Discrete element modelling of the influence of inherent anisotropy on the shear behaviour of granular soils

Abstract

The laboratory tests had revealed that the fabric anisotropy plays an important role in the mechanical behaviour of the granular materials. However, the fabric anisotropy includes two aspects, the degree and the principle direction, and their contributions to the mechanical behaviour cannot be separated in the laboratory tests. In this study, granular soil specimens with different degrees and principle directions of inherent anisotropy were successfully produced. The mechanical behaviours of these specimens were numerically investigated by drained biaxial tests using discrete element method (DEM). Meanwhile, the evolutions of the microstructure, including coordination number, anisotropy of the contact normal and the clump orientation, were monitored during the shearing. It was found that not only the principal direction of inherent anisotropy can significantly influence the strength and the deformation characteristics, but also the degree of inherent anisotropy. The peak shear strength first decreases as the bedding angle increases and reaches the minimum value at a bedding angle of 60–75°. Meanwhile, the peak shear strength increases with increasing fabric anisotropy when the bedding angle is small, but decreases when the bedding angle is large.