布孔间距影响瓦斯预抽效果的模拟及应用研究

依据小庄矿40205综放工作面煤层瓦斯实际赋存条件,同时考虑吸附游离两态瓦斯,建立了煤层瓦斯预抽理论模型,利用COMSOL Multiphysics模拟了不同布孔间距下的煤层瓦斯压力分布情况,确定了合理的顺层预抽钻孔布孔间距,并应用于现场实际抽采工作。数值模拟显示:布孔间距在1.8~2.5 m时,两孔中心最大瓦斯压力的增长速率较大;布孔间距在2.5~3.5 m时,其增长速率有所降低;当布孔间距为3.0 m时,预抽0~90 d时煤层瓦斯压力下降速率较大,预抽90~210 d时煤层瓦斯压力下降速率逐渐减缓;抽采过程存在最佳抽采时间;40205综放工作面顺层预抽孔布孔间距设置为3.0 m,预抽90 d时,钻孔间最大瓦斯压力降至182.435 kPa;预抽210 d时,钻孔间最大瓦斯压力降至178.230 kPa,可将煤层瓦斯压力降至50%以下,保障预抽达标。现场应用显示:40205工作面回风巷瓦斯抽采纯流量大且较为稳定,基本稳定在1.50 m³/min左右,预抽效果较理想。

Simulation and application research on effect of spacing of holes on gas pre-drainage

According to the actual occurrence conditions of coal seam gas in 40205 fully mechanized top coal caving face of Xiaozhuang Coal Mine,and considering the adsorbed and free state gas,the theoretical model of coal seam gas pre-drainage was established,and the distribution of coal seam gas pressure with different hole spacing was simulated by COMSOL Multiphysics.The reasonable spacing of pre-drainage holes along the seam was determined and applied to the actual gas drainage work.The numerical simulation showed that when the hole spacing was 1.8-2.5 m,the growth rate of the maximum gas pressure in the center of two holes was large,while it decreased when the hole spacing was 2.5-3.5 m;when the hole spacing was 3.0 m,the decrease rate of coal seam gas pressure was larger when the pre-drainage time was 0-90 days,while it gradually slowed down when the pre-drainage time was 90-210 days.There was an optimal gas drainage time in the process.When the hole spacing was 3.0 m,the maximum gas pressure between holes was reduced to 182.435 kPa after 90 days and 178.230 kPa after 210 days,when the the coal seam gas pressure could be reduced to less than 50%to ensure the pre-drainage up to the standard.The field application showed that the gas drainage pure flow of 40250 working face was large and relatively stable at about 1.50 m³/min,the pre-drainage effect was preferable.