  Force chain networks are generally applied in granular materials to gain
insight into inter-particle granular contact. For conservative spherical
particle systems, i.e. frictionless and undamped, force chains are information
complete due to symmetries resulting from isotropy and constant curvature of a
sphere. In fact, for conservative spherical particle systems, given the
geometry and material, the force chain network uniquely defines the contact
state that includes elastic forces, penetration distance, overlap volume,
contact areas and contact pressures in a particle system. This is, however, not
the case for conservative non-spherical particle systems. The reason is that a
force chain network is not sufficient to uniquely define the contact state in a
conservative non-spherical particle system. Additional information is required
to define the contact state of non-spherical granular systems. Traction chain
networks are proposed to complement force chain networks for the improved
quantification of the state of contact of a granular system.
