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,以古城煤矿1301工作面为工程背景,运用理论分析、现场监测等手段研究扰动效应下两工艺厚底煤稳定性和断层滑移特性。分别建立了底煤力学模型和断层力学模型并揭示了其致灾机理,提出了底煤冲击危险系数ηd、断层失稳评价指标Ic,对比两者在不同采煤工艺下的变化特征,分析得到连采连充工艺的防冲机理,最后通过微震实测结果进行验证。研究表明:底煤失稳破坏的基本条件为水平应力大于其承受的临界水平应力,ηd与底煤厚度z呈现负相关,连采连充工艺下临界回采破坏长度为50 m,较综采工艺提高69%;断层失稳滑移的基本条件为断层面岩层处于极限破坏状态时的黏聚力大于实际黏聚力,Ic随着断层倾角θ增加而升高且其增长速率呈现非线性递增趋势,连采连充工艺下迎头距断层面临界破坏距离为30 m,较综采工艺降低100%。工作面开采期间未出现1×104 J以上的大能量事件,回采初期随着工作面推进长度的增大,各支巷单次微震平均能量呈现渐进式上升且增幅较小,断层近场活跃阶段与远场稳定阶段相比,微震频次增长270%但未呈现高能级事件阶跃式增长,连采连充工艺显著提高工作面防冲效果。

     

    Abstract: In order to explore the differential mechanical response mechanism of fully mechanized coal mining and continuous mining and continuous backfilling processes under thick coal seams and fault structures, and to clarify the anti-scouring mechanism of continuous mining and continuous backfilling coal mining under the disturbance effect, the stability and fault slip characteristics of the thick-bottomed coal of the two processes under the disturbance effect were studied by means of theoretical analysis and on-site monitoring. The bottom coal mechanical model and fault mechanics model were established and their disaster mechanism was revealed, the bottom coal impact risk coefficient ηd and the fault instability evaluation index Ic were proposed, and the anti-scouring mechanism of the continuous mining and backfilling process was analyzed by comparing the change characteristics of the two under different coal mining processes, and finally verified by the microseismic measurement results. The results show that the basic conditions for the instability failure of bottom coal are that the horizontal stress is greater than the critical horizontal stress it bears, ηd is negatively correlated with the thickness of the bottom coal z, and the critical mining failure length is 50 m under the continuous mining and continuous backfilling process, which is 69% higher than that of the fully mechanized coal mining process. The basic condition of fault instability and slip is that the cohesion of the rock layer on the fault plane is greater than the actual cohesion when the rock layer is in the ultimate failure state, the Ic increases with the increase of the fault dip angle θ and its growth rate shows a nonlinear increasing trend, and the head-on failure distance from the boundary of the fault under the continuous mining and continuous backfilling process is 30 m, which is 100% lower than that of the fully mechanized coal mining process. During the mining of the working face, there was no large-energy event of more than 1×104 J, and the average energy of a single microseismic in each branch roadway showed a gradual increase and a small increase in the initial stage of mining, and the microseismic frequency increased by 270% compared with the far-field stable stage in the near-field active stage of the fault but did not show a step-like increase in high-energy level events. The continuous mining and continuous backfilling; process significantly improves the anti-scouring effect of the working face.

     

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