小纪汗井田地层介质渗透特性及煤层为主含水层成因机制

Experimental study on permeability properties of stratum medium of Xiaojihan coal mine and genetic mechanism of the coal seam becoming a main aquifer

以陕北榆横矿区特殊地质背景为基础,通过瞬态渗透试验研究小纪汗煤矿煤系地层的渗透力学特性,基于采集的岩样两端孔隙压差时间序列,通过差分得到渗流速度及其变化率的时间序列,基于最小二乘法计算得到了各层岩样在不同围压下全应力应变过程中的渗透率、非达西流因子及加速度系数,比较了不同岩层的最大渗透率及最小渗透率。研究表明:1随着压缩应变的增加,煤样应力峰值滞后于渗透率峰值;2应力峰后阶段,煤样非达西流因子及加速度系数先急剧增加后显著下降,两者峰值滞后于应力峰值;3洛河组中粒长石砂岩与2号煤层岩样峰后的最高渗透率显著高于其他岩层;4煤样的渗透率峰后约为1×10-15m2量级,普遍高于一般煤矿煤层的渗透率;5所有岩层中,富县组砂质泥岩的渗透率最低,可视为隔水层。

Based on Yulin-Hengshan coal field in northern Shaanxi of the special geological background,the permeating mechanical properties of coal-bearing strata in Xiaojihan Coal Mine were studied by transient permeation tests in this paper. According to the collected time series of pore pressure at both ends of the rock samples,the authors obtained the time series of seepage velocity and its change rate by the difference method,and then by the least squares method,the authors calculated and obtained the permeability,non-Darcy flow coefficient and the acceleration factor during the total stress and strain process of the rock samples from different strata under different confined pressures,and the authors compared the maximum and minimum permeability of different strata. The research results are as follows： 1 with the increase in compression strain,the stress peak of coal samples lags its permeability peak; 2 during the stage after the peak stress,the non-Darcy seepage factor and acceleration coefficient of coal samples firstly increase dramatically and then decrease significantly,both these two peak values lag the stress peak; 3 the highest permeability of the destructed samples from the Luohe group Medium-grained feldspar sandstone and the No. 2 coal stratum are sig-nificantly higher than that of the other rock strata; 4 the permeability of the destructed coal samples achieve 1 × 10-15m2 magnitude,which is much higher than that of coal seam from the other coal mines; 5 the sandy mudstone in Fuxian group has the lowest permeability in all strata and it can be considered as a water resisting layer.