干湿循环条件下季冻区黄土状盐渍土的力学特性试验研究

    Experimental study on mechanical properties of loess-like saline soil in seasonal frozen regions under wetting-drying cycles

    • 摘要: 为探究季节性冻土区域中黄土状盐渍土在干湿及冻融循环作用下的力学性能和微观结构变化,利用不固结不排水三轴剪切试验(UU)和电镜扫描试验(SEM),分析了不同循环次数下黄土状盐渍土的应力-应变曲线和抗剪强度指标的变化规律以及微观特性。结果表明:在不同干湿冻融循环条件下,试样的应力-应变曲线均呈现为应变软化型。在单一干湿循环、干湿+冻融循环条件下,随循环次数的增加,黏聚力呈现先增大后减小的变化趋势,最终趋于一个相对稳定的水平。单一冻融循环条件下,随循环次数的增加,黏聚力逐渐降低;不同循环条件下内摩擦角的变化不显著。历经多次循环后,土体内部单粒结构体积减少,架空结构逐渐增多,致使土体结构疏松,强度降低。

       

      Abstract: To examine the impacts of wetting-drying and freeze-thaw cycles on the mechanical properties and microstructure of loess-like saline soil in seasonally frozen regions, unconfined undrained triaxial shear tests (UU) and scanning electron microscopy (SEM) are employed. The study analyzes the variations in stress-strain curves and shear strength parameters of saline-alkaline loess under different cycles of wetting-drying and freeze-thaw, as well as their microstructural characteristics. The results indicate that the stress-strain curves of the samples subjected to various drying-wetting and freeze-thaw cycles exhibited a strain-softening behavior. Under wetting-drying and wetting-drying-freeze-thaw conditions, as the number of cycles increase, the cohesion first increases, then decreases, and eventually stabilizes, with the lowest cohesion observed at six cycles. In contrast, under freeze-thaw conditions, cohesion gradually decreases with increasing number of cycles. The variation in the internal friction angle is relatively small across different cycling conditions. After multiple cycles, the volume of single-grain structures within the soil decreases, and the proportion of bridged structures increases, leading to a loosening of the soil structure and a reduction in strength.

       

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