复杂地质条件下连采连充式采煤防冲理论分析

Theoretical analysis of rockburst prevention in continuous mining and continuous backfilling under complex geological conditions

  • 摘要: 为探究厚煤层、断层构造下综采与连采连充工艺的差异化力学响应机制,厘清扰动效应下连采连充式采煤防冲机理,本文以古城煤矿1301工作面为工程背景,运用理论推导研究扰动作用下两工艺底煤稳定性和断层滑移特性,分别建立了底煤、断层两类力学模型并揭示了各自致灾机理,提出了底煤冲击危险系数η、断层失稳评价指标I,对比其在两工艺下的变化特征并揭示了内在差异本质,最后通过微震实测结果进行验证. 研究表明:冲击危险系数η与底煤厚度呈负相关性,厚底煤条件下两工艺冲击危险性差异不显著,风险差值随底煤厚度减小及回采长度增加呈指数级飙升;失稳评价指标I随断层倾角增大而显著增强,两工艺风险差值在高倾角断层邻近区域急剧增加;回采初期各支巷单次微震平均能量仅小幅上涨,断层近场阶段微震频次较远场明显升高,但未呈现高能级事件阶跃式增长,微震事件以“高频低能”形式渐进释放,体现了复杂地质条件下连采连充工艺对动载传递与能量聚集的抑制作用.

     

    Abstract: This study investigates the differential mechanical response of fully mechanized coal mining and continuous mining versus continuous backfill technology under thick coal seams and fault structures, and to clarify mechanisms of preventing coal bursts under mining disturbances. The 1301 working face of Gucheng Coal Mine was used as a case study. This study uses theoretical derivation to research the stability of the bottom coal and the characteristics of fault slip under disturbance effects for both ming methods. We established mechanical models for bottom coal and faults, revealing their respective disaster mechanisms. This study proposes the impact danger coefficient of bottom coal η and the fault instability evaluation index I, comparing their variations under the two mining technologies and revealing the essence of internal differences. Finally, validation is carried out through microseismic measurement results. The study shows that the mechanism of impact ground pressure under dynamic loading disturbance, associated with the bottom coal instability, occurs when the horizontal stress of the bottom coal exceeds its critical structural stress, leading to impact destruction in the excavation roadway. The mechanism of impact ground pressure under mining disturbance with fault instability type is that the rock mass at the fault bends and sinks, superimposing self-static load to form a high static load, combined with the action of horizontal stress, accumulating substantial elastic potential energy, causing a local adjustment of the stress field in the fault, thereby unlocking and activating it. The impact danger coefficient η is negatively correlated with the thickness of the bottom coal. Under thick bottom coal conditions, the impact danger between the two mining technologies is insignificant. The risk difference increases exponentially with decreasing bottom coal thickness and increasing mining length, indicating that under conditions of thin bottom coal and long mining distances, the continuous mining with backfill significantly reduces the intensity and dynamic load disturbances during the key layer rupture cycle of the roof of the working face, thereby significantly reducing the impact risk. The instability evaluation index I significantly increases proportionally with the fault dip angle, and the risk difference between the two technologies tends to moderate in the far field of low-dip faults, while sharply increasing in the adjacent area of high-dip faults. This indicates that continuous mining with backfill technology can effectively weaken the superposition of the mining stress field and the fault structural stress field in the nearby area of high-dip faults, thus inhibiting the shear slip of coal-rock bodies at the fault and reducing elastic energy release. The risk difference shows a slight increase with decreasing distance to the fault, but linearly increases with the increase in dip angle, indicating that the dip angle θf of the fault has a more sensitive impact on the risk difference of the two mining technologies. In the initial stage of mining, the average energy of single microseismic events in each branch roadway increases marginally. The frequency of microseismic events in the near field of the fault significantly increases compared to the far field, and increases stably in high-energy events; instead, microseismic events are released progressively as 'high frequency and low energy,' reflecting the suppression effect of the continuous mining and continuous backfill technology on dynamic load transmission and energy accumulation under complex geological conditions.

     

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