Abstract:The deep porous sandstone has many unique features,such as high consolidation level,high compactability,lower porosity,oil/gas/water-included pore,pore fluid with pressure holding and so on. The existing studies have shown that the pore fluid pressure of porous media has some effects on the deformation and damage of rock,and the influential level is distinct to different rock masses. Based on the pore fluid pressure which is composed of regular hydrostatic pressure,actual formation pore pressure and atmospheric pressure,the experimental study has been carried out to analyze the effect of different loading paths owing to the change of internal pore pressure on the deformation and damage of rock samples. The results have shown that the existence of pore fluid pressure enhances the plasticity of rock sample. This means that the triaxial compressive strength,the axial strain,the radial strain;and the Poisson¢s ratio obtained by simulating the actual pore pressure and confining pressure are greater than those obtained under the other two conditions,while the elastic modulus is less than that obtained under the other two conditions. In order to declare the mechanical behavior of the deep porous sandstone,the existence and influence of pore fluid pressure should be considered. If possible,the actual overlying pressure of deep embedded rock and the actual formation pore pressure should be simulated to test the stress-strain characters of rock samples.