Study On Runoff Reduction And Water Quality Purification Effect Of Permeable Asphalt Pavement In Beijing Area

Permeable pavement is a low-impact development measure for regulating urban rainwater runoff by increasing urban permeable area.Permeable pavement can effectively control the total amount of runoff and runoff pollution,so it has a wide range of application prospects.This paper takes permeable asphalt pavement as the research object,and the permeable asphalt pavement is carefully designed from the aspects of pavement structure,pavement structure material and pavement structure analysis.On this basis,the effect of runoff reduction and water quality purification on permeable asphalt pavement are deeply explored.The main research results and conclusions of this paper are as follows:(1)Type II permeable asphalt pavement with pavement structural strength and drainage performance is the best choice for the application of high grade urban roads in Beijing area;The difference in pavement structure materials is mainly reflected in the selection of permeable base materials.Porous cement stabilized crushed stone is a permeable base material with wide application and good comprehensive performance;Combined with the structural combination form of permeable asphalt pavement at home and abroad,two structural forms of permeable asphalt pavement,type A and type B,which are suitable for high grade urban roads in Beijing are proposed.(2)On the basis of the existing research results,a suitable conversion model of the mixture voidity-connected voidity-permeability coefficient is selected for the permeability of pavement structural materials.Table choose road deflection,layer upon layer at the bottom of asphalt mixture tensile strain,tensile stress of semi-rigid base material layer bottom and asphalt mixture layer shear stress as indicators of the design of pavement structure calculation.The pavement structure of A type and B type permeable asphalt pavement is analyzed with the finite element analysis software ANSYS,and the appropriate thickness of each structural layer that can meet the pavement bearing capacity is determined.(3)The surface runoff can be eliminated by setting permeable asphalt pavement within certain rainfall recurrence period,and the thickness of permeable structure layer directly determines the critical value of rainfall recurrence period corresponding to the runoff elimination effect.Type A permeable asphalt pavement eliminates surface runoff with A recurrence period of 5 years or less.Type B permeable asphalt pavement caneliminate surface runoff with a recurrence period of 50 years or less.(4)When the rainfall return period exceeds the critical value corresponding to the runoff elimination effect,the permeable asphalt pavement reaches the state of full storage,which will generate runoff on the pavement surface.When the rainfall return period exceeds the critical value corresponding to the runoff elimination effect,and is less than 100 years,the runoff amount and peak runoff value of type A permeable asphalt pavement can be reduced by 55-85% and 56-86%,and the runoff coefficient can be controlled within 0.45.Type B permeable asphalt pavement can reduce the total runoff amount by 91.4% and the peak runoff by 90%,and control the runoff coefficient within 0.1.Therefore,permeable asphalt pavement can effectively control the total amount of runoff and peak runoff,and has a significant effect on the reduction of surface runoff.(5)In a complete rainfall event,the variation trend of pollutant concentration in road storm water pipeline is divided into two stages.The first stage is the flushing stage in which the pollutant concentration rises sharply to the maximum and then drops sharply to a smaller stable value.The second stage is the stable stage when pollutant concentration remains at a small stable value until it drops to 0.After the application of permeable asphalt pavement,the concentration of various pollutants in the surface runoff is only in the stable stage,but not in the flushing stage,which indicates that the permeable asphalt pavement has the filtration and adsorption effect on pollutants.(6)When the rainfall return period is less than the critical value corresponding to the runoff elimination effect,since no runoff is generated on the surface,the flushing amount of surface pollutants can be reduced to 0 by permeable asphalt pavement.When the rainfall recurrence period exceeds the critical value corresponding to the runoff elimination effect and is less than 100 years old,due to both the runoff reduction effect and the pollutant filtration effect,type A permeable asphalt pavement can reduce the flushing amount of surface pollutants by 93% ～ 98%;Type B permeable asphalt pavement can reduce more than 98% of the surface pollutant flushing.Therefore,permeable asphalt pavement has a significant effect on water quality purification and is less affected by the thickness of permeable structural layer.