回采工作面及采空区瓦斯运移的数学模型及数值模拟研究

为更真实可靠地还原回采工作面及采空区内流场和瓦斯场的分布特征,基于回采工作面和采空区不同的介质属性,并考虑瓦斯扩散能力的差异,建立了各自的强耦合多物理场数学模型,并给出了瓦斯涌出所满足的质量通量边界条件。采用COMSOL Multiphysics构建了强耦合的自由和多孔介质流动以及自由和多孔介质稀物质传递等物理场,以龙煤矿业集团股份有限公司双鸭山分公司的东保卫井田二水平一采区36号煤-570左面为研究对象,研究了回采工作面及采空区稳态下的瓦斯运移特征。结果表明:采空区浅部瓦斯体积分数较小但梯度较大,且随着采空区向深部延伸,瓦斯体积分数的梯度逐渐降低,但其数值逐渐增大并趋于稳定;另外,采空区内实测的瓦斯体积分数分布与数值模拟结果具有较好的一致性,验证了建立的回采工作面及采空区瓦斯运移的数学模型和数值模型的可靠性和准确性。

Mathematical model and the numeri-cal simulation in regard to the gas migration in the coal-mining goaf

The paper has established a mathematical model of the strongly coupled multi-physical field in the coal face and goaf respectively so as to restore the distribution characteristic features of the migrate field and the gas field in the coal face and goaf more truthfully and trustfully. At the same time,we have also taken into account the gaps in physical and mechanical properties in the gas diffusion capability of the mining face and goaf. In addition,we have also given the boundary conditions of the mass flux for the gas emission in the strongly coupled multi-physical field in our math models. With the COMSOL Multiphysics,we have built up the strongly coupled physics,such as the free and porous media flow and the free and porous media dilute matter transfer,to trace and detwermine the gas migration features of the coal face and goaf in the steady state,and the relevant parameters in the study measured or gathered from the-570 left coal mining face in the No. 36 coal seam,No. 2 mining level and No. 1 mining area of the Dongbaowei coal mine,Shuangyashan Branch under the Longmei Mining Group Co.,Ltd.. The results show that the gas diffusion capability of the rock and coal body in the goaf has been affected noticeably by the spatial distribution porosity features,for the spatial distribution of the gas volume fraction and the gas volume fraction gradient in the goaf ought to be quite different. Thus,the numerical results prove that in the shallow layer of the goaf,the gas volume fraction is little whereas the gas volume fraction gradient has to be greater,which can be extending to the deep goaf. However,with the gas volume fraction increasing gradually and getting to be ultimately stable,the gas volume fraction gradient should be getting gradually declining. And,in such a situation,the gas volume fraction distribution in the goaf measured on the spot may turn to be in nice agreement with the numerical simulation results. And,such a situation can help to verify the reliability and accuracy of the mathematical model and the numerical model of the gas migration in the coal face and goaf we have established in the given paper.