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 κ is a function of the cell thickness. Dependence of global normal stresses as well as κ on the friction coefficients between the grains (µp) and with walls ( µw) are also studied. The results show that in the range of our simulations κ usually increases with wall-grain friction coefficient. Meanwhile by increasing µp while the other system parameters are fixed, we witness a gradual increase in κ to a parameter dependent maximal value.