Induced and Inherent Anisotropies of Saturated and Unsaturated Soil Shear Properties

Abstract

Anisotropies of shear properties were examined for saturated and unsaturated soils. Induced anisotropy arises when an anisotropic stress is applied to a soil. Using a hollow cylinder torsional shear apparatus, cohesive saturated and unsaturated specimens were anisotropically consolidated in different directions. Then the shear strengths under an undrained condition for saturated soil and a constant water content condition for unsaturated soil were measured using those specimens. Inherent anisotropy develops from the orientation of soil particles during sedimentation. Specimens with different depositional angles were extracted from sand samples deposited in an inclined container. Finally, the shear properties under a drained condition for saturated sand and a constant suction condition for unsaturated sand were evaluated using the triaxial apparatus. The experimental results indicate that anisotropy, especially of the shear strength, is present for both the cohesive soil and the sand. However, shear strength anisotropy is lesser for the cohesive soil in the unsaturated condition than in the saturated condition.