承压水上开采倾斜底板破坏特征与突水危险性分析

Investigation on failure characteristics and water inrush risk of inclined floor mining above confined aquifer

我国煤炭资源的开采受水害威胁严重。为了研究承压水上煤层开采倾斜底板破坏特征,分析底板突水危险性,基于FLAC3D软件模拟研究倾斜底板开采破坏形态和突水通道形成过程,利用双端封堵测漏装置进行底板深度破坏特征原位测试,并建立倾斜底板隔水关键层理论力学模型,探讨采空区岩石垮落、重新压实和非均匀分布承压水等协同作用对倾斜隔水关键层稳定性的影响。研究表明:(1)采后倾斜底板形成明显的三带破坏特征,塑性破坏区的分布非对称性特征明显,沿工作面走向底板近似勺形破坏形态,沿工作面倾向具有上小下大的倒马鞍形剪切破坏特征,且数值模拟的最大破坏深度为16.71 m,与现场实测倾斜底板法向的破坏深度15.49 m大致相当;(2)理论计算倾斜底板隔水关键层的预先破坏并不是发生在其边界中部,而是分别从经过最大挠度点的曲线与右侧边界、下端部边界的法向相交处起裂,并沿边界相互贯通,逐渐扩展至整个隔水层内部区域;(3)计算得到倾斜隔水关键层的易突水部位分别为A、B和C且突水危险性R(B)>R(A)>R(C),这与模拟得到的倾斜底板突水通道的形成部位和数量、形成顺序及突水危险程度均较吻合。该研究成果可为带压开采下倾斜底板突水的评价及安全治理提供一定的理论指导和参考。

The exploitation of coal resources in China is seriously threatened by water hazards.A coupled hydromechanical modeling of mining above a confined aquifer with FLAC3D was carried out to numerically investigate the fractured behavior of inclined floor and water outburst risk.Based on the double-end plugging leak detection device,the in-situ testing of mining-induced damage depth was implemented.Furthermore,the mechanical model of inclined water-resisting key strata was constructed to theoretically calculate the stability of inclined floor under the synergistic action of the roof caving rock mass,floor mining-disturbed rock mass and non-uniformly distributed confined aquifer.Results show that obvious three-zone failure characteristics in an asymmetric state are formed in the inclined floor after excavation.The mining failure zones along the strike and inclination are approximately spoon-shaped and upper small and lower large inverted saddle-shaped,respectively,and the maximum failure depth of numerical simulation with 16.71 m is approximately equivalent to the measured result of 15.49 m.The theoretical calculation shows that the pre-failures of inclined water-resisting key strata are not located in the middle of its boundary,but occur near the normal intersection points between the curves passing through the maximum deflection position and the right or lower boundary.The pre-failure areas may intersect with each other along the boundary,and gradually extend to the whole inner region of the aquifer.The water inrush location and risk of inclined water-resisting key strata calculated by the theoretical model are in good agreement with that of numerical simulation.The research results in this paper can provide some theoretical guidance and reference for the evaluation and safety control of floor water inrush under mining with pressure.