Phenomenological modeling of the compaction dynamics of shaken granular systems

Granular systems such as powder or sand can compact because of shaking. Using a phenomenological decay law for the successive inverse packing fractions, we obtain the relaxation dynamics for the packing fraction recently found in the experiment by Knight et al. [Phys. Rev. E 51, 3957 (1995)] and discuss the physical implications as well as the physical origin of the proposed decay law. {} 1996 The American Physical Society.