On the angles of dry granular heaps

We perform careful experiments in a turnable cell to determine the angle of repose and various other angles of dry granular materials. We study the dependence of the angle on the presence of walls and find an exponential decay on the distance between the walls. Modification of the granular fabric close to the surface changes the static angle of repose and the effect can still be noted after several inclinations of the cell indicating the existence of a memory effect. The dynamic angle of repose is particularly small after the first inclination of the cell. When part of the heap is removed through an outlet, three different angles are obtained showing the effect of fabric and heap preparation on the dynamic angle.