| Cities have a heat and rain island effect.In the global context of intensifying climate change,short duration,high intensity rainfall in urban areas is gradually increasing,coupled with a high proportion of impermeable urban sub-base and poor permeability,which exacerbates the risk of urban flooding.Permeable paving has significant infiltration,storage and drainage effects on rainwater runoff,improving the urban hydrological cycle and reducing the risk of flooding,as well as purifying water quality and improving urban surface pollution.Therefore,it is important to construct permeable paving structures with better runoff control performance,especially in relation to the hydrological processes under different rainfall conditions.This paper analyses the hydrological processes of sponge permeable paving under different precipitation events with different intervals of days and rainfall intensities by constructing a small test facility for sponge permeable paving.The performance of the sponge permeable paving in removing pollutants at different pollutant concentrations and intervals of days is investigated in relation to the infiltration,storage,purification and discharge characteristics of the sponge permeable paving.At the same time,a one-dimensional hydrodynamic model of the sponge permeable installation is constructed by combining numerical simulation methods to obtain the optimal structural layer ratio and related parameters.The main findings of the thesis are as follows:（1）The sponge permeable paving has a good effect on the regulation of rainfall runoff,delaying the outflow time,reducing the total amount of runoff and reducing the peak flow rate.Under low rainfall intensity conditions,the delayed outflow time,water storage performance and peak flow reduction performance are positively correlated with the number of dry days before rainfall,but under high rainfall intensity,the peak flow reduction performance,water storage performance and the number of dry days before rainfall are not significantly correlated,and the peak flow reduction effect is weakened.The best water storage performance was achieved at a rainfall event interval of 3 days,and the best peak reduction performance was achieved at a smaller rainfall intensity at an interval of 9 days.（2）sponge permeable pavement has a stable drainage process,can significantly retard the outflow process.In the storage and drainage process of sponge body,capillary water dominates in the absorption and storage process,when the sponge body is saturated with gravity flow,the role of capillary water gradually increases in the drainage process,gravity water plays a major role in the coarse sand and graded gravel layer percolation storage and drainage process.（3）Hydrus-1D can better simulate the permeable sponge pavement infiltration storage and discharge process.The mathematical model of the total flow process curve fits well with the physical test,and the simulated curve of the flow process is shifted to the right compared with the measured curve when the precipitation event is 11 days apart.The numerical simulation curve is a good fit for the water storage process of the permeable sponge paving,but there is a lag in the drainage curve after the rainfall has stopped.（4）Under high rainfall intensity,the more significant the influence of the thickness ratio of the base structure material on the runoff control effect,the porous fibre wool layer has the best runoff control effect when the thickness ratio of the layer to the gravel layer is 1:3 under the test conditions,therefore,when optimising the design of waterway smoothness in areas with low rainfall intensity,the adjustment of the thickness ratio of the paving base material can be considered.（5）The sponge permeable paving can remove typical pollutants from runoff by adsorption and retention and microbial action,with high removal rates for COD,NH3-N,NO3-N,TP,and the heavy metals Cu and Pb.Ecological porous fibre wool provides a high number of cationic adsorption sites for the chemisorption of pollutants.The concentration of pollutants in different runoffs and the interval between rainfall events have an influence on the removal rate.At low concentrations,NO3-N removal was significantly reduced at an interval of 7 days;While the best COD removal was achieved at an interval of 5 days. |
