| With the rapid development of urbanization,the original underlying surface of the city has gradually been replaced by hardened urban facilities,and the hardened pavement has brought great convenience to people's travel,but it also led to the ecological environment problems such as the accumulation of water in the city and the pollution of stormwater runoff have gradually increased.As one of the main factors of urban water and runoff pollution,urban roads are important research objects in the field of rainwater research.Domestic and foreign research has found that permeable asphalt roads can effectively reduce urban road runoff,which is an effective way to solve the problem of urban road water accumulation.At present,there are few studies on the law of runoff for permeable asphalt roads in China.Most of them are about the hydrological control effect of permeable asphalt roads and the mix ratio of mixed materials,and the flow pattern of permeable asphalt roads is not the same as impervious roads.Therefore,this paper takes the rainfall return period,rainfall duration and peak rainfall position as test variables,and conducts the following research on the law of runoff of permeable asphalt roads:(1)The flow generation mechanism of the permeable asphalt road and the calculation model of the seepage flow in the surface layer are analyzed,which lays a theoretical foundation for the subsequent research;(2)The runoff situation of the permeable asphalt road with 1%horizontal and vertical slope is analyzed.It is found that the flow rate of the permeable asphalt road surface at the beginning of rainfall and the end of rainfall is very small,almost all at 0.02m~3/h.In the middle of the rainfall corresponding to the peak rainfall,the runoff flow of the pavement changes significantly,and the peak value of the pavement runoff is basically after the peak of rainfall.And the peak reduction rate of road runoff under different rainfall types is above 90%,but it gradually decreases with the increase of rainfall return period;while the change of road surface seepage changes is similar,rainfall intensity,rainfall duration And the peak position will affect the magnitude of the seepage peak in the surface layer,and its change is similar to the theoretical change;(3)The proportion of flow rate of runoff and surface runoff of permeable asphalt roadway is analyzed.It can be found that when the rainfall intensity is less than 43.76mm/h,the runoff of the permeable asphalt road is dominated by surface seepage,which is higher than the proportion 95%.When the rainfall intensity is greater than 43.76mm/h,the flow rate of the permeable asphalt road surface begins to increase,and the corresponding proportion begins to increase,indicating that the permeable asphalt road begins to generate road surface flow,because the rain inlet is at the end of the road,so Most of this flow enters the rain inlet,which also leads to a small flow of surface runoff;(4)The fitting analysis of each part of the runoff on the permeable asphalt road was carried out,and the fitting formula between the surface runoff flow,the gully flow,the longitudinal seepage and the lateral seepage and the rainfall intensity were obtained.And using the data of the variable rainfall test,the fitting formula was verified and analyzed.It was found that the fitting formula has higher accuracy without considering the influence of time factors such as the convergence time;(5)The relationship between the runoff coefficient of permeable asphalt pavement and time is studied.The study shows that the flow coefficient of the permeable asphalt channel is a dynamic process in the process of a rainfall,not a certain value,and the maximum value of the flow coefficient of the permeable asphalt road,the peak value of the runoff coefficient and the mean value of the runoff coefficient under different rainfall types are analyzed.The relationship between runoff coefficient and rainfall intensity is also studied.It is found that when the rainfall intensity is less than 50mm/h,the mean value of runoff coefficient is 0.029.It is considered that the permeable asphalt road does not generate road runoff at this time;At50mm/h,the permeable tunnel began to produce surface runoff,and the runoff increased rapidly with the increase of rainfall intensity,and the fitting formula was obtained,which provided a certain theoretical basis for the permeable asphalt road. |
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