Evaluation of dynamic properties of unsaturated soils under cyclic loading

This study investigates the cyclic response of unsaturated soils, focusing on the dynamic properties such as damping characteristics and soil stiffness, under varying matric suction and confining stress conditions during cyclic triaxial loading. Despite challenges in evaluating unsaturated soils compared to saturated ones, cyclic triaxial testing emerges as an efficient method for exploring their cyclic behavior. Through a series of experiments with different loading frequencies, stress levels, and suction conditions, the research reveals that as matric suction increases, stiffness rises while the damping ratio decreases. Additionally, comparisons between isotropic and anisotropic stress conditions show that the shear modulus is higher under anisotropic consolidation due to particle reorientation. The study proposes a semi-empirical equation to address the stress and suction dependency of shear modulus, finding a consistent trend between predicted and measured values. Ultimately, the findings underscore the significance of stress state, suction, cyclic shear strain, number of loading cycles and confining pressure in determining soil shear modulus.