夹矸对煤层瓦斯抽采影响的数值模拟研究

摘要

In order to solve problem of reasonable arrangement of gas drainage borehole in coal seam containing gangue,a solid-gas coupling model of gas drainage was deduced with initial and boundary conditions by establishing control equation of coal and rock deformation,control equation of gas migration and evolution equation of porosity and permeability.Distribution laws of gas pressure,permeability and displacement deformation of coal body around single borehole were numerical simulated and analyzed by use of multiphysics field analysis software COMSOL Multiphysics combining with actual geological conditions of IV13 coal seam of a mine.Hole spacing of gas drainage boreholes in coal seam containing gangue was also determined,which provided basis for optimal arrangement of drainage boreholes in coal seam containing gangue.The research results show that during gas drainage process,along with decrease of distance between coal body and borehole,falling range of gas pressure and rising range of permeability of coal body around borehole are the minimum,and displacement of coal body around borehole is the maximum when coal seam contains no gangue;falling range of gas pressure and rising range of permeability of coal body around borehole are the maximum,and displacement of coal body around borehole is the minimum when borehole does not cross gangue.%为解决含夹矸煤层瓦斯抽采钻孔的合理布置问题,通过建立瓦斯抽采的煤岩体变形控制方程、瓦斯运移控制方程和孔隙率与渗透率演化方程,结合瓦斯抽采的初始及边界条件,推导出了瓦斯抽采固气耦合模型.利用多物理场分析软件COMSOL Multiphysics,并结合某矿IV13煤层的实际地质条件,对煤层单一抽采钻孔周围煤体的瓦斯压力、渗透率、位移的分布规律进行了数值模拟与分析,确定了含夹矸煤层瓦斯抽采钻孔的孔间距,从而为含夹矸煤层抽采钻孔的优化布置提供了依据.研究结果表明,在瓦斯抽采过程中,随着煤体距钻孔距离的减小,煤层不合夹矸时钻孔周围煤体瓦斯压力下降幅度、渗透率上升幅度最小,钻孔周围煤体位移量最大;钻孔未穿过夹矸时钻孔周围煤体瓦斯压力下降幅度、渗透率上升幅度最大,钻孔周围煤体位移量最小.