渠道單階跌水與箱涵結構物之水理研究

Discussion of Hydrualic Characteristics of Canal Unit Step Overfall And Box Culvert Structure

吳玉輝(Yu-Hui Wu)

指導教授 ： 張德鑫

中原大學/工學院/土木工程學系/碩士(2007年)

https://doi.org/10.6840/cycu200700592

摘要

人工渠道可概分為灌溉、輸水、排水及灌排兩用等不同類型渠道，平坦地區之渠道並不需跌水工設計，但是在地形落差劇烈處常採用跌水工設計，其目的在減緩渠道水流流速及消能，以減少對渠底之沖蝕，並約束流心。
箱涵是一種束縮水流的水工構造物，箱涵入口之幾何形狀、坡度、斷面形狀與大小、箱涵內面粗糙度、箱涵長度與水深、上游水位及尾水狀況等，均可能影響箱涵之水理現象，箱涵如設計不當會造成淹水、造成生命及財產損失，因此設計上必須瞭解其水理特性。
本研究依據前人理論，並進行單階跌水後進入箱涵之模型實驗，以探討箱涵之水理情況，根據實驗結果可知：
（1） 跌水之消能效果，隨著入流量增加於跌水井中可觀查出效果更明顯，跌水後流經長箱涵時使得水流趨於穩定。
（2） 箱涵的設計與坡度、粗糙度、水深、箱涵長度（L）、管徑高度（D）等有關。本實驗結果，當流量增加則入口處潛没為下射閘流型箱涵，管內只有部分滿管且尾水無潛没，屬於第三類型箱涵流動型式。
本研究在模型實驗中量測出矩形箱涵與圓形箱涵流量與水位關係。在實驗中得出箱涵及涵管流況，其量測流速皆小於計算流速，可能主要原因在水力短箱涵情況下，水流尚未達到穩定流，而實驗中在大流量時無發生滿管現象。結果顯示，在入口跌水及水力短箱涵之情況下，並無法達到滿管流之情況；以及入口未潛沒時無法達到箱涵設計流量。

關鍵字

箱涵結構物 ； 單階跌水

並列摘要

Man-made channels can be roughly classified by function into irrigation, water transfer, drainage, and dual purpose of irrigation and drainage. Hydraulic drop design may not be required for channel running on a flat area; however, the hydraulic drop is usually designed for a channel is running on an area featuring drastic topographical falls to minimize erosion to the bottom of the channel while containing the core flow.
Box culvert is a structure to contract water flow, conditions including geometry, slope, and sectional shape and size of the box culvert inlet, roughness of the inner side of the box culvert, length of box culvert, depth of water, water level at the upper stream, and tail water affect the hydraulic behavior of the box culvert. These conditions can never be overlooked since a poor design of a box culvert may attract flooding and result in loss of life and property. full understanding of hydraulic characteristics of the box culvert is a must before designing one.
Based on those theories disclosed and performance of experimental design of a single level drop inlet to box culvert, this study explores into hydraulic conditions of a box culvert and its experimental results and has found that:
（1） It is observed that the energy dissipation effect after drop becomes more significant in the drop inlet as the inflow increases and the water flow tends to stabilize in a longer culvert pipe after the drop.
（2） Design of a box culvert is correlated to multiple factors including slope, roughness, water depth, and length (L) and pipe bore height (D) etc. Therefore, the results of the present experiment indicate that when the flow increases, the inlet is submerged, the box culvert becomes a down emission gate flow type; partially full pipe, pipe tail not submerged to become the third flow type of box culver.
This study achieved the measurement of correlation respectively between rectangular box culvert and circular box culvert flow vs. water level in a model experiment; the flow rates measured in the experiment are all slower than that as computed according to the box culvert and pipe culvert conditions in the experiment; the failure of the water flow to become a stabilized flow due to shorter box culvert may be the primary cause attributable to the slower flow rates measured; and the absence of full pipe was not observed in presence of larger flow. Findings indicate that it is impossible to achieve full pipe given with shorter inlet drop and hydraulic box culvert and that design flow for the box culvert was frustrated when the inlet is not submerged.

並列關鍵字

Canal Unit Step Overfall ； Box Culvert Structure

參考文獻

26. 陳建富（2002），「單階自由跌水之數值模擬」，中原大學土木工程研究所碩士論文。

25. 張德鑫、陳獻、賴俊程（2006），「預鑄生態塊石運用在灌溉及排水渠道之水理研究」。

18. David L. Yarnell, Floyd A. Nagler, and Woodward (1926), Flow of water throught culverts, University of Iowa,

5. Gill, M.A. (1979), “Hydraulica of Rectangular Vertical Drop Structures,” IAHR Vol.17, No.4, pp289-302.

6. Rajaratnam, N. and Muralidhar, D. (1968), “Characteristics of rectangular free overfall,” J. of Hyd. Res., IAHR, Vol.6, No.3, pp233-258.