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重复采动下亚关键层联动破断致震机制与采空区减震效应

Seismic mechanism induced by coordinated fracturing of sub-key strata under repeated mining and seismic mitigation effect of goafs

  • 摘要: 矿震作为采矿活动诱发的非天然地震,对煤矿的安全生产危害性极大,通常伴随弹性能的迅速释放,造成地下工程结构或地面建筑物的损坏。矿震的发生机制多种多样,针对黑龙江某矿矿震事件地表震感明显而工作面无震感的现象,采用理论分析、数值模拟与现场监测相结合的研究方法,分析了重复采动影响下上覆采空区亚关键层联动破断诱发矿震机理,根据不同区块的力学特性构建了弹簧−麦克斯韦元件的三分区位移力学模型,通过多种数值模拟方案对比分析不同覆岩条件下矿震动载波的传播及衰减规律。结果表明:下伏工作面大面积回采为上覆采空区提供了新的运移空间,使得脆弱的采空区平衡状态被打破,原采空区顶板未破断亚关键层断裂,释放积聚的大量弹性能造成矿震事件发生;矿震动载波穿越采空区后引发的质点峰值速度和加速度与同等条件下无上覆采空区情况相比分别衰减约84%和90%,至下伏煤层工作面处引发的质点峰值速度和加速度近乎归零。采空区在矿震动载波传播中起到明显的缓冲与耗能作用。基于上述认识,提出了以“爆破断顶+煤层钻孔卸压”为核心的卸压隔减震区域性防护措施。后续微震监测结果表明:该措施显著降低了高能量矿震事件的发生次数,有效提升了深部开采动力灾害防控能力。

     

    Abstract: Mining-induced seismicity, a type of non-natural seismic event triggered by mining activities, poses a major threat to the safety of coal mine production due to the rapid release of elastic energy and the potential damage to underground structures and surface buildings. Focusing on a seismic event in a coal mine in Heilongjiang Province, where strong ground vibration was observed at the surface but not perceived at the working face, a combined approach of theoretical analysis, numerical simulation, and field monitoring is employed. The study analyzes the mechanism of mining-induced seismicity associated with cooperative fracture of sub-key strata in overlying goaf areas under repeated mining. A three-zone displacement mechanical model based on spring–Maxwell elements is established to represent the distinct mechanical behaviors of different overburden blocks. Multiple numerical simulation schemes are designed to comparatively investigate the propagation and attenuation characteristics of seismic wave carriers under different overburden conditions. The results show that large-scale retreat mining in the underlying working face creates new migration space for the overlying goaf, disrupting the original stress balance. Fracture of the sub-key strata in the uncollapsed roof of the original goaf then releases a large amount of accumulated elastic energy, triggering mining-induced seismicity. After seismic waves propagate through the goaf, the peak particle velocity and acceleration are attenuated by approximately 84% and 90%, respectively, compared with conditions without an overlying goaf, and both parameters approach zero at the underlying coal seam working face. These results indicate that the goaf acts as an effective buffer and energy-dissipating medium for seismic wave propagation. On this basis, a regional protective technology centered on “blasting-induced roof fracturing combined with coal seam borehole pressure relief ” is proposed to pre-fracture the hard roof and relieve stress concentration in advance. Subsequent microseismic monitoring shows that the frequency of high-energy mining-induced seismic events decreases compared with the period before implementation, and the capability for dynamic disaster prevention and control in deep mining is enhanced.

     

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