Janssen effect and the stability of quasi-two-dimensional sandpiles

Abstract

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.

Avalanche behavior of weakly perturbed bead piles

“…For example, the estimate that we obtained for the critical value in the case of PILE.R50, with L = 50 (figure 11) is closer to unity (α = 1.2). We can possibly find an explanation for this phenomenon on the basis of the pressure screening effect in granular columns [36,41,42]. In fact, by keeping track of the motion of all added grains, we can distinguish a core in the bead pile in which the grains do not move significantly during the avalanches (see figure 1).…”