DEVELOPMENT OF A WAVE DISSIPATING CAISSON ENHANCING SEAWATER EXCHANGE

The authors developed a wave dissipating caisson breakwater having a function of seawater exchange. Thiscaisson is a permeable slit caisson with a submerged vertical plate in a water chamber. This caisson generates aone-way flow from offshore to harbour. This flow enhances the exchange between contaminated harbour water andclean offshore water. Originally, this caisson was intended for calm sea. However, the function of seawaterexchange came to be required even for outer breakwaters at large harbours facing rough sea. In offshore areas thewidth of a caisson must be extended to resist against strong wave forces. Therefore, the caisson needs to havechannels piercing itself. In order to make clear its hydraulic characteristic, a two-dimensional hydraulic modelexperiment was carried out. It revealed that the channels never spoiled the seawater exchange, even in the conditionof smaller wave height.