Study On Structure Of New Greenroof And Its Effect On Storage And Purification Of Rainwater

Sponge City is the preferred way of sustainable urban development today.The new planting roof is an important measure in the rainwater control of sponge cities.The new planting roof can control and purify the stormwater runoff through vegetation layer and soil layer,which can effectively solve the problem of rain and flood in urban development.In the development process of planting roof,although it can play an important role in the beautification environment and rainwater management of the city,its structure is complicated,the construction process is cumbersome,and the maintenance is difficult.The structure of the planted roof is simplified and optimized.The research and analysis of runoff control and rainwater quality have realized the simplification of the structure of the planting roof,the improvement of runoff control and the purification of water quality,and have provided solid theoretical support for its promotion and application.Based on the study of traditionally planted roofing,traditionally planted roofing has up to 11 layers of structural layers,complex construction and large loads.Based on these shortcomings,this study constructed new planting roofs to optimize these problems.This study has a comprehensive understanding of planting roofing by constructing simulated planting roofing modules and selecting field planting roofing.The structural layers of new planting roofing include: vegetation layer,matrix layer,geotextile filter layer,drainage board layer,and water-resistance Layer and waterproof coating layer,in the structure,the new planting roof reduces the 11 layers of the traditional planting roof to 7 layers,directly reducing the structural layer of the traditional planting roof and the joint surface between the layers by 4,simplifying the planting roof Construction process;In terms of load,the new planting roof reduces the traditional planting roof by 35%,which greatly reduces the load pressure on the building roof.In terms of rainwater storage,the new planting roof is superior to traditional planting in delaying the flow time and the stagnant rate.The new planting roofing module is a PVC box with a drainage layer,a filter layer and a matrix layer.The matrix layer is a mixture of planting soil and vermiculite.The project examples of planting roof include two types of roofing and traditional planting roofing.The new planting roof is located on the roof of the kindergarten of Anhui Provincial Sports Commission for three years.The traditional planting roof is located on the roof of the East Podium of the Experimental Building of Anhui University of Architecture for one year.Through the construction of new planting roof and traditional planting roof module,the rainwater runoff experiment is carried out.The rainfall is artificial rainfall.The artificial rainwater is prepared according to the natural rainwater quality of Hefei City.The artificial rainfall return period is 2a,5a,10 a,20a,50 a and 100 a.Hydrological aspects mainly analyze the runoff delay time,rainwater retention rate and runoff process.Through research,it is found that the new planting roof module has a delay of 5-15 min in the flow period of 6 different storms,and the delay time is the longest when the thickness of the matrix layer is 200 mm,and the return period with the rainstorm Increasing,the delay time is shortened;and the amount of runoff reduction is 15%-40%,and the reduction rate is maximized when the substrate layer thickness is 250 mm.The flow curve of the new planting roof is in line with the law of flow generation.With the increase of rainfall intensity,the runoff curves of the new planting roof tend to coincide,indicating that the rainfall intensity increases,and the influence of the thickness of the matrix layer on the rainwater retention is reduced.Finally,through SWMM and Hongye software simulation,the rainfall intensity is 2a,10 a and 50 a for runoff experimental simulation,mainly analyzing the total amount of rainwater runoff and flood peak.The SWMM and Hongye software simulations use three different rainfall return periods,the return periods are 2a,10 a and 50 a.In the simulation results of SWMM software,the new planting roof was reduced by 4.76%,1.97%,and 3,04%,respectively,compared with the traditional planting roof.The peak reduction rate increased by 0.67%,0.9%,and 0.22%.In the simulation results of Hongye Software,the new planting roof was reduced by 10.8%,15.7%,and 1.9%,respectively,compared with the traditional planting roof.The peak reduction rate increased by 10.9%,3.8%,and 5.5%.Rainwater runoff purification experiments were carried out by constructing new planting roofing and traditional planting roofing modules.Rainfall was combined with artificial rainfall and natural rainfall.Artificial rainwater was prepared according to the natural rainwater quality of Hefei City.The artificial rainfall return period was 2a,10 a and 50 a.Natural rainfall selects 4 rainfalls with moderate rainfall.The main aspects of water quality are analysis of total nitrogen,ammonia nitrogen,COD and pH.Through research,it is found that the new planting house has a certain degree of purification effect on the concentration of total nitrogen,ammonia nitrogen and COD in the water quality index.When the thickness of the matrix layer is 200 mm,the total nitrogen,ammonia nitrogen and COD concentrations are the lowest,and the removal rates are 43.83%,64.02% and 33.02%.When the thickness of the new planting roofing substrate is 200 mm,the total nitrogen in the effluent,Ammonia nitrogen and COD have the best removal effect.Compared with traditional planted roofing,the removal rate of total nitrogen,ammonia nitrogen and COD in new planting houses increased by 15.43%,8.75% and 9.23%.Through the research on the new planting roof,it can be concluded that the new planting roof is simpler than the traditional planting roof structure,and the load is reduced.In the two aspects of rainwater runoff reduction and rainwater quality purification,the new planting roof is more than the traditional planting roof.Advantages,which provide a theoretical basis for the promotion of new planting roofs.