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復雜地質條件下連采連充式采煤防沖理論分析

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

  • 摘要: 為探究厚煤層、斷層構造下綜采與連采連充工藝的差異化力學響應機制,厘清擾動效應下連采連充式采煤防沖機理,以古城煤礦1301工作面為工程背景,運用理論分析、現場監測等手段研究擾動效應下兩工藝厚底煤穩定性和斷層滑移特性。分別建立了底煤力學模型和斷層力學模型并揭示了其致災機理,提出了底煤沖擊危險系數ηd、斷層失穩評價指標Ic,對比兩者在不同采煤工藝下的變化特征,分析得到連采連充工藝的防沖機理,最后通過微震實測結果進行驗證。研究表明:底煤失穩破壞的基本條件為水平應力大于其承受的臨界水平應力,ηd與底煤厚度z呈現負相關,連采連充工藝下臨界回采破壞長度為50 m,較綜采工藝提高69%;斷層失穩滑移的基本條件為斷層面巖層處于極限破壞狀態時的黏聚力大于實際黏聚力,Ic隨著斷層傾角θ增加而升高且其增長速率呈現非線性遞增趨勢,連采連充工藝下迎頭距斷層面臨界破壞距離為30 m,較綜采工藝降低100%。工作面開采期間未出現1×104 J以上的大能量事件,回采初期隨著工作面推進長度的增大,各支巷單次微震平均能量呈現漸進式上升且增幅較小,斷層近場活躍階段與遠場穩定階段相比,微震頻次增長270%但未呈現高能級事件階躍式增長,連采連充工藝顯著提高工作面防沖效果。

     

    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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