Europhys. Lett., 74 (4), pp. 644-650 (2006)
DOI: 10.1209/epl/i2005-10578-y

Rheophysics of cohesive granular materials

P. G. Rognon^{1, 2}, J.-N. Roux¹, D. Wolf^{1, 3}, M. Naaïm² and F. Chevoir<sup>1

1</sup>  LMSGC, Institut Navier - 2 allée Kepler, 77420 Champs sur Marne, France
²  CEMAGREF - 2 rue de la Papeterie, BP 76, 38402 Saint-Martin d'Hères, France
³  Department of Physics, University Duisburg-Essen - 47048 Duisburg, Germany

received 9 December 2005; accepted in final form 24 March 2006
published online 12 April 2006

Abstract
We investigate the rheology of dense cohesive granular media outside the quasistatic regime using molecular dynamic simulations of homogeneous plane shear flow in the steady state. Friction as well as dilatancy are governed by two dimensionless numbers, the inertial number and the cohesion number. The internal friction coefficient and the solid fraction depend linearly on the inertial number, as in the cohesionless case. Weak cohesion leads to an expansion of the material, while the friction remains unchanged. Above a characteristic cohesion strength, a strong increase of friction combined with a decrease of solid fraction is observed. We relate this behavior to the growing space-time heterogeneities and to the increase of the cohesion-enhanced microscopic friction between the grains.

PACS
45.70.Mg - Granular flow: mixing, segregation and stratification.
81.05.Rm - Porous materials; granular materials.
83.10.-y - Fundamentals and theoretical.

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