Arches and contact forces in a granular pile

• Published in: The European physical journal. E, Soft matter and biological physics Soft matter and biological physics, 2012-06, Vol.35 (6), p.44-44, Article 44
• Main Authors: Carlevaro, C. M., Pugnaloni, L. A.
• Format: Article
• Language: English
• Subjects: Biological and Medical Physics; Biophysics; Complex Fluids and Microfluidics; Complex Systems; Exact sciences and technology; Mechanical Phenomena; Models, Theoretical; Nanotechnology; Physics; Physics and Astronomy; Polymer Sciences; Regular Article; Soft and Granular Matter; Stress, Mechanical; Surfaces and Interfaces; Thin Films
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2012-12044-7

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.