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不同围压下砂岩渗透性规律试验研究

An Experimental Study of Permeability of Sandstone under Different Confining Pressures

  • 摘要: 利用岩石全自动三轴力学伺服试验系统,研究不同围压下砂岩在变形至破裂过程中的渗透率变化及其与应变的关系。结果表明:随着围压的增大,偏应力与渗透率达到峰值时对应的应变越大,岩样的变形由脆性逐渐向延性转化;相较于轴向应变,环向应变的变化规律更能反映渗透率的发展规律;砂岩渗透率的变化规律与应力-应变关系密切,弹性阶段,随偏应力增加渗透率逐渐减小,弹塑性阶段,随岩样裂隙的发育渗透率先缓慢增加后急剧增大,残余强度阶段,渗透率陡升至峰值随后下降;岩样的最小渗透率出现在体积应变拐点前;围压的增大阻碍岩样原生与新生裂隙的扩展,影响岩样的最小渗透率。

     

    Abstract: The permeability variation of sandstone during deformation to fracture under different confining pressures and its relation with strain were studied by using rock automatic triaxial mechanical servo test system. The results show that with the increase of confining pressure, the deformation of rock sample changes from brittleness to ductility with the increase of strain corresponding to deviator stress and permeability peak. Compared with axial strain, the change law of annular strain can reflect the development law of permeability. The change rule of sandstone permeability is colosely raleted to stress-strain relation, in the elastic stage, with the increase of deviator stress, the permeability decreases gradually, in the elastic-plastic stage, with the development of sample fracture, the penetration first increases and then increases sharply, in the residual strength stage, the permeability rises sharply to the peak value and then decreases. The minimum permeability appears before the inflection point of the volumetric strain. The increase of confining pressure hinders the expansion of primary and new fractures, thus affecting the minimum permeability of rock sample.

     

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