Abstract: The expansive soil canal in the Middle Route of South-to-North Water Transfer Project is easily subjected to the effect of freeze-thaw cycles. In order to investigate the influence of freeze-thaw cycles on soil-water characteristics of expansive soil, we measured the total suction and matric suction of Nanyang expansive soil subjected to different freeze-thaw cycles using the filter paper method, and fitted the relationship between matric suction, total suction and water content with Van Genuchten model and power function model, respectively. Results show that as the freeze-thaw cycle proceeds, the soil and water characteristic curves (SWCCs) of the matric suction and total suction shifted to the lower left side, with the air entry value and water holding capacity both declining. The osmotic suction decreased gradually with the increase of water content, but the osmotic suction at different freeze-thaw cycles did not vary significantly. Finally, the fitting models used in the paper are of high correlation coefficients and simple forms, and the parameters of the models tend to be stable as the number of freeze-thaw cycles increases.

Key words: expansive soil, freeze-thaw cycles, soil-water characteristics, filter paper method, total suction, matric suction, curve fitting