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为从微观角度研究冻融循环条件对天然盐渍土结构的影响,以罗布泊地区一定深度的天然盐渍土为试样,进行了室内3、5、7次冻融循环试验,在每次试验后测定土样的密度、含水率,并利用SEM提取微观结构图片,进而对试验后的土样在1000倍放大扫描电子显微镜下的微观结构变化进行分析。研究结果表明:随着冻融循环次数的增加,水分自下而上向冷端迁移,冷端含水率较高;土样的密度不断减小,且在深度方向呈现出不规则的正“3”字形的变化规律。冻融前后土体微观结构特征明显不同,经过冻融循环后,土体颗粒间孔隙增大,密实度降低,内部骨架结构发生位移,易引发土体盐胀变形、翻浆、溶陷等不良现象,会严重影响道路工程的稳定性。
In order to study the effect of freeze-thaw cycles on the structure of natural saline soils from a microscopic point of view, three or seven cycles of freeze-thaw cycles in the laboratory were conducted using natural saline soil at a certain depth in the Lop Nur region. The density and moisture content of the soil samples were determined. The microstructure of the soil samples was extracted by SEM. The microstructure of the soil samples after 1000 times magnification scanning electron microscopy was analyzed. The results show that: with the increase of the number of freeze-thaw cycles, the moisture migrates from the bottom to the top and the moisture content of the cold end increases; the density of the soil sample decreases continuously and irregular in the depth direction appears, 3 "shape changes. The microstructure characteristics of soil before and after freezing and thawing are obviously different. After the freeze-thaw cycles, the pores between soil particles increase, the compactness decreases, and the internal skeleton structure displaces, which can easily lead to soil salt deformation, , Will seriously affect the stability of road works.