循环加卸载下砂岩能量演化特性分析与损伤表征

为探究饱和及干燥砂岩在加卸载过程中的能量演化与耗散特征,以西部砂岩为研究对象,开展常温下饱和及干燥砂岩单轴循环加卸载试验,通过能量法分析不同状态下砂岩弹性模量、泊松比、能量密度与循环次数之间的关系。结果表明：干燥及饱和砂岩在加载阶段和卸载阶段的弹性模量、泊松比均随加载次数的增大而增大,在相同卸载次数下干燥砂岩的弹性模量、泊松比均大于饱和砂岩;干燥及饱和砂岩的能量储存率随着循环次数先增大后减小,耗散比则相反,由于浸水软化饱和砂岩的能量密度拐点略迟于干燥砂岩;通过累计耗散能变量定义干燥及饱和砂岩的损伤特征,其损伤变量D值与循环次数变化规律相类似均呈下凹曲线。

Energy Evolution and Damage Characterization of Sandstone under Cyclic Loading and Unloading

In order to explore the energy evolution and dissipation characteristics of saturated and dry sandstone in the process of loading and unloading, uniaxial cyclic loading and unloading tests of saturated and dry sandstone at room temperature were carried out with the western sandstone as the research object. The relationship between elastic modulus, Poisson"s ratio, energy density and cycle number of sandstone in different states was analyzed by energy method. The results show that the elastic modulus and Poisson''s ratio of dry sandstone and saturated sandstone increase with the increase of loading times and unloading times, and the elastic modulus and Poisson"s ratio of dry sandstone are greater than that of saturated sandstone at the same unloading times. The energy storage rate of dry and saturated sandstone first increases and then decreases with the number of cycles, while the dissipation ratio is opposite. The inflection point of energy density of saturated sandstone softened by water is slightly later than that of dry sandstone. The damage characteristics of dry and saturated sandstone were defined by the cumulative dissipated energy variable, and the damage variable D showed a concave curve with the number of cycles.