傳統海堤與緩坡海堤之水理特性實驗研究

Abstract

本研究主要目的為探討緩坡海堤及傳統海堤上，入射波浪反射率、波浪溯升及波浪越波等水理特性，並就兩者做深入的比較，發現緩波海堤的水理特性方面比傳統海堤有較佳的抑制波浪效果。 由本文研究分析結果顯示，入射波浪反射率、波浪溯升均與波浪尖銳度成反比，與碎波相似參數呈正比，波浪越波則受堤前碎波位置影響，在相對堤頂高程小於約0.85時與相對堤頂高程成正比，另當大於0.85時則與相對堤頂高程成反比。另外，越波量與相對堤頂出水高之關係，本文迴歸結果得越波量約與相對堤頂出水高的二次方成正比。

The wave reflection, runup, and overtopping on a traditional seawall and on a mildly sloping seawall were examined by physical model tests. The results proved that the mildly sloping seawall has less wave reflection, runup and overtopping than the traditional seawall. Both wave reflection and runup on a seawall decrease as the incident wave steepness increases, but are proportional to the surf parameter. Wave breaking has a strong effect on wave overtopping. The position of wave breaking is far from the toe of a seawall when the incident wave steepness is large. Therefore, wave overtopping decreases when wave breaks at far distance from the toe of a seawall. The experimental results showed that the wave overtopping is proportional to the relative freeboard, which is defined a ratio of the freeboard to wave height, when its value is less than 0.85, and that wave overtopping decreases as the relative freeboard increases when its value is larger than 0.85. We also found that the wave overtopping is quadratically proportional to the relative freeboard.