All you need is shape: Predicting shear banding in sand with LS-DEM

Reid Kawamoto (1) , Edward Andò (2) , Gioacchino Cinno Viggiani (2, 3) , José E. Andrade (1)

1 CALTECH - California Institute of Technology
2 3SR - Laboratoire sols, solides, structures - risques [Grenoble]
3 GéoMécanique

This paper presents discrete element method (DEM) simulations with experimental comparisons at multiple length scales—underscoring the crucial role of particle shape. The simulations build on technological advances in the DEM furnished by level sets (LS-DEM), which enable the mathematical representation of the surface of arbitrarily-shaped particles such as sands. We show that this ability to model shape enables unprecedented capture of the mechanics of granular materials across scales ranging from macroscopic behavior to local behavior to particle behavior. Specifically, the model is able to predict the onset and evolution of shear banding in sands, replicating the most advanced high-fidelity experiments in triaxial compression equipped with sequential X-ray tomography imaging. We present comparisons of the model and experiment at an unprecedented level of quantitative agreement—building a one-to-one model where every particle in the more than 53,000-particle array has its own avatar or numerical twin. Furthermore, the boundary conditions of the experiment are faithfully captured by modeling the membrane effect, as well as the platen displacement and tilting. The results show a computational tool that can give insight into the physics and mechanics of granular materials undergoing shear deformation and failure, with computational times comparable to those of the experiment. One quantitative measure that is extracted from the LS-DEM simulations that is currently not available experimentally is the evolution of three dimensional force chains inside and outside of the shear band. We show that the rotations on the force chains are correlated to the rotations in stress principal directions.

Domaines: Mécanique des solides [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Science des matériaux [cond-mat.mtrl-sci]; Mécanique statistique [cond-mat.stat-mech]; Matériaux

Reid Kawamoto, Edward Andò, Gioacchino Cinno Viggiani, José E. Andrade. All you need is shape: Predicting shear banding in sand with LS-DEM. Journal of the Mechanics and Physics of Solids, 2018, 111, pp.375 - 392. ⟨10.1016/j.jmps.2017.10.003⟩. ⟨hal-01665568⟩