Breakwater for the Port of Dande, Angola:report on 3-D model testing of roundhead solution

This report deals with a 3-D model test study of the new breakwater at Porto de Dande, Angola. Part of the trunk and the roundhead were tested in 3-D for stability, overtopping and run-up under various sea conditions. The model testing of the breakwater in a 3-D basin was requested for some relevant aspects: 1. The structural and hydraulic response of the breakwater roundhead is a clearly spatial problem that cannot be examined in a flume; 2. Since the swell and wind waves main directions are not perpendicular to the trunk, 2-D tests are not sufficient to describe the response of the prototype. Indeed, in 2-D tests the direction of the waves is the same and normal to the trunk section; 3. Both swell and wind waves have directional spreading. 3-D tests are therefore necessary to reproduce the effect of wave spreading (directional spread). The main purpose of the 2-D tests was to provide a proper design for the trunk section. Modifications and adjustments could easily and economically be executed on this type of model in order to obtain a base for the 3-D model layout, in which adjustments would be much more expensive. Moreover, the response of the structure towards waves that are normal to it is (at least as far as the trunk is concerned) conservative if compared to oblique waves.