  The presence of interparticle cohesion can drastically change the behavior of
granular materials. For instance, powders are challenging to handle, and one
can make a sandcastle using wet grains. In this study, we report experimental
results for columns of model cohesive grains collapsing under their own weight
in air and spreading on a rough horizontal surface. The effects of two
different sources of interparticle cohesion on two collapse geometries are
compared and rationalized in a common framework. Grains are made cohesive by
adding a small amount of water, such that they are in the pendular state, or by
applying a polymer coating. The effects of cohesion are reported for a
cylindrical column that spreads unconfined axisymmetrically and a confined
rectangular column that flows in a single direction. A dimensionless number,
comparing macroscopic cohesive strength to particle weight, is shown to capture
the effects of cohesion on the final morphology. To this end, a
characterization of the cohesive strength of the granular materials is
obtained, independent of the physical source of cohesion at the particle scale.
Such a framework allows for a common description of cohesive granular materials
with different sources of cohesion.
