摘要 當波浪作用於海堤時，在堤面上發生溯升現象後，水體沿堤面迴流下刷， 再與入射之波浪產生交互作用，此一繁雜之機構常導致堤趾沖刷。本研究 係以動床模型試驗方式，探討堤面粗糙度對下刷水流強度與堤趾沖刷深度 之影響。經由實驗結果發現，粗糙堤面可削減堤面下刷水流強度、波浪反 射率及溯升高度；而原先光滑堤面堤前沖刷劇烈之L 型沖刷，堤面披覆粗 糙物後能使其堤前之最終沖刷深度及堤前沖刷坑距離減小；而原先屬於N 型之沖刷型態，其外海波浪節點處的沖刷深度則有隨著粗糙度提高而減少 之趨勢。此外，本研究由堤趾處水流強度之能譜分析可得，當堤面披覆粗 糙物後，堤趾處水流能譜主頻上之能量強度相較於光滑面有很明顯的減弱 ，而各粗糙面之間，其主頻上之能量強度則沒有顯著之差距。由於非線性 之效應，入射波浪與下刷水流交互作用時，水流能譜會產生次主頻之能量 。原先屬於L
... [Show full abstract] 型之沖刷型態當主頻上之能量受粗糙度之削減而變小，若其 次主頻之能量又與主頻相差不遠時，則其底床沖刷型態會有變成N 型之趨 勢。 ABSTRACT The variation of the toe scours profile by the surface roughness of a slope seawall was investigated experimentally in this research. The effects of the roughness on the wave characteristics, including the wave run-up on the slope, the flow in the down-rushing wave and the wave reflection from the wall, are also explored. Two types of the toe scours, named the L-type and N-type, were performed in the experiments. It was found from the experiments that the surface roughness was potentially reducing the intensity of the down- rushing flow and the wave run-up height, even the reflection of wave. The maximum depth of the scours as well as the scouring distance was thus reduced in the light of the surface roughness. The scouring depth and the values of the wave characteristics on the slope were descended obviously due to the surface roughness, from comparing with the smooth surface. However,these descended values were limitedly increased as the surface roughness became larger.
