Experimental study of water and salt redistribution of clay soil in an opening system with constant temperature

Temperature changing in soil has an influence on the redistribution of water and salt. With constant temperature in an open system we performed two unidirectional freezing tests with different temperature settings of clay collected at Beiluhe test site along Qinghai-Tibet Railway. The groundwater supply of the soil was simulated during the experiments by attaching a liquid replenishment system to the bottom of the sample container. Water content and ions content of the soil were measured after the experiments. By analyzing the two main ions in the soil we obtained the laws and the properties of water and salt redistribution during freezing of clay soil. The results show that the water content increases in freezing section while it decreases in unfrozen section compared with initial water content. To the salt, under this circumstance the diffusion due to the concentration gradient dominated the transfer way in clay soil, so the ions content in the unfreezing section decreased with the decreasing of the distance to freezing front. At the ice segregation layer the ions content is less due to the ice self-purification, and almost nothing changed in frozen section.