Experimental Study Of Effects Of Saturation And Confining Pressure On Mechanics Properties

Effects of stress states and water content on rock mechanics properties, such as elastic modulus, peak strength, residual strength and permeability, which are key factors to analysis of engineering surrounding rock deformation, strength and stability. Study mechanics characteristics rules of sandstone under stress and saturation,(1) To obtain the effects of varied saturation and confining pressures on mechanical properties of Balikun sandstone, by TAW-2000 three axis test machine carry out triaxial tests. Then the modulus, peak strength and residual strength were obtained. The effects of varied saturation and confining pressures on mechanical properties of Balikun sandstone were analyzed.(2) The permeability of the samples including air drying, bounding water and saturating were tested with self-made equipment respectively, and the effects of axial pressure, confining pressure, pore pressure on permeability for coal were studied.(3) Base on study residual strength influences with confining pressure, the deformation process is simply comprised of three phases including linear-elastic, brittle and ideal plasticity. The Fish function method within FLAC software is adopted to realize the model in this paper. The study mainly obtained the following conclusions:1) With confining pressure increasing, the sandstone modulus increases, and the relationship between confining pressure and modulus follows linear form. With saturation increasing, the modulus decreases. The relationship between saturation and modulus follows linear or negative exponential form.2) With saturation increasing, the peak strength decreases. The uniaxial compression strength of saturated sandstone decreases 44.2%.The relationship between saturation and peak strength follows natural logarithm form.3) The effects of confining pressure on residual strength be described by degradation index and confining pressure of Balikun sandstone follows negative exponential form. With saturation increasing, the residual strength decreases.4) With confining pressure increasing,the effects of varied saturation on modulus, peak strength residual strength decrease. Less than 60% of saturation variation of saturation greatly influences the modulus and peak strength. Less than 80% of saturation, variation of saturation greatly influences residual strength.5) With increasing water saturation degree and confining pressure, the permeability of coal decreases.6) With increasing pore pressure, the permeability increases. The samples with air drying and bound water take on slippage effects, however saturating samples never do.