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特厚煤层动压巷道水力致裂卸压护巷技术研究

Research on hydraulic fracturing and pressure relief technology in ultra-thick coal seam dynamic pressure roadway

  • 摘要: 针对坚硬顶板难以及时垮落,造成工作面回采矿压强烈,巷道变形剧烈,治理难度大的问题,以马道头煤矿5209辅助运输巷为工程背景,通过现场调研、理论分析、围岩地质力学参数测试、工业性试验等多种手段,提出了基于单孔分段多次压裂为核心的特厚煤层坚硬顶板、强烈动压条件下巷道水力压裂切顶卸压控顶成套技术,包括钻孔布置、压裂参数、压裂装备及压裂工艺等。在5209辅助运输巷不同地段进行了单排孔和双排孔水力压裂切顶卸压现场工业性试验,工作面超前应力卸压以煤柱侧L孔为主,在终采线前方100 m范围增加采煤侧S孔卸压钻孔,并进行了现场试验与监测。压裂试验显示,K3粗粒砂岩最大起裂压力超过50 MPa,保压压力在15~30 MPa,压裂过程中临近观测孔出水效果较好,能够对坚硬难跨顶板实现分层分段预裂与软化。矿压监测数据表明:实施水力压裂切顶卸压后,动压巷道变形情况显著降低,巷道变形量降低70%,端头支架工作阻力降低35%,工作面回采超前应力影响距离从70 m降低至30 m内。研究成果在现场工程实践的成功实施,对于水力压裂切顶卸压技术在特厚煤层坚硬顶板工作面开采的推广应用提供了借鉴。

     

    Abstract: It is difficult for the hard roof to fall down in time, resulting in strong mining pressure on the working face, severe deformation of the roadway and difficult management. The No.5209 auxiliary transportation roadway of Madaotou Coal Mine was taken as the engineering background. Through on-site investigation, theoretical analysis and surrounding rock, geological mechanics parameter test, industrial test and other means, a set of technologies were put forward based on single-hole segmental multiple fracturing as the core of hard roof with extra-thick coal seam and hydraulic pressure fracturing and top-loading roof under strong dynamic pressure, including drilling arrangements, fracturing parameters, fracturing equipment and fracturing processes. On-site test of single-row and double-row hydraulic fracturing and top-cutting pressure relief was carried out in different sections of No.5209 auxiliary transportation roadway. The pre-stress relief of the working face was dominated by the L-hole of the coal pillar, the S-hole pressure relief borehole on mining side was added 100 m in advance of the final mining face and field test and monitoring were carried out there. The fracturing test shows that the maximum cracking pressure of K3 coarse sandstone exceeds 50 MPa, and the pressure is 15~30 MPa. The effect of water in the adjacent observation hole during fracturing is good, and it can realize layered pre-splitting for hard and difficult roof. The monitoring data of mine pressure shows that after the hydraulic fracturing and topping pressure relief, the deformation of the dynamic pressure roadway is significantly reduced, the deformation of the roadway is reduced by 70%, the working resistance of the end support is reduced by 35%, and the impact distance of the working face is reduced from 70 m to within 30 m. The successful implementation of the research results in the field engineering practice provides a reference for the promotion and application of the hydraulic fracturing and topping pressure relief technology in the mining of the hard roof of the extra-thick coal seam.

     

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