From force distribution to average coordination number in frictional granular matter

We study the joint probability distribution of normal and tangential frictional forces in jammed granular media, P-mu(f(t), f(n)), for various values of the friction coefficient mu, especially when mu = infinity. A universal scaling law is found to collapse the data for mu = 0 to infinity, demonstrating a link between the force distribution P-mu(f(t),f(n)) and the average coordination number, z(c)(mu) The results determine z(c)(mu) for a finite friction coefficient, extending the constraint-counting argument of isostatic granular packing to finite frictional packings. (C) 2010 Elsevier B.V. All rights reserved.