Study On Optimization Design Of Urban Main Road Spongy Body Based On SWMM

With the proceeding speed of urbanization,the hardening area of underlying surface increases,and results in the frequent occurrence of “sea view” in urban areas.The traditional road rainwater discharge mode,dominated by fast drainage,imposes great pressure on old drainage pipe network when heavy rains come,which causes necessary waste of water resources and easy occurring of urban water logging disaster.To solve this problem of urban road drainage,there is one way that Low Impact Development measures(LID),which is based on the design philosophizing of low impact development and becomes one of the guiding concepts of sponge cities in China.This thesis proceeds with the concept of “sponge city” and analyzes the current situation and existing shortcomings of domestic and foreign research.With the Storm Water Management Model(SWMM)as the basic software the study is carried out,which is about urban main road spongy body optimization design,aiming at the lack in combination measures of the city main road sponge and the deficiency of corresponding measures.The simulation principle of hydrology,hydraulics and water quality in SWMM model are introduced in the study.Take one main road in Chi Zhou,An Hui province for example,the SWMM model is established to analyze the advantages and disadvantages of five kinds of sponge measures.On the one hand,four measures(permeable pavement,biological retention pool,sunken green space and grass planting ditch)are selected to construct ten combination scenarios of measures.On the other hand,six kinds of rainfall in different recurrence periods are generated based on the formula of rainfall pattern in Chicago and rainstorm intensity in Chi Zhou.The hydrologic and water quality changes were simulated relatively under employing traditional measures and ten combination scenarios of measures and in different recurrence periods by the SWMM.Combined with the rainfall difference between north and south of China,the regional adaptability analysis is carried out according to the results of the double measure combination,in order to provide ideas for the construction of road sponge measures in the future.The study results show that the ten combined scenarios can effectively reduce the surface runoff,peak discharge,node overflow number and total overflow flow,increase the infiltration amount of rainwater in the region and the rainwater storage amount of sponge measures,and have a good removal effect on three common rainwater pollutants(TSS,COD and TN).According to the comparison of infiltration amount of rainwater,surface runoff and rainwater storage amount,S7 combination scenario(permeable pavement + biological retention pool + sunken green space)and S10 combination scenario(permeable pavement + biological retention pool + sunkengreen space + planting gullies)have the best effect.From the perspective of total annual runoff control rate and economic benefits,the combination scenario of measures S10 is better than that of measures S7.And from the point of view of design,optimization design was carried out for the four sponge measures in the S10 combination scenario,and the sponge measures were added and optimized for the original road.According to the analysis of regional adaptability,the combination of permeable pavement and biological retention pool is applicable to the south where rainfall is frequent,and the combination of permeable pavement and sunken green space is applicable to the north where rainfall is short and instantaneous.