Publication: Hydraulic performance of dual road drainage system: a case study of butterworth–kulim expressway
Date
2021-10-01
Authors
Md Wakif, Sarah Alia
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Abstract
In urban areas, stormwater runoff is drained by both major and minor drainage systems; these two systems are linked by a linking element/linkage structure. Linking element determines and regulates the degree of flood damage on the road surface caused by surcharge flow. General references on this subject, on the other hand, often disregard the flow interactions behaviours within the linking elements, assuming that the inlet capacity is solely determined by the type of inlet and flow on the road networks. Though, the linking element should be designed in such a way that it can cope the volume of flow exchanges. In order to comprehend the complexities of the dynamics flow interactions between these two systems, this study was therefore conducted with the aim of elucidating the hydraulic behaviours of dual-drainage concept (surface-linkage-subsurface) under variousconditions. A 1:2 scaled drainage network physical model was built and assembled in the USM Integrated Research Space (RPS). A total of 82 tests were carried out on a rectangular testing platform, that is 6.30 m long and 2.0 m wide which drains a total area of 12.6 m2. The open drain has a width of 0.36 m and a depth of 0.10 m, connected by inlet openings located at every 1.5 m. Three types of modifications have been made to the laboratory system: (i) road drainage conditions, (ii) crossfalls and (iii) clogging factors. Six different inflow rates
ranging from 20.0 l/s to 70.0 l/s were tested for each type of modifications performed. Experimental results show that clogging condition reduces the inlet efficiency by 24.65% for a flatbed, 26.44% for a 2.5% slope, and 29.86% for a 4.0% slope. This shows that the clogging phenomenon restricts the quantity of flow intercepted at the intakes. During the experimentation, vorticities were observed in almost all test conditions with varied flow regimes: weir-like, transition, and full flow. In addition, CFD tool was used in order to approach the prediction made to the laboratory system. All simulations are the results of the 10-year return period design rainfall with an estimated peak discharge of approx. 40.0 l/s. The simulations were performed under non-clogging scenario and a flatbed condition. The simulation results were then validated with experimental analysis data, and a good agreement was achieved with relative error, RE less than 10.8%. Modifications to the laboratory system have been rendered by changing the diameter of VPDs from 10 cm to 15 cm, and SDP from 250 mm to 375 mm. Hence, by broadening the established dataset of the hydraulic interactions within the linking elements, the findings of this study will serve as a basic guideline and comparison for future research.