Extensible shells and related methods for constructing a support pier are disclosed. An extensible shell can define an interior for holding granular construction material and define a first opening at a first end for receiving the granular construction material into the interior and a second opening at a second end. The extensible shell can be flexible such that the shell expands when granular construction material is compacted in the interior of the shell. A method may include positioning the extensible shell in the ground and filling at least a portion of the interior of the shell with the granular construction material. The granular construction material may be compacted in the interior of the extensible shell to form a support pier.