Abstract: A dead heap or pile is prepared on a circular surface in the form of a sector defined by two radii of the circular surface. With respect to the median plane of the dead heap, such heap has two slopes, each with an inclination equal to that at which particulate material is retrieved from piles (on semicircular plots) which are alternately laid, first on one side and then on the other side of the dead heap. Each such pile (on a semicircular plot) is laid directly against a slope of the dead heap and is retrieved from the edge of the pile which is most remote from the dead heap.