Studying the water migration characteristics of clay is of great significance for assessing the engineering impact of freeze-thaw on the filling soil. Taking clay which is the important filling soil of the dam core wall of the Lianghekou Hydropower Station in China as the research object, and according to the environmental characteristics of daily cycle freezing-thawing effect on the construction site in winter, a series of repeated one-dimensional freeze-thaw experiments with short-time, high-frequency and shallow freezing conditions under a closed system are carried out indoor, and the characteristics of ice lens, water migration and frost heave of soil under repeated freeze-thaw effect are studied. The results indicate that under the diurnal freeze-thaw effect, ice lens will be quickly formed in the affected part of soil, and with the change of freeze-thaw conditions, thin-layered ice lens which are obviously perpendicular to the freezing direction and with different morphology and thickness are formed, which are significantly different from previous studies. Among them, compared with the previous research, the thickness of ice lens is relatively thin and uniform in the part where is affected by freeze-thaw. The difference in spatial distribution is that the average thickness of ice lens in the lower part is thicker than that in the upper part, but the number of ice lens increases. This characteristics are greatly affected by the initial moisture content, cooling temperature and the number of freeze-thaw cycles. Among them, the initial moisture content has the greatest influence on the change of the thickness of ice lens. Cooling temperature has a great influence on the development and distribution of the layered cryostructure. The development degree of cryostructure is most prominent at a cooling temperature of -5℃, while both the thickness of ice lens and the distribution of the layered cryostructure are more uniform at the cooling temperature of -10℃. The effect of freeze-thaw on the layered cryostructure is a cumulative process, and the number of ice lens increases with the increase of the number of freeze-thaw cycles. In addition, the amount of frost heave of soil is small, and the ice lens in the lower part of soil where is affected by freeze-thaw plays a major role. The research results have important guiding effects on the prevention and control of freeze-thaw process in the winter construction of dams in seasonally frozen soil areas. © 2021, China Water Power Press. All right reserved.
