Positioning of cubes on a breakwater slope

Recent research has shown that it is possible to use concrete cubes as a single armour layer on breakwaters. However, this is only possible in case a placing density of at least 70 % is achieved. In lab-tests it is no problem to place cubes with this density, however it is questionable if such a placing density can be achieved in prototype situations. A number of tests have been carried out in order to determine the requirements for dropping concrete blocks from a crane onto a breakwater slope. The conclusion is that at a waterdepth of approximately 10 times the block size this just can be achieved and that at smaller depth this placing density can be reached without too many difficulties. However, in all cases a good quality toe is vital for a high placing density. Blocks have to be placed at an angle of 45° with respect to the breakwater axis; blocks placed parallel to the breakwater axis will lead to large voids