title: Effect of packing fraction on shear band formation in a granular material forced by a penetrometer.
abstract: Granular ensembles subjected to confinement forces can reach metastable states that often break down via formation of shear bands for sufficiently high deviatoric stress. In this article we investigate the flow induced in a granular ensemble that is perturbed by a vertically moving finger in a quasiplanar geometry. The flow exhibits spiral-like shear bands and evolves discontinuously in time, in concert with an oscillating penetration force. We characterize the nature of this nucleation-relaxation type process for loose to dense packing fractions. The nucleation dynamics is reasonably well described by a simple Mohr-Coulomb failure criterium in which the friction coefficient is a function of packing fraction. We contrast our findings with the recent work of Gravish et al. [Phys. Rev. Lett. 105, 128301 (2010)].
authors: Departamento de Física de la Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
authors: Franco
authors: F
authors: Tapia
authors: David
authors: D
authors: Espíndola
authors: Eugenio
authors: E
authors: Hamm
authors: Francisco
authors: F
authors: Melo
mesh_terms: D000465:Algorithms; D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D008962:Models, Theoretical; D011312:Pressure; D033081:Shear Strength; D013314:Stress, Mechanical
chemical_list: D003102:Colloids