拋石控制固床工趾部局部淘刷之研究

Riprap Protection in Controlling Local Scour at the Toe of Groundsill

黃炳錡(Ping-Chi Huang)

指導教授 ： 吳嘉俊

國立屏東科技大學/工學院/水土保持系所/碩士(2015年)

https://doi.org/10.6346/NPUST.2015.00151

摘要

局部淘刷常發生在橫向河工結構物的趾部，因此，本研究利用1:50縮尺之系列固床工模型，以三種流量、四種渠床坡降、三種拋石粒徑及兩種拋石保護長度進行水工實驗。研究結果顯示，固床工趾部拋石雖可以減輕趾部淘刷，但並不能完全消除投潭水流對溪床的衝擊，而淘刷規模及深度隨拋石保護長度的增長而減小。單寬淘刷體積與流量、拋石保護長度及渠床坡降有關，而淘刷之規模與淘刷坑總長度有隨拋石粒徑增大而增加之趨勢，因拋石間的間隙隨粒徑增大而增加，局部淘刷從界面開始發生，最後導致拋石與渠床間的落高隨粒徑增大而增加。本研究亦推導出無因次關係式，可用以估計拋石保護段長度和拋石粒徑的選擇。

關鍵字

拋石保護 ； 局部淘刷 ； 拋石長度 ； 拋石粒徑 ； 固床工

並列摘要

Local scour at the toe of groundsill is always inevitable. Therefore, an array of 1:50 scaled groundsill models was installed in a semi-circulating flume to study the effectiveness of protection lengths and riprap sizes. Three flow rates, four channel slopes, three riprap sizes, and two protection lengths were studied in the experiments. Results of this study show that riprap at the toe of a groundsill do not completely eliminate the impact force of plunge flow but it is capable of reducing the local scour at the toe. The scale and depth of scour reduces along with the increase of riprap protection length. The scour volume per unit width is related to flow rate, riprap protection length and channel gradient. Scale and total length of scour increases with riprap size due to wider gaps between riprap, which initiates local scour and creates higher elevation drops. Several dimensionless relationships were derived from this study to help estimate the geometry of local scour, which in turns helped select the riprap protection lengths and riprap sizes.

並列關鍵字

riprap protection ； local scour ； riprap length ； riprap size ； groundsills

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