弱胶结覆岩下顶分层综放面强矿压机理及拱形工作面控制技术

Strong ground pressure mechanism and arched face control technology during slicing longwall top coal caving in ultra thick coal seam

  • 摘要: 弱胶结覆岩可导致工作面强矿压,甚至压架事故,严重威胁安全和影响生产。以准东二矿55 m巨厚煤层顶分层综放开采为研究背景,采用现场实测、理论分析、室内试验以及数值模拟等方法对弱胶结覆岩下特厚综放面矿压规律及控制技术进行研究。结果表明:准东二矿首采区覆岩赋存表现为基岩厚度大,整体胶结程度弱,软或极软岩层占比87%;顶分层首采1101综放面推进期间,基本顶砌体梁在高位岩块回转的动荷载下二次破断失稳,原砌体梁承载结构被破坏,支架由给定载荷转为与直接顶共同承担体系变形,导致强矿压;据此,建立了支架上方拱结构岩块段的稳定方程并揭示了不同位置的受力规律,进而提出工作面“拱形”布置及回采工艺,以便顶板形成倾向承载结构从而控制强矿压,并揭示其将部分覆岩载荷转化为拱块段之间的相互作用力的矿压控制机理;数值模拟结果进一步得出新工艺下工作面顶板塑性区发育程度降低,顶板下沉量减小33.1%,支架上方拱结构将部分上覆载荷转化为内力,结构的应力水平上升,垂直应力高于原来的18%,最终降低了支架整体承受的载荷。现场实践表明,该技术对强矿压控制发挥着重要作用,支架受力最高峰值下降12%,较强来压范围由20~120号支架缩小至40~100号支架,同时,拱脚处最大挤压力有利于工作面两端三角煤及顶板及时折断垮落。

     

    Abstract: Weakly cemented overlying strata could induce intense ground pressure in working faces, potentially leading to support crushing, which severely threaten safety and impede production. This study focused on the top coal caving mining of a 55 m ultra-thick coal seam in the top slice of Zhundong No.2 Coal Mine. Field measurements, theoretical analysis, laboratory experiments, and numerical simulations were employed to investigate the ground pressure behavior and control strategies under weakly cemented overlying strata. The results indicate that the overlying strata in the first mining area of Zhundong No.2 Coal Mine are characterized by thick bedrock layers with weak overall cementation, where soft or extremely soft rock strata account for 87%. During the advancement of the 1101 top coal caving face, the main roof masonry beam experienced secondary fracture instability under dynamic loads from high-position rock block rotation, disrupting the original masonry beam bearing structure. Consequently, the supports transitioned from bearing predetermined loads to jointly resisting deformation with the immediate roof, triggering intense ground pressure. Based on this, a stability equation for the arched structural rock blocks above the supports was established, revealing stress distribution patterns at different positions. A novel “arch-shaped” layout of the working face and corresponding mining technology were proposed to form a dip bearing structure in the roof, thereby controlling strong ground pressure. This structure converted partial overburden loads into internal forces between arched blocks. Numerical simulations further demonstrated that the new technology reduced the development of plastic zones in the roof, decreased roof subsidence by 33.1%, and elevated vertical stress by 18%, as the arched structure transferred part of the overburden load into internal stresses, effectively lowering the overall load on supports. Field implementation confirmed the efficacy of this technology, the peak load on supports decreased by 12%, the range of intense pressure manifestation narrowed from supports No. 20−No. 120 to No. 40−No. 100, and maximum compressive stress at the arch foot facilitated timely fracturing and caving of triangular coal and roof at both ends of the face.

     

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