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针对在深厚白垩系和侏罗系孔隙砂岩含水层底部开采煤层是否引起上部含水层失水沉降问题,利用轴压恒定、变围压和孔隙水压的三轴压缩排水试验,研究不同粒径孔隙砂岩的轴向应变随孔隙水压降低的变化规律,以推导出一定厚度含水层的底部失水沉降计算公式。研究结果表明,(1)随着砂岩内的孔隙水压u降低,岩样会产生轴向压缩变形,并呈非线性增大,且砂岩粒径越大变形越大;(2)砂岩轴向排水变形ε_z与孔隙水压降△u以及初始孔隙水压u0有关,与围压σ3关系不大,且当u0不变、△u越大以及△u不变、u0越小时,所产生的轴向应变ε_z越大;(3)利用ε_z、△u、u0三者间的拟合函数所推导出的砂岩含水层失水沉降计算公式,在一定范围内能够进行多含水层失水沉降计算,为含水孔隙砂岩地层失水沉降计算提供一种新方法。
Aiming at the problem of water loss and sedimentation in the upper aquifer caused by the mining of coal seam at the bottom of the deep Cretaceous and Jurassic pore sandstone aquifer, the triaxial compression drainage experiment with constant axial pressure, variable confining pressure and pore water pressure was carried out to study the effect of different size pores The axial strain of sandstone changes with the decrease of pore water pressure to deduce the formula of bottom water loss and sedimentation at a certain thickness aquifer. The results show that: (1) With the decrease of pore water pressure u in sandstone, the compressive deformation of rock specimen will occur and increase nonlinearly, and the larger the sandstone particle size, the larger the deformation will be. (2) Drainage deformation ε_z is related to pore water pressure drop Δu and initial pore water pressure u0, and has little to do with confining pressure σ3. When u0 is constant, Δu is larger and Δu is constant, the smaller the u0 is, (3) The calculation formula of water loss and sedimentation of sandstone aquifer derived from the fitting function of ε_z, △ u and u0 can calculate the water loss and sedimentation of multi-aquifer within a certain range, A new method for calculation of water loss and sedimentation in aquiferous porous sandstone.