Internal avalanches and restructuring in granular media

We study the phenomenon of internal avalanching within the context of recen tly proposed "Tetris" lattice models for granular media. We consider a pack ing of particles subjected to two different dynamics. In the first case, we arrest the system at different instances during an "aging" dynamics during which the packing slowly compactifies under shaking, and study the distrib ution of internal avalanches at each of these instances. In the second case , we define a recycling dynamics under which the system reaches a steady st ate under continued avalanching. We study the distribution of avalanches in this steady state. In the former case we investigate numerically the effec t of the density of the medium on the avalanche distribution. In the latter case we develop a mean-field theory to help understand the reciprocal effe ct of the avalanches on the medium. (C) 1999 Published by Elsevier Science B.V. All rights reserved.