A study of principle stress rotation on granular soils using DEM simulation of hollow cylinder test

Abstract

This study presents the numerical modeling of a hollow cylinder test (HCT) on granular soils by modifying the TRUBAL code. The discrete element method (DEM) was employed for this purpose. Owing to the significant expenditure of the HCT, a verified numerical modeling for this test was developed. The introduced numerical model (HCTBALL) defines plane and cylindrical walls for the boundary conditions to be applied. In addition, the article presents an efficient method to apply the torque. The displacements of the inner and outer walls are interdependent while torsion was applied to control the intermediate principal stress parameter (b). To verify the model, the paper employs results from experimental HCTs on Firoozkooh sand under both monotonic loading and drained conditions. A comparison of the presented model and the experimental results shows that both are closely concordant.It was shown that the deviatoric stress decreases as the principal stress angle (α) increases. In addition, it was observed that by increasing the confining pressure, the internal friction angle (φ′) decreases; however, at higher confining pressures, this reduction is insignificant. Furthermore, this study investigates the coordination number and its relationship to volumetric strain variations.