STORMWATER DETENTION IN ROAD SHOULDER USING STORMPAV GREEN PAVEMENT SYSTEM

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 10, Issue 04, April 2019, pp Article ID: IJCIET_10_04_043 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed STORMWATER DETENTION IN ROAD SHOULDER USING STORMPAV GREEN PAVEMENT SYSTEM Zi Sheng Lui Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia Darrien Yau Seng Mah Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia Fang Yenn Teo Faculty of Engineering, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia ABSTRACT Computational Fluid Dynamics (CFD) is applied on StormPav Green Pavement system as combined road shoulder and stormwater detention structure. Applicability of the system is tested by simulating flow through the multiple chambers within StormPav system via road curb-opening inlet and outlet. The CFD simulations demonstrate flow patterns resulted from 5-minute 10-year ARI design rainfall. The distance of inlet and outlet is found to play a major role in the flow pattern in the StormPav system. The further the outlet away from the inlet, the more the CFD simulations show flow trajectory plots that suggest a water mixing quality. This finding is interestingly point to a self-cleansing ability in the StormPav system that suggests the flow pattern is favourable to flush out sediments carried by stormwater from roads. Keywords: CFD, On-Site Detention, SolidWorks, StormPav, Stormwater. Cite this Article: Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo, Stormwater Detention in Road Shoulder using Stormpav Green Pavement System, International Journal of Civil Engineering and Technology, 10(4), 2019, pp INTRODUCTION Stormwater detention structures are one of the human interventions to the urban hydrological processes to reduce the volume of running water in the built environment [1-2]. Pertaining to editor@iaeme.com

2 Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo urban road drainage, surface runoffs generated from road surfaces are directed to stormwater detention structures, in which parts of the running waters are trapped and stored within over the course of storm events. Some of the examples are infiltration trench, pervious road pavement, vegetative swale and rain garden that are adjacent to roads (see Figure 1). These are hence the control-at-source approaches [3] so that running water could be controlled near its source and less water being discharged to water ways. (a) (b) (c) (d) Figure 1 Stormwater detention for urban road drainage, (a) Infiltration trench, (b) Pervious road pavement, (c) Vegetative swale and (d) Rain garden. Infiltration trench in the figure is filled with aggregates, in which the voids between the small stones could store stormwater. Pervious road pavement is laid with a layer of pavers that the joints between them allow water to infiltrate to the underlying layer. Vegetative swale and rain garden, on the other hand, are filled with porous media that is able to absorb stormwater. In a study in Malaysia [4], a function of stormwater detention is integrated with road curb system as depicted in Figure 2. The researchers present a way to capture the road runoff within a manmade chamber that connects to the road curb-road shoulder structure and stormwater inlet. Otherwise, running waters from the road are normally discharged to urban drains directly. Extending from the above-mentioned project, this paper is intended to improve the structure further. We are introducing StormPav Green Pavement System as an alternative construction method to create the stormwater detention chamber [5] editor@iaeme.com

3 Stormwater Detention in Road Shoulder using Stormpav Green Pavement System Figure 2 Existing road drainage system and proposed stormwater detention [4] 2. STORMPAV GREEN PAVEMENT SYSTEM StormPav consists of precast concrete pieces which a hollow cylinder piece is sandwiched between two concrete plates to make up a single modular unit. The units are made of G50 concrete specially designed to withstand up to 10 tons of loading [6]. The hexagonal plate is used as top and bottom covers, in which the former functions as road pavement with service inlet to drain stormwater; and the latter functions as a base with service inlet to allow infiltration. The surface area on a single plate is m 2 with a service inlet of 0.04m in diameter. Height of each plate is 0.075m. The hollow cylinder functions as storage chamber to hold water at a capacity of 0.19m 3 /m 2 of pavement area. Generally, stormwater permeates the road pavement to reach storage chambers placed underneath. Each cylinder has an inner diameter of 0.28m and a thickness of wall of 0.06m. Height of each cylinder is 0.3m. A pilot scale of using StormPav units as road is reported in [7]. These units are interlocked to form a 11m x 4m low volume road in the suburb of Kuching city, Sarawak. The pilot project demonstrates successful implementation of StormPav as multipurpose road, namely pavement at the top layer to support passing of vehicles, stormwater detention in the middle layer replacing the use of aggregates in the conventional road making, and lastly raft foundation at the bottom layer that could have lessen the compaction works a conventional road should need. Other than road, it could be adopted as road shoulder. The concept is presented in Figure 3, an enhancement to those in Figure 2. StormPav plates at the top layer could be used as footpath. Its hollow cylinders in the middle layer could be the tool to capture road runoff when the road-curb and stormwater inlet are merged with StormPav. Moreover, the StormPav units could be assembled on site that allows faster construction than conventionally having concrete mixtures cast in-situ. 3. MODELLING APPROACH A typical road shoulder in a housing estate is taken as case study. Referring to Figure 4, the maximum width of road shoulder is 1.5m. There is no limit to the length of the road shoulder. However, a length of road shoulder is needed to demonstrate the usefulness of stormwater detention being incorporated in it editor@iaeme.com

4 Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo Figure 3 StormPav units as road shoulder A length of 6.5m is the shortest length, usually between two residential houses. As such, 6.5m x 1.5m road shoulder is engaged as a single unit of stormwater detention for flow pattern visualization in the next section. Such a size allows a stormwater detention capacity of 1.85m 3. Figure 4 Case study The associated road and road shoulder contribute to a catchment size of 6.5m x 7.5m. Running water generated from the catchment is directed to a curb-opening inlet before entering the StormPav road shoulder. Water leaves the StormPav road shoulder via outlet connected to the adjacent urban drain. Appropriate sizing and placement of inlet and outlet are crucial to ensure proper functioning of the stormwater detention [10]. Too small may cause overflow and editor@iaeme.com

5 Stormwater Detention in Road Shoulder using Stormpav Green Pavement System congestion of flow, while too big may cause rapid disposal of stormwater to compromise its detention functionality. In this project, the component parts consist of road curb and road shoulder to form a rectangular tank and StormPav units are arranged within the tank. As such, it forms a complex system with multiple chambers due to the empty spaces in the cylinders and also between the cylinders. A CFD model is needed to represent the complex system and SolidWorks is the tool used to resemble the 3D StormPav modular units as well as the curb-opening inlet and outlet. SolidWorks Flow Simulation that comes along with the SolidWorks 2018 package is used to simulate flow through the StormPav system. Three designs are explored here (see Figure 5). Standard curb opening of 300mm as the curb opening is adopted in all the three designs at the centerline of the StormPav system. The difference lies in the placement of outlet. Design 1 has a 10mm outlet placed in a straight line as the curb opening. This arrangement is common in conventional drainage inlet and outlet designs so that the stormwater could be discharged rapidly. Because Design 1 has one inlet and one outlet setting, Designs 2 and 3 follow the same number and size of inlet and outlet for meaningful comparison. The outlet of Design 2 is moved to the edge of the StormPav system, about 3m from the centerline. The outlet of Design 3, on the other hand, is put between the centerline and edge, about 1.7m from the centerline. These outlet arrangements are made to explore the flow patterns compared to the common inlet/out setting in Design 1. Figure 5 Illustrations of (a) Design 1, (b) Design 2 and (c) Design 3 4. RESULTS AND DISCUSSION Replicating the models done by [4], taking the worst-case scenario, 210 mm/hr of rainfall intensity based on 5-minute 10-year ARI design rainfall is modelled on the about 50 m 2 of road editor@iaeme.com

6 Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo and road shoulder surfaces. An amount of 0.85 m 3 of runoff is calculated with a peak discharge of m 3 /s from the catchments to enter the StormPav system. The amount of runoff is lower than the maximum capacity of the water storage when directed to StormPav system and is expected to be fully captured. Table 1 shows that the velocities for the inlet and outlet are maintained similar throughout the three designs. The computed flow patterns between inlet and outlet are depicted in the following Figures 6 to 8. Table 1 Computed pressure and velocity at inlet and outlet of StormPav road shoulder Design Inlet Outlet Pressure (Pa) Velocity (m/s) Pressure (Pa) Velocity (m/s) The followed plots are started with a plan view of the StormPav system at the top with velocity contour across the system. Three cross sections are highlighted, and the locations are specifically related to the position of outlet for Designs 1 to 3. Cross-section 1A Cross-section 1B Cross-section 1C Figure 6 Design 1 subjected to 5-min 10-year ARI design rainfall editor@iaeme.com

7 Stormwater Detention in Road Shoulder using Stormpav Green Pavement System Design 1 shows dense variations of velocity at the centerline line of the StormPav system, while less velocity towards the left and right edges. Pressure is maintained the same across the system. The flow pattern is imbalance, in which flow is found concentrated at the centerline region. Moving to Design 2, with the outlet being located the furthest left from the curb opening, the computed flow pattern shows stark contrast with Design 1. Velocities are the highest at the vicinity of the inlet and outlet. However, dense variations of velocity are found in the spaces from the centerline to the left edge. It is obvious on the plan view; and the densities of velocity are reflected in the plots of Cross-sections 2A to 2C. Pressure is maintained the same across the system. Cross-section 2A Cross-section 2B Cross-section 2C Figure 7 Design 2 subjected to 5-min 10-year ARI design rainfall Design 3 shares similar flow pattern as of Design 2, but on a lesser scale. Dense variations of velocity are found between the inlet and outlet. However, velocity is found less than Design 2 at the left edge. Pressure is maintained the same across the system. Velocity plots are transformed to flow trajectory plots presented in Figure 9. Generally, Designs 2 and 3 have demonstrated a better distribution of flow within the StormPav system than that of Design 1. Flow trajectory shows how the water passing through the tight spaces of editor@iaeme.com

8 Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo StormPav modular units. It allows the research team to decipher further the performance of each of the design. Cross-section 3A Cross-section 3B Cross-section 3C Figure 8 Design 3 subjected to 5-min 10-year ARI design rainfall The velocity plots show little velocity within the hollow cylinders as water flows more outside the hollow cylinders. The flow trajectory plots give a better explanation, particularly on Design 2. All spaces between centerline to left edge is found more fluent than the other two designs. As such, Design 2 has the best distributed flow. While the StormPav system is intended as temporary stormwater storage, the research team would appreciate the distributed flow more pertaining to the nature of stormwater from roads usually is laced with sediments. The stagnation portion at the left and right edges demonstrated in Designs 1 and 3 could encourage sedimentation of what brought by the stormwater. In contrary, the flow trajectory of Design 2 shows the characteristics of good mixing in all corners half of the StormPav system. It could be of use to allow self-cleansing among the modular units and lengthen the life cycle of StormPav system from sedimentation. Another point worth mentioning, by adding another outlet to the right edge of Design 2, the flow trajectory on the left could be duplicated to the right. This is possible because the system is symmetrical editor@iaeme.com

9 Stormwater Detention in Road Shoulder using Stormpav Green Pavement System 5. CONCLUSION Incorporating StormPav Green Pavement System as road shoulder with an added function of stormwater detention is possible. CFD simulation of the StormPav system is found to provide informative flow visualization. The most interesting finding through the flow visualization technique reveals another unexpected function that by moving apart the distance between the stormwater inlet and outlet, a more distributed flow could be achieved. The distributed flow pattern suggests a self-cleansing ability within the StormPav system to alleviate built up of sediments carried by stormwater from roads. Design 2 with an inlet at the centerline and possibly two outlets at the furthest left and right edges of the StormPav system suggests the best distributed flow that could have maintained the above much desired characteristics for stormwater detention structure. (a) (b) (c) Figure 9 Flow Trajectories within (a) Design 1, (b) Design 2 and (c) Design editor@iaeme.com

10 Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo ACKNOWLEDGEMENT The authors thank the financial support from Exploratory Research Grant Scheme ERGS/TK03(02)/1009/2013(06), rendered by the Malaysian Ministry of Education. REFERENCES [1] Lin, J.-Y., Chen, C.-F., Ho, C.-C. Evaluating the effectiveness of green roads for runoff control. Journal of Sustainable Water in the Built Environment, 4(2), 2018, pp , DOI: /JSWBAY [2] McPhillips, L. E., Matsler, A. M. Temporal evolution of green stormwater infrastructure strategies in three US cities. Front. Built Environ., 4(26), 2018, DOI: /fbuil [3] Blecken, G.-T., Hunt III, W. F., Mohammed Al-Rubaei, A., Viklander, M., Lord W. G. Stormwater control measure (SCM) maintenance considerations to ensure designed functionality. Urban Water Journal, 14(3), 2017, pp , DOI: / X [4] Mah, D. Y. S., Ng, T. C., Putuhena, F. J. Integrating infiltration facility to urban road drainage. International Journal of Engineering and Technology, 7(3.18), 2018, pp , DOI: /ijet.v7i [5] Mannan, M. A., Bateni, N., Teo, D. C. L., Mah, Y. S., Putuhena, F. J., Ng, C. K., Bustami, R. A., Ibrahim, W. H. W., Lee, C. L. F., Lim, H. L. StormPav, System and Method of Green Pavement, Application Number PI Kuala Lumpur: MyIPO, [6] Mah, D. Y. S. Potential of Road Subsurface On-Site Stormwater Detention System. Kota Samarahan: UNIMAS Publisher, 2016, ISBN [7] Mah, D. Y. S., Mannan, M. A., Ibrahim, W. H. W. Pilot study of StormPav Green Pavement System. International Journal of Research in Engineering and Advanced Technology, 6(5), 2018, pp [8] Ngu, J. O. K., Mah, D. Y. S., Bong, C. H. J. Flow characteristics of individual lot stormwater detention. Water Practice and Technology, 11(4), 2016, pp , DOI: /wpt [9] Liow, C. V., Mah, D. Y. S., bin Mohd Arif Zainol, M. R. R. Modelling of stormwater detention under urban road for conveyance and storage. International Journal of Research in Engineering and Advanced Technology, 6(5), 2018, pp [10] Senior, M., Scheckenberger, R., Bishop, B. Modeling catchbasins and inlets in SWMM. Journal of Water Management Modeling, 26, 2018, C