冻融循环后岩石的物理力学特性及强度模型

Physical and Mechanical Properties and Strength Model of Rocks After Freeze-thaw Cycles

为研究冻融循环对岩石物理力学特性的影响,设计了一系列不同围压和冻融循环次数下的岩石三轴剪切试验;并利用微观分析研究冻融循环后岩石样本的微观结构和矿物成分的变化规律,以此解释宏观力学行为。剪切试验表明,随着冻融循环次数的增加,试样的强度逐渐降低,而泊松比呈,上升趋势;SEM结果表明,冻融循环后岩石内部出现明显的孔隙和裂缝;切片扫描和XRD结果表明,方解石等矿物成分也发生溶解流失,进而导致岩石的力学特性不断弱化。基于力学试验和微观分析,利用Hoek-Brown经验模型建立了一个考虑冻融循环效应的岩石强度准则。模拟结果与试验结果的对比表明该准则能较好地预测岩石强度随冻融循环次数的弱化规律。

In order to study the impact of freeze-thaw cycles on the physical and mechanical properties of rocks, a series of rock triaxial shear experiments were designed under different confining pressures and freeze-thaw cycles. The microscopic analysis was used to study the microstructure and minerals of rock samples after freeze-thaw cycles. The changing law of the composition is studied to explain the macroscopic mechanical behavior. The shear test shows that the strength of the sample gradually decreased with the increase of the number of freeze-thaw cycles while the Poisson’s ratio showed an upward trend. The SEM results show that obvious pores and cracks appeared in the rock after the freeze-thaw cycles. The slice scan and XRD results show that the calcite and other minerals are also dissolved and lost, which leads to the continuous weakening of the mechanical properties of the rock. Based on mechanical tests and microscopic analysis, the Hoek-Brown empirical model was used to establish a rock strength criterion considering the effects of freeze-thaw cycles. The comparison between the simulation results and the experimental results shows that the criterion can better predict the weakening law of rock strength with the number of freeze-thaw cycles.