Experimental Study on Reduction of Water Level behind a Caisson-Type Submerged Breakwater

Abstract

In this study, hydraulic model experiments were performed for four types of cross sections depending on the presence or absence of drainage channel of Caisson-Type submerged breakwaters, in which slit-upper-level and lower-level drainage channels are installed to lower the water level behind the submerged breakwaters. Additionally, based on the measured water level data, compared the changes in the average water level behind the submerged breakers for cases with or without drainage channels with a Solid-Caisson that has no slit-upper-level and lower drainage channels. Hence, in submerged breakwaters with a slit-upper-level drainage channel, the rear water level was reduced by 27.1 similar to 52.5% compared to that with Solid-Caisson, and it was reduced by 36.8 similar to 62.2% and 67.4 similar to 81.5%, in the case of lower-level drainage channel and the combined case, respectively. Therefore, lowering of water level behind the submerged breakwaters is better using the lower-level drainage channel than with the slit-upper-level drainage channel. Moreover, its effect is excellent when both are used. The Caisson-Type submerged breakwater proposed herein was found to be effective in reducing the rear water level and the flow in the openings, thereby securing the stability of the submerged breakwaters.