孔隙水压作用下主井砂岩变形强度特性研究

Study on Deformation Strength Characteristics of Sandstone at Main Shaft under Pore Water Pressure

以湖北祥云磷矿矿区含水层的砂岩为研究对象,开展了水-力耦合试验,探讨围压和孔隙水压对岩石变形特性和强度特性的影响。研究结果表明:水-力耦合作用下砂岩试件的应力-应变曲线的发展趋势基本一致,其轴向应变-应力曲线均经历了原生裂隙压缩闭合阶段、线弹性阶段、裂纹稳定扩展阶段、裂纹不稳定发展阶段和峰后残余阶段等5个阶段;试件的峰值轴向应变与孔隙水压呈负相关,与围压呈正相关,而峰值环向应变和体积应变随着孔隙水压的增大而上下波动;砂岩的峰值偏应力、残余偏应力、起始扩容偏应力与孔隙水压呈线性正相关关系,而与围压呈现负相关。研究成果展现了地下水对祥云磷矿砂岩力学性能的影响规律和影响程度,可为该矿区砂岩的稳定性分析提供参考。

Taking the sandstone in the aquifer of Xiangyun phosphate mine in Hubei Province as the research object,the influence of confining pressure and pore water pressure on the deformation and strength characteristics of rock was discussed by water-force coupling test.The results are concluded as follows.Firstly,the development trend of stress-strain curves of sandstone specimens under the action of water-force coupling is basically the same.The axial strain-stress curves of sandstone specimens have experienced five stages:the primary fracture compression closure stage,the linear elastic stage,the stable crack propagation stage,the unstable crack development stage and the post-peak residual stage.Secondly,the peak axial strain of the specimen is negatively correlated with pore water pressure and positively correlated with confining pressure,while the peak circumferential strain and volume strain fluctuate with the increase of pore water pressure.Thirdly,the peak deviator stress,residual deviator stress and initial dilatancy deviator stress of sandstone are linearly positively correlated with pore water pressure,but negatively corelated with confining pressure.The research results show the influence law and degree of groundwater on the mechanical properties of sandstone in Xiangyun Phosphate Mine,which can provide reference for the stability analysis of sandstone in this mining area.