slippage effect.