下射式洩水閘門是一般堰壩和灌排渠道常使用的水工結構物，當水流經洩水閘門形成邊牆射流，沖擊底床泥沙顆粒，再由懸浮載或底床載方式將顆粒攜離沖刷坑至下游堆積。此對水工結構物下游河床之淘刷，造成水工結構物基礎裸露，危及結構物本身之穩定和安全性。一般下游底床會有護坦和尾檻的保護工設施，以防止底床的淘刷。本研究著重在一固定之流量及閘門開口下，分別比較邊牆射流、邊牆射流護坦保護工及邊牆射流尾檻保護工等三種不同的試驗模型在不同尾水深度時，其沖刷坑的沖刷機制與型態。本文並比較尾檻保護工和護坦保護工下游端之沖刷坑，進一步瞭解保護工與在水流作用下，下游河床之互制作用，以做為最佳保護水工結構物設計之參考。 When flowing throught the sluice gates, such as dams or irrigation channels, wall jets usually cause severe scouring problems at the downstream of those hydraulic structures. The formation and development of the scour hole will influence the stability and safety of structures. Aprons and sills are the common countermeasures for protecting the downstream riverbed. In the condition of homogeneous sand beds by wall jet, three models, which are the wall jet, the wall jet with apron, and the wall jet with end sill, are compared. By analyzing experimental data, a predicitive model is developed, and is used to explore the characteristics of local scour near those structures.
