浅埋近距房柱式采空区上下残采围岩结构及失稳机理研究

With the depletion of coal resources in Shen fu mining area，the upper or lower level of residual coal in the room-and-pillar mining gob needs to be mined，while，the upward or downward mining often occurs large area caving and dynamic pressure disaster，which poses a great threat to the mine production safety. This project intends to carry out the mechanism of rock break induced disaster between upward or downward residual mining close to the room-and-pillar mining gob in shallow coal seam. According to the research of the structure and instable mechanism for surrounding rock in residual mining，the key stratum theory in ground control is applied to establish the structural model of the room-and-pillar mining gob and rock strata between coal seams to the untapped coal. In this study，we researched the interaction，destruction and evolution process of surrounding rock with coal pillar in residual mining to reveal the disaster mechanism of the transient instability as well as the large-area weight；analyzed the multiple-mining action mechanism，transfer law for mechanics and the damage law of rock strata between coal seams，indicating the influence factors to the structural instability of roof and floor key strata area；proposed a feasible judgment method for upward mining and prediction method for instability of the key stratum structure forming a dynamic pressure disaster for downward mining；and finally developed the technology in the upward or downward residual mining，which can lay a theoretical foundation for the safety of the Shen fu energy base.

随着神府矿区煤炭资源的枯竭，多煤层房柱式采空区上层或下层遗留煤需要回采，而在这种上行或下行残采中常发生大面垮落和动载矿压灾变，严重威胁矿井生产安全。本项目拟开展浅埋近距离房柱式采空区上行或下行残采层间岩层破坏致灾机理研究，应用岩层控制的关键层理论，通过对残采围岩结构及失稳机理研究，建立房柱式采空区与待采煤层间岩层控制结构模型。研究残采过程中围岩与煤柱的相互作用、破坏及演变过程，揭示瞬时失稳大面积来压灾变机理。分析层间岩层受多次采动的作用机理、力学传递规律、层间岩层变形破坏规律，揭示残采区顶、底岩层关键层结构失稳的影响因素。提出上行残采可行性的判定方法，下行残采关键层结构失稳形成动载矿压灾害的预测方法。开发房柱式采空区上下的残采技术，为神府能源基地安全残采奠定理论基础。

项目在国家自然科学基金面上项目的资助下，对浅埋近距房柱式采空区上下残采围岩结构及失稳机理进行了系统深入研究。分析了下行回采时房柱式采空区下回采过程中关键层断裂岩块失稳时下煤层工作面支架受力特征，演化了下煤层工作面开采过程中上覆岩层失稳特征，揭示了房柱式采空区下回采工作面发生动载矿压的主要原因为房采煤柱在超前支撑压力的作用下使得工作面上方房采煤柱承受载荷过大，进而诱发房采煤柱群发生“多米诺骨牌”式失稳，对下煤层工作面形成载荷冲击形成动载矿压。过集中煤柱下开采时，由于下煤层关键层对上覆集中煤柱集中载荷的有效承载面积不断减小，而集中煤柱上覆载荷在煤柱中形成的弹性应变能不断增大，随着工作面推进，聚集在关键层断裂岩块中的能量瞬间释放，对下煤层工作面产生冲击，最终产生动载矿压。建立了浅埋近距离房柱式采空区上行开采“箱梁桥”结构承载模型，揭示了“箱梁桥”结构的形成机理，确定了应力壳高度、腹板宽度等参数的计算公式，推导了其系统平衡时需满足的解析条件，并应用“箱梁桥”结构模型进行了工程验证。下煤层房柱式回采后，在层间岩层形成的应力平衡壳对覆岩起到了良好的支撑效果，且层间岩层上方岩体所受应力与原岩应力相比基本无变化，上煤层回采过程中，基岩运动引起的内部承载结构将围岩所受应力向采场周围转移对结构内岩层的稳定起到了保护作用，当工作面宽度为210m时能够发挥有效的承载作用。提出了房柱式采空上下回采围岩的控制，预防了动压事故的发生，确保了矿井安全生产。