Characterising the resilient behaviour of unsaturated sandy soils under suction-controlled tests

This study investigates the influence of moisture and suction on the resilient modulus (MR) of subgrade soils. The research employs suction-controlled Repeated Load Triaxial (RLT) tests on three sandy materials with varying fines content. The soil water retention curves (SWRC) for the three materials were obtained and allowed expediting suction equilibrium outside the triaxial chamber by controlling the water loss and thus inferring the yielded suction with the SWRC parameters. The results show that MR increases with lower moisture content and higher suction. Two stress-based models and two moisture-based models are evaluated for predicting MR. The findings indicate that stress-suction models provide a good fit for the silty sands, but only the model where suction is an independent variable suits all tested materials. Additionally, a proposed suction-based model demonstrates promising results. Overall, the study highlights the importance of considering both moisture and suction for accurate MR characterisation of subgrade soils.