MODELING STRATIFICATION IN 2-DIMENSIONAL SANDPILES

When a mixture of small and large grains is poured between two vertica l slabs, the mixture spontaneously stratifies in alternating layers of small and large grains. We describe a possible mechanism and we devel op a model that reproduces stratification of the large and small grain s in alternating layers. We find that the requirement for stratificati on is that the angle of repose of the large pure species is larger tha n the angle of response of the small pure species, prediction confirme d by the experimental findings. (C) 1998 Elsevier Science B.V. All rig hts reserved.