易自燃煤层顺层抽采钻孔封孔参数优化研究

针对平煤十矿顺层抽采钻孔封孔不佳导致钻孔自然发火问题,用钻屑法试验研究巷道围岩应力分布特征,深入分析钻孔周围存在的漏气情况及导致钻孔自然发火的条件,并利用Comsol Multiphysics软件,数值模拟不同封孔深度与长度下钻孔周围漏风速度的分布状况,得到最优封孔参数,并探讨其对瓦斯抽采效果的影响。结果显示,距巷道0~7 m为破碎区,8~19 m为塑性区,20~28 m为弹性区;巷道周围破碎区、钻孔周围漏气圈、封孔材料漏风及抽采管路漏风为钻孔漏风区域,为钻孔自然发火提供通风供氧条件。研究表明:当封孔深度为17 m,封孔长度为8 m,最大抽采负压低于30 kPa时为最优封孔条件,既能保证抽采效果又能防止钻孔自然发火;封孔参数优化后单孔瓦斯抽采体积分数达到70%。

Study on optimization of borehole sealing parameters based on extraction drilling spontaneous combustion control

To solve the problem of spontaneous combustion of boreholes caused by poor sealing of boreholes in bedding extraction in No. 10 Coal Mine of Pingdingshan Coal Mine, the stress distribution characteristics of surrounding rock of roadway were studied by means of drilling cuttings method, the leakage passage around boreholes and the conditions leading to spontaneous combustion of boreholes were analyzed in depth, and distribution of air leakage velocities around boreholes as a function of both sealing depth and sealing condition was simulated by using the Comsol Multiphysics software. Optimum sealing parameters were obtained and their effects on gas extraction were discussed. The results show that 0-7 m away from the roadway is the broken area, 8-19 m is the plastic area, 20-28 m is the elastic area, the broken area around the roadway, the air leakage around the borehole, the air leakage of sealing material and the air leakage of the extraction pipeline are the air leakage ways of the borehole, providing the ventilation and oxygen supply conditions for the spontaneous combustion of the borehole, that when the sealing depth is 17 m, the sealing length is 8 m, the maximum negative extraction is achieved, and when the pressure is less than 30 kPa, it can not only guarantee the effect of drainage but also prevent the spontaneous combustion of boreholes, and that volume fraction of single hole gas drainage reaches 70% after optimization of sealing parameters, which can effectively prevent spontaneous combustion of drainage holes.