针对大同矿区石炭系3-5号特厚煤层坚硬顶板综放开采时工作面易出现压架、临空巷道超前区域变形、破坏严重等强矿压显现问题,采用理论分析、物理模拟及现场实测等方法,建立了特厚煤层开采大空间采场岩层结构演化模型。结果表明:特厚煤层综放开采覆岩远、近场关键层运动都可能会对采场矿压产生影响,近场关键层为"竖O-X"破断的"悬臂梁+砌体梁"结构,远场关键层为"横O-X"破断的"砌体梁"结构模型。近场关键层结构主要影响工作面支架压力及其稳定性,近场关键层结构中,以"悬臂梁"结构破断运动的关键层层数越多,对支架安全越不利;远场关键层结构则主要对工作面临空侧巷道变形产生影响,其破断块体的回转运动对临空侧巷道围岩产生径向挤压作用,是造成巷道超前底臌的主要原因。据此开发了基于地面钻孔压裂与井下顶板预裂相结合的远、近场协同弱化的坚硬顶板预控技术,将有效降低岩层破断的能量释放和关键层结构失稳的压力传递,减轻特厚煤层综放开采采场矿压的显现强度。

In order to overcome the problems,such as the emerging support crushing disaster,advance supported de- formation and severe destruction of roadway on gob side and some other strong strata behavior problems when the fully- mechanized sublevel caving mining method is applied for mining the Carboniferous No. 3-5 extremely thick coal seam with hard roof in Datong mining area,this study used the methods such as theoretical analysis,physical simulation and field measurement to develop an evolving model for strata structure of mining extremely thick coal seam in large space stope. The result shows that both the key stratum motion at near and far fields in fully-mechanized sublevel caving min- ing at extremely thick coal seam may exert an influence on strata behavior. The structure model for near field key stra- tum is “cantilever beam + voussoir beam” broken in the shape of “vertical O-X” while that of far field key stratum is “voussoir beam” broken in the shape of “horizontal O-X”. The key stratum structure at near field mainly affects sup- port pressure and its stability on the working face. In the key stratum structure at near field,the more key stratums that move in “cantilever beam”,the more harm will be done to the safety of the support. The key stratum structure at far field mainly exerts an influence on the deformation of roadway on gob side of the working face. The rotary motion of the broken block will produce radial extrusion on wall rock in roadway on gob side,which is the main reason for the floor heave of roadway. Accordingly,the hard roof control technology,based on the near and far field synergetic ally weaken which combines ground drilling fracturing with underground pre-splitting roof,is developed. This technology will effec- tively reduce the pressure transmission from the energy release of rock breaking to the structural instability of key stra- tum and mitigate the mine pressure intensity of fully-mechanized sublevel caving mining stope for mining the extremely thick coal seam.