Experimental Study On Two Types Of Permeable Pavement Flow Generation Mechanisms And Simulation Analysis Of Their Application In Northern Cities

With the rapid development of urban modernization,the weak and impermeable areas within cities continue to increase.Under extreme weather conditions,frequent flooding has become a major obstacle to the healthy development of cities.In recent years,the concept of Sponge city and the construction of sponge facilities have made permeable pavement a favorable facility to alleviate urban drainage problems.Its good permeability and drainage can maximize the infiltration and drainage of rainwater,which can alleviate the occurrence of flooding to a certain extent.Runoff coefficient is an important parameter to measure the actual application effect of permeable pavement,which is related to whether the runoff control goal of Sponge city can be achieved.In the current Sponge city design code,the value of permeable pavement runoff coefficient is mostly determined based on experience,and the permeable pavement reconstruction on campus lacks relevant guidance.Therefore,this paper takes the Yanta Campus of Chang’an University as the research area,takes permeable concrete and permeable plastic as the research objects,and uses the artificial rainfall simulation test device to conduct model simulation tests.By analyzing the yield,sink,flow process and runoff coefficient changes of two permeable paving materials under different rainfall intensities,and using the Green Ampt soil moisture infiltration model to analyze the rainwater infiltration of the pavement surface,According to the test results,the total runoff and runoff coefficient of SWMM are simulated using the test rainfall parameters,and the runoff reduction of permeable pavement and the change between the test runoff coefficient and the simulation value are analyzed.Finally,the permeable pavement design planning is carried out for Yanta Campus of Chang’an University,and its costs and economic benefits are analyzed.The main research results obtained are as follows:(1)The results of rainfall runoff simulation tests on pervious concrete and pervious plastic show that the runoff coefficients of pervious concrete range from 0.06-0.47 when the rainfall intensity is from 70mm/h to 200mm/h and the rainfall duration is 45min and 60min;the runoff coefficients of pervious plastic range from 0.07-0.48.When the rainfall intensity is from 100mm/h to 200mm/h and the rainfall duration is 45min,the runoff coefficients are between 0.15-0.30 for the double-layer structure of pervious concrete and pervious plastic.(2)In the runoff simulation test of permeable pavement,for single-layer permeable pavement,the time of flow production is advanced with the increase of rainfall intensity and the time of runoff coefficient stabilization is also advanced.The runoff coefficient growth can be divided into a rapid rise section and a runoff coefficient gradual stabilization section.When the test material is double-layered permeable pavement,the flow production time and runoff coefficient stabilization time are delayed compared with single-layered,and the overall delay time is about 5-10min.(3)Referring to the test parameters in Chapter 3 for the total SWMM runoff simulation,the results show that when the rainfall intensity is 130mm/h,150mm/h,170mm/h,200mm/h,the total runoff before the permeable paving renovation is 2199.99m~3,2611.688m~3,3045.975m~3,3684.75m~3,and the total runoff after the renovation The abatement rates are51.06%,45.39%,40.64%and 36.74%,respectively.(4)According to the rainfall parameters used in the test to simulate the runoff coefficient of permeable pavement,the analysis of the SWMM model simulation results shows that the runoff coefficient of permeable concrete is between 0.17 and 0.40;the runoff coefficient of permeable plastic is between 0.19 and 0.41.There is a small difference between the software simulated values and the experimental measured values.The reason for the difference may lie in the runoff collection device,but the effect of this difference can be ignored in practical applications.(5)The permeable pavement benefit analysis of Chang’an University Yanta Campus,the cost of permeable pavement and ordinary pavement is 2,021,500 yuan and 1,998,500 yuan respectively,and its cleaning cost is about 470,400 yuan.During the 10-year trial period,permeable paving can reduce municipal drainage costs by about 60,900,000 yuan,obtain rainwater recharge benefits of about 106,700 yuan,and obtain water quality benefits of about365,700 yuan.In summary,the values of pervious concrete and permeable plastic runoff coefficients are stable within a certain range at different rainfall intensities,indicating that they can have a controlling effect on rainfall runoff.The cost-benefit analysis of permeable pavement renovation on the campus shows that the difference in cost between permeable pavement and ordinary pavement is small,but permeable pavement will generate cleaning and maintenance costs,and at the same time will generate certain socio-economic as well as ecological benefits.Accordingly,it can provide some reference for the subsequent campus sponge city complaints will pavement renovation.