Clogging of permeable pavements in semi-arid areas

Abstract

Urban development and consequently covering more areas by the impervious surfaces, has led to the decrease in natural process of rainfall infiltration and as a result deduction in ground water recharge. This decrease in ground water recharge has caused number of environmental concerns such as the decrease in base flow in streams and drying up of drinking water supplies. In arid and semi arid areas with low annual rainfall and high evapotranspiration (P/ET<0.5) no excess water for run-off or ground water recharge would be available. Therefore capturing the rainfall for water supplies in such regions is more important. Due to these problems and by considering the role of permeable pavements in capturing water and replenishment of aquifers, using this kind of paving has been considered as a sustainable solution. Although permeable pavements have been used as a sustainable way to reduce the impacts of urbanization on water quality and improving water management in urban areas but they also have some disadvantages. Clogging in these pavements is the main problem which causes the decrease in infiltration rate. Review of existing researches shows that most of the researches about clogging have been limited to western countries with almost the same climatic condition and the effect of climate on clogging has not been considered yet, especially in dry regions. Although in these areas capturing more rainfall to recharge ground water is really vital. Therefore the effect of climate on clogging of the permeable pavements should be investigated more to choose the proper pavement for dry climate and increasing the infiltration rate. In order to investigate the effect of semi-arid climate on clogging of the permeable pavements, porous concrete was chosen in this research as the proper type to apply in these areas. As the fine dust in these areas is the main cause of clogging, the pavement behavior under this condition was evaluated by the lab experiment. During the lab experiment different sub-bases (sand and stone) were also examined to see the differences in clogging process under various conditions. The results from this research shows that the wind suspended particles, as the main cause of clogging in semi-arid areas, can be washed through the pavement and cause a very slow clogging process. Comparison the results of different sub-bases shows the significant effect of the pores size in the sub-base on the clogging process. In case of higher porous sub-base, sediments can be migrated from the pavement to the sub-base easily. But in case of less porous sub-base the blocking of the interface and first layers of the sub-base can create more resistance through the flow migration. As the clogging in case of larger particles happens rapidly, therefore in order to design the pavement, average size of particles that can go through it should be taken into account.Water ManagementCivil Engineering and Geoscience