水工跌水結構物下游河床局部沖刷乃源於水流溢過結構物形成沖射水流，沖擊並起動底床泥沙顆粒，再由水流以懸浮載或推移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行為，造成壩體基礎裸露，因而危及結構物本身之穩定性及安全性。本研究分別以礫石及矽砂為渠床質，控制上游流量及下游尾水位高度，進行通氣寬頂堰之跌水沖刷試驗，以探討深淺尾水流況下，沖刷坑的沖刷機制與型態。利用理論分析配合實驗結果，建立沖刷坑特徵尺度(最大沖刷深度εｍ∞、最大堆積丘高度△∞、最大刷深位置Xm、沖刷坑長Xs和堰趾處刷深ε0)預測模式，可用於推估投潭水流對下游河床造成之局部沖刷情形，以期能進一步準確的預測與控制沖刷，達到保護水工結構物安全之目的。 When flowing over the drop structures, such as weirs or check dams, plunging jets usually cause severe scouring problems at the base of those structures. The formation and development of the scour hole will influence the stability and safety of those hydraulic structures. The scouring process for homogeneous gavel and sand beds by plunging jet at drops has been investigated in this study using experimental measurement. By using theory and experiment data, a prediction model is developed, and being used to predict the local scour at drops.
