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  • 學位論文

消能砥墩於渠道中之水理現象探討

The Hydraulic Analysis of Stilling Baffle Pier in Canals

指導教授 : 張德鑫

摘要


台灣地區屬亞熱帶型氣候,而地形起伏相當大,在集水面積小及河流長度短之前提下,使得台灣大多數河川水流速度相當快,除了因流量大而常氾濫成災外,另外也常因渠床或護岸淘刷使得水工結構物損壞而造成破堤洪災。為降低此種災害發生,所以渠道中常採用消能砥墩之設計,以達到消能及降低流速之目的。 本研究依據現地實際流速、渠道坡度與混凝土的材料等相關資訊進行消能砥墩之水工模型試驗。利用試驗室水工渠槽,對不同排列情況之高度、間距、流量和渠道坡度等之混凝土消能砥墩,進行清水流之水理試驗,以探討在不同狀況下,於不同流速中其曼寧係數與水理特性之變化,並根據不同凸出高度及排列間距,可得其試驗室模型之曼寧係數值,經由因次分析即可轉換為現地場址之曼寧係數值,故本研究之試驗模型可做為後續相關設計及水理演算之參考。 根據實驗結果可知,當消能砥墩之凸出高度最高且排列緊密時,其曼寧係數值為最大。於本實驗中當消能砥墩之凸出高度5 cm及間距3 cm排列方式,其曼寧係數值為最大;當凸出高度5 cm及間距4 cm之排列時次之,再次之為間距5 cm及凸出高度為3cm的排列,其曼寧n值也隨間距不同而有不同之結果。 根據渠槽水工模型試驗成果,可得當混凝土消能砥墩凸出高度為3 cm及5 cm,其排列間距為3 cm、4cm及5cm時,其表面粗糙度介於0.180~0.833之間,其曼寧係數值範圍為0.015~0.033間,及模型之粗糙度與曼寧係數值之關係式為n=0.0033ln(fr)+0.0271,經過試驗模型轉換至原型之關係式為n=0.0066ln(fr)+0.0421,希冀本實驗結果可做為往後於渠流中設計消能砥墩之參考。

關鍵字

消能 渠道 水理現象

並列摘要


Taiwan has a subtropical climate and great topography. Due to small watersheds and short length of rivers, most of rivers have high velocity flow. Except for floods which are caused by large discharge, channel bottom and the dig brush of revetment destroy the construction and break levees. To reduce damage adopting stilling baffle pier design in canals can stilling and slower the flows. In this study, based on actual flow velocity, cannel slope and concrete materials such as hydraulic modeling experiment test. Use flume tests to analysis the concrete stilling baffle pier. Which has the different arrangement of the pier height, spacing, flow and cannel slope to execute the hydraulic model test of clean water. To investigate this in different situation, the change of Manning coefficient and physical parameters of water under different velocity of flow for future references. According to the test result, when stilling baffle pier is in its highest and sticks tightly together, Manning coefficient is the greatest. In this test, when stilling baffle pier projects in height 5cm and space 3cm, Manning coefficient is the greatest. Height 5cm, space 4cm is the second. Height 5cm, space 5cm is the third. Manning coefficient varies by height and space. According to the test result of canals models, it shows when concrete stilling baffle pier is in height 3cm and 5cm and distance is in 3cm, 4cm and 5cm, its roughness is between 0.180-0.833; Manning coefficient is between 0.015-0.033. After the regression analysis, the related formula of distance and roughness is fr =0.5221(D/W)- 0.0856, Manning coefficient is n = 0.0033ln(fr)+0.0271. This result can be used as a reference for stilling baffle pier in canals.

參考文獻


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