Reflection From Hollow Armour Units : COPEDEC V, Cape Town, South Africa, 19-23 April 1999

Model investigations are carried out in using irregular and monochromatic waves synchronously acting on 2 sloping structures 1:n = 1:2 in order to demonstrate the advantages of a new designed structure composed from hollow armour units (“Hollow Cubes”) versus a conventional smooth sloping structure. The energy of the water level deflections in front of the hollow armour units piled up to form a stepped-face hollow seawall structure appears to be reduced by about -65% with refer-ence to a smooth structure. Reflection coefficients found for the new design are appreciably less than those found previously for 1-layer hollow revetment elements on a slope 1:n = 1:3,- particularly at the longer waves. The efficiency of such a structure can be explained (1) by the existence of the cavities in the armour blocks affecting the washing movement, (2) by causing energy losses at the inflow and outflow from the structure and (3) by wave splashing at the stepped structure