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含煤层隧道施工中瓦斯抽排是关系到隧道安全施工的关键。利用有限元软件Midas GTS对高瓦斯低渗透性煤层段掌子面处煤层水力压裂过程进行数值模拟,研究注水孔周围煤体裂隙的起裂原因和裂隙发育过程,结果认为:在水力压裂作用下煤体原始裂隙主要受拉压破坏,周围煤体主要受压剪破坏,剪应力随水压力增加而增加,并向四周裂隙移动。针对贵州正在施工的某煤层隧道,分析该工程中利用水力压裂进行瓦斯抽排的技术及过程,并与数值模拟结果进行对比,证实了水力压裂增透技术有助于增加低渗透性煤层的透气性。进一步对比分析认为:由于煤体原始裂隙降低了裂缝起裂条件,而导致实际施工中水压力大小要普遍小于理论模拟结果。论文的研究丰富了水力压裂技术的实验研究资料,为今后煤层隧道揭煤方案提供重要参考。
Gas drainage in coal seam tunnel construction is the key to safety construction of tunnel. The finite element software Midas GTS was used to simulate the hydraulic fracturing process of coal seam at the face of coal seam with high gas and low permeability and to study the cause of fracture initiation and fracture development of coal fractures around water injection hole. The results show that in hydraulic fracturing Under the action of coal, the original fracture of coal is mainly affected by tension and compression, and the surrounding coal is mainly damaged by compression shear. The shear stress increases with the increase of water pressure and moves to the surrounding cracks. Aiming at a certain coal seam tunnel under construction in Guizhou, the technology and process of gas drainage using hydraulic fracturing in this project are analyzed. Compared with the numerical simulation results, it is confirmed that hydraulic fracturing anti-seepage technology can help increase the permeability of low-permeability coal seam Breathability. Further comparative analysis shows that: due to the fact that the original fracture of coal reduces the crack initiation and fracture conditions, the water pressure in the actual construction is generally less than the theoretical simulation results. The research of the paper enriches the experimental research data of hydraulic fracturing technology and provides an important reference for the coal seam tunnel coal uncovering plan in the future.