为探究不同侧压力系数下瓦斯抽采孔的最佳布孔间距,采用数值模拟的方式,建立基于塑性破坏的流固耦合模型,模拟钻孔周围的塑性区分布以及塑性区连接状态.研究结果表明:瓦斯单孔抽采时,抽采钻孔形成的塑性区半径随侧压力系数呈类指数增长,塑性区半径越大,裂隙分布更广,利于瓦斯流通;多孔抽采时,瓦斯流场范围与侧压力系数呈正相关,抽采时间与侧压力系数呈负相关;由于多孔抽采存在叠加效应,布孔间距大于单孔抽采的塑性区半径的 2 倍;采用数值软件模拟侧压力系数为 2.48 时的最佳布孔间距为 3.4 m,与嘉禾煤矿 2365 工作面的实际布孔间距一致.模拟结果具有一定的参考价值,在实际工程中可将瓦斯抽采钻孔布置在侧压力系数高的区域,或者人为增加偏应力以便于瓦斯抽采.
In order to explore the optimal spacing of gas holes under different lateral pressure coefficients,a numerical simulation method is used to establish a fluid solid coupling model based on plastic failure,simulating the distribution of the plastic zone around the borehole and the connection state of the plastic zone.The research results show that during single hole gas drainage,the radius of the plastic zone formed by gas drainage boreholes increases exponentially with the lateral pressure coefficient,and a large number of cracks are formed in the plastic zone,which is conducive to gas flow.That is,a high lateral pressure coefficient is a necessary and sufficient condition for increasing the spacing of gas drainage holes.During multi hole extraction,the range of gas flow field is positively correlated with the lateral pressure coefficient,while the extraction time is negatively correlated with the lateral pressure coefficient.Due to the superimposed effect of multi hole pumping,the spacing between holes is greater than twice the radius of the plastic zone of single hole pumping.Using numerical software to simulate the optimal hole spacing when the lateral pressure coefficient is 2.48,the optimal hole spacing is 3.4 m,which is consistent with the actual hole spacing of the 2365 working face of Jiahe Coal Mine.The simulation results have some referential value.In practical engineering,gas drainage boreholes can be arranged in areas with high lateral pressure coefficient,or the bias stress can be artificially increased for gas extraction.