Effect of extended drying on the mechanical behaviour of a sand

This study investigates the influence of prolonged drying on the hydro-mechanical response of a quartz sand. Oedometer tests were performed under saturated, unsaturated, and dry conditions, on specimens prepared at different initial void ratio. The experimental results interpreted in terms of net stress, indicate that the yield stress does not exhibit a monotonic increase with suction, in contrast to the assumptions commonly adopted by elasto-plastic constitutive models for unsaturated soils. In fact, the yield stress reaches a maximum value for a given suction, followed by a continuous decrease as the samples approach the dry state. Moreover, the yield stress under dry conditions returns to value similar to that observed in the saturated state. Moreover, as expected, initial relative density plays a fundamental role in the evolution of yield stress across the entire range of investigated degree of saturation. These findings emphasize the importance of considering drying effects when assessing long-term behaviour of unsaturated granular soils.