Abstract: Compacted granular or stone columns are constructed in soil to increase the load-bearing capacities of the native soil. The upper portion of the compacted granular column is provided with a rigid central core such that vertical loads imposed on the composite column are transferred to a deeper level on the compacted column where the column operates more efficiently. A probe is centrally penetrated downwardly into the compacted granular column, and the resulting cavity is filled with cementitious grout to form a solid core after hardening. The grout may be injected into the cavity so formed in the compacted column at the bottom of the probe as the probe is being withdrawn in predetermined quantities metered in synchronization with the rate of withdrawal of the probe from the core cavity.