For the economical construction of breakwaters in relatively deep sea ports, we have already proposed a jackettype breakwater with water chambers consisting of more than two vertical walls and one submerged horizontal plate. In the practical application of pile supported breakwaters of this kind, inclined support piles are usually adopted because of economical points of view. In such a situation, the shape of the water chamber may become trapezoidal because of inclinations of support piles. In addition to the rectangular-shaped water chamber, the trapezoidal-shaped water chamber was used for a jacket type breakwater. Hydraulics performance of the breakwaters, such as reductions of transmitted waves and water exchange abilities etc., is examined experimentally and theoretically.
