COMPACTION OF WELL-COORDINATED LUBRICATED GRANULAR PILINGS

We have performed numerical simulations of the isotropic compaction of dense lubricated two-dimensional assemblies of rigid circular grains. Neighbouring discs are separated by a thin layer of a viscous fluid, of minimal thickness h, within which creeping flow gives rise to central forces on the solids that are proportional to their normal relative velocity and to 1/h(alpha). With alpha greater than or equal to 1 true intergranular contact never occurs, and we show that, starting from a triangular lattice of slightly polydisperse discs, heterogeneities increase in the course of compaction until forces totally concentrate onto an alpha-independent isostatic structure.