Please use this identifier to cite or link to this item:
|標題:||The Flume Experiment on Scouring and Depositiog in Downstream of Non-deposition Check Dam
|關鍵字:||防砂壩;Check Dam;下游河道沖淤;護坦;水墊;副壩;消能設施;Scouring and Depositiog in Downstream;apron;water cushion;secondary dam;energy dissipation component||出版社:||水土保持學系||摘要:||
本試驗旨在探討防砂壩未淤積時，溢壩水流對下游河道泥砂的沖淤影響。在清水流條件下，由渠槽試驗分別觀測河道構建不同壩高和消能設施的防砂壩後，對下游河道沖淤變化之影響，以四種沖淤指標因子：全區泥砂運移比 、強沖刷區泥砂運移比 、弱沖刷區泥砂運移比 等判斷河道各個區域的沖淤情形。由試驗結果顯示，河道構建防砂壩後，其下游河床泥砂因沖刷而外移的單位長度泥砂流出量較無設壩時高，而且隨著壩高的增加，全區泥砂運移比 也跟著變大，下游河床的泥砂流出量隨之提高；強沖刷區泥砂運移比 與壩高成正比，顯示壩高越高，強沖刷區的沖刷越嚴重；弱沖刷區泥砂運移比 大致與壩高成反比，壩高越高，弱刷區反而呈現泥砂淤積的情形。此外，當河道構建不同消能設施的防砂壩後，依據壩體下游需要，設置護坦、水墊、副壩等消能設施予以消能，就三種消能設施對整個河道的全區泥砂運移比 影響，水墊設施的全區泥砂運移比 最小，所以水墊消能最能有效降低整個河道的沖刷，副壩次之，護坦再次之；就三種消能設施對強沖刷區泥砂運移比 的影響，副壩設施的強沖刷區泥砂運移比 最小，能夠有效降低強沖刷區的沖刷，所以副壩消能效果最好，護坦次之，水墊再次之；雖然消能設施減緩強沖刷區的沖刷，但是卻增加弱沖刷區泥砂比 ，加劇弱沖刷區的河床沖刷。
The experiment aims to explore the scouring and depositing influence overflow makes to downstream on a non-deposition check dam. Under clean water condition, using flume experiment to monitor check dam of different height and energy dissipation components and its influence of scouring and deposition change to downstream; and using four factors of scouring and deposition: whole area gravel sand transported ratio qs/qw, serious area gravel sand transported ratio qss/qw, weak area gravel sand transported ratio qls/qw to decide the scouring and deposition condition in every area of river course. From the result of experiment, it shows that building check dam will scour riverbed in downstream and transport unit-length gravel sand to downstream. The volume gravel sand transported after building check dam is much more than that before check dam built; and whole area sand transported ratio qs/qw increases with increasing dam height, and sand exited in downstream riverbed increases consequently. The direct proportion between qss/qw and dam height shows the higher the dam height is the more it scours in serious area; and conversely, the inverse proportion between dam height and qls/qw shows that it deposits in weak area while height of dam increases. Besides, after building check dam different of energy dissipation component in river course, apron, water cushion, secondary dam and so on will be set for energy dissipation according to downstream need of dam. Among the influence these three kinds of energy dissipation component make to qs/qw of the whole river course, qs/qw of water cushion is the smallest, downstream is for better, and apron is bad; thus cushion water can effectively reduces scouring in the whole river course for best. As far as influence of these three energy dissipation components make to, qss/qw of downstream shell is the smallest and can effectively reduce scouring in serious area; thus the effect of energy dissipation of downstream shell is the best, apron for better, and water cushion bad. Although energy dissipation components reduce scouring in serious area, it increases qls/qw in weak area, and improves riverbed scouring of weak area.
|Appears in Collections:||水土保持學系|
Show full item record
TAIR Related Article
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.