We investigate the stresses and pressures under a 2-dimensional heap using a simulation of convex polygonal particles. Former Experiments and simulations on granular cones strongly suggest that for cones no generic pressure distribution exists but that the pressure and stress distribution is highly sensitive to the size distribution of the grains and the building history of the heap.
The seeming contradiction that virtually no pressure dip was found experimentally under granular wedges can be resolved by simple analytic superposition of pressure distributions under cones: The minimum is averaged out the symmetry plane of the wedge.
For flat bottoms, monodisperse systems do hardly exhibit a presure minmium, even not in the presence of cohesive forces. Nevertheless, if one lets the bottom deform under the weight of the heap, a minimum in the pressure starts to develope.