河床沖淤演變是天然河川中常見的重要現象，但是當輸砂不平衡時會造成河道的淤積或刷深。臺灣近二十年來，因公共工程建設之蓬勃發展而對河床沖淤演變產生嚴重之影響，促使河床上下游輸砂不平衡的情況更為嚴重，進而造成本省跨河橋樑的橋基裸露，嚴重影響橋樑安全，所以橋基裸露是目前台灣跨河橋樑設計及其安全維修所面臨最急迫的問題之一。本研究期分為二年進行。第一年已完成現場調查、實驗分析及一維、二維數值模擬三方面技術，有系統地針對目前及未來本省可能廣用之橋基保護工法－柔性攔砂堰工法及蛇籠工法或其它相關工法在施作上已面臨或可能遭遇之相關問題進行研究探討，計畫成果可提供國內交通單位對柔性攔砂堰工法及蛇籠工法或其它相關工法之設計及施作時參採。本年度結合現場調查及實驗分析之技術，研究本省橋基保護工法最常遭受破壞之側向侵蝕及束縮沖刷等相關沖刷機制與其影響範圍，並研擬相關防治工法改善措施，將可提供國內交通單位對施作橋基沖刷防治工法時，如何有效抑制側向侵蝕及束縮沖刷，以提昇橋基沖刷防治工法成功率之建議。 Most rivers in Taiwan are severely degrading during last two decades due to fast growing in-stream sand mining and construction of water supply or diversion works. Consequently, piers or abutments at bridge crossings are frequently damaged during flood seasons. Suitable countermeasures for scour at bridge crossings is very crucial from the viewpoint of bridge foundation design, as well as for the concern of the operation of bridge maintenance system. The countermeasures at bridge crossings were studied in this project by employing field study, laboratory experiments and numerical simulations in a two-year period. In first year, the protection works were focused on the check dams and the gabion works. Check dams are effective to mitigate the river bed degradation problems, while the gabion protections are for reducing the local scours at bridge piers. A numerical model capable of simulating both the profiles at the water surface and at riverbed were developed in this project. The scouring process and the effect of energy dissipation downstream of the check dams were explored in terms of laboratory experiment. During this (second) year, the countermeasures for lateral erosion, contraction scour and exposed foundations are explored by employing field and experimental studies. Useful relationship for evaluating the scouring process and the guidance to mitigate the scour problems are also proposed. The comparisons of different countermeasures are summarized for the practical engineers. The countermeasures such as apron, sill , submerged vanes and spur dikes are investigated in further detail by experimental work. 研究期間：9001 ~ 9012
