On the contact force distributions of granular mixtures under 1D-compression

We investigate the distribution of the inter-particle contact forces inside granular mixtures of a sand-particle-size material and of a finer-particle-size material using the Discrete Element Method for frictional spherical grains. The numerical granular samples were compressed vertically with no lateral expansion following a common stress path in soil mechanics; the material states varied from jammed states towards highly jammed states with increasing solid fraction. The inter-particle contacts were categorized depending on the particle sizes of the two contacting entities. The force distributions of the contact networks were calculated depending on the contact types. It was found that different contact networks possess a similar shape of the probability distribution function of the contact forces when the populations of the respective particle sizes are involved in the percolation of the strong forces in the systems. For systems of a small percentage of the fine particles, the fine particles do not actively participate in the strong force transmission and the related contact force distributions reflect the characteristic of an unjammed state for the subsystem consisted of these particles.