Force-chain distributions in granular systems.

We study experimentally the distributions of force chains in granular materials, which are slightly different in sheared systems compared to isotropically compressed systems, especially at the tails, reflecting the shear-induced anisotropy of the contact force network. Ignoring this anisotropy allows us to establish a relationship between the mean force-chain length Lm and the average contact number Z of particles for both systems, independent of the system size. We also demonstrate that force-chain distributions are not related to the exponential-like distributions of stresses. [ABSTRACT FROM AUTHOR]