Water and salt migration mechanisms are of great significance for understanding the frost heave and thaw settlement of saline soils during freeze-thaw (F-T). In this study, unidirectional open-system F-T tests were conducted on saturated clay specimens with various chloride salt contents to investigate water and salt migration mechanisms. Relevant parameters, including temperature, unfrozen water content, bulk electrical conductivity, matric suction, and water intake volume, were measured continuously during testing. Besides, the water molecule mobility was obtained by the Nuclear Magnetic Resonance relaxometry tests to help understand the water and salt migration mechanisms. The test results indicated that the freezing front development was highly dependent on salt content. The matric suction gradient was found to be the driving force of water-salt migration, which was larger in specimens with lower salt content and led to more water intake. The migration of water and salt was asynchronous due to their different driving mechanisms during F-T. Specifically, salt migration was affected by both convection and diffusion, while water migration was primarily driven by convection. This phenomenon was also confirmed by the different patterns in water and salt redistributions after F-T. Meanwhile, pore water in the frozen specimens with different salinity and the same unfrozen water content was found to have the same water molecule mobility. Both the matric suction and water molecule mobility were dependent on unfrozen water content but independent on salt content. However, the salt content has a significant effect on the soil freezing point depression, which further affects the matric suction and water molecule mobility.

水分和盐分的迁移机制对于了解冻融过程中盐渍土的冻胀和融化沉降具有重要意义。在这项研究中，对具有各种氯化物盐含量的饱和黏土样品进行了单向开放系统FT试验，以研究水和盐的迁移机理。在测试过程中连续测量了相关参数，包括温度，未冻结的水含量，总电导率，基质吸力和进水量。此外，通过核磁共振弛豫法测试获得了水分子迁移率，以帮助了解水和盐的迁移机理。测试结果表明，冻结前沿的发展高度依赖于盐含量。基质吸力梯度是水盐迁移的驱动力，在盐含量较低的样品中吸力梯度较大，导致进水量增加。水和盐的迁移是异步的，因为在FT期间它们的驱动机制不同。具体来说，盐的迁移受对流和扩散的影响，而水的迁移主要受对流的驱动。FT后水和盐的重新分配方式不同也证实了这一现象。同时，发现不同盐度和相同冻结水含量的冻结标本中的孔隙水具有相同的水分子迁移率。基质吸力和水分子迁移率均取决于未冻结的水含量，但与盐含量无关。然而，