  We report the results of three dimensional molecular dynamic simulations on
the angle of repose of a sandpile formed by pouring mono-sized cohesionless
spherical grains into a granular Hele-Shaw cell. In particular, we are
interested to investigate the effects of those variables which may impact
significantly on pattern formation of granular mixtures in Hele-Shaw cells. The
results indicate that the frictional forces influence remarkably the formation
of pile on the grain level. Furthermore, We see that increasing grain insertion
rate decreases slightly the angle of repose. We also find that in accordance
with experimental results, the cell thickness is another significant factor and
the angle of repose decays exponentially by increasing the cell thickness. It
is shown that this effect can be interpreted as a cross-over from two to three
dimensions. In fact, using grains with different sizes shows that the behaviour
of the angle of repose when both size and cell thickness are varied is
controlled by a scaled function of the ratio of these two variables.
