The flow of binary granular mixtures made of sand and glass spheres into a vertical Hele Shaw cell give rises to heaps exhibiting different structures. We first give the phase diagram of heap morphologies classified as a function of the size ratio of rough to smooth particles. We also point out that the size ratio can modify the stratification only if the absolute particle sizes are sufficiently different. We also give a simple determination of the layer wavelength based on mass conservation.
Granular stratification is one type of size segregation induced by surface flows.
This phenomenon is of interest in geological avalanching, industrial processes and has recently experienced a growing interest as research subject. Granular stratification is found to result from the flow of a binary mixture composed of large rough particles and small smooth ones. The conditions that the large particles have a higher angle of repose than the small ones must also be satisfied. Makse et al. In that case, a continuous segregation between the two media is predicted within the pile.