Sun Zhongguang, Li Xuelong, Wang Kequan, Wang Fakai, Chen Deyou, Li Zhen
State Key Laboratory of the Gas Disaster Detecting, Preventing and Emergency Controlling, Chongqing 400037, China.
China Coal Technology and Engineering Group Chongqing Research Institute, Chongqing 400039, China.
Int J Environ Res Public Health. 2022 Apr 19;19(9):4968. doi: 10.3390/ijerph19094968.
Coal is affected by the concentrated stress disturbance of mining, the disturbance of drilling hole formation, and the concentrated stress of coal shrinkage and splitting of gas desorption from the hole wall; these result in a large number of secondary cracks that collect and leak gas. As a result, it is difficult for the coal seam sealing process to meet engineering quality sealing requirements, which results in problems such as low gas concentration during the extraction process. In this paper, based on the analysis of coal pore and fissure characteristics, and in view of the current situation of gas drainage and sealing in this coal seam, combined with the existing grouting and sealing technology, it is proposed to use pressure grouting and sealing to realize the sealing of deep coal bodies in the hole wall. According to the field conditions, the experimental pressure sealing parameter index is as follows: theoretical sealing length = 9.69 m, the sealing length = 13.98 m is verified, and the final sealing length is determined to be 15 m; the sealing radius is determined to be 0.6 m; the cement slurry was prepared on site with a water: cement ratio of 2:1; = 0.43 MPa was calculated; the range of the slurry diffusion radius was 93.4-176.6 cm; the grouting pressure was determined to be 0.516 MPa. Field application practice has proved that: (1) Under the same drilling parameters and sealing parameters, the gas drainage effect of drilling with pressure sealing is 2.3 times higher than that without pressure sealing; (2) Using traditional sealing technology for drilling holes, the gas extraction concentration is far lower than the sealing operation effect of using the pressure sealing process; (3) Reasonably extending the length of the gas extraction drilling and sealing is a basic guarantee for realizing a substantial increase in the gas extraction concentration; (4) Sealing with pressure leads to a reliable and stable hole process.
煤炭受到开采集中应力扰动、钻孔成孔扰动以及煤炭收缩和钻孔壁瓦斯解吸导致的集中应力影响；这些因素会产生大量次生裂隙，致使瓦斯汇集和泄漏。因此，煤层密封过程难以满足工程质量密封要求，进而导致抽采过程中瓦斯浓度低等问题。本文在分析煤孔隙裂隙特征的基础上，针对该煤层瓦斯抽采与密封现状，结合现有注浆密封技术，提出采用压力注浆密封实现钻孔壁深部煤体的密封。根据现场条件，试验压力密封参数指标如下：理论密封长度 = 9.69 m，验证后的密封长度 = 13.98 m，最终确定密封长度为15 m；密封半径确定为0.6 m；现场制备水灰比为2:1的水泥浆；计算得到 = 0.43 MPa；浆液扩散半径范围为93.4 - 176.6 cm；注浆压力确定为0.516 MPa。现场应用实践证明：(1) 在相同钻孔参数和密封参数下，带压密封钻孔的瓦斯抽采效果比无压密封高2.3倍；(2) 采用传统密封技术进行钻孔，瓦斯抽采浓度远低于采用带压密封工艺的密封作业效果；(3) 合理延长瓦斯抽采钻孔的密封长度是实现瓦斯抽采浓度大幅提高的基本保证；(4) 带压密封可使钻孔过程可靠且稳定。
