Effect of Intermediate Principal Stress on the Behavior of Granular Materials at a Low Mean Stress by DEM

This study examines the macro- and micro-mechanical behaviors of granular materials at a low mean stress in general triaxial loading using the discrete element method. Spheres were used to model the particles to reduce the computational costs. They were placed in the grid points of a cube with their random values of diameters. The generated cubical sample was compressed isotropically with periodic boundaries to reach the target mean stress of 25 kPa. The isotropically compressed dense sample prepared in this way was subjected to shear by varying a non-dimensional parameter, \(b = (\sigma^{\prime}_{2} - \sigma^{\prime}_{3} )/(\sigma^{\prime}_{1} - \sigma^{\prime}_{3} )\) from 0 to 1. From the numerical study, it is observed that the simulated macro-results agree well with the experimental results. The evolution of principal stress and strain components and angle of shearing resistance is strongly dependent on b. However, the evolution of coordination number and slip coordination is not a function of b. The evolution of the components of contact fabric tensor considering the strong contacts has excellent similarity with that of stress components. The ratio of strong contact to total contact strongly depends on the values of b and it decreases at small strain level regardless of b and starts accumulating afterward as the strain increases.