Investigating the shear behaviors of unsaturated structured loess in direct shear test by the discrete element method

Abstract

This study investigates the shear behaviors of unsaturated structured loess in direct shear test by the discrete element method (DEM). A bond contact model characterized by the consideration of inter-particle attraction and van der Waals force was used. The direct shear tests were simulated under different suctions and vertical pressures. The simulation results were analyzed in terms of stress-strain relationships, volumetric responses, bond breakages and contact fabric. It is shown that: 1) The shear strength of structural loess samples can be enhanced by decreasing water content and increasing vertical pressure; the strain softening and dilatancy behaviors of structural loess enhance with the decrease of water content and vertical stress, respectively. 2) The bond breakage rate in shear band is related to the macroscopic mechanical response. 3) The anisotropy of the contact fabric changes more significantly in the shear band during shearing, it is of great significance to study the microcosmic properties of particles in shear band.