A method and apparatus for producing short aggregate piers in situ in the ground including the steps of forming a cavity in the ground, compacting the soil in the vicinity of a bottom portion of the cavity to prestress and densify the soil beneath the cavity, adding a layer of loose aggregate to partially fill the cavity, compacting the layer of loose aggregate (37) with an implement (10) adapted to reduce the height of the layer and adapted to prestress and densify the soil laterally by forcing some of the aggregate laterally into the sides of the cavity and thereby also enlarging the cavity in the vicinity of the layer, and repeating the steps of adding aggregate and compacting aggregate until the cavity is filled substantially completely with compacted aggregate or is filled to the desired elevation. The resulting pier has a bulging, undulating outer surface which the surrounding prestressed soil is better able to support.