Wu Haijin, Li Xuelong, Gao Xin, Chen Deyou, Li Zhen
School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China.
College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, China.
ACS Omega. 2021 Dec 30;7(1):733-743. doi: 10.1021/acsomega.1c05385. eCollection 2022 Jan 11.
The poor sealing effect of gas extraction boreholes causes low efficiency of gas extraction. As a consequence, the requirements of coal mine safety production are often not attained. The sealing effect of boreholes depends not only on the sealing material itself but also on the combination degree between the material and the hole wall and the structural change characteristics of the material during operation. Our theoretical analysis shows that the amount of liquid leakage increases with the gap width Δ in a cubic law, decreases with the sealing hole viscosity in a hyperbolic form, increases linearly with the diameter of the borehole, and increases with the eccentricity in a quadratic function. We have developed a PD sealing material that has good compactness and sealing effects, excellent water retention performance, and an expansion rate of 1.29. The material can generate secondary expansion through microscopic development, which is beneficial to improve the quality of the sealing hole. HV-CMC has good stability in plugging mucus. In addition, the manual pump has been redeveloped to be portable and also to overcome the blockage of the suction valve of the original device. In addition, the auxiliary device for drilling and sealing has been invented. The field application demonstrates that the gas concentration and flow pressure difference of the new sealing borehole can be maintained at a high level in a short period of time and then decrease slowly with time. The resulting improved sealing effect demonstrates that our new approach has important theoretical and practical significance for mine gas drainage.
瓦斯抽采钻孔密封效果差导致瓦斯抽采效率低下。因此，往往无法达到煤矿安全生产的要求。钻孔的密封效果不仅取决于密封材料本身，还取决于材料与孔壁之间的结合程度以及材料在运行过程中的结构变化特性。我们的理论分析表明，漏液量随间隙宽度Δ呈三次方规律增加，随密封孔粘度呈双曲线形式减小，随钻孔直径呈线性增加，随偏心度呈二次函数增加。我们研发了一种PD密封材料，其具有良好的致密性和密封效果、优异的保水性能，膨胀率为1.29。该材料可通过微观发育产生二次膨胀，有利于提高密封孔质量。HV-CMC在封堵黏液方面具有良好的稳定性。此外，对手动泵进行了重新研发，使其便于携带，还克服了原装置吸阀堵塞的问题。此外，还发明了钻孔密封辅助装置。现场应用表明，新型密封钻孔的瓦斯浓度和流量压差能在短时间内维持在较高水平，然后随时间缓慢下降。由此得到的改进密封效果表明，我们的新方法对矿井瓦斯抽采具有重要的理论和实际意义。
