A system for stabilizing gravity-based offshore structure anchored in a seabed includes a plurality of upper locking element sets installed in a keel on the bottom of the structure; a plurality of caissons embedded in the seabed; a plurality of inserts, each of which is removably installed in one of the caissons; and a lower locking element set in each of the inserts. Each of the lower locking element sets is lockably engageable with one of the upper locking element sets when the keel is set down on top of the caissons. The inserts are permanently attachable to the keel by a grouting material that may be pumped into the inserts through the keel. The arrangement stabilizes the structure against lateral shear forces, while allowing the structure to be easily removed from the caissons, with the inserts attached to the keel, by the application of a vertical lifting force. The structure may then be moved and installed on a second plurality of caissons embedded at second seabed site.