An Experimental Study of Permeability of Sandstone under Different Confining Pressures

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.