  We investigate the flow and jamming through small apertures of a column of
granular disks via a pseudo-dynamic model. We focus on the effect that the
preparation of the granular assembly has on the size of the avalanches
obtained. Ensembles of packings with different mean packing fractions are
created by tapping the system at different intensities. Surprisingly, packing
fraction is not a good indicator of the ability of the deposit to jam a given
orifice. Different mean avalanche sizes are obtained for deposits with the same
mean packing fraction that were prepared with very different tap intensities.
It has been speculated that the number and size of arches in the bulk of the
granular column should be correlated with the ability of the system to jam a
small opening. We show that this correlation, if exists, is rather poor. A
comparison between bulk arches and jamming arches (i.e., arches that block the
opening) reveals that the aperture imposes a lower cut-off on the horizontal
span of the arches which is greater than the actual size of the opening. This
is related to the fact that blocking arches have to have the appropriate
orientation to fit the gap between two piles of grains resting at each side of
the aperture.
