千米深井超长工作面采动应力旋转轨迹及其推进方向效应

Mining-induced stress rotation trace and its sensitivity to face advance direction in kilometer deep longwall panel with large face length

随着浅部煤炭资源开采殆尽,深部煤炭资源开发成为我国东部矿区面临的一大难题。深部矿井具有高应力、强扰动、节理裂隙发育等特点,导致煤壁高程度片帮、顶板大范围漏冒、巷道大变形破坏等围岩失稳现象频发,威胁安全生产。为提高深部开采围岩控制效果,以安徽省口孜东矿千米深井超长工作面为工程背景,采用现场实测、室内实验、数值计算和理论分析等手段研究超前采动应力旋转轨迹及其推进方向效应。结果表明:千米深井超长工作面支承压力呈现以峰值影响区为边界的空间分区特征,超前影响范围和煤壁破坏宽度分别达到150和8~12 m,采动应力发生大幅度旋转现象,高应力和应力旋转共同驱动工作面围岩破坏失稳。强采动影响下超前采动应力向采空区倾斜,走向影响范围达到200 m;两侧采动应力向巷道倾斜,倾向影响范围达到15 m。以平行于工作面推进方向的竖直平面为基准,采动应力旋转轨迹经历面外慢速偏离、面外快速靠近和面内协同旋转3个阶段。工作面推进方向对采动应力旋转轨迹具有强烈控制作用,当其与最小地应力方向平行或垂直时,采动应力旋转轨迹呈对称分布形态,2者处于其他空间位置关系时,采动应力旋转轨迹呈非对称分布形态。推进方向与最小地应力方向之间的夹角增大,采动应力面外慢速旋转阶段缩短,快速回旋阶段增长,但面内协同旋转阶段始终落在平行于工作面推进方向的竖直平面。基于围岩裂隙分布特征,实现围岩稳定性的应力方向敏感区识别,裂隙赋存稳定,应力方向敏感区为局部覆盖型;裂隙随机分布,应力方向敏感区转为全区覆盖型。根据应力方向敏感区形态提出了优势采动应力旋转轨迹确定原则,指导推进方向选择与优化,为深部开采围岩控制提供新思路。

Due to the quick depletion of coal resource in shallow-buried coal seams, the mining of deep-buried coal resource becomes critical in the eastern mining area of China.Deep mining is characterized by high ground stress, strong disturbance and well developed fractures, which result in a series of surrounding rock instabilities, such as drastic face sloughing, large-scale roof falling and large displacement experienced by the gate road.In order to improve ground control, a kilometer-deep longwall panel with large face length in Kouzidong mine in Huainan, China, is taken as a typical engineering background.Field measurement, lab experiment, numerical simulation and theoretical analysis are applied to the study of mining-induced stress rotation and its sensitivity to face advance direction.In the kilometer-deep longwall panel with large face length, the spatial distribution of front abutment stress presents regional pattern, divided by the boundary of peak point influenced zone.Influence scope and failure region reach 150 m and 8-12 m, respectively, in the coal seam.Large amplitude rotation occurs to mining-induced stress.High stress level and stress rotation result in a drastic failure of surrounding rock.After the extraction of coal seam, mining-induced stress dips to gob area at the position 200 m ahead of face line.The stress on two sides of the face dips to gate road.Influence scope of the side gate reaches 15 m in dip direction.By taking the vertical plane parallel with face advance direction as a reference, the stress rotation trace is divided into slow deviation stage, fast approaching stage out of the reference plane and cooperative rotation stage within the plane.The rotation trace is strongly influenced by face advance direction.When the face advance direction is parallel with or perpendicular to minimum ground stress, the mining-induced stress rotation trace presents a symmetrical distribution on the stereogram.Otherwise, the rotation trace presents an asymmetrical distribution.With increase in the angle made by face advance and minimum ground stress directions, the slow deviation stage shrinks while the fast approaching stage expands out of the reference plane.But the cooperative rotation stage remains in the reference plane constantly.Based on fracture distribution, the stress orientation sensitivity area of surrounding rock stability is identified on the stereogram.If the fracture orientation remains stable, the stress orientation sensitivity area covers local region of the stereogram.If the fracture presents a random distribution, the stress orientation sensitivity area realizes full coverage.Moreover, a determination method is proposed for favorite stress rotation trace, which helps to choose and optimize face advance direction, and provides new method for ground control in deep mining.