Evaluation of surface infiltration performance of permeable pavements

Evaluation of moisture migration characteristics of permeable asphalt pavement: Field research

To analyse the moisture migration characteristics of permeable asphalt pavement (PAP) in engineering applications, a PAP sample with a length and width of 163 m and 12 m, respectively, was designed and paved. The pavement comprised PAC-13, PAC-20, ATPB-25, graded grade, and sandy soil subgrade from the top to the bottom. Moisture sensors were set at 4 cm, 10 cm, 28 cm, 46 cm, 61 cm, 76 cm, 101 cm, 126 cm, 176 cm, and 226 cm below the pavement surface to ascertain the volumetric water content during and after rainfall. This data were used to analyse the changes in the infiltration depth, infiltration rate, water level height, and water emptying time of the PAP under different rainfall conditions. The results show that the prediction model for the infiltration depth can be established using the water adhesion rate and rainfall. According to the moisture changes of the pavement layer after rainfall, the water migration process of the PAP can be divided into the drying stage, wetting stage, emptying stage, and recovery drying stage. The relationship between the average rainfall intensity and the average infiltration rate is a linear function. The water emptying time at the depth of 0-10 cm is less than 20 h, and the emptying time at a depth below 10 cm is less than 6 d.

The control efficiency and mechanism of heavy metals by permeable pavement system in runoff based on enhanced infiltration materials

As one of the commonly used stormwater management measures, permeable pavement system (PPS) played a prominent role in controlling runoff pollution and alleviating urban waterlogging. In this study, new enhanced infiltration materials (construction waste brick, coal gangue, activated carbon, multi-walled carbon nanotube, multi-layer graphene) were applied in PPS and the control efficiency and mechanism of typical heavy metals (HMs, Mn²⁺, Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Ni²⁺) was investigated in runoff. Furthermore, the influences of different rainfall intensities and antecedent dry periods on HMs removal by PPS were evaluated. The results showed that all PPS with enhanced infiltration materials have little leaching effect on HMs (＜3 μg/L). All the selected enhanced infiltration materials meet the requirements of PPS. The concentration of HMs in the effluent of PPS dropped sharply first, followed rebounded and then maintained at a stable range. Activated carbon PPS (AC), Multi-walled carbon nanotube PPS (MCN), and Multi-layer graphene PPS (MG) could significantly improve the control effect of PPS on nearly all selected HMs. The average removal rates of AC, MCN and MG for six HMs were 75.48%-99.35%, 81.30%-97.59%, and 73.03%-99.33%, respectively. Compared with Traditional PPS (TR), the effluent concentrations of HMs in construction waste brick PPS (CW) and coal gangue PPS (CG) were relatively higher and unstable. AC, CN and MG could adapt to different rainfall conditions and the maximum removal rates of most HMs exceed to 99%. With antecedent dry periods increased, the control effect of HMs was significantly improved. The influences of the antecedent drying period on HMs removal followed as: CW＞CG＞TR＞MG＞CN＞AC. This study provided novel methods to eliminating HMs in runoff and provides implications for the design of PPS.

An experimental and modeling study on the penetration of spilled oil into thawing frozen soil

Oil spills are significant environmental accidents that have significant impacts on environmental and ecological health. Spill pollution in the cold regions may pose a particular challenge. To achieve a fast response, the oil transport mode such as penetration should be well understood. In this study, the oil penetration behavior in thawing frozen soil at different temperatures and water contents were investigated. The results showed the penetration behavior of spilled oil in the thawing frozen soil and the influence of salinity level. The modified Green-Ampt model could simulate the penetration process well especially with high water content, relatively cold temperature, and slow thawing rate. This study reveals the new features of oil penetration behavior and distribution patterns in thawing frozen soil under different conditions. Hence, it is of significant importance to support the rapid response measures and reduce the contamination of oil spill accidents in cold regions.

Permeable Pavements for Flood Control in Australia: Spatial Analysis of Pavement Design Considering Rainfall and Soil Data

Permeable pavements allow rainfall and surface runoff to infiltrate through their surface, and this reduces urban flooding by increasing water management efficiency. The design of permeable pavements depends heavily on rainfall and soil conditions for a particular area. This study investigates the required base course thickness in different areas across Australia that can effectively reduce flood intensities. A detailed hydraulic analysis was conducted, considering the pavement materials, soil characteristics and rainfall intensities across Australia. The research also developed a relationship between base course thickness, rainfall intensity and soil classification, which can facilitate reasonable predictions of required design thickness for any location. The results showed a strong relationship between soil characteristics and pavement thickness, with clay soils requiring increased pavement thickness correlated with rainfall intensity. A spatial analysis was conducted, producing a tool for initial screening on the design requirements, before proceeding with a detailed design.

Comparison between different infiltration models to describe the infiltration of permeable brick pavement system via a laboratory-scale experiment

The permeable brick pavement system (PBPs) is one of a widely used low impact development (LID) measures to alleviate runoff volume and pollution caused by urbanization. The performance of PBPs on decreasing runoff volume is decided by its permeability, and it was general described by hydraulic conductivity based on Darcy's law. But there is large error when using hydraulic conductivity to describe the infiltration of PBPs, and which infiltration process is not following Darcy's law, so it is important to find more accurate infiltration models to describe the infiltration of PBPs. The Horton, Philip, Green-Ampt, and Kostiakov infiltration models were selected to find an optimal model to investigate infiltration performance of PBPs via a laboratory-scale experiment, and the maximum absolute error (MAE), Bias, and coefficient of determination (R²) were selected to evaluate the models' errors via fitting with experiment data. The results showed that the fitting accuracy of Kostiakov, Philip, and Green-Ampt models was significantly affected by the monitoring area and hydraulic gradients. Meanwhile, Horton model fitted well (MAE = 0.25-0.32 cm/h, Bias = 0.07-0.11 cm/h, and R² = 0.98-0.99) with the experiment data, and the parameters of the Horton model often can be achieved by monitoring, such as the maximum infiltration rate and the stable infiltration rate. Therefore, the Horton model is an optimal model to describe the infiltration performance of PBPs, which can also be adopted to evaluate hydrological characterization of PBPs.

Improved approach for evaluating saturated surface infiltration capacity of interlocking-block permeable pavements

Different infiltration tests of permeable pavements provide different measurements of the infiltration capacity. These measurements often do not represent the fundamental flow properties, and hence cannot be directly compared. This presents an undesirable obstacle to the sharing of experience and to obtaining a better understanding of the infiltration performances of different permeable pavements. This problem is especially acute in the case of interlocking-block permeable pavements (IBPPs), owing to the presence of joints and the different sizes, shapes, and laying patterns of paving blocks. To overcome this problem, the present study proposed a new approach for evaluating the infiltration capacity of an IBPP while retaining the same measuring devices in use today. This approach makes use of a finite-volume computational fluid dynamic method to develop a simulation model for an infiltration test. Once calibrated to define the hydraulic parameters of the IBPP being tested, the model can be applied to calculate the saturated infiltration capacity of the IBPP under actual rainfall conditions. The model also permits the calculation of a conventional infiltration capacity measurement, such as the average infiltration rate in mm/h as measured by a particular infiltration test, or the time required to drain the tested water depth. Thus, the proposed approach provides a meaningful common basis for comparing the infiltration capacities of different permeable pavements, including porous asphalt, pervious concrete, and IBPPs.

A Systematic Review of the Hydrological, Environmental and Durability Performance of Permeable Pavement Systems

Due to urbanization, large portions of vegetated territory have been replaced by waterproof surfaces. The consequences are greater outflows, lower infiltration, and lower evapotranspiration. Pavement systems made with permeable surfaces allow the infiltration of water, ensuring reduction of runoff volume. In this paper, the methods of analysis of the hydrological and environmental performance of the pavement systems are reviewed in the context of urban drainage and regarding their durability. The purpose is to present an overview of the studies published during the last decade in the field. The Pubmed and Web Science Core Collection electronic databases were used to conduct the scientific literature survey. This generated 1238 papers, of which only 17 met the criteria and were included and discussed in this review. The evidence drawn from the knowledge on which the document is based provides useful critical interpretations of existing studies to progress the current understanding on hydrological performance and environment impacts in terms of conventional pollutant removal efficiency and the current permeable pavement systems.

Assessment of clogging of permeable pavements by measuring change in permeability

Permeable pavements are a common solution for stormwater management. Porous areas in the pavements allow water to percolate into the subsurface layers, reducing surface runoff. However, it is common for substances to clog the voids, decreasing the porous area and permeability of the pavement system. This study examined the change in permeability over time at a site with two permeable pavement systems, the JW Eco-technology (JW) and pervious concrete (PC). Square frames SF-4 and SF-9 were used to perform falling-head and constant-head permeability tests, respectively. Results show that JW had a similar permeability across the test locations, 6.27-7.64 cm/s when using SF-4, and 0.95-1.00 cm/s when using SF-9. While the permeability at the center locations of PC showed no significant loss of permeability, there was a significant reduction of permeability on the corner and edge areas, where permeability ranged 0.28-1.73 cm/s using SF-4 and 0.14-0.36 cm/s using SF-9, suggesting the occurrence of clogging over time at corner locations. Furthermore, the measured values highlighted the measurement variability in permeability between the falling-head based method and the constant-head method, with measurements from SF-4 being approximately 6.2-7.6 and 2.0-5.7 times higher than those from SF-9 on JW and PC, respectively. In addition, as no current literature quantifies the relationship between permeability and extent of clogging for the JW Eco-technology pavement, evaluation of the proportionate change in permeability with respect to voids, or individual aqueducts, of JW pavement were investigated. While not a 1:1 linear relationship, data indicate that the permeability increased with an increase in non-blocked aqueducts. The JW pavement maintained more than 50% of its capacity when half of the aqueducts were fully blocked. Even when only one aqueduct was clear from clogging, the system had 36% (SF-4) and 19% (SF-9) of maximum permeable capacity.

Evaluation of Permeable Brick Pavement on the Reduction of Stormwater Runoff Using a Coupled Hydrological Model

In several cities, permeable brick pavement (PBP) plays a key role in stormwater management. Although various hydrological models can be used to analyze the mitigation efficiency of PBP on rainfall runoff, the majority do not consider the effect of multi-layered pavement on infiltration in urban areas. Therefore, we developed a coupled model to evaluate the potential effect of PBP in reducing stormwater runoff at a watershed scale. Specifically, we compared the hydrological responses (outflow and overflow) of three different PBP scenarios. The potential effects of PBP on peak flow (PF), total volume (TV), and overflow volume (OV) were investigated for 20 design rainstorms with different return periods and durations. Our results indicate that an increase in PBP ratio reduces both PF (4.2–13.5%) and TV (4.2–10.5%) at the outfall as well as the OV (15.4–30.6%) across networks. The mitigation effect of PBP on OV is linearly correlated to storm return period and duration, but the effects on PF and TV are inversely correlated to storm duration. These results provide insight on the effects of infiltration-based infrastructure on urban flooding.

Urban stormwater characterization, control, and treatment

This review summarizes over 280 studies published in 2019 related to the characterization, control, and management of urban stormwater runoff. A summary of quantity and quality concerns is provided in the first section of the review, serving as the foundation for the following sections which focus on the control and treatment of stormwater runoff. Finally, the impact of stormwater control devices at the watershed scale is discussed. Each section provides a self-contained overview of the 2019 literature, common themes, and future work. Several themes emerged from the 2019 literature including exploration of substrate amendments for improved water quality effluent from stormwater controls, the continued study of the role of vegetation in green infrastructure practices, and a call to action for the development of new models which generate reliable, computationally efficient results under the physical, chemical, biological, and social complexity of stormwater management. PRACTITIONER POINTS: Over 280 studies were published in 2019 related to the characterization, control, and treatment of urban stormwater. Studies on bioretention and general stormwater characteristics represented the two most common subtopics in 2019. Trends in 2019 included novel substrate amendments, studies on the role of vegetation, and advancements in computational models.

Influence of fillers on the removal of rainwater runoff pollutants by a permeable brick system with a frame structure base

To fully investigate the effectiveness of fillers in the removal of pollutants from rainwater, gravel, zeolite, slag, volcanic rock and iron filings with a 3-5 cm particle size were applied to construct a brick paving system with a frame structure for the removal of pollutants. Total suspended solids (TSS), chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), total nitrogen (TN), total phosphorus (TP) and heavy metals (Cu, Zn, and Pb) in the influent and effluent were measured, and the effectiveness and mechanism of pollutant removal were further investigated. The results showed that the permeable brick system effectively reduced TSS, TP, Zn, Cu and Pb and was relatively ineffective in reducing NH₃-N, TN and COD. The removal results obtained using different materials show that (1) physical interception is the main reason for TSS and TP removal, (2) the adsorption and ion exchange properties of zeolite enable it to highly absorb ammonia nitrogen, (3) iron filings can effectively reduce NO₃-N, and (4) adding fillers rich in iron oxide, such as volcanic rock or slag, can contribute to COD adsorption. The study provides a feasible technical path for improving the practicability of permeable pavement.