Pressure within Granular Materials

Though the behavior of fluids is well understood, granular materials display many phenomena that are still modeled only approximately. Applications as disparate as hour glasses and the construcion of grain silos use these phenomena that are at once simple yet mysterious. I will present the century-old standard approach -- the Janssen model of granular pressure [1] -- and describe current experiments and simulations that test the model. [2-3] I will then show the results for the "photo-elastic" experiments we have performed here at Duke, noting where the model succeeds and fails. I will conclude by sketching an expanded model explaining the differences.

1. Janssen, H. A., Z, Ver. Dtsch. Ing. 39, 1045 (1895).
2. Sereno, D. et. al., Eur. Phys. J. E 6,169 (2001).
3. Kolb, E. et. al., Eur. Phys. J. B 8, 483 (1999).

The implications of the physics of sand is not limited to sandworms and ant-lions, but serves as a model for developing a statistical understanding of a non-equilibrium systems and networks.