Effect of fabric anisotropy on the cyclic liquefaction of sands: Insight from DEM simulations

Abstract

To interpret the effects of fabric anisotropy on the cyclic liquefaction of sands, undrained cyclic triaxial tests on the vertical and horizontal specimens were simulated using the discrete element method with ellipsoidal clumps. The simulation captured the anisotropic cyclic responses of sands observed experimentally: (a) the vertical specimen is more prone to liquefaction than the horizontal one under symmetrical cyclic loading conditions; (b) the axial strain is accumulated at the extension side for the vertical specimen and at the compression side for the horizontal specimen. At the particle scale, the mechanical coordination number, redundancy index, contact-normal and particle-orientation based fabrics were investigated to provide insight into the macro response. It is found that at the onset of liquefaction, the redundancy index is equal to 1, the mechanical coordination number is equal to 3.3, and the contact-normal based fabric anisotropic variable is always negative. Furthermore, the anisotropic critical state theory was applied to investigate the relationship between the macro-mechanical behavior and the evolution of contact-normal based fabric, which facilitates the development of constitutive models for simulating cyclic liquefaction behavior of anisotropic sands.