IE37296B1 - Marine structures - Google Patents

Abstract

1430084 Marine structures REDPATH DORMAN LONG (NORTH SEA) Ltd 9 March 1973 [9 March 1972] 11086/72 Heading E1H A marine structure, comprises a foundation raft 10 formed as a caisson section and founded in a subaqueous bed 12, a tower structure 16, 18 .. 24 extending upwardly from the foundation raft 10 but terminating below the water surface, a wave-penetrable structure 28 disposed upon the tower structure and projecting through the water surface, and a superstructure 36 supported on said wave-penetrable structure. The foundation raft 10 is a hollow cylindrical concrete caisson which is floated into position with a pontoon (48) and controllably sunk by flooding its chambers 42. Cables (52) connecting the caisson 10 to the pontoon control positioning of the caisson during sinking. After founding of the caisson in the sea bed 12 by the technique described in Specification 1380586, the tower structure in the form of caisson sections 16, 18 .. 24 is built up using the method employed for the caisson 10. An inflation buffer (62) is inserted in the bores 14 of adjacent sections as they are brought together, inflation thereof ensuring accurate alignment. Thereafter the wave-penetrable structure 28 in the form of a concrete raft 30 supporting either wholly tubular steel columns 32, wholly lattice columns, or, as shown, part tubular and part lattice columns, is sunk onto the tower structure. Finally the superstructure 36 is hoisted onto the tops of the columns 32. The abutting surfaces of adjacent caisson sections are sealed by fiexible seals (66) and by injecting between the surface sealing compound (68) followed by grouting (72). This allows the shaft defined by the bores 14 in the caissons and a tube 40 supported by the structure 28, to be emptied of water whereby drilling of the subaqueous bed 12 through the shaft is possible. After construction of the structure the chambers 42 may be emptied of water and used as oil storage tanks. In a second embodiment, Fig. 9 (not shown) the tower structure is in the form of vertical steel columns (92), the wave-penetrable structure and superstructure being in the form of a legged platform positionable over the columns so that lowering of the legs causes the platform to lift clear of the water. [GB1430084A]