Evaluation of the Effect of Anisotropic Consolidation and Principle Stress Rotation on Undrained Behavior of Silty Sands

Abstract

The dependence of undrained behavior of silty sand on initial state of stress and direction of principal stresses with respect to vertical (α) is assessed under generalized loading paths using hollow cylinder apparatus. During applying shear load, value of intermediate principal stress parameter (b) is held constant and α value is increased from zero to the aimed value and held constant. Specimens are consolidated both isotropically and anisotropically to evaluate the effect anisotropic consolidation on the behavior of these soils. Wet tamping method was selected to prepare specimen. Shear loading was carried out under strain-controlled condition to capture post-peak strain-softening response. The results of this study reveal that the principal stress direction and initial anisotropy in stress condition have considerable effects on the behavior of silty sands. By increasing α, susceptibility of silty sand to instability increases. In addition, increase in silt content, silty sand mixtures present higher tendency to flow compared to pure sand. For specimens with high silt content, it is observed that stress-strain response has a sudden reduction in shear strength after a peak. This study reveals that shear strength, steady state friction angle of the silty sands are affected by α and the amount of fines present in the sand.