| 研究生: |
康琮斌 Kang, Chung-Pin |
|---|---|
| 論文名稱: |
都市排水溝淤積及植生對水流影響之研究 Influence of Sedimentation and Vegetation on Water Flow of a City Drainage Canal |
| 指導教授: |
呂珍謀
LEU, JAN-MOU 賴泉基 LAI, CHAN-JI |
| 學位類別: |
碩士 Master |
| 系所名稱: |
工學院 - 水利及海洋工程學系碩士在職專班 Department of Hydraulic & Ocean Engineering (on the job class) |
| 論文出版年: | 2003 |
| 畢業學年度: | 91 |
| 語文別: | 中文 |
| 論文頁數: | 53 |
| 中文關鍵詞: | 表面流速 |
| 外文關鍵詞: | surface velocity |
| 相關次數: | 點閱:67 下載:2 |
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都市的渠溝大多為明渠定床渠道,渠道完成之後經過長時間水流及淤沙,渠道內往往生長一些大小不一的植物,這些淤沙及植生會增加水流阻力及減少通水面積。為了探討都市渠溝內淤積與植生對渠溝水流之影響,本研究到高雄市小港區大坪頂地區都市雨、污水匯集之營口路旁都市排水溝渠,研究長度由高松里自營前路起至松和路,總長約600公尺。研究分為A、B、C三段,A段自營前路起至便橋平台,B段為便橋平台接至松平街、C段自松平街至松和路,原設計斷面為鋼筋混凝土U型溝渠,A段斷面寬度3.42公尺、深度3.59公尺,B段、C段斷面寬度3.42公尺、深度3.48公尺。
在中低水期間經過二次現場調查及量測水流狀況,採用電磁式流速儀、大尺度表面流速影像量測法與浮標法,三種方法流速量測,並由渠道區分之A段、B段及C段加以討論,然後進行流量及水流阻力分析,分析結果可得結論歸納如下:
(一)依渠溝植生,產生阻礙水流之現象而相同水深減少通水流量之觀點來分析。觀測其平均水深配合原設計斷面條件,計算出該水深之設計流量,與推算之實測流量相互比較仍可得出部分結論,即在低水期間,渠溝流量平均減少66﹪〜92﹪,中水流量時,渠溝流量平均減少率約為3﹪〜47﹪。
(二)若依渠溝植生,造成阻力係數曼寧n值增大,由實測流量反推曼寧n值,得到結果,以低水期間而言,此時水深較小,底部污泥淤積及植生相對影響增大。就本研究都市排水溝渠道而言,糙度係數曼寧n值在A渠段平均增加為13.2倍,B渠段平均增加為2.9倍,C渠段平均增加為5.2倍,而中水期間,溝渠水量較為充沛,污泥淤積及植生之影響相對減少,糙度係數在A渠段增加為2倍,B渠段增加為1.6倍,C渠段增加為1.2倍。
(三)本研究渠段之植生,由於渠段A受底泥淤積之影響,淤積最為嚴重,所以影響最大,而因植生所產生之影響相對較小,對排水能力之減低效應最大,在低水時平均減少92.43%而在中水期間亦逹46.14%。B渠段次之,在低水期平均減少66.20%,而在中水期為31.17%。對渠段C之影響最小,在低水期為80.68%,而水深約40公分之中水期則僅有3.2%。除了因植生之種類與分佈狀況不一,產生不同結果的因素外。渠溝之水深及流速為影響底泥淤積及植生遲滯排水效應之最重要因子,水深及流速愈大,底泥淤積及植生之相對影響愈小,而且影響之遞減率相當快速。
Most of city drainage canals are made of concrete and lined with cement. Very often sediment will deposit in the channel and cause vegetations to grow at some extent. The sedimentation and vegetation increase the flow resistance and at the same time decrease the area of passage. How the sedimentation and vegetation could affect the flow capacity in the canal is assessed in this thesis.
We choose a city drainage canal beside the YinKo Road, in the area of DaPingTin in XiangGang District, Kaohsiung, as the object for present study. The length of the canal, from JiIngChen Rd. to SounHe Rd. in KouSoun Li, is about 600 meters and it is divided into there reaches, called A, B, and C. The original cross-section of the whole canal is concreted U-typed. The reach A is from IngChen Rd. to bridge terrace and it has a width of 3.42 meters and a depth of 3.59 meters. The B stage is from bridge terrace to SounPing Rd and the C stage is from SounPing Rd. to SounHe Rd. The width and depth of B and C reaches are 3.42 and 3.48 meters respectively.
In these reaches, we have conducted two flow measurements, one in low flow and the other one in high flow periods. Velocities are measured by using methods of current meter, image Velocimetry and drogue tracing. Canal flow capacity and Manning’s n resistance coefficient are estimated from these velocity distributions and are compared to the values of the original design. From these comparisons we have the following conclusions on the influences of canal vegetation and sedimentation:
1. The flow reduction percentage at low flow is higher than that in the high flow. In the study cases, a reduction of 66% to 92% at low flow and a reduction of 3% to 47% at high flow, on the average, are observed.
2. Manning’s n Roughness Coefficients increase dramatically in comparing to the original design value, particularly at low flow period. In the present studies, Values of Manning’s n increases by 13.2, 2.9 and 5.2 times for reaches A, B and C respectively at low flow period, and increases by 2, 1.6 and 1.2 times for reaches A, B and C respectively at high flow period.
3. Although the vegetation type and distribution changes the flow resistance and discharge capacity, the water depth and velocity in the canal are also the dominant factors. For two canals that both have the similar sedimentation and vegetation pattern, the influence of sedimentation and vegetation is less important for the canal that has larger water depth or higher flow velocity.
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