一般洩水閘門下游常會設置護坦及尾檻保護工，以防止下游底床之嚴重淘刷。本研究採用清水流渠槽試驗，配合下洩式閘門並搭配不同之護坦及尾檻，探討在不同護坦長度及尾檻形式下，其下游之水流型態及沖刷機制，並探討沖刷坑之特徵尺度(沖刷坑深度、護坦末端刷深、沖刷坑坡度等)。並於實驗過程中觀察護坦基礎淘空長度隨時間之變化及循環沖刷現象之發生。本研究採用二級尾檻進行挑流以改變出口水流條件，使高速水流挑離基礎處，達到削減能量及轉沖為淤之功效，且將實驗結果並與前人實驗之結果相互比較，期望能了解護坦長度與尾檻形式變化所造成之影響，以提供水工結構物設計之參考。 實驗結果顯示護坦長度越長，基礎處之刷深及沖刷坑之最大刷深越淺。並利用實驗結果繪出於不同尾檻高度及護坦長度之配置下其刷深之等高線圖，可供工程設計參考，並得知使用二級尾檻時則須搭配較長之上、下檻間距，才能得到良好之防沖效益。 In order to protect downstream riverbed of sluice gates, many energy dissipaters such as aprons and sills are installed on the channel bed. This study examines the effect of length of aprons and types of double sills on the local scour behaviors. The variation of head cutting length and cyclic scouring are observed and measured in the experiments. The characteristics of scouring holes caused by the wall jets with aprons and the wall jets with double sills are compared. The characteristics of local scour near structures is explored by analyzing the experimental data. According to experimental data, The protection of downstream riverbed is better when the length of aprons is longer ,. Double sills with long length of apron provide excellent protection for riverbed.
