Abstract: A coupler for coupling together a lead pile segment and an extension pile segment of a driven pile comprises: a cylindrical pipe segment, having first and second formed ends and a cylindrical body extending therebetween, each of the first and second formed ends having an inner diameter that is greater than an inner diameter of the cylindrical body. The first formed end is sized to snugly receive an end of the lead pile segment and the second formed end is sized to snugly receive an end of the extension pile segment. Each of the first and second formed ends has an initial length. When an axial force is applied to the extension pile segment, each of the first and second formed ends undergo secondary end forming to thereby achieve a final length of each formed end, wherein the final length exceeds the initial length of each formed end.

Abstract: A coupling between lead and extension pile segments of a driven piling. The extension segment has a formed end, an opposite driven end and a body extending therebetween. The formed end has an inner diameter equal to an outer diameter of an exposed end of the lead segment and greater than an outer diameter of the extension segment's body. The formed end has an initial length prior to coupling the extension and lead segments; the formed end undergoes secondary end forming when a driving force is applied, such that the formed end has a final length exceeding the initial length after the extension and lead segments are coupled. In some embodiments, the extension segment has an external ring portion positioned upstream of the formed end, and the exposed end of the lead segment is cold extruded into and through the external ring portion of the extension segment.