A New Symmetrical Unit for Breakwater Armour: First Tests

A new and symmetrical single layer armour unit, the crablock, has been designed in the UAE. One breakwater was reconstructed with crablock, but very limited testing had been performed. Just to become more acquainted with this new unit, precompetitive research at a university has been performed, which is the subject of this paper. Being a new armour unit, the placement was investigated first. Then physical model tests were performed in a wave flume to come up with results on stability and wave overtopping. Moreover, to determine the interlocking properties of armour units, pull tests were also conducted in this research. Those results are not part of this paper. Test results on stability showed that the longer waves affected the armour layer a little more, with larger movements and earlier displacements. Packing density as well as placement pattern showed no influence on wave overtopping. The overtopping tests gave larger overtopping than expected, which might be due to the fairly steep 1:30 foreshore.