软煤层瓦斯抽采半径和钻孔间距的数值模拟研究

Numerical simulation study on gas drainage radius and hole spacing in soft coal seam

为得出软煤层瓦斯抽采有效半径,确定最佳的抽采钻孔间距,基于质量守恒定律、Darcy扩散定律、Langmuir瓦斯吸附方程及Kozeny-Carman渗透率和孔隙率的关系方程,建立了考虑含瓦斯软煤体流变特性情况下的固流耦合控制方程。在此基础上采用数值模拟方法对软煤层瓦斯抽采过程进行分析。模拟结果表明:瓦斯抽采第32d时,抽采钻孔完全塌陷,因此确定钻孔有效抽采时间为32d;通过分析钻孔周围煤体瓦斯压力变化规律可得,单钻孔抽采有效半径为0.9m,多钻孔抽采时最佳布孔间距为3.4m。以合阳煤矿1508工作面为试验工作面,采用相对压力法分别对单钻孔和多钻孔瓦斯抽采效果进行考察试验,试验结果验证了数值模拟结论的可靠性,为该矿软煤层瓦斯抽采提供了科学依据。

In order to confirm the effective radius of gas drainage and the best drainage hole spacing,based on the conservation of mass,the Darcy diffusion law,Langmuir gas absorption equation and Kozeny-Carman permeability-porosity equation,the fluid-solid coupling control equation was established which mainly considered the rheological properties of the gas seepage in the soft coal seam.And on the basis of these results,numerical simulation method was used to analyze the gas drainage process.The simulation results showed that the drainage hole was completely collapsed after 32 days of gas drainage,therefore the effective drainage time of the hole was 32 days;through analyzing the gas pressure change law around the hole,a single hole＇s effective drainage radius was determined as 0.9 m,and the best hole spacing was 3.4 mwhen multi-hole gas drainage.According to the engineering practice effects of single-hole and multi-hole gas drainage by using relative pressure method in 1508 working face in Heyang Coal Mine,the reliability of the numerical simulation was verified,which provided a scientific basis for gas drainage in soft coal seam.