Stability of breakwater roundheads during construction

The presented study focussed on issues related to the hydraulic stability during the construction of rubble mound breakwaters. During construction the temporary roundheads differ from the roundheads in the final stage. Often a submerged uncompleted part of the breakwater is present in front of the section that reached its final crest elevation. This can occur because often the breakwater is being constructed with maritime-based equipment up to a certain elevation while the upper part of the breakwater is being constructed with land-based equipment. Three-dimensional physical model tests were performed to analyse the influence of the submerged part on the stability of the emerged part. The locations incurring the most damage clearly differ. Furthermore, for some combinations of water level, wave direction and structure geometry more damage was found for structures with a submerged part, although most combinations showed that the amount of displaced stones is generally lower for the structures with a submerged part.