深部厚硬复合砂岩顶板区域压裂卸压防冲技术及应用
Regional fracturing technology for pressure relief and rock burst prevention in thick and hard composite sandstone roof and its application
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摘要: 门克庆煤矿3-1煤层具有强冲击倾向性, 煤层埋深大, 工作面开采强度高, 煤层上覆存在厚度较大的复合砂岩顶板, 工作面开采期间易诱发冲击地压。针对中高位厚硬顶板常规卸压措施处理高度和范围有限, 难以达到理想卸压效果, 本文在分析冲击主控致灾因素基础上, 采用顶板岩性分析、关键层理论计算、微震监测及岩层破断能量传递计算, 综合确定了冲击致灾关键岩层, 揭示了井下长孔区域压裂卸压防冲机理, 开展了井下长孔区域压裂卸压防冲工程实践, 并进行了卸压防冲效果分析。结果表明: 工作面大埋深提供了充足的基础静载荷, 3-1煤层及顶底板具有发生冲击地压的能力, 完整性强、连续性好的复合砂岩顶板破断动载是诱发冲击地压的主要力源。井下长孔区域压裂对厚硬复合砂岩顶板进行超前预裂, 压裂后岩层裂隙扩展明显, 顶板预裂效果良好。工作面开采期间压裂区域大能量微震事件频次、能量、集中程度显著降低, 工作面来压强度降低, 来压步距减小。工程实践表明井下长孔区域压裂技术具有有效性, 显著降低了冲击地压发生风险, 保障了工作面安全开采, 研究成果可为类似条件矿井冲击地压防治提供借鉴。Abstract: The 3-1 coal seam in Menkeqing Coal Mine has strong propensity for rock burst. Given the large coal seam burial depth, high mining intensity, and the presence of a thick composite sandstone roof overlying the coal seam, rock burst disasters are likely to be induced during mining of the working face. Conventional pressure relief measures targeting medium- to high-position thick and hard roofs are limited in both treatment height and range, often failing to achieve the desired pressure relief effect. In response to this problem, dominant disaster-inducing factors for rock burst were analyzed first. On this basis, roof lithology analysis, key strata theory calculation, microseismic monitoring, and strata fracture energy transfer calculation were performed to identify the dominant strata responsible for rock burst and reveal the mechanism of regional fracturing with long boreholes for pressure relief and rock burst prevention. Furthermore, the engineering practice of regional fracturing with long boreholes was conducted, and the corresponding effect analysis was carried out. The results show that the large burial depth of the working face provides sufficient foundation static load. The 3-1 coal seam and its roof and floor have the potential to generate rock burst, and the dynamic load arising from the breakage of the highly integral and continuous composite sandstone roof is the main source triggering rock burst. Regional fracturing with long boreholes was used for advanced prefracturing of the thick and hard composite sandstone roof. After the construction was completed, cracks propagated notably in fractured strata, and a remarkable prefracturing effect was achieved. During mining of the working face, the frequency, energy, and concentration of high-energy microseismic events in the fracturing area were significantly reduced, the intensity and distance of periodic weighting of the working face decreased. The engineering practice demonstrates the effectiveness of regional fracturing with long boreholes in significantly reducing the risk of rock burst disasters and ensuring safe mining of the working face. The research results can provide reference for the prevention and control of rock burst in coal mines with similar conditions.
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