Volume 34, Issue 5 (September 2011)
Strength and Small-Strain Stiffness Characteristics of Unsaturated Sand
Experiments were performed to investigate the effects of initial matric suction and net confining pressure on the small-strain stiffness and shear strength of reconstituted unsaturated sand. A series of constant water content tests was carried out using a modified triaxial apparatus equipped with local displacement transducers and bender elements. Reconstituted sand specimens were allowed to equalize at the required matric suction under net confining pressure using the axis- translation technique before shearing. After reaching matric suction equilibrium, shear wave velocities were measured prior to shearing. Multi-stage shearing tests were performed in order to investigate the effect of initial matric suction using the same specimen. The experimental results showed that at each net confining pressure, small-strain stiffness and peak shear strength showed a nonlinear relationship with matric suction with the change point near the air-entry value of the soil-water characteristic curve. Relationship between small-strain stiffness and net confining pressure was observed to be similar for saturated and unsaturated sands.