  We present the results of three dimensional molecular dynamics study of
global normal stresses in quasi two dimensional sandpiles formed by pouring
mono dispersed cohesionless spherical grains into a vertical granular Hele-Shaw
cell. We observe Janssen effect which is the phenomenon of pressure saturation
at the bottom of the container. Simulation of cells with different thicknesses
shows that the Janssen coefficient $\kappa$ is a function of the cell
thickness. Dependence of global normal stresses as well as $\kappa$ on the
friction coefficients between the grains ($\mu_p$) and with walls ($\mu_w$) are
also studied. The results show that in the range of our simulations $\kappa$
usually increases with wall-grain friction coefficient. Meanwhile by increasing
$\mu_p$ while the other system parameters are fixed, we witness a gradual
increase in $\kappa$ to a parameter dependent maximal value.
