基于含瓦斯煤岩固气耦合模型的钻孔抽采瓦斯三维数值模拟

通过在多孔介质的有效应力原理中引入瓦斯吸附产生的膨胀应力，得出适用于含瓦斯煤岩的有效应力计算公式。同时利用含瓦斯煤岩的孔隙率和渗透率的动态模型，建立了能描述含瓦斯煤岩固气耦合情况下的骨架可变形性和气体可压缩性的固气耦合模型。以平顶山十矿的相关物性参数为基础进行了数值模拟，首先对建立的三维模型进行了开挖处理，得到了开挖后煤层的应力分布状态，而非简单的均布载荷，然后利用所建立的数学模型进行钻孔抽采瓦斯三维数值模拟。从数值模拟结果得到：① 抽采负压对钻孔抽采瓦斯的影响不明显；② 随着抽采时间的增长，煤层的孔隙率逐渐减小；③ 随着时间的推移，钻孔抽采瓦斯的有效抽采半径均逐渐增大，最后会迫近一个定值。

3D numerical simulation of gas drainage from boreholes based on solid-gas coupling model of coal containing gas

An effective stress calculation formula was proposed for coal containing gas with considering the swelling stress of gas adsorption based on the effective stress principles for porous media.Referring to dynamic model of porosity and permeability in coal containing gas，solid gas coupling model which could describe the skeleton deformability of coal containing gas and the compressibility of gas under the solid gas interaction condition was built.First we made excavation on the three dimensional model based on the physical parameters of Pingdingshan tenth coal mine to obtain the stress distribution of coal seam after excavated instead of easy uniform loading.Then we simulated the gas drainage from boreholes based on constructed mathematical model.From the results we got：① Negative pressure didn’t have a great influence on gas drainage.② The porosity of coal seam decreased gradually over time.③ The effective radius increased gradually to a fixed value over time.