Discrete numerical modeling of loose soil with spherical particles and interparticle rolling friction

Discrete numerical simulations were carried out to reproduce experimental results obtained on loose cohesionless soil samples subjected to triaxial tests. Periodic boundary conditions were adopted and 3D spherical discrete elements were chosen. However, to overcome excessive rolling of such an oversimplified particle's shape, contact rolling resistance was taken into consideration. The influence of both the elastic and the plastic local parameters is discussed. It is shown that the plastic macroscopic behavior of the granular assembly depends only on the plastic parameters at the microscopic scale, and mainly on the plastic rolling moment reflecting the particle's shape. Moreover, a procedure to obtain an initial density, ranging from loose to dense samples, is proposed by adding adhesion at contacts during the preparation phase. Finally, a calibration procedure is proposed to reproduce experimental results and the limitations of the model are discussed.