不同成岩作用程度砂岩物理力学性质三轴试验研究

Triaxial test on physical and mechanical properties of sandstone for different diagenesis degree

采用三轴岩石力学测试系统分析了不同侧压条件下砂岩岩石的孔渗性和力学特性及变形破坏机制 ,建立了砂岩岩石物理力学性质与侧压之间的相关关系。研究表明 ,砂岩的孔隙度和渗透率均随侧压的增大而减小 ,且服从对数函数变化规律。砂岩的刚度和强度均随侧压的增大而增大 ,具有明显的压硬性。岩石破坏后的残余强度随着侧压的增加下降梯度减小 ,而残余强度值相对提高。不同侧压下岩石的破坏机制表现出随着侧压的增大 ,成岩作用程度较弱的岩石应力 -应变曲线由应变软化性态向近似应变硬化性态过渡 ;而成岩作用程度相对较强的岩石在单轴压缩条件下表现为脆性张破坏 ,随着侧压的增加 ,便进入剪切破坏 ,岩石应力

The paper systematically analyzes the failure mechanism, the pore ratio, permeability and the mechanical property of sandstone under different confining pressure by using of triaxial test system. And the qualitative and quantitative relationship is established between the mechanical property of sandstone and confining pressure. It is shown that the pore ratio and permeability of sandstone are reduced with the increasing of confining pressures conforming to the rule of logarithmic function. The stiffness and strength of sandstone increase with increasing of its confining pressures presenting obvious compressive hardening. The descending gradient of residual strength after rock failure reduces when the confining pressure increases,but the residual strength was relatively improved. The failure mechanism was obviously different under different confining pressures. When confining pressure increases, the stress strain curve of sandstone with relatively weak diagensis transits from strain softening to approximate strain hardening. But the sandstone with relatively strong diagensis performs brittle tensile failure in uniaxial compressive test, and with increasing of confining pressure,the rock comes to shearing failure and its stress strain curve performs obviously brittle and strain softening properties.