Anisotropic Influence on the Mechanical Behavior of Aeolian Sand under True Triaxial Conditions

Abstract

Granular materials usually copossess inherent and stress-induced anisotropy that significantly influences their mechanical behaviors. This paper presents a series of true-triaxial tests on aeolian sands to consider the inherent and stress-induced anisotropy in terms of soil deposition angles and intermediate principal stress coefficients, respectively. These results show that the deposition angle primarily affected the elastic–plastic stage under axisymmetric conditions. Otherwise, the deposition angle affects all deformation processes after the elastic stage when the intermediate principal stress coefficient changes. Moreover, the critical state is not unique but depends on the combined effect of the deposition angle and the intermediate principal stress coefficient, which indicates that the strength, stress–strain response, and dilatancy behavior of sands are affected by both inherent and stress-induced anisotropy. Geomaterials are generally heterogeneous, and the heterogeneity is associated with deposition direction. This property seriously affects the soil’s strength, deformation, and stability, and hence is a crucial consideration in geotechnical, civil, and mining engineering. This experimental study focuses on the influence of deposition direction on the geomaterial’s behavior by conducting a series of true-triaxial tests. The experimental results in this study reveal that the strength and deformation in three dimensions depend on the deposition direction and intermediate principal stress coefficients. The failure stress and dilatancy increase with the increase of the deposition angle. When the intermediate principal stress is applied, the strength of the soil is significantly reduced. These findings contribute to enhancing our comprehension of soils’ mechanical behavior and serve as valuable insights for addressing geotechnical engineering issues such as ground settlement, slope instability, and landslides, associated with deposition directions. Therefore, in practical engineering, the influence of the deposition direction, especially in three dimensions, should be properly considered and the designed results should be modified according to the influence of deposition direction and stress conditions.