Apparatus and an associated method for forming a pier in a soil matrix includes a hollow tube with a restricted expansion section connected to and adjacent a soil penetrating bottom head element which is configured to facilitate discharge of pier forming material such as grout. An expansion device in the form of an expandable bladder or expandable mechanical device is positioned along a section of the length of the restricted expansion section. The hollow tube structure is inserted into a soil matrix with the expansion device in the retracted condition. Subsequently, the expansion device is expanded to enlarge the formed cavity in the soil matrix. Then grout or other pier forming material is injected into the cavity as the expansion device is retracted or deflated and as the hollow tube structure is raised incrementally to form a pier with one or more uniquely shaped lifts.