孤岛工作面回采巷道围岩变形规律及水力压裂卸压控制技术研究

    Deformation laws and hydraulic fracturing pressure relief control technology for mining roadway surrounding rock in isolated island working face

    • 摘要: 孤岛工作面回采巷道经历相邻工作面和本工作面二次采动作用,变形破坏严重、支护难度大。尤其在坚硬顶板条件下,采动影响更为强烈。针对上述难题,以陕西渭南某矿1505孤岛工作面为工程背景,分析了孤岛工作面回采巷道应力集中效应、变形破坏特征及动压显现机理,揭示了水力压裂卸压机制,提出采用定向长孔水力压裂技术实现覆岩结构软化和应力传递路径阻断,建立了压裂层位优选准则(首选关键层或厚硬顶板),确定了定向长孔区域水力压裂具体实施方案,并开展了工业性试验。研究结果表明:回采巷道非压裂段底鼓变形严重、煤柱应力集中程度高,而压裂段底鼓量及煤柱应力均大幅降低,平均底鼓量为32 cm,煤柱峰值应力平均为11.5 MPa,相较于回采巷道非压裂段分别减少了60.5%、49.6%。回采巷道压裂段的微震事件次数、事件总能量、最大能量、平均能量、3次方及以上事件次数、现场动压显现次数等,均明显低于非压裂段,定向长孔水力压裂卸压技术有效解决了1505孤岛工作面回采巷道围岩大变形难题。该研究成果为孤岛工作面安全高效开采提供了保障。

       

      Abstract: The mining roadway of the isolated island working face experiences the secondary mining action of the adjacent working face and the working face, and the deformation and damage are serious and the support is difficult. Especially under the condition of hard roof, the influence of mining is more intense. In view of the above problems, taking the 1505 isolated island working face of a mine in Weinan, Shaanxi as the engineering background, the stress concentration effect, deformation and failure characteristics and dynamic pressure behavior mechanism of the mining roadway in the isolated island working face are analyzed, and the pressure relief mechanism of hydraulic fracturing is revealed. The directional long-hole hydraulic fracturing technology is proposed to soften the overburden structure and block the stress transfer path. The optimization criterion of fracturing horizon (preferred key layer or thick and hard roof) is established. The specific implementation scheme of hydraulic fracturing in directional long-hole area is determined, and industrial tests are carried out. The results show that the floor heave deformation of the non-fracturing section of the mining roadway is serious and the stress concentration of the coal pillar is high, while the floor heave and the stress of the coal pillar in the fracturing section are greatly reduced. The average floor heave is 32 cm, and the average peak stress of the coal pillar is 11.5 MPa, which is 60.5% and 49.6% lower than that of the non-fracturing section of the mining roadway. The number of microseismic events, the total energy of the event, the maximum energy, the average energy, the number of events of three or more times, and the number of on-site dynamic pressure appearances in the fractured section of the mining roadway are significantly lower than those in the non-fractured section. The directional long-hole hydraulic fracturing pressure relief technology effectively solves the large deformation problem of the surrounding rock of the mining roadway in the 1505 isolated island working face. The research results provide a guarantee for safe and efficient mining of isolated island working face.

       

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