Abstract: Protective barrier consisting of at least two ballastable elements (3, 4) adapted to surround at least partially the work to be protected (1).The height of the individual elements is greater than the water depth. The elements comprise a connection device permitting the structural continuity of the elements after assembly. The protective barrier is entirely independent of the work to be protected. The positioning of the elements around the work is effected by means of a positioning system provided in the sea bed and/or the individual elements of the protective barrier.

Abstract: The structure is made in several "storeys" (D1, D2, D3). These are floated away from their construction site in conventional manner. Once in sufficiently deep water, the storeys are tilted over so that they float on their side, and they are then joined together end-to-end. With tilting and rotating operations performed by suitable ballasting and unballasting of compartments in the storeys, the joining operations can all be performed on members at or near (just above or just below) the surface of the water. Once the storeys are assembled together, the entire structure may be towed on its side to a point of use, and then immersed so that it stands vertically on the sea bed.