FIELD EXPERIMENTS ON A DUAL CYLINDRICAL CAISSON BREAKWATER

Abstract

A deepwater caisson breakwater as shown in Fig.l has been developed by the Ministry of Transport, Japan. The new breakwater is a composite breakwater with a cylindrical caisson named as dual cylinder caisson. The caisson has dual cylindrical walls and its outer cylinder has a perforation in the fore half of the upper portion, forming a wave chamber of a doughnut shape bounded by its inner impermeable cylinder. A series of laboratory experiments had been carried out at the Port and Harbour Research Institute from 1985 to 19881'3). According to the laboratory experiments, the caisson was found to have advantages of low reflection and high stability. The design method of the caisson was proposed through intensive laboratory studies in 1988. Prototype experiments of the dual cylindrical caisson breakwater have been conducted in order to verify its proposed design method against waves at Sakai Port by the Third District Port Construction Bureau, since 1989. A distinguished attempt in the field experiments was tried to measure the displacement of caisson as well as wave pressures during sliding due to high waves. This attempt was accomplished by a storm occurred on February 17, 1991.