Issue
EPL
Volume 81, Number 3, February 2008
Article Number 34006
Number of page(s) 6
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
DOI http://dx.doi.org/10.1209/0295-5075/81/34006
Published online 03 January 2008
EPL, 81 (2008) 34006
DOI: 10.1209/0295-5075/81/34006

Characterizing the shear and bulk moduli of an idealized granular material

V. Magnanimo1, L. La Ragione1, J. T. Jenkins2, P. Wang3 and H. A. Makse3

1  Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Bari - 70125 Bari, Italy
2  Department of Theoretical and Applied Mechanics, Cornell University - Ithaca, NY 14853, USA
3  Levich Institute and Physics Department, City College of New York - New York, NY 10031, USA


received 2 October 2007; accepted in final form 30 November 2007; published February 2008
published online 3 January 2008

Abstract
Physical experiments on wave propagation on granular material control two macroscopic parameters that are assumed to characterize the response of a given assembly: the isotropic pressure p0 and the solid volume fraction $\phi $. Here, by means of numerical simulation, we investigate the effect of the coordination number $\overline{Z} $ (the average number of contacts per particle) and the fluctuation of the number of contacts per particle $Z^\prime $. We adopt a numerical protocol to create several initial packings characterized by the same volume fraction and, for a given isotropic pressure, we are able to obtain different coordination numbers. That is, pressure and coordination number, for a given volume fraction, are independent. The result is that packings with fixed volume fraction and isotropic pressure exhibit a different elastic response. We attribute this behavior only to the coordination number as we find, surprisingly, that $\overline{Z} $ is linked to $Z^\prime $.

PACS
45.70.-n - Granular systems.
45.70.Cc - Static sandpiles; granular compaction.
46.40.-f - Vibrations and mechanical waves.

© EPLA 2008