冻融循环作用下受荷砂岩的能量演化与破碎分形特征

Energy evolution and fractured fractal characteristics of loaded sandstone under freeze-thaw cycles

为研究冻融循环作用对岩石力学特性的影响,对砂岩试件依次进行冻融循环处理、单轴压缩实验以及筛分实验,分析不同冻融循环次数下砂岩试件加载过程中的能量演化、分配规律以及破坏后碎屑尺度分布的分形特征,并讨论冻融循环作用的影响效应。结果表明:随着冻融循环次数的增加,单轴抗压强度和弹性模量均呈指数衰减的趋势,峰值应力点对应的耗散应变能及其与总能量比值表现出类似的变化规律。这些试件破坏后的碎屑尺度分布具有分形特征,分形维数在2.50~2.61之间。数据拟合进一步表明冻融循环作用下耗散应变能与分形维数之间呈显著的线性正相关关系,这是因为冻融循环次数越大使得砂岩试件的抗压强度越小,破坏所需的耗散应变能越小,试件破碎程度越不严重,导致相应的分形维数越小。

In order to study the influence of freeze-thaw cycle effect on the mechanical characteristics of rock,the freeze-thaw treatment,the uniaxial compression tests and the sieve tests were carried out in turn on the sandstone specimens.The energy evolution and distribution laws and the fractal characteristics of fragment size distribution after failure during the loading process of sandstone specimens under different numbers of freeze-thaw cycles were analyzed,and the influence effect of freeze-thaw cycles was discussed.The results showed that the uniaxial compressive strength and elastic modulus decreased exponentially with the increase in the number of freeze-thaw cycles,and the dissipative strain energy corresponding to the peak stress point and its ratio to the total energy presented the similar variation law.The scale distribution of fragments after the failure of these specimens had the fractal characteristics,and the fractal dimension was between 2.50 and 2.61.The data fitting further showed that there existed a significantly linear positive relationship between the dissipative strain energy and the fractal dimension under the effect of freeze-thaw cycles.The larger the number of freeze-thaw cycles,the smaller the compressive strength of sandstone specimen,the smaller the dissipation strain energy required for failure,and the less severe the fracture degree of specimen,which caused the smaller the corresponding fractal dimension.