8 feet below the ground surface the voids were then loosely backfilled with sand the ebp elements of this example were formed within the backfilled holes in this embodiment of the invention the ebp was formed by filling the mandrel described in fig7 with concrete the mandrel of this embodiment featured a u201c closed top u201d as opposed to the u201c open hopper u201d configuration as described with reference to example i the mandrel in this embodiment was attached to a similar hammer as in the embodiment of example i the full mandrel was advanced to a depth of 8 feet below the ground surface the mandrel was then raised 3 feet and then lowered 2 feet for three repetitions to create the expanded base a process of raising the mandrel 3 feet and then lowering 1 foot was then used to complete the full length of the pier once the concrete had cured each of the piers was excavated and the pier base and shaft diameters were measured the lower chamber in this embodiment had a nominal 12 inch diameter outer dimension the excavated and measured piers had an average nominal diameter of 18 inches expanded bases at the bottoms of the piers exceeded 24 inches demonstrating the effectiveness of this construction technique as yet another example the embodiment of the present invention from example ii was used on a site in washington d c the site was characterized by 20 to 30 feet of soft clay and clayey sand underlain by dense sand or hard clay the embodiment of the present invention at the site was used to support mechanically stabilized earth mse walls and embankments the mandrel.