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標題: 滯洪池水文演算模式之研究
Study of Hydrological Routing Models for Detention Pond
作者: 洪耀明
Hong, Yao-Ming
關鍵字: detention pond
hydrological continuity equation
perturbation method
numerical method
unsteady flow
discharge formula
出版社: 土木工程學系
摘要: 台灣山區坡陡流急,夏秋之際多颱風豪雨,常帶來嚴重之坡地災害,同時地狹人稠,山坡地開發為必然之趨勢。但坡地開發常使地表覆蓋減少及不透水面積增加,導致雨水入滲率減低及地表逕流量增加;而開發過程中大量的土石方挖填工程,又經常造成大量泥沙流失。為避免因坡地開發造成基地與基地下游地區之洪水與泥砂災害,需運用滯洪沈砂池處理開發後所造成逕流量變大及泥砂產量增加等問題。因此,本研究旨在解析滯洪池之相關設計問題,提出設計滯洪池之方法。 本文首先收集各種常見計算滯洪容積之簡化模式,經由歸納與解析,訂定完整的比較與計算方法,並發現採用梯形入流及三角形出流歷線之滯洪容積最大,而出流若採用特殊設計,如洪水一開始便抽水之梯形出流時,可有效減少滯洪容積,使滯洪池所需體積變小;隨後考量洪水流經滯洪池之水理現象,並以適當的滯洪池入流歷線、滯洪體積與高程關係及出流口流量公式代入水文連續方程式,藉以數值方法求解,發展一套水理計算模式。同時,配合滯洪池定量流與變量流試驗驗證,證實本水理模式能夠描述洪水流經滯洪池之過程。經由試驗與數值方法計算,證明矩形孔口式出流口之滯洪容積均較矩形溢流口式為小;近似三角形入流歷線之退水時間除以洪峰到達時間比值越大,洪水遲滯時間越久;而梯形入流歷線中,洪峰持續時間越久會使洪水遲滯時間越長。 本研究之另一重點為提供一簡便但符合上述水理模式的計算方法,因此發展出圖解法及攝動解法。圖解法係經由歸納影響滯洪容積之相關因素,利用內插法原理建立相關圖表,經由查圖即可計算滯洪容積;攝動解法則採攝動法求出水文連續方程式之近似解,並以曲線擬合方式減少誤差;上述方法均經數值解之驗證相當吻合,希望能提供設計與應用之參考。
During the rainy season in Taiwan, mud slides and heavy floods often occur. Steep mountains and hillsides aid this dangerous phenomenon. The hillslope development is necessary to protect the growing population and the amount of livable land that is reducing. As land cover decreases and impervious area increases, the infiltration rate will reduce and add to the overland flow rate. An extremely high amount of sediment runoff comes from earthwork and bare land. Using detention facilities to control storm water runoff and the sediment outflow rate will avoid such adverse downstream effects. The purpose of this study is to analyze the detention pond design problem, and to propose a complete design method. This study collected many simplified models for a start. By using inductive reasoning and complete comparisons, a method for calculating the detention pond was concluded. Detention volume was found to be the biggest for trapezoidal inflow and triangular outflow. A special design, such as pumping water after runoff beginning, can reduce detention volume. Moreover, a numerical hydrological model is developed after considering the hydraulic phenomena of the detention pond in which the inflow/outflow hydrograph and the storage-elevation relationship is analyzed carefully. This hydrological model also uses many steady/unsteady flow tests of detention pond experiments to verify this model can make a good simulation. By utilizing numerical calculation and experimentation, the detention volume of the rectangular orifice was determined to be smaller than the volume of the rectangular spillway; therefore the large ratio between recession time dividing peak time of the triangular inflow, and longer peak inflow time duration of trapezoidal inflow makes the delay time longer. The second aim of this study was to propose easy calculation methods that can fit the above hydrological model. The graphical and perturbation methods were developed. After concluding the experiments and using the intersection method from established correlated graphs, the detention volume can be calculated. The perturbation method can calculate the approximate solutions for the hydrological continuity equation. The curve fitting method is adopted to reduce the error of calculation. The above methods were checked by the numerical solution, and can give some suggestions and applications for designers.
Appears in Collections:土木工程學系所



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