Characteristics of wave forces by waves were studied based on physical model test with regular waves. The ratio of obliquely incident wave forces to normal incident wave forces on unit length of vertical wall was related with various factors. A linear reduction of the mean force of obliquely incident waves was confirmed with an increase in the relative caisson length. Also the characteristics of reflection coefficients of diagonal waves are discussed.
Naturally, most ocean waves acting on vertical walls are obliquely incident, but just a few of studies [Goda (1985), FDINE (1990), Mallayachari (1995), Franco (1996), Hiraishi (1999)] have been undertaken on the interaction between diagonal waves and vertical walls for the time being. Therefore, engineering purposes permit us easy to appreciate why much attention should be given to the effects of diagonal standing waves on vertical walls, although there have already existed a great many papers on the interaction between normal incident waves and vertical walls. This being so, one of the China Key Projects for the Ninth Five-Years Economic Development Project, "Construction Techniques for Breakwaters in Deep Water" includes a subproject "The Interaction Between Diagonal Standing Waves and Breakwaters", which aims at investigating the characteristics of diagonal wave forces and reflecting waves for engineering applications through systematic physical model studies. This paper demonstrates the test results as far as the action of regular waves on breakwaters is concerned. EXPERIMENTAL CONDITIONS (1) The width of tested breakwater caisson is 18m and the water depth in front of the breakwater is 15m. (2) Two kinds of foundations were tested. The water depth on the higher foundation is 7.5m and that on the lower one is 11.25m. The top width of the two foundations is 34m, the width in front of caisson is 8m and their slope is 1:2.
