不同型式滯洪池探討

Study on Different Types of Detention Pond

鄧學謙(Shiue-Chian Deng)

指導教授 ： 黃宏斌

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701428

摘要

本研究主要探討滯洪池設計之水文、水理特性。影響滯洪池設計有許多因子，其中洪峰流量、滯洪量與滯洪池型式等皆為相當重要的一環。本研究利用案例演算將合理化公式與三角形單位歷線法針對開發案進行滯洪量之推估，再使用定床水槽試驗，配合前人之研究成果分析探討，針對常見不同型式滯洪池，如在槽式、離槽式與抽排式滯洪池等各項特性，與在相同流量下滯洪量之差異，最後比較在槽式滯洪池試驗與現行水土保持手冊中常用的合理化公式之滯洪量與安全係數，探討其適用性。
本研究之水槽試驗單寬流量範圍為0.003~0.0177cms，在槽式使用圓形孔口之滯洪壩，其出流口為十孔水平排列，可調整出流孔數，孔口直徑為3公分，距離底部2公分，滯洪壩高30公分，滯洪池長4公尺，寬1公尺；離槽式滯洪池則以側流堰方式將水引入池內，側流堰長60公分，高度為1~4公分可調整，而滯洪池則長為2公尺、寬50公分，深為30公分；而抽排式則以離槽式為基礎，配合沉水式抽水馬達，馬力為1/6馬，抽水量0.000556cms。
由案例演算與試驗數據分析，本研究可得主要結果如下：
1.推估滯洪量時，大面積(50公頃)時合理化公式之滯洪量12315.6m^3較兩種三角形單位歷線法之6833.97m^3大約1.8倍較為保守，在開發面積小(2公頃與1公頃)時則合理化法會小於美國SCS法但大於修正三角單位歷線法。
2.在槽式滯洪池試驗使用孔口式出流較為有效率，試驗流量係數皆與水保手冊中使用之0.6相近，在相同總入流量為1.944m^3試驗中，後峰型式之降雨不僅洪水來臨較晚，滯洪量1.01m^3也較前鋒0.83m^3與中鋒0.95m^3大，較易造成淹水之災害。
3.離槽式滯洪池試驗中，側流堰越低則側流量越大，在試驗入流量為0.0097與0.011cms下，1公分高側流堰之側流量0.00195與0.00225cms較4公分高側流堰之側流量0.00046與0.0007cms多4.2與3.2倍，使用側流堰可有效控制超過設計高度之洪水流入滯洪池內。
4.抽排式滯洪池試驗中，利用抽水機抽水量為0.000556cms輔助，滯洪池體積為0.3m^3在側流堰高1~4公分流量0.0043~0.0177cms下，可使滯洪池滿水時間延長約1.5~2.5倍之時間，大幅增加滯洪量體。
5.在試驗之相同入流量與出流峰值下，在槽式與離槽式之滯洪量比值為0.54與0.8，離槽式皆小於在槽式，而在相同池底面積4m^3，試驗之相同入、出流量時離槽式之滯洪量與水深為在槽式之0.76倍，在相同滯洪容量時會有較佳之滯洪效果。

關鍵字

洪峰流量 ； 滯洪量 ； 在槽式滯洪池 ； 離槽式滯洪池 ； 抽排式滯洪池

並列摘要

The object of this study was to explore the hydrological and hydraulic characteristics of detention pond. The designation of detention pond may be affected by many factors, especially the relationship of the peak discharge, the detention volume and the forms of detention pond. After reviewing the paper, this study used the Rational Formula and the Triangular Unit Hydrograph method to estimate the detention volume of the development case, and with the flume experiment under fixed slope to analyze the difference at the same flow rate between the different types of the detention pond, such as the on-site detention pond, the off-site detention pond, and the pumped-type detention pond. Finally, comparing the detention volume and safety factor between the experiment in on-site detention pond and the Rational Formula which is commonly use in the Handbook of Soil and Water Conservation to discuss they’re applicability
The per unit width of discharge of the flume experiment in this study is between 0.003~0.0177cms. The on-site detention pond use the circular orifice of the detention dam, the outflow is 10 orifices with horizontal arrangement, and can adjust the number of outflow orifices, the orifice diameter is 3 cm, and 2 cm from the bottom of the bottom, the dam height 30 cm, the detention pond is 4 metes long and 1 cm wide. The off-site detention pond use the side weir which is 60 cm long and the height is 1 to 4 cm. The detention pond is 2 metes long and 50 cm wide and 30 cm height. The pumped-type detention pond is based on off-site detention pond with submergible motor pump, horsepower for the 1/6 horse, Pumping capacity is 0.000556cms.
After analyzing the example of calculus and experimental data, the principle results were as follows:
1.When estimating detention volume in large area(50hectares), the Rational Formula’s detention volume of 12315.6m^3 is more than two types of Triangular Unit Hydrograph’s 6833.97m^3,also more conservative ,and when the development area is small(2 and 1 hectares) ,the Rational Formula’s detention volume will be less than the US SCS Triangular Unit Hydrograph method but greater than the Modify Triangular Unit Hydrograph.
2.The on-site detention pond use the orifice outflow is more efficient, and the flow coefficients in the experiment are similar to those used in the Handbook of Soil and Water Conservation. In the experiment of same total inflow of 1.944 m^3, the posterior peak type rainfall is not only the flood coming later , the detention volume 1.01m^3 is also higher than the front peak type’s 0.93m^3 and the in the peak type’s 0.95m^3, which is more likely to cause flooded.
3.In the off-side detention pond, the lower the side weir height is, the higher the lateral flow is, and in the inflow of 0.0097and 0.011cms, the side flow of 1cm high side weir which is 0.00195 and 0.00225cms is more than 4 cm side weir’s 0.00046 and 0.0007cms about 4.2 and 3.2 times, while using side weir can effectively control the water level that will exceed the over water into the pond.
4.The experiment of pumped-type detention pond , using the pumping capacity of the pump is 0.000556cms ,in the volume of detention pond is 0.3m^3 ,the height of side weir is 1~4cm ,and the flow rate is 0.0043~0.0177cms , can delay the detention pond full of water time extended about 1.5 to 2.5 times the time , and a substantial increase in the amount of detention volume.
5.Under the same inflow and the same outflow peak value in experiment, the ratio of the detention volume between on-site and off-site detention pond is 0.54 and 0.8, and at the same pool bottom area of 4m^3 ,the same inflow and outflow of variable flow ,the off-site detention pond’s detention volume and water depth are 0.76 times of the on-site, and at the same volume the off-site detention capacity will be better.

並列關鍵字

peak discharge ； detention volume ； on-site detention pond ； off-side detention pond ； pumped-type detention pond

參考文獻

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