浅埋特大采高综采工作面关键层“悬臂梁”结构运动对端面漏冒的影响

通过对神东矿区大柳塔煤矿52304综采工作面7.0 m支架开采时端面漏冒的现场实测、模拟实验与理论分析,从特大采高综采工作面覆岩关键层"悬臂梁"结构运动对直接顶作用的角度,阐述了端面漏冒的发生机理,并提出了相应的控制对策。结果表明:综采工作面的端面漏冒不仅与顶板岩性、构造和裂隙发育以及支护工况有关,还与关键层破断块体的回转运动密切相关。特大采高综采工作面覆岩第1层关键层易破断进入垮落带而形成"悬臂梁"结构,不同于低采高综采工作面关键层稳定铰接的"砌体梁"结构,由于其破断块体后方无水平的侧向约束力,它将无法形成自稳的承载结构;当支架初撑力不足以平衡该"悬臂梁"破断块体及其上覆垮落带岩层的载荷时,易造成该块体发生失稳错动而切割直接顶,从而导致贯穿式的端面漏冒的发生。这是造成52304特大采高综采工作面在顶板完整、煤壁片帮并不突出的条件下,仍发生严重端面漏冒的主要原因。由此提出了以提高支架初撑力来防止关键层"悬臂梁"破断块体发生失稳错动为思路的端面漏冒控制对策,并依此确定了52304综采工作面7.0 m支架的合理初撑力为12 405 kN,现有支架的初撑力仍显不足。

Influence of key strata cantilever structure motion on end-face fall in fully-mechanized face with super great mining height

By analyses of the field measurement，simulation experiments and theoretical analysis of the end-face fall while mining with 7.0 meters height supports in No.52304 working face of Daliuta Coal Mine，the mechanism of the end-face fall and its control measures in fully mechanized face with super great mining height were studied from the angle of the influence of key strata(KS)cantilever structure motion on the immediate roof.The results show that the problems of end-face fall in fully-mechanized face not only have relations with roof lithologic character，geological structure distribution and support condition，but also connected with the turning motion of the KS broken block.In the super great mining height workface，the first KS of overburden is easy to enter the caving zone and periodically breakage as “cantilever” structure，which is clearly different with the stable “voussoir beam” structure in the low mining height face.And the breaking block of the KS will not form a stable bearing structure all along due to the losing lateral binding effect of the broken block in the back goaf.When the setting load of the supports can not balance the loading of the “cantilever” block and its overburden strata in the caving zone，it is easy for the block to lose its stability and cut the immediate roof，and then the pulling-through end-face fall happens.This is the main source for the severe end-face fall in the situation that the coal wall caving is not prominent and the immediate roof is intact in No.52304 face.According to these above，the control countermeasure of the end-face fall was proposed in the thinking of improving the support setting load to avoid the instability of the KS “cantilever” breaking block.Then the reasonable setting load of the 7.0 meters height support in 52304 working face should be 12 405 kN，and the existing setting load during mining is still insufficient.