Test scheme.

To investigate the characteristics of water and salt migration (WSM) in saline soils subjected to climate conditions characterized by large temperature differences. In this paper, salted soil highway roadbeds in Uzbekistan were selected as the background for the study, and the salted soils in the region of the site were remodeled through a field study and based on field data. Subsequently, utilizing the assembled laboratory test apparatus, a model test of the WSM on the remodeled saline soil was carried out to analyze the behavior of the WSM in response to large temperature differences, the resulting soil deformation, and the influence of varying cold-end temperatures and alternating cooling and heating times on the WSM. The findings indicated that the temperature profile with in the soil column (SC) exhibits a “wavy” pattern as a result of thermal conductivity. During the freezing phase, water migrates from the lower section to the upper section in response to the temperature gradient and soil-water potential. Conversely, during the melting phase, water diffuses and migrates from the upper section downward in the form of steam molecules due to the action of evaporation. This process culminates in a “C” shape distribution of the curve of the water content inside the SC. During the freezing process, salt migrates from the bottom to the top along with the liquid water. Conversely, during the melting process, salt accumulates at the top of the SC accumulates. This phenomenon results in an “S” distribution of the salt content inside the SC. At the end of the freeze-thaw cycle (FTC), the deformation of the saline soil increased with the decrease of the cold end temperature, and the alternating time between heat and cold did not produce significant changes in the deformation of the saline soil. The moisture content at the upper end of the SC increases with decreasing cold-end temperature. The increase in the number of FTCs exacerbates the salinization of the soil in a certain part of the interior of the SC. The findings of this research may offer a theoretical foundation and technical assistance for the design of subgrade structures in saline soils subjected to climates characterized by large temperature differences.

为探究大温差气候条件下盐渍土内的水盐运移（Water and Salt Migration, WSM）特性，本文以乌兹别克斯坦境内盐渍土公路路基为研究背景，通过现场调研结合实测数据对该区域原位盐渍土进行重塑。随后，利用组装完成的室内试验装置，针对重塑盐渍土开展水盐运移模型试验，分析大温差条件下的水盐运移规律、由此引发的土体变形，以及不同冷端温度与冷热交替时长对水盐运移的影响。研究结果表明，受导热系数影响，土柱（Soil Column, SC）内部的温度分布呈现“波浪形”特征。冻结阶段中，水分会在温度梯度与土水势的驱动下从土柱下部向上运移；反之，融化阶段中，受蒸发作用影响，水分以蒸汽分子形式扩散并从上部向下运移，最终使得土柱内部含水率分布曲线呈“C”形分布。冻结过程中，盐分随液态水从底部向上运移；而融化过程中，盐分则在土柱顶部富集，该现象使得土柱内部含盐量分布呈“S”形分布。冻融循环（Freeze-Thaw Cycle, FTC）结束后，盐渍土的变形量随冷端温度降低而增大，而冷热交替时长对盐渍土变形无显著影响。土柱上端的含水率随冷端温度降低而升高。冻融循环次数的增加会加剧土柱内部局部区域的盐渍化程度。本研究成果可为大温差气候条件下盐渍土路基结构的设计提供理论依据与技术支撑。