Eur. Phys. J. E (2012) 35: 44
https://doi.org/10.1140/epje/i2012-12044-7

Regular Article

Arches and contact forces in a granular pile

¹ Instituto de Física de Líquidos y Sistemas Biológicos (CONICET La Plata, UNLP), Calle 59 Nro 789, 1900, La Plata, Argentina
² UDB Física, Universidad Tecnológica Nacional - FRBA, Mozart 2300, C1407IVT, Buenos Aires, Argentina

^* e-mail: luis@iflysib.unlp.edu.ar

Received: 6 December 2011
Revised: 13 April 2012
Accepted: 22 May 2012
Published online: 13 June 2012

Abstract

Assemblies of granular particles mechanically stable under their own weight contain arches. These are structural units identified as sets of mutually stable grains. It is generally assumed that these arches shield the weight above them and should bear most of the stress in the system. We test such hypothesis by studying the stress born by in-arch and out-of-arch grains. We show that, indeed, particles in arches withstand larger stresses. In particular, the isotropic stress tends to be larger for in-arch grains whereas the anisotropic component is marginally distinguishable between the two types of particles. The contact force distributions demonstrate that an exponential tail (compatible with the maximization of entropy under no extra constraints) is followed only by the out-of-arch contacts. In-arch contacts seem to be compatible with a Gaussian distribution consistent with a recently introduced approach that takes into account constraints imposed by the local force balance on grains.