Researches On Retention And Infiltration Capacity Of Sunken Lawn Of Beijing

With Chinese government’s strong support for the construction of sponge city,low impact development has attracted a lot of attention.Due to its simple structure,sunken lawn has become the most widely utilized technique among lots of LID techniques in China.In this research,several vital factors that affect the infiltration and retention capacity of sunken lawn were analyzed,and some corresponding proposals for the construction of sunken green space were raised.The SWMM model of aresidential area was built to analyze the hydrological performance of the sunken lawn under different circumstances.The influences of sunken depth and permeability coefficient of soil was analyzed with the computing using SWMM,where the peak flow,volume of runoff,time of peak flow were simulated under precipitation recurrence period of 5a,10a,20a.The main conclusion of this dissertation is as below:(1)Simulation results of sunken lawn depth showed that the volume of runoff and peak flow under different amount of precipitation were effectively reduced with the depth of sunken lawn between 100mm and 150mm.Nevertheless,adding the depth of sunken lawn had a weak effect on delaying the peak flow,which reduces the marginal benefit.(2)Simulation results of the combination of sunken lawn depth and area ratio showed that the optimal performance of sunken lawn could be achieved with the depth of sunken lawn between 100mm and150mm regardless of area ratio.And the volume of runoff and peak flow could be reduced increasingly by adding area ratio of sunken lawn.(3)Simulation results of different type of soil showed that compare to doras with a permeability coefficient of 76.2mm/h,sandy soil with permeability coefficient of 127mm/h didn’t give an obvious reduce of peak flow and runoff.Thus,the area ratio of sunken lawn should be raised during the building of sponge city,the depth and soil type of sunken lawn should be chosen in consideration of precipitation intensity.