单向冻结过程中NaCl盐渍土水盐运移及变形机理研究

冻结过程中的水盐迁移机理一直是冻土学研究的热点。通过单向冻结试验,研究了冻结过程中的水盐运移过程及土体变形。研究表明,在土体初始含盐量为0.8%的条件下,土体的冻胀变形显著减小,盐分的存在强烈影响着冻结缘处水分的集聚,盐对土体的冻胀具有抑制作用。在补给不同浓度NaCl溶液的条件下,土体初期的冻胀变形规律一致,随着盐分在冻结锋面处的累积,土体在后续冻结过程中水分迁移动力不足,从而使得土体冻胀过程中冻胀明显减小。基于溶液的性质并考虑盐分对土体冻结温度和未冻水含量的影响,建立了冻结过程中NaCl盐渍土水盐迁移规律及变形的计算模型,计算结果显示,计算模型能够很好地反映含盐土体在冻结过程中的温度、水分、盐分及变形的规律,从而为深入了解盐渍土在冻结过程中的变形机理提供理论参考。

Water and salt migration and deformation mechanism of sodium chloridesoil during unidirectional freezing process

The mechanism of water and salt migration in the freezing process has long been a hot spot in the study of frozen soil. The water and salt transport processes and the deformation of soil are studied through the unidirectional freezing experiments. The results show that the deformation of soil with the initial salt content decreases significantly compared with that of desalinized soil, and the salt has a strong impact on the accumulation of water in the frozen fringe, and it can mitigate the frost heave of soil in the freezing process. Supplied with different concentrations of NaCl solution, the deformations of the samples are consistent in the early stage. With the accumulation of salt at the freezing front, the driving force of moisture migration is not so sufficient during the subsequent period when the frost heave decreases significantly. Based on the properties of the solution, a model is established to describe the water and salt migration and deformation in the freezing process, where the influence of salt on the freezing temperature and unfrozen water content are considered. The calculated results illustrate that the proposed model can reflect the laws of temperature, water, salt and deformation in the freezing process well, and it will provide a theoretical basis for understanding the deformation mechanism of saline freezing soil.