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- Permeable pavements – green infrastructures as a flood mitigation measurePublication . Afonso, Márcia Isabel Lopes; Almeida, Marisa S. Dinis; Fael, Cristina Maria SenaPermeable asphalt pavements have been one of the solutions used to increase the permeability of road pavements given the growing urbanization and climate change. The high porosity and permeability of surface layers with PA (porous asphalt) mixtures allows the water infiltration and, consequently, reduces superficial runoff and contributes to the recharge of underground aquifers. However, the infiltration capacity may be impaired by clogged pores with sediments. The double layer porous asphalt (DLPA) was developed to mitigate this effect. This is a key issue in the pavements’ service life. Information on the clogging processes in these layers is not yet well characterized. The study was carried out using a rainfall simulator in order to generate design storm events with a known intensity and duration. The experimental methodology adopted took into account different phases of evaluation of the infiltration capacity with two clogging cycles (500 and 1000 g m-2). The DLPA infiltration capacity was evaluated in the different phases after different precipitation events (100, 200 and 300 mm h-1). The results showed that, in general, the double layer porous asphalt has the capacity to drain the water, even after clogging and with lower voids content. The infiltration capacity was partially restored when subjected to simple maintenance.
- Permeable asphalt pavement as a measure of urban green infrastructure in the extreme events mitigationPublication . Afonso, Márcia Isabel Lopes; Fael, Cristina Maria Sena; Almeida, Marisa S. DinisPopulation growth in cities has led to an increase in the infrastructures construction, including buildings and roadways. This aspect leads directly to the soils waterproofing. In turn, changes in precipitation patterns are developing into higher and more frequent intensities. Thus, these two conjugated aspects decrease the rainwater infiltration into soils and increase the volume of surface runoff. The practice of green and sustainable urban solutions has encouraged research in these areas. The porous asphalt pavement, as a green infrastructure, is part of practical solutions set to address urban challenges related to land use and adaptation to climate change. In this field, permeable pavements with porous asphalt mixtures (PA) have several advantages in terms of reducing the runoff generated by the floods. The porous structure of these pavements, compared to a conventional asphalt pavement, allows the rainwater infiltration in the subsoil, and consequently, the water quality improvement. This green infrastructure solution can be applied in cities, particularly in streets or parking lots to mitigate the floods effects. Over the years, the pores of these pavements can be filled by sediment, reducing their function in the rainwater infiltration. Thus, double layer porous asphalt (DLPA) was developed to mitigate the clogging effect and facilitate the water infiltration into the lower layers. This study intends to deepen the knowledge of the performance of DLPA when subjected to clogging. The experimental methodology consisted on four evaluation phases of the DLPA infiltration capacity submitted to three precipitation events (100, 200 and 300 mm/h) in each phase. The evaluation first phase determined the behavior after DLPA construction. In phases two and three, two 500 g/m2 clogging cycles were performed, totaling a 1000 g/m2 final simulation. Sand with gradation accented in fine particles was used as clogging material. In the last phase, the DLPA was subjected to simple sweeping and vacuuming maintenance. A precipitation simulator, type sprinkler, capable of simulating the real precipitation was developed for this purpose. The main conclusions show that the DLPA has the capacity to drain the water, even after two clogging cycles. The infiltration results of flows lead to an efficient performance of the DPLA in the surface runoff attenuation, since this was not observed in any of the evaluation phases, even at intensities of 200 and 300 mm/h, simulating intense precipitation events. The infiltration capacity under clogging conditions decreased about 7% on average in the three intensities relative to the initial performance that is after construction. However, this was restored when subjected to simple maintenance, recovering the DLPA hydraulic functionality. In summary, the study proved the efficacy of using a DLPA when it retains thicker surface sediments and limits the fine sediments entry to the remaining layers. At the same time, it is guaranteed the rainwater infiltration and the surface runoff reduction and is therefore a viable solution to put into practice in permeable pavements.
- Influence of clogging on the hydrologic performance of a double layer porous asphaltPublication . Afonso, Márcia Isabel Lopes; Fael, Cristina Maria Sena; Almeida, Marisa S. DinisNowadays, the increasing urbanisation and the effect of climate change in cities has been a constant concern. In particular, the floods cause a significant increase in surface runoff, mostly on roads and parking areas. As an alternative to asphalt pavements, usually used in these areas, permeable pavements have been developed with Porous Asphalt (PA). These pavements allow the infiltration of water from the surface to the ground due to the high void content of the PA, thus reducing the surface runoff and increasing recharge of groundwater. Over the years, the infiltration capacity of the mixtures decreases with the clogging by sediments from the vehicles themselves and/or from the local environment. In order to mitigate this effect, a Double Layer Porous Asphalt (DLPA) was developed. This research intends to deepen the knowledge about the influence of the clogging of a DLPA, with respect to the infiltration capacity, since it is an essential theme in the pavements lifespan and that needs to be developed. This study considered different evaluation phases of the infiltration capacity with two clogging cycles (500 and 1000 g/m2). The materials used were: sand, region soil, and rubber waste. The infiltration capacity test was performed in different phases after a rainfall event of 100 mm/h with a rainfall simulator developed for this purpose. Furthermore, the permeability test with the falling head permeameter was carried out in parallel, obtaining outflow times for each clogging phase and subsequent maintenance phase. The research concluded that DLPA has a high infiltration capacity after the first clogging cycle in both performed tests. In the second clogging cycle, the results show that the infiltration decreased due to the partial filling of the pores, mainly, for the rubber-filled DLPA. The type of clogging material influences the infiltration capacity, nevertheless partially recovered after simple maintenance was performed.