为解决昭通瓦斯隧道地应力高、煤层透气性低、瓦斯质量分数高、煤层松软等难题，通过理论计算对比分析平导洞与主洞分2次抽排瓦斯、平导洞与主洞一次性抽排瓦斯以及高低位钻场一次性抽排瓦斯3种隧道瓦斯抽排方案，择优选择高低位钻场瓦斯抽排方案，对昭通隧道M7—M9煤层开展现场瓦斯钻孔布局。在此基础上，选用高压水力冲孔技术进行煤层增透。现场研究表明： 1）相对于2种平导洞+主洞方案，高低位钻场方案的钻孔施工量分别减少约44%与19%，分别缩短施工周期0.5个月及3个月； 2）月累计抽排瓦斯纯量约20万m3，高位钻场消突效果达83%，低位钻场消突效果达85%，综合消突效果为84%。采用高低位钻场+水力冲孔相结合的瓦斯抽排技术，高效治理了昭通隧道瓦斯难题，确保了隧道顺利穿越高瓦斯煤层。
The Zhaotong gas tunnel faces various challenges, such as high ground stress, low permeability of coal seams, high gas content, and soft coal layers. Herein, three tunnel gas drainage schemes—two-phase gas drainage in the parallel guide tunnel and main tunnel, single-phase gas drainage in the parallel guide tunnel and main tunnel, and one-time gas drainage using high- and low-level drilling fields—are theoretially analyzed and compared. The optimal gas drainage scheme using high- and low-level drilling fields is selected, and a gas drilling hole layout for the Zhaotong tunnel′s M7－M9 coal seams is implemented. Based on this, high-pressure water jet fracturing technology is employed to enhance coal seam permeability. The field study shows that: (1) Compared to other two schemes, the drilling workload of the high and low-level drilling field scheme is reduced by approximately 44% and 19%, respectively, and the construction period is shortened by 0.5 and 3 months, respectively. (2) The monthly cumulative pure gas drainage volume is approximately 200 000 m3, the gas extraction efficiencies in the high- and low-level drilling fields are 83% and 85%, respectively, reaching a 84% comprehensive gas drainage efficiency. The scheme has successfully controlled the gas outburst volume and guaranteed the construction safety of the project.
