错层位工作面弧形底板破坏机制研究

Split-level longwall layout effectively mitigates problems encountered in mining of deep thick/ultra-thick coal seams with large dip angle. Failure characteristics of arc-shaped floor of split-level longwall panel are significant for stability of gob-side entry driven under it. Therefore, Failure mechanism of arc-shaped floor of split-level longwall panel is studied in this program. Physical and mechanical parameters of coal and rock, and compressive features of gob rocks are determined through rock mechanical tests. Theoretical analysis, physical modelling and DIC technique are used to study the regulation and control mechanism of the structural model of “gob at the arc section-key block-solid surrounding rock”, probe the interaction of key block, immediate roof, gob and the floor coal and rock at the arc section. Physical modelling, numerical modelling DIC technique, and field observation are employed to investigate the rule of gob development and stress distribution within the gob; look into the stress, deformation and displacement, plastic zone development and failure modes of the arc-shaped floor, reveal the arc-shaped effect; By studying changes of stress distribution and failure of surrounding rock mass of the gob side entry at typical locations before and after the excavation of the entry, uncover the mechanism of range of yielded zone induced by the gob side entry excavation within rock mass of varied destress degree. Probe into the connection of the yield zone within the surrounding rock mass of the gob side entry and the arc-shaped floor, so as to determine the proper location of the gob side entry. The results of this study serve to provide theoretical support and scientific basis for determining location of gob side entry under the gob edge and surrounding rock mass control in mining of deep ultra-thick coal seams with large dip angle.

错层位工作面可有效缓解深部大倾角厚/特厚煤层开采难题，工作面弧形底板破坏规律直接影响其下方巷顶沿空掘巷的稳定性，为此，项目拟对错层位工作面弧形底板破坏机制进行研究。通过岩石力学试验确定煤岩物理力学参数和破碎矸石压缩应力-应变关系解析式。采用理论分析、相似模拟及DIC技术研究“圆弧段采空区-大结构-实体围岩”结构体对圆弧段采空区和围岩应力分布的调控机制，探究大结构、直接顶、采空区和弧形底板的耦合作用。采用相似模拟、DIC技术、数值模拟和现场实测研究采空区发育和应力分布规律；探究弧形底板受力、变形位移、塑性区发育及破坏模式特征，阐明弧形效应；研究典型位置巷顶沿空掘巷开挖前后围岩应力分布和破坏变化规律，明确不同卸压程度围岩体中巷道开挖对围岩破坏的影响；探究巷顶沿空掘巷围岩破坏区与弧形底板破坏区的沟通联络规律。研究可为深部大倾角厚/特厚煤层巷顶沿空掘巷合理布巷位置和围岩控制提供理论支持和科学依据。

错层位巷道布置能够有效缓解厚/特厚煤层区段临空巷道冲击威胁大、工作面设备稳定性差、区段回采率低等问题，应用于我国近百个矿井，且不断增加。但由于大倾角厚/特厚煤层错层位工作面下端存在弧形底板，其应力分布及破坏规律直接影响下方沿空回风巷的稳定性。因此本项目针对上述问题，综合理论分析、实验室试验、相似模拟试验、耦合数值模拟技术以及现场实测等多种研究手段，对大倾角错层位工作面圆弧段采空区及其围岩特征、弧形效应对圆弧段底板破坏规律的影响以及弧形底板与巷顶沿空掘巷围岩的交互影响作用展开深入研究。研究表明：(1)大倾角错层位工作面受煤层倾角影响，一方面导致工作面不同位置埋深不同，所受地应力亦不同，另一方面导致工作面回采后矸石滑移滚落，形成非对称堆积状态；(2)工作面围岩应力分布亦呈现非对称性，受埋深与矸石非对称堆积两者共同作用，埋深较深一侧受矸石作用较显著，部分应力转移至矸石上，降低了实体煤应力集中程度；埋深较浅一侧实体煤缺少矸石约束，在侧向支承应力下逐渐破碎，使该侧应力集中程度增强；底板应力呈现出“下大上小”的勺形分布状态；(3)工作面围岩破坏特征呈现非对称性，矸石非对称堆积导致埋深较深一侧顶板覆岩受到支撑，进而造成顶板两侧垮落角不一致，垮落形态呈现非对称性。底板则由于埋深较浅一侧缺少矸石形成自由空间，发生较大底鼓。底鼓和顶板关键块回转垮落形成“瓶颈”结构，反作用于矸石使其无法进一步向下滑移；(4)巷顶沿空掘巷最优布巷位置位于圆弧段正下方，一方面远离上一工作面侧向支承应力峰值位置，另一方面，与上一工作面采空区之间有足够厚的顶煤，能够进行锚杆索有效支护。本项目揭示了弧形效应对错层位工作面下端底板应力分布和破坏规律的影响机制，探明了巷顶沿空掘巷围岩破坏区与弧形底板破坏区的沟通联络规律，确定了合理的巷顶沿空掘巷位置，为其围岩稳定性控制奠定了基础。