Patent ID: 7226246

Claim:
Apparatus for construction of a multiple lift, compacted pier in a soil matrix comprising, in combination: an elongate hollow tube having a longitudinal axis, a top material entrance and, an open bottom material discharge end and a first outer surface diameter, and a unitary, shaped bottom head element at the open discharge end having a second outside surface diameter greater than the first surface outside diameter and configured to provide a combination of axial and transaxial stress components upon lowering the hollow tube, said head element comprising a unitary attachment of the hollow tube; said head element including a leading bottom end including a generally frustoconical configuration between the head element outside surface and a bottom discharge opening in the leading bottom end and a trailing end including a generally frustoconical configuration; and a head element cap covering the bottom discharge opening; said bottom head element with said cap and said hollow tube being shaped for insertion in a soil matrix to effect displacement of the soil as the hollow tube with the bottom head element and said cap are lowered into the soil matrix to form a cavity in the soil matrix, said cap being at least partially removable from the bottom discharge opening as the hollow tube is subsequently raised from said formed cavity to allow material flow through the bottom discharge opening into the portion of the cavity vacated by the hollow tube and bottom head element, said bottom head element having a cross sectional shape and size greater than the cross sectional shape and size of the hollow tube to reduce frictional forces on the hollow tube when penetrating into and withdrawing from the soil matrix.