Abstract: The effect of wet-dry cycles on the deformation characteristics of compacted weak expansive soil used in subgrade was investigated by simulating two working conditions (changes in loading and changes in moisture content). Results revealed that the swelling-shrinkage deformation of expansive soil was not completely reversible. The linear swelling ratio in the second wetting cycle was the largest, while the linear shrinkage ratio in the first shrinkage cycle was the largest. With the increasing of wetting-drying cycles, the swelling and shrinkage of specimens both reduced and stabilized gradually. The height of stabilized soil was different from that of the origin specimen. Moreover, changes in loading and moisture content both had great effect on the deformation characteristic of expansive soil. The results suggest that the influence of wet-dry cycle on the deformation of expansive soil used inside subgrade is smaller than that of working conditions on the subgrade. The position of filling expansive soil should be considered when determining the feasibility and treatment measures of subgrade.

Key words: weak expansive soil, subgrade filling, loading, wetting-drying cycle, deformation