Permanent deformation of unsaturated granular material under multiple drying and wetting cycles

This investigation proposes an empirical–analytical model for the soil–water retention curve (SWRC) as well as the permanent deformation prediction of unsaturated granular materials under multiple hydraulic cycles. To calibrate and verify the proposed approach, the normalized SWRC model was firstly applied to predict the normalized SWRCs of two unsaturated soils under multiple drying and wetting cycles. The predicted and experimental results showed a good correspondence of the model. The normalized permanent deformation model is subsequently used to estimate the final permanent deformations of two granular materials (clay-crushed tuff aggregates (CTAs) mixture and Missillac sand), with suction under multiple drying and wetting cycles. The results showed that the proposed approach can effectively evaluate the normalized SWRCs and the final permanent deformations of the studied granular materials.