Time-Dependent Deformation Characteristics of Unsaturated Sand–Bentonite Mixture under Drying–Wetting Cycles

Abstract

The main objective of this study was to investigate the primary consolidation and creep characteristics of two unsaturated sand–bentonite mixtures subjected to drying–wetting cycles. An extensive array of laboratory testing was performed to examine index physical, mineralogical properties, soil-water retention characteristics, and compressibility of the tested materials. A modified osmotic oedometer was used to measure compressibility, creep, and swelling indexes of the sand–bentonite mixtures under three sets of drying–wetting at matric suction values of 200, 400, and 800 kPa. The results showed that the elastic compressibility indexes of the tested sand–bentonite mixtures were not affected by hydraulic loading. The results demonstrated kinematic hardening under hydraulic and mechanical loadings. Hydraulic loading stimulated hardening behavior and a decrease in creep index at all suctions. Results from the two test sets performed in the current study were used along with three other sets of laboratory measured data from the literature to calibrate and validate a model to determine the creep index of unsaturated soils by incorporating the role of stress state and matric suction.