Calculation of expected sliding distance of breakwater caisson considering variability in wave direction

Abstract

In this study, the reliability design method developed by Shimosako and Takahashi in 2000 for calculation of the expected sliding distance of the caisson of a vertical breakwater is extended to take into account the variability in wave direction. The effects of directional spreading and the variation of deepwater principal wave direction about its design value were found to be minor compared with those of the obliquity of the deepwater design principal wave direction from the shore-normal direction. Reducing the significant wave height at the design site by 6% to correct the effect of wave refraction when using Godas model was found to be appropriate when the deepwater design principal wave direction was about 20 degrees. When we used the field data in a part of the east coast of Korea, taking the variability in wave direction into account reduced the expected sliding distance to about one third of that calculated without taking the variability in wave direction into account, and the required caisson width was reduced by about 10 % at the maximum.