Analysis of factors effect on the shear characteristics of granular soils under conditions of increasing axial stress in biaxial compression test via DEM

The physical and mechanical properties of granular soils are strongly related to the overlying stresses to which they are subjected. In particular, during the engineering construction phase, which involves activities like foundation stacking and building construction, the applied loads on the soil increase continuously over time. Unfortunately, current stress-controlled compression geotechnical tests have not adequately considered this situation. Therefore, this study aims to examine the effects of various factors, including void ratio, confining stress, stress loading rate, and particle shape, on both macroscopic shear properties and microscopic characteristics of granular soils under conditions of increasing axial stress in biaxial compression numerical simulations. The results show that: (1) In stress-controlled tests on granular soils, samples exhibit three different shear behaviors as the void ratio varies; (2) the confining stress and particle shape will change the magnitude of the deviatoric stresses and axial strains in the peak state of the sample, but not their trends; (3) the stress loading rate does not affect the strength of the samples. Therefore, the loading rate can be increased appropriately to improve the computational efficiency of the numerical model. These findings will enhance understanding of the time-dependent behavior of granular soils and provide valuable insights for engineering applications, particularly in soil mechanics, foundation treatment, and slope stability.