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赵固矿区厚煤层开采实践与采场围岩控制技术进展

Mining practice and stope ground control technology for deep-buried thick coal seams with thin bedrock in the Zhaogu Mining Area

  • 摘要: 赵固矿区位于焦作煤田东部,太行山南麓,主采煤层埋深大于700 m,平均厚度6 m,硬度系数达到2~3。受造山运动影响,煤层上覆基岩厚度仅为0~120 m,基岩之上为厚度大于600 m的巨厚冲积层,且地层断裂构造发育,厚煤层开采面临顶板控制难题。为科学指导深埋薄基岩厚煤层安全开采,以赵固二矿开采实践为背景,梳理深埋弱胶结覆岩条件下厚煤层开采与围岩控制技术进展。赵固二矿已经形成了由东向西(由浅及深)的开采格局,分层开采阶段,煤柱留设宽度大、形状不规则,巷道掘进率高;上分层开采超前采动应力集中程度高,但开采厚度小,围岩破坏程度低;下分层开采超前采动应力集中程度低,但上分层采动破碎顶板下沉量大,存在顶板漏冒问题;为解决矿井采掘接替紧张问题,开发了深埋薄基岩厚煤层大采高开采技术,确定了三阶段全覆岩运动特征,包括基岩渐进破断阶段、厚冲积层垮落拱发育阶段和地表裂隙发育阶段;建立了覆岩垮落拱与拱脚高耸岩梁复合承载结构模型,揭示了薄基岩全厚破断和顶板动载冲击效应产生机理,开发了工作面“高强度−高刚度支护、坚硬顶板爆破预裂、煤壁超前注浆”多元协同围岩控制技术。为解决厚煤层开采与煤壁加固之间的矛盾,开展了深埋薄基岩厚煤层放顶煤开采创新实践,顶板压力和煤壁破坏程度显著降低,但坚硬顶煤存在悬顶与大块垮落问题,实测顶煤回收率仅为65%;为提高顶煤冒放性,研制了ZFG17600/29.5/50D型放顶煤支架,通过提升割煤高度(采放比2∶1)、增大控顶区宽度、优化放煤机构,促进顶煤破碎进程。

     

    Abstract: Zhaogu No. 2 Coal Mine is in the eastern area of Jiaozuo Coalfield, at the southern foot of the Taihang Mountain. The primary mineable coal seam of the mine is buried at a depth of more than 700 m, with an average thickness of 6 m and a hardness coefficient of 2-3. Influenced by orogenic movement, the thickness of the overlying bedrock is only 0-120 m, above which lies an alluvial formation with a thickness of more than 600 m, coupled with well-developed fault structures in the strata, all of which bring severe challenges to roof control in thick coal seam mining. To provide scientific guidance for the safe mining of deep-buried thick coal seams with thin bedrock, the mining practice of Zhaogu No. 2 Coal Mine is taken as the engineering background, and the research progress of thick coal seam mining and surrounding rock control technology under deep-buried weakly cemented overlying strata is systematically summarized. Zhaogu No. 2 Coal Mine has formed a mining layout progressing from east to west (from shallow to deep). In the slicing mining stage, the upper slice mining had a high concentration degree of advanced mining-induced stress, but the mining thickness was small, so the failure degree of surrounding rock was low. In contrast, the lower slice mining had a low concentration degree of advanced mining-induced stress, but the fractured roof affected by upper slice mining had a large subsidence, resulting in roof leakage and caving problems. In addition, slicing mining required a large width of coal pillars, leading to a high roadway drivage rate. To solve the problem of tight mining and drivage succession in the mine, the large mining height mining technology for deep-buried thick coal seams with thin bedrock was developed, and the three-stage movement characteristics of the full overburden were identified, including the progressive fracture stage of bedrock, the development stage of caving arch in thick alluvial formation, and the development stage of surface fissures. A composite load-bearing structure model of overburden caving arch and towering roof beam at the arch foot was established, the formation mechanism of full-thickness fracture of thin bedrock and dynamic load impact effect of roof was revealed, and a multi-element synergistic surrounding rock control technology for the working face was developed, integrating "high-strength and high-stiffness support, pre-split blasting of hard roof, and advanced grouting of coal wall". To resolve the contradiction between thick coal seam mining and coal wall reinforcement, innovative practice of top-coal caving mining for deep-buried thick coal seams with thin bedrock was carried out. The roof pressure and the failure degree of coal wall were significantly reduced, but problems such as hanging of hard top-coal and caving of large coal blocks still existed, with the measured top-coal recovery rate of only 65%. To improve the cavability of top-coal, the ZFG17600/29.5/50D top-coal caving hydraulic support was developed. By increasing the cutting height (with a mining-to-caving ratio of 2∶1), widening the roof control area, and optimizing the caving mechanism, the fragmentation process of top-coal was effectively promoted.

     

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