Investigation of water retention and volumetric deformation characteristics of soils subjected to wetting–drying cycles

Abstract

The variation in soil moisture can lead to unfavourable deformation of highway embankments, threatening their long-term stability under seasonal groundwater level fluctuations and frequent changes in evaporation and precipitation. This paper conducted unsaturated soil triaxial tests to examine soil water retention and volumetric deformation behavior during wetting–drying cycles. The results show that soil water retention decreases with increasing wetting–drying cycles, particularly in the low suction range from 0 to 100 kPa, where gravimetric moisture content (GMC) declines sharply. With more wetting–drying cycles, the soil’s capacity for volumetric deformation diminishes. The soil has a loose soil structure and is more prone to plastic deformation. Furthermore, three soil water retention models, the Gallipoli, Tarantino, and Hu models were employed to analyse soil’s hydromechanical behaviours and evaluate the effect of wetting–drying cycles. It was found that Tarantino’s model used only three fitting parameters, which were more concise and maintained a good fitting effect. This study clarifies soil–water retention and volumetric deformation behavior during wetting–drying cycles, which is essential for effective water control in subgrade construction and operation.