基于采空区孔隙率动态演化模型的卸压瓦斯运移规律研究

Study on the migration law of pressure relief gas based on dynamic evolution model of goaf porosity

为了获得工作面推进过程中采空区卸压瓦斯的运移规律,以大佛寺煤矿40118工作面为研究对象,基于煤岩层的物理力学参数,建立了基于采空区应力分布特征的采空区孔隙率动态演化模型,采用数值模拟的方法获得了工作面不同通风量、高位钻孔不同抽采负压,以及不同瓦斯涌出量条件下的采空区瓦斯运移规律。研究结果表明:采空区孔隙率动态演化模型可以较好地适应该矿的地层条件,其随着工作面推进而动态变化;在高位钻孔抽采条件下,随着工作面通风量和抽采负压的增大,采空区瓦斯浓度(甲烷体积分数)逐渐减小,但浓度值处于爆炸界限内的区域却有所增加,这在一定程度上增大了发生瓦斯爆炸风险的范围;随着采空区瓦斯涌出量的增加,采空区内甲烷体积分数整体上升,但瓦斯爆炸风险有所降低。

In order to obtain the migration law of pressure relief gas in goaf during working face advancing,40118 working face of Dafosi Coal Mine was taken as the research object.Based on the physical and mechanical parameters of coal strata,a dynamic evolution model of goaf porosity based on the stress distribution characteristics of goaf was established.By the numerical method,the gas migration in goaf under the conditions of various ventilation air volumes,different negative extraction pressure of high-level boreholes and different gas emission volume in the working face were obtained.The results show that the dynamic evolution model of goaf porosity can adapt well to the strata conditions of the coal mine,and it changes dynamically with the advance of the working face.Under the condition of high-level borehole extraction,the gas concentration(methane volume fraction)in goaf gradually decreases with the increase of ventilation volume and negative extraction pressure.However,there is an increase in the concentration within the blast limit,which increases the scope of gas explosion risk to some extent.With the increase of gas emission in goaf,the volume fraction of methane in goaf increases,but the risk of gas explosion decreases.