The uncanny weight of granular columns

Abstract

The results obtained by Janssen in 1895 showed that when filling a silo with corn, there is a certain point where the pressure measured at the bottom saturates and does not linearly increase with added mass. Recent work with spherical grains found that when the silo is narrow enough a reverse Janssen effect is found and the pressure, rather than just saturate first increases faster than linearly due to the configuration the grains adopt inside the container. Via experimental investigation this work demonstrates that this behaviour is still fulfilled when changing the geometry of the grain to an oblate ellipsoid and that the deviation from fluid behaviour requires less added mass due to the larger packing fraction acquired in this case