为保障突出煤层隧道安全掘进，揭示抽排钻孔消突机制，以扎西隧道揭煤抽排瓦斯为工程背景，综合采用理论分析和COMSOL模拟对抽排钻孔周围煤体内的瓦斯压力、瓦斯含量、瓦斯有效抽排半径等的变化规律开展研究，并与现场瓦斯抽排监测数据进行对比。根据数值模拟结果可知： 1）抽排钻孔周围煤体内将形成瓦斯压力剧烈降低区、显著降低区、缓慢降低区和原始压力区，瓦斯抽排钻孔的有效抽排半径为2.58 m； 2）随着累计抽排时间和到抽排钻孔距离的增加，煤体内瓦斯含量和瓦斯压力逐渐减小，有效抽排半径不断扩大，且与累计抽排时间呈负指数关系； 3）单抽排钻孔与煤层夹角每增加5°，抽排效率可增加约0.5%。现场70个顺层超前瓦斯抽排钻孔抽排后，煤层中最大残余瓦斯含量为5.95 m3/t，揭煤的突出危险性显著降低。
A case study is conducted on the Zhaxi tunnel to
ensure the safe excavation of gas outburst tunnels and investigate the gas
outburst elimination mechanism by drainage drilling holes. Theoretical analysis
and COMSOL simulation methods are comprehensively employed to examine the
variation rules of pressure, content, and effective drainage radius of gas in
coal seam around the drainage holes. The obtained results are compared with the
monitoring data of gas drainage on site, as follows. (1) The gas pressure
drastic reduction zone, significant reduction zone, slow reduction zone, and
original pressure zone are formed in the coal seam body around the drainage
holes, which have an effective drainage radius of 2.58 m. (2) The gas content
and pressure in the coal seam body gradually decrease with the increase in
distance to the drainage holes, but the effective drainage radius expands,
which is exponentially related to the cumulative drainage time. (3) The gas
drainage efficiency increases by ~0.5% when the angle between a single row
drilling holes and the coal seam increases by 5°. 〖ＪＰ２〗The maximum residual gas content in the coal seam is found to be
5.95 m3/t after gas drainage of 70 advance gas
drainage holes along the bed, indicating a significant reduction effect of gas.
