本文主要以實驗的方式來觀測兩種不同擋水閘門之潰壩情形，分別是抽取式全潰壩型式與前傾潰倒式部分潰壩型式。前傾潰倒式閘門係根據前人文獻所統計之堰塞湖潰壩情況，及許多現地實際潰壩之比例來設計，觀測之結果發現兩種型式之潰壩情況、洪峰流速與碎波射流等流體情形之差距極大，將分別討論之。
本文利用電容式波高計與CCD觀測系統量測洪峰前緣流速與射流之流況，全潰壩試驗條件之壩內水深為30與40公分，壩內與外之水深比例分別為0、0.1、0.2與0.3，其中水深比0即代表下游為乾底床之情況，而部分潰壩之潰倒比則有1/10、1/5、1/3三種。CCD主要觀測範圍為閘門後下游270公分，可清楚觀察所有試驗條件下，洪峰行經下游底床之流況與射流情形，本試驗精確擷取各蘑菇狀射流產生之位置，並整理其與壩內與壩外之水深比及水深差之關係。另以洪峰之斷面平均流速與理論值比較，得到最接近之水深條件為r=0.1，並觀測出洪峰最大流速之位置即為蘑菇狀射流產生之位置。

This study uses the upward-moving gate (full dam-break) and the collapse-type gate (partial dam-break) to observe dam-break flow under two different conditions. We collect and analyze previos literatures to design the upward-moving and collapse-type gate respectively. The results revel that the dam-break process, wave front velocity, and generation of mushroom jet are very different due to dam-break type.The mechanism of different dam-break flow will be examined and discussed in this paper.
The capacitancy wave gages and CCD camera were used to catch the front velocity and dam-break process.The experimental upstream water depth is kept at 30cm and 40cm for full dam-break conditions, and the ratio of downstream and upstream water depth is 0, 0.1, 0.2, and0.3. Zero value is dry-bed case. The collapse ratio for partial dam-break is 1 / 10, 1 / 5, 1 / 3. The filed of view of camera is 270cm long starting from the gat. From the experiments, the bore movement and the jet generation through down-stream are observed. Further, the position of mushroom jet was identified accurately, and the relationships among generation position, ratio of water depth, and maximum velocity were also obtained.

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