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深部多层位水压预裂岩层运移特征与矿压调控机理

Strata movement characteristics and ground pressure control mechanism under deep multi-level hydraulic pre-fracturing

  • 摘要: 深部矿井回采过程中远近场岩层对矿压的耦合作用复杂,单一层位的治理效果有限,多层位岩层的治理对高强度开采和高产能矿井十分必要。研究基于红庆河煤矿地面水力压裂防冲减震工程实践,开展了多层位水力压裂后岩层载荷传递、覆岩运动、应力与能量释放的理论、试验数值与工程实践分析。结果表明:增加压裂程度、选择毗邻岩层岩性较软的岩层作为压裂层,利于载荷的传递,压裂程度与毗邻岩层岩性刚度非线性耦合且与传递载荷呈指数相关,而上覆岩层载荷与传递载荷呈线性正相关。压裂在煤层回采前期可对低位岩层弱化使岩层破断块度减小,回采后期可通过形成复杂缝网致使高位岩层破断,有效避免了覆岩的大面积垮落与高位砌体梁的形成。压裂后覆岩破断沿压裂形成的裂缝发展,致使总垮落次数增加50%以上,裂隙数量增幅达2.6倍。压裂岩层致使低位与高位岩层连续破断,有效避免了工作面的应力与能量集中,工作面最大应力降幅达20%以上,最大应变能降低60%以上。覆岩低位压裂直接造成工作面应力集中程度降低,多层位压裂及采动影响,使得裂纹缝网沟通更加丰富,促进了避免大范围垮落的覆岩协调运动,降低了矿震风险。此外,岩层的充分运动会使得压裂的效果逐渐减小,需要采取进一步治理措施。研究结果可为地面多层位的水压致裂防冲减震工程实践提供科学借鉴。

     

    Abstract: During deep underground mining, the coupled effects of near-and far-field strata on mining-induced ground pressure are complex, while control measures targeting a single stratum are often insufficient. Therefore, coordinated treatment of multiple strata is essential for safe high-intensity extraction and high-production mining. Based on surface hydraulic fracturing for rockburst prevention and seismic mitigation at the Hongqinghe Coal Mine, this study investigates load transfer, overburden movement, stress redistribution, and energy release after multi-level hydraulic fracturing through theoretical analysis, physical experiments, numerical simulations, and field applications. The results show that increasing the degree of fracturing and selecting target strata adjacent to relatively weak rock layers facilitate load transfer. The fracturing degree and adjacent-strata stiffness exhibit a nonlinear coupling relationship and are exponentially correlated with the transferred load, whereas the overburden load shows a positive linear correlation with it. During the early mining stage, hydraulic fracturing weakens lower-level strata and reduces the block size generated by strata breakage. During the later stage, the development of a complex fracture network promotes the breakage of higher-level strata, thereby suppressing large-scale overburden collapse and the formation of high-level masonry-beam structures. After fracturing, overburden fractures preferentially propagate along induced fracture paths, increasing the total number of caving events by more than 50% and the fracture number by 2.6 times. Successive breakage of lower- and higher-level strata effectively mitigates stress and energy concentrations at the working face, with the maximum stress and strain energy decreasing by more than 20% and 60%, respectively. Moreover, multi-level fracturing combined with mining disturbance enhances fracture-network connectivity, promotes coordinated overburden movement, and reduces the likelihood of large-scale strata collapse and mining-induced seismic events. However, the effectiveness of hydraulic fracturing gradually diminishes as overburden movement becomes fully developed, indicating the need for additional control measures during later mining stages. These findings provide a scientific basis and engineering reference for surface multi-level hydraulic fracturing in rockburst prevention and seismic mitigation in deep coal mines.

     

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