Tetrapods
Placing a Tetrapod unit using a crane with a sling rigging to lift the unit.
These devices are solid precast concrete. They may be constructed in various sizes as per site-specific requirements. The most useful applications are for constructing breakwater and revetment systems along the shorelines of large bodies of water. The units are cast in 2-part metal forms. The two halves of the forms are held together with clamps or bolts. Concrete is poured into the forms and vibrated to eliminate as many "honeycombs" as possible. After the concrete has hardened, the form halves are separated. Weight of each unit is about 25 tons. They are usually placed with a crane. The units are shaped so as to offer a self-interlocking feature and subsequent adjustment is of little concern. The units may be stacked parallel to a shoreline, to form a revetment, or perpendicular to the shoreline, to serve as a breakwater.