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区段大煤柱水力压裂切顶护巷技术研究

Research on hydraulic fracturing roof cutting and roadway protection technology with wide sublevel coal pillar

  • 摘要: 针对工作面回采过程中沿空留巷围岩应力高、蠕变变形大的难题,以赵庄矿井1309工作面为研究背景,用理论计算的方法开展了沿空留巷区域围岩结构力学分析,并提出了适用于该矿井的顶板双向水力压裂护巷工艺和效果检测方法。研究结果表明:13092巷道变形程度由煤体单轴抗压强度、煤层埋深、顶板岩梁强度共同决定,在以上因素的叠加作用下采空区侧向顶板挤压煤柱,煤柱塑性区范围扩大,侧向应力向煤柱深部转移,顶板断裂前煤柱内弹塑性过渡区域垂直应力达到最大值,受侧向应力峰值影响13092巷道发生强烈蠕变变形,巷道断面维护困难;通过在13091巷道布置双向水力压裂孔,提前弱化顶板,破坏其应力传递和能量积聚的条件,有效地进行了人为断裂线的预制,并改善断裂线在煤柱上方的倾向位置,减缓了煤柱受挤压程度;在巷道上方施工的水力压裂孔能够有效促使关键岩块B回转下沉,减小了1309工作面侧向悬顶的长度,垮落的关键岩块B能够较好地对高位岩层形成支承作用;在施工水力压裂孔后相应区域巷道变形量缩小40%,煤柱边界区域微震事件数和微震能量值均有大幅度减小,保证了沿空巷道在回采期间的围岩稳定性。该研究成果探索了顶板水力压裂护巷在晋煤矿区应用的可行性,并为类似矿井条件下开展压裂工艺提供了工程指导。

     

    Abstract: In view of the difficult problems of high stress and large creep deformation of the surrounding rock in the gob side entry during the mining process of the working face, the mechanical analysis of the surrounding rock structure along the remaining roadway was carried out using the theoretical calculation method with the No.1309 working face of Zhaozhuang mine as the research background and put forward the two-way hydraulic fracturing technology and effect detection method for the roof of the mine.The research results show that the deformation degree of the No.13092 roadway is determined by the uniaxial compressive strength of the coal body, the burial depth of coal seam and the strength of roof rock beam.Under the superimposition of the above factors, the lateral roof of the gob squeeze the coal pillar, resulting in the expansion of the plastic area within the coal pillar and the transfer of the side stress to the deep part of the coal pillar.Before the roof fracture, the vertical stress of the elastic-plastic interface area in the coal pillar reaches the maximum value, and the strong creep deformation of the roadway No.13092 is affected by the peak of the lateral stress,which makes the maintenance of the roadway section difficult; By arranging two-way hydraulic fracturing holes in No.13091 roadway, the integrity of roof are weakened in advance, and the conditions of stress transmission and energy accumulation are destroyed.It effectively prefabricates the artificial fracture line, improves the tendency of the fault line above the coal pillar, and slows down the degree of coal pillar extrusion; In addition, the hydraulic fracturing hole constructed above the roadway can effectively promote the rotation and subsidence of key rock block B, reducing the length of lateral overhang of the No.1309 working face, and the collapse of key rock block B can better form the supporting effect on the high-level rock stratum; After the construction of hydraulic fracturing hole, the tunnel deformation in the corresponding area is reduced by 40%, and the number of microseismic events and microseismic energy values in the boundary area of coal pillar are greatly reduced, ensuring the stability of surrounding rock during the mining of the roadway.The research results explored the feasibility of roof hydraulic fracturing roadway in Shanxi coal mine area, and provided engineering guidance for fracturing technology under similar mine conditions.

     

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