冻融后不同含水状态砂岩的剪切破坏特性

Shear failure properties of sandstone with different moisture contents after cyclic freezing-thawing

针对冻融循环作用后不同含水状态砂岩展开剪切性能试验研究,探讨试样的剪切破坏机制,分析内摩擦角、黏聚力随试样破坏面分形维数的变化规律。结果表明:随冻融循环次数的增加,砂岩剪切应力–位移曲线特征发生明显改变,同时,峰值剪应力有不同程度的降低,而剪切位移显著增大。内摩擦角、黏聚力较冻融前有不同程度的劣化,并随饱水率的增大而加剧。相同含水状态下,分形维数随冻融循环次数的变化呈显著的幂函数递增关系,黏聚力损伤因子随分形维数的变化呈指数函数递增。干燥状态下,内摩擦角损伤因子随分形维数的变化呈指数函数递增,而含水状态下呈线性递增。

The experiment to investigate the shearing performance of sandstone at different moisture states after cyclic freezing-thawing was carried out. The shear failure mechanism of sandstone specimen was discussed. The variations of internal friction angle and cohesion with the fractal dimension of failure surface of sandstone specimen were analyzed. The results show that with the increasing of freezing-thawing cycles,the characteristics of shear stress-displacement curves of sandstone change obviously,meanwhile,the peak shear stresses decrease in varying degrees,but the shear displacements increase significantly. After the cyclic freezing-thawing,the internal friction angle and cohesion of sandstone are deteriorated differently,and the degree of deterioration increases gradually with the increasing of the degree of saturation. When the moisture content is the same,the relationship between the fractal dimension of failure surface and the number of freezing-thawing cycles is a power function,and the relationship between the cohesion damage factor and the fractal dimension is an exponential function. The relationship between damage factor of internal friction angle and fractal dimension is an exponential function in the dry state,but is linear function in the moisture state.