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A Study on Energy Dissipators and Local Scouring in Downstream of Check Dam
|關鍵字:||apron;護坦;water cushion;secondary dam;energy disspators;水墊;副壩;消能設施||出版社:||土木工程學系||摘要:||
本研究參酌既有堰壩投潭水流作用於河道渠床局部沖刷之相關研究，針對在堰壩鋪設護坦(apron)、水墊(water cushion)及副壩(secondary dam)等消能設施(energy dissipators)其下游沖刷現象探討之，藉由變換不同消能設施的佈置尺寸進行渠槽試驗，瞭解沖刷坑特性與不同消能設施之相對關係，以及其對下游床面之沖刷保護功效，並利用消能的觀念來剖析兩者相互間之關係。
According to the related research about the scouring effects of free over-fall will be used in this study. The situation will be discussed in steady flow by using different energy dissipators — apron, water cushion and secondary dam. Facilities, the protected effect and the comparative characteristics of scouring hole will be found (such as the max. depth, max. length, shape factor and volume) in downstream of the energy dissipators. The result would be determined by energy dissipating theory, which is the relations between the scale of dissipators and energy variation.
In view of energy disspators, the water cushion had the result of protection better than apron, because of the current hits mutually at the water pond. And the height factorβ=0.13 is the best. The situation of the secondary dam is the moving bed, therefore analysis of the scouring characteristic to make use energy variety of system. In both the rigid and soft energy disspators, the energy loss of scouring increased with slop. The degree of scouring depth and volume could be lowered effectively in rigid energy disspators. In water cushion, the average decreased rate of the scouring length about is 40 percent, and the scouring volume quantity decreases rate reaches 40 percent at least. Although, scouring length can't be decreased at apron disspators. The scour phenomenon be mollified to a downstream region for protective effects. Scouring is more serious between major and secondary dam if the distance is too short from both of them. Character factorα>1.56 is the suggested application. In this experiment condition, a simple formula is proposed for a relevant establishment. It is expected to be helpful in designs of energy disspators.
|Appears in Collections:||土木工程學系所|
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