黄陇侏罗纪煤田松软富水顶板灾变机理研究

Roof disasters, featured by large-scale supports crushing and water inrush under condition of water-enriched stratum, frequently occurred in Yonglong and Binchang mining area, which has posed a serious threat to mining activity. The preliminary site investigation showed that unconsolidated roof as above soften (muddy) seriously when encountering water. The upper aquifers such as LuoHe formation have a significant effect on mechanical properties and macroscopic broken feature of overlying strata including mudstone and sandstone. With the intention of combining support crushing and water inrush as associated roof disaster, starting from site measurement of coal/rock mineral components and microstructure, the applicants will study physical properties weakening law of mudstone & sandstone under effect of hydration and strength damage characteristics of water-bearing sandstone with different moisture state from view of micro-scale. Overburden strata failure model will be established by means of rock mass hydraulics and ground pressure theory, mining-induced instability mechanism of unconsolidated and water-rich roof will also be studied. Based on associated effect of water level change in surface long drilling, movement of overlying strata, roof pressure and support crushing, combining dynamic theory of groundwater, roof disasters precursor recognition and warning method will be proposed.

黄陇侏罗纪煤田永陇、彬长等矿区频繁发生大面积压架突水等顶板事故，松软富水地层条件下的顶板灾害成为制约矿区安全生产的重大隐患。前期的现场调研发现，该类松软顶板遇水软（泥）化现象严重，洛河组等上覆含水层对泥岩、砂岩等覆岩的力学性能及宏观破断特征影响显著。本申请项目拟将采场压架与顶板突水视为伴生性顶板灾害进行研究，从实测矿区煤岩矿物组分、微观结构特征入手，从细观尺度研究水化作用下矿区泥岩、砂岩物理性质的弱化规律及不同含水状态下含水砂岩强度损伤特征。采用岩体水力学及采场矿压理论构建岩体水化损伤的采场覆岩破断模型，以覆岩水化损伤与支架承载响应为主线，研究松软富水顶板的采动失稳机制与灾变机理。基于地表长观孔水位变化、覆岩运移、顶板来压、支架压架的联动效应，结合地下水动力学原理，提出该类富水地层顶板灾害前兆识别及预警方法，为预防大面积采场压架等顶板灾害提供理论基础。

本项目实测分析了水化作用下松软地层岩石物理力学及水理性质的变化特征，阐释了松软富水顶板的强度损伤机制。研究了工作面不同停滞时期（检修、长时间停产）支架工作阻力的“蠕变”特性，采用西原简化模型分析了支架阻力与时间的关系。基于关键层理论揭示了试验矿区综放采场大、小周期来压交替发生、大周期来压显现异常强烈的机理。揭示了顶板离层水害的灾变机理，得到了顶板来压异常与富水层水位降速的联动效应。针对压架与突水这一伴生性顶板灾害，建立了出水压架的预警方法及防控体系。研究表明，①上覆松软岩层呈现严重的遇水软化特征。浸水后砂岩强度降低了23%；泥岩遇水软化后强度不可测。②检修或长时间停产期间顶板蠕变活动是支架阻力升高的主要原因，支架阻力曲线与岩石蠕变曲线具有良好的相似性，符合简化西原模型蠕变方程，研究结果解释了工作面推进速度与支架工作阻力成反比的关系。③亚关键层破断的时空差异导致采场“一大多小”来压交替出现。由于破断步距大、控制岩层组厚度大，复合亚关键层破断导致采场大周期来压显现异常强烈；近场亚关键层1破断步距小，其破断引发小周期来压。④试验矿区水害类型为洛河组离层水害。复合亚关键层与上部主关键层破断特征的显著差异是离层蓄水的必要条件，洛河组含水层底部形成离层储水空间；综放开采导水裂隙带高度大，顶界面逼近洛河组含水层，致使安定组泥岩隔水层厚度不足。在离层水压和含水层的补给作用下，离层积水越层下泄引发采场出水。⑤出水压架事件属于大周期来压引发的伴生性灾害，大周期来压、离层积水下泄和含水层水位波动存在联动效应。⑥构建了以“大周期来压、支架阻力高位预警、水位降速、宏观矿压显现异常”为关键指标的预警机制；建立了以装备选型优化、危险区域划分、出水压架预警机制及工作面日常管控为主体的防控体系。研究成果已成功指导了矿区多个工作面的顶板水害防控，取得了良好的推广应用效果。