不同堵塞情況之道路格柵進水口入流效應試驗研究

Abstract

臺北市位於臺北盆地之中央，四面環山地勢低窪，地理位置使其在夏季容易受到午後雷陣雨的影響，而全球氣候變化加劇的極端降雨天氣現象對城市排水系統構成了更大的挑戰。進水口作為道路和雨水下水道之間的關鍵連接部件，其在排水系統中的角色至關重要，且其堵塞狀態對排水效率有顯著影響。因此本研究聚焦於道路格柵進水口入流效應問題，特別是探討進水口在不同堵塞狀態下的入流效應。目的是深入理解城市集水區的水力特性及其地表排水系統，並為改善道路及進水口的設計提供實證基礎。 本研究參考現行道路排水設計規範及文獻相關經驗，選用尺寸為 65 cm x 45 cm（試驗尺寸：32.5 cm x 22.5 cm）之格柵進水口，並綜合考量實際試驗條件，搭建了一個實體比例為1:2的試驗模型平台，尺寸為長 7.69 m、寬 3.11 m、高 0.91 m。因試驗台為縮比模型，因此需進行模型相似率探討，確保模型在幾何形狀、福祿數上與實際情境一致，以保證試驗結果的準確性和可靠性。 試驗分為無堵塞、塑料袋遮蔽堵塞、落葉堵塞三種情境，依據臺北市各時雨量約30、65、100、130mm並進行因次轉換，轉換後流量分別為0.295 l/sec、0.602 l/sec、0.906 l/sec、1.235 l/sec，共 32 組試驗，透過模擬道路進水口入流試驗，量測了水深、水面寬、單位時間入流量等相關物理量，對各種情境下進水口入流能力的影響進行量化並加以探討。無堵塞試驗方面，得出進水口堰流係數為 1.8774，其結果略大於之前設計所給定之參考值，當入流量為 0.906 l/sec 時，已會跨越進水口，且其入流效應 E 隨著流量的變大而逐漸降低。塑料袋堵塞試驗分為矩形堵塞與斜向堵塞兩類，對於矩形堵塞由於其改變了進水口開口面積，因此入流效應相較於無堵塞有所下降，且隨著堵塞面積不斷增加而小幅度降低，而斜向堵塞對入流效應影響較大，同樣50%遮蔽率下，斜向堵塞入流效應比矩形堵塞低7.1%。落葉堵塞試驗則更真實模擬現實街道落葉移動至進水口全過程，並於進水口附近形成隨機堵塞，因此入流效應受到流量以及落葉隨機擺放位置影響，總體表現為葉片數越多，入流效應亦越低，此外，試驗還加入了對落葉堆疊面積和密度的分析，但因變量太多，並未精確建立其與入流效應之間關係。

Taipei City, located in the central Taipei Basin and surrounded by mountains, is prone to afternoon thunderstorms in summer due to its low-lying geography. Global climate change, with intensified extreme rainfall events, poses significant challenges to the city's drainage system. Inlet grates, key components connecting roads and stormwater sewers, play a crucial role in this system, and their blockage status significantly impacts drainage efficiency. This study focuses on the inflow effect of road grate inlets, particularly under different blockage conditions. The aim is to deepen the understanding of the hydraulic characteristics of urban catchment areas and surface drainage systems, providing empirical evidence for improving road and inlet design. This research, referencing current road drainage standards and literature experiences, utilizes a grate inlet of 65cm*45cm (experimental size: 32.5cm*22.5cm). Considering practical test conditions, a 1:2 scale physical model platform was constructed, measuring 7.69 meters in length, 2.11 meters in width, and 0.91 meters in height. To ensure accuracy and reliability of test results, the model's similarity ratio in terms of geometry and Froude number to real-life situations was discussed in Section 3.1, along with the conversion results of relevant physical quantities. The experimental design also detailed the methodology, including specifics of the experimental operation procedure and measurement items. The experiments were divided into three scenarios: clear water without blockage, plastic bag shield blockage, and leaf blockage. Assuming an upstream catchment area of 200 square meters, the converted flow rates were 0.295 l/sec, 0.602 l/sec, 0.906 l/sec, and 1.235 l/sec for 32 test groups. The experiments measured parameters such as water depth, surface width, and unit time inflow rate under various scenarios, quantifying and discussing the impact on the inlet's inflow capacity. In conclusion, this thesis evaluates the inflow effect of road drainage inlets in Taipei City's drainage system, providing references and suggestions for future urban drainage system designs, aiming to reduce the risk of urban flooding.