An Experimental Study On Runoff Control Efficiency And Clogging Maintenance Of Permeable Pavement With Underdrainage

As a stormwater runoff control measure at source,permeable pavements with underdrainage have performed well in reducing the runoff volume,lowering and delaying runoff peak flow rate,and controlling runoff pollution.However,various factors such as atmospheric sedimentation and rainfall erosion can easily make sediment enter and clog permeable pavement,lowering the runoff control efficiency.Reasonable maintenance measures could effectively mitigate clogging in permeable pavement and restore the permeability.Although current studies have extensively monitored the runoff control efficiency of permeable pavements with underdrainage,the monitoring results are difficult to guide the project due to the wide variation caused by the difference in monitoring conditions.In order to quantify the effects of pavement surface structure,antecedent dry period and rainfall return period on runoff control efficiency of permeable pavement with underdrainage,five types of permeable pavements with underdrainage and different surface structures were constructed in the field: : impermeable interlocking concrete paver pavement(IICP),permeable interlocking ceramic paver pavement(PICP),permeable interlocking ceramic paver pavement,pervious concrete pavement(PCP)and gravel pavement.Rainfall events were simulated under two antecedent dry periods and seven rainfall return periods,and runoff of the permeable pavement was monitored under each rainfall event.The effects of pavement surface structure,antecedent dry period and rainfall return period on runoff control efficiency were analyzed and quantified by the use of effective retention volume.The results showed that,compared with rainfall within permeable pavement,for permeable pavements with the surface infiltration rate greater than or equal to 2.73 mm/s under rainfall with 18.0-241.8 mm/h of rainfall intensity and 0-2 d of antecedent dry,the ranges of volume reduction ratio,peak reduction ratio of and peak delay of runoff were 22%-100%,41-100% and 6-44 min,respectively.PCP had the best runoff control efficiency among five types of permeable pavements.Runoff control efficiency was positively correlated with antecedent dry period but negatively correlated with rainfall return period.The efficiency reduced significantly with increasing rainfall return period and then stabilized.Regression analysis results could better quantify the efficiency of permeable pavement in controlling runoff under different conditions.The research results can provide a reference for the selection and design of permeable pavement with underdrainage and the assessment of its runoff control efficiency.The runoff control efficiency of permeable pavements is closely related to their clogging and maintenance,but current research on the clogging and maintenance is insufficient.In order to investigate the effects of sediment characteristics(mass,particle size,gradation)and maintenance choices(maintenance duration,maintenance period,clogging ratio,absolute relative pressure,type of maintenance measure)on clogging and maintenance,three types of maintenance measures such as high-pressure water washing(HW),low-pressure suction(LS),high-pressure gas flushing(HA)were used to maintain three types of permeable pavements with different permeable surface structures such as PCP,IICP and PICP after simulated clogging,and the permeabilities before and after maintenance were monitored.The results showed that the permeable pavement surface infiltration rate showed an exponential decrease with the increase of sediment mass.The sediment particle size(0.3-1.16 mm)causing the most serious clogging was 1-2 times the permeable pavement characteristic aperture which was related to the number distribution and area distribution of the pavement pore size.The effect of sediment grade on permeable pavement surface infiltration rate was more significant than that of the particle size.The optimal maintenance duration of the three maintenance measures was 30-45 s in the test.Under the maintenance of the initial clogging ratio greater than 37%,the stable infiltration ratio did not change significantly and stabilizes at about 35% after maintenance.Maintenance efficiency decreased exponentially with increasing clogging ratio.When HW was used to maintain PCP and IICP,the clogging recovery ratio first increased significantly with increasing water pressure,and then increased slowly and finally stabilized.The clogging recovery ratio increased linearly with the increasing absolute relative pressure when HW maintained PICP,LS and HA maintained PCP.The optimal maintenance measures of PCP was LS,based on a comprehensive evaluation using four indicators such as maintenance efficiency,maintenance period,energy consumption,and absolute relative pressure.This study provides a reference for permeable pavement in clogging prevention and maintenance selection.Based on two tests,including the quantitative test on runoff control efficiency of permeable pavement with underdrainage and the test on the clogging maintenance,a model was built for quantifying the control efficiency of permeable pavement runoff with underdrainage.The model can provide a reference for the selection,design,and maintenance of permeable pavement with underdrainage.