Evolutions of Fabric and Contact Forces of Granular Materials Under Continuously Varying b Value Using DEM

Abstract

The b value [$= (\sigma_{2} - \sigma_{3} )/(\sigma_{1} - \sigma_{3} )$] has been used to illustrate the influence of intermediate principal stress σ₂ on the major and minor principal stresses, σ₁ and σ_3, respectively, on the macroscopic as well as the micromechanical behaviors of granular materials under general stress systems. The anisotropic characteristics of fabric and contact forces have been used to describe the micromechanical behaviors of granular materials. However, most related studies were conducted under constant b value stress paths. The objective of this paper is to study influences of the b value on the evolutions of fabrics and contact forces of granular materials under continuously varying b value stress paths, using the Discrete Element Method (DEM). To this end, the six continuously varying b value stress paths were simulated in this study. The stress-controlled method with constant mean stress 100 kPa on 8000 spheres was conducted. This study found that changing the b values continuously show different distributions of the fabric and contact forces evolutions. The increments of anisotropy coefficients of fabric, normal contact forces, and tangential contact forces differ depend on the b value. However, the differences in the directions of stress paths do not affect those anisotropy coefficients at the peak stress.