Research On Infiltration,storage,drainage Properties Of Permeable Pavement & Grassed Swales

With the speeding up of urbanization in China,rigid pavement replaced primitive surface,which shortened the concentration time,cut the runoff infiltration path,increased the frequency of floods.The traditional plan and design method of road drainage system mainly focused on rapid drainage,which is not consistent with the concept of sustainable development.Consequently,a new ecological pattern which integrated permeable pavement&grassed swales was proposed in the paper.It can absorb,storage and infiltration when it rains,and release the stored water after the rain.The paper analysed the infiltration,storage,drainage properties of permeable pavement&grassed swales and quantified the effect of permeable pavement&grassed swales system in road runoff control by using the SWMM.The conclusions are as follows:The paper researched the structure design,runoff path and operating condition of permeable pavement&grassed swales system,put forward the theoretical formula of runoff reduction rate,water storage rate and runoff coefficient,carried out a complete system of LID runoff reduction.A water infiltration model for permeable asphalt pavement was established in the paper.According to the vertical penetration test,the suitable permeability coefficient for soil of permeable pavement&grassed swales ranged from 3.47×10^-6m/s to 1.00×10^-5m/s,and according to the horizontal penetration test,the functional relationship between horizontal infiltration coefficient and infiltration head was K_h=-19.985h²+19.723h+4.200.The result of field storage&drainage teat indicated that consumptive ability of rainwater showed saturate tendency with the increase of rainfall intensity.More and more surface runoff drained through overland flow or percolation tube rather than timely infiltration,which showed permeable pavement&grassed swales system mainly played the role of rainwater transmission rather than storage when it rained heavily.In addition,the fitting formula between runoff coefficient,longitudinal gradient and the rainfall recurrence period was?=11i+0.114+?2.157i+0.051?Ln?P-46.667i²-3.3i-0.225?,the fitting formula between runoff coefficient,longitudinal gradient and inflow strength was?=?5.343i+0.074?Lnq+13.743i+0.180.Assessment model of infiltration,storage,drainage properties and traditional development model was established by using SWMM.It was concluded that when the rainfall repetition period ranged from 0.33a to 10a,the reduction rate of total runoff in assessment model ranged from 100%to 27.5%,the reduction rate of peak flow ranged from 100%to 15.9%,the runoff-yielding time was eliminated or delayed by 13min to 5min and the peak flow occurrence time was eliminated or delayed by 17min to 5min.The operation effect of permeable pavement&grassed swales system was better than ordinary grassed swales in terms of reduction effect in total runoff and peak flow,delay effect in occurrence time and peak flow time.