Study On Rainwater Retention Of Planting Roof With Different Matrix Layer Ratio And Its Application

With the rapid development of China’s economy,environmental problems have gradually become prominent.The rapid development of industrial manufacturing has caused a large accumulation of heat in the sky above the city,which is much higher than that in the suburbs.This makes the city easy to form a "heat island effect",and the city’s "heat island effect" will further cause the occurrence of the urban "rain island phenomenon",making the frequency of extremely heavy rainstorms higher than the expected design value,and increasing the peak flow,causing most of the rainfall and stagnant water to seep out through the underlying surface,and it cannot be discharged in time through the drainage network.,And finally stay in the city.In order to alleviate this situation,the country has gradually begun to promote the construction of sponge cities.Planting roofs is an important measure in the low-impact development facilities of the sponge city.That is,planting soil or container planting on the roof of the building or the roof of the underground building.The planting roof can hold a large amount of rainwater from the source.This article analyzes and researches planted roofs of different planting substrate ratios.In order to analyze the rainwater retention effect of seven different kinds of improved soils under different rainstorm intensity,the artificial rainfall simulation equipment designed by ourselves and three thicknesses of 100mm,200mm and 300mm were used for simulation outdoors.Three types of rainfall intensities:once in two years,once in five years,and once in ten years(using the Zhengzhou area’s rainstorm intensity formula)were tested for rainwater retention,and the test found that:(1)When the rainfall intensity is once in two years,there is no obvious difference in the effect of the seven kinds of planting roofs on the amount of rainwater retention.However,under the rainfall intensity of the once-in-five years and the once-in-ten years,the planting roofs have obvious rainfall retention difference.Among them,light sandy loam shows its strong rainwater retention capacity.Under the rainfall intensity of once every five years,the lowest rainwater flow rate of 100mm thickness and 200mm thickness is respectively the light sandy loam soil:humus:vermiculite=5:3:2 G group and the light sandy loam soil:rot.Planting soil:Perlite:Vermiculite=2.5:5:2:0.5 F group,all of which are planting substrates with higher composition of light sandy loam;under the rainfall intensity once in ten years,the lowest rainwater production flow of 100mm thickness and 300mm thickness is G group.(2)Several groups of planting roofs in the three rainfall intensities have significant effects on delaying rainwater runoff generation.And through comparison,it is found that the greater the natural density of the matrix,the more difficult it is for rainwater to infiltrate,and the better the delay effect on rainwater runof.Under the rainfall intensity of once in two years and once in five years,G group is the latest runoff in the thickness of 100mm,200mm and 300mm.In the case of the once-in-ten-year rainfall intensity,the G group has the latest runoff when the thickness is 100mm,but when the thickness is 200mm and 300mm,the ratio of the matrix layer is pastoral soil:lightweight bone=1:1 A group occurred the latest.(3)Based on the comparison between the amount of rainwater retention and the delayed runoff generation time,in the case of the once-in-five-year and once-in-ten-year rainfall intensity,the G group has the best effect on rainwater retention.Based on the test results,this paper selects planting roof with suitable retention rate and moderate load for the design of the sponge city in the Hexi Village Resettlement Area Project.In this project,a planting roof is set on the roof of Building 9#,and the planting roof is located in the sink water.District 1,9#Building,the planting roof area is 396.47m2,the planting substrate layer is 300mm thick,and the substrate layer ratio is pastoral soil:grass charcoal:pine needle soil:perlite=1:1:1:1 D group planting substrate.The courtyard can meet the review requirements of 75%of the total annual runoff control index of the project location.