Force and weight distributions in granular media: Effects of contact geometry

The influence of the local contact network on interparticle forces and effective particle weights is studied in simulations of two-dimensional packings of frictionless, Hertzian spheres. The weight distribution $\mathcal{P}\mathrm{}\left(w\right)\mathrm{}$ changes qualitatively when approaching a boundary and differs for regular and irregular packings, while the interparticle force distribution $P\left(f\right)\mathrm{}$ is robust. We provide examples where $\mathcal{P}\mathrm{}\left(w\right)\mathrm{}$ at the boundary, which is the quantity probed experimentally, deviates substantially from $P\left(f\right)\mathrm{}$ in the bulk. Discrepancies between the $\mathcal{P}\mathrm{}\left(w\right)\mathrm{}’\mathrm{s}$ predicted by the q model and measured in experiments are due to differences in the contact geometry.