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    小煤柱沿空巷道抽采钻孔失效机理及全周期严密封孔技术

    Failure mechanism of gas extraction boreholes in small coal pillar gob-side entry and full cycle tight hole sealing technology

    • 摘要: 针对小煤柱沿空巷道矿压显现剧烈、瓦斯抽采效果差等难题,对比分析了10 m和30 m煤柱实体煤侧应力分布规律,查明了小煤柱沿空巷道抽采钻孔失效机理,采用分时段、分区段方法研发了抽采钻孔全周期严密封孔技术,确定了全周期严密封孔技术关键参数,并在高河能源进行了现场应用。研究结果表明,小煤柱沿空巷道实体煤侧承担着大部分顶板压力,实体煤侧支承压力峰值达32.66 MPa,远高于大煤柱的16.45 MPa,并在多重采动应力作用下,煤体裂隙更为发育,导致钻孔封孔段容易形成漏气通道,在封孔管底部易发生塌孔、堵孔现象,且封孔段容易被剪切破坏导致钻孔失效。初期采用“浅卸−深封”一体化技术,即浅部卸压、深部严密封孔,实现矿压与瓦斯共治;中期采用二次注浆精准堵漏提浓技术对漏气通道进行封堵,恢复钻孔抽采能力;后期待巷道围岩变形稳定后,采用“三堵两注”技术对卸压段注浆,提高封孔质量及抽采效果。初期封孔阶段,平均瓦斯抽采浓度为44.28%,是“两堵一注”封孔工艺的3.29倍;中期采用二次注浆精准堵漏技术,平均瓦斯抽采浓度从24.65%提升至67.61%;后期采用“三堵两注”技术对卸压段注浆,平均瓦斯抽采浓度从27.57%提升至39.27%,表明全周期严密封孔技术可有效提升瓦斯抽采效果,缩短抽采达标时间。

       

      Abstract: To address the problems of intense mine pressure behavior and poor gas extraction performance in small coal pillar gob-side entry, the stress distribution characteristics on the solid coal side of 10 m and 30 m coal pillars were comparatively analyzed. The failure mechanism of extraction boreholes in small coal pillar gob-side entry was clarified, and the full cycle tight hole sealing technology for extraction boreholes was developed using a time staged and zonal control method. The key parameters of the full cycle tight hole sealing technology were determined and subsequently applied in the field at Gaohe Energy. The results indicate that the solid coal side of small coal pillar gob-side entry bears most of the roof pressure. The peak abutment pressure on the solid coal side reaches 32.66 MPa, which is much higher than the 16.45 MPa observed in the large coal pillar. Under the superimposed influence of multiple mining induced stresses, fractures in the coal mass become more developed, thereby causing air leakage channels to form readily within the borehole sealing section. In addition, borehole collapse and blockage tend to occur at the bottom of the sealing pipe, while the sealing section is susceptible to shear failure, ultimately leading to borehole failure. During the initial stage, an integrated shallow pressure relief and deep sealing technology was adopted, in which pressure relief was conducted in the shallow section and tight sealing was implemented in the deep section, thereby enabling the coordinated control of mine pressure and gas. During the intermediate stage, accurate plugging of secondary grouting was used to seal air leakage channels and restore the gas extraction capacity of the boreholes. During the later stage, after the deformation of the roadway surrounding rock became relatively stable, the three sealing and two grouting technology was applied to grout the pressure relief section, thereby improving the sealing quality and gas extraction performance. In the initial sealing stage, the average gas extraction concentration reached 44.28%, which was 3.29 times that of the two sealing and one grouting sealing process. During the intermediate stage, after accurate plugging of secondary grouting was applied, the average gas extraction concentration increased from 24.65% to 67.61%. During the later stage, after the three sealing and two grouting technology was used to grout the pressure relief section, the average gas extraction concentration increased from 27.57% to 39.27%. These results demonstrate that the full cycle tight hole sealing technology can effectively enhance gas extraction performance and shorten the time required to meet the gas extraction standard.

       

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