吸附气体对突出煤渗流特性的影响

煤层中瓦斯渗流特性不仅受地应力、煤孔隙结构等因素的影响,还因气体吸附而发生变化。以重庆市万盛区某煤矿突出煤层原煤为实验对象,在有效轴向应力和有效围压为1 MPa条件下,利用自制的三轴渗流试验机研究突出煤吸附二氧化碳、甲烷气体对渗流特性的影响。结果表明:1突出原煤吸附-渗流过程具有明显的阶段特征,煤体变形经历了初始快速变形阶段、缓慢变形发展阶段、变形稳定阶段、收缩变形阶段和渗流稳定阶段;2气体压力越大,煤体膨胀变形越大,相同气体压力下,煤体吸附二氧化碳变形增量大于吸附甲烷变形增量;3随着气体压力的增大,气体渗流速度逐渐增大,呈显著的指数函数关系,突出煤渗透率先减小后增大,具有明显的阶段性。

Effect of adsorptional gases on permeability of outburst coal

Seepage characteristics of coal seam are not only affected by stress and coal pore structure，but also gas adsorption.Based on the coal samples from the outburst coal seam of a mine at Wansheng District in Chongqing，China，the laboratory experiments of adsorption of pure carbon dioxide and methane on the characteristics of the coal permeability under constant effective axial stress，effective confining stress and different gas pressures were conducted using a self-developed triaxial gas-seepage experimental apparatus.The results show as follows:① In the adsorption and seepage process of outburst coal，coal deformation undergo five deformation stages:initial rapid deformation stage，tardiness deformation development stage，deformation stabilization stage，shrinkage deformation stage，seepage stabilization stage.② The swelling deformation of coal increases gradually with the gas pressure increase;the deformation increment of the outburst coal with the adsorptions of carbon dioxide is greater than that the outburst coal with the adsorption of methane under the same gas pressure.③ As the gas pressure increase，gas seepage velocity increases gradually and the relationship between gas seepage velocity and gas pressure could be described as exponential function，the permeability of outburst coal decreases firstly and then increases，which show distinct phases.