| The soil-planting green belt is a new structure of sponge city funded and developed by the key science and technology research and development project of Hebei Province(Nos.18276109D).The soil-planting green belt has good water purification function,water storage function and rainwater infiltration function.The soil-planting green belt working principle is that the road runoff rainwater goes through the impervious pavement to the planting soil green belt.Road runoff rainwater contains a large amount of pollutants due to rain scouring air and pushing road surface.The pollutants in the rainwater will be deposited when rainwater infiltrates into the ground through the soil-planting green belt.It is still unclear whether pollutants will cause the soil lifting silt pore and affect the service life of the soil-planting green belt.In order to investigate these issues,this paper investigates the pollution situation of road runoff rainwater in Shijiazhuang,makes experimental equipment of soil-planting green belt,produces road runoff rainwater and executes lifting silt experimental study.Furthermore,a one-dimensional lifting silt mathematical model of soil-planting green belt was established.There are four main conclusions through research:(1)The result of existing literature show COD(chemical oxygen demand)and SS(suspended matter)in the road run-off rainwater would cause soil lifting silt.(2)Within the first 30 min,road runoff rainwater has large concentration of SS and COD by field investigation in Shijiazhuang.It is easy to cause the soil lifting silt of the soil-planting green belt structure.In the study,the road runoff rainwater within the first 30 min can be studied.The road runoff rainwater concentration recommended values of lifting silt material in the 30 min of the main road in the city are: SS is 784.00 mg/L,COD is 252.21 mg/L;the road runoff rainwater concentration recommended values of lifting silt material in the 30 min of the branch road in the city are: SS is 420.00 mg/L,and COD is146.64 mg/L(3)According to the road runoff rainwater concentration design recommended values of initial 30 min,the road path flow rainwater is configured.The lifting silt experiment was carried out by using a self-made full-scale model such as a bucket,a pressure water pump,a flow meter,a spray head,a test bucket,water pipes and an outer frame.When the equivalent time is two years,the soil-planting green belt be blocked inthe case of planting soil thickness by 60 cm and 100 cm.The planting soil thickness has little effect about the lifting silt time.(4)The infiltration rainwater is a one-dimensional steady seepage,the propulsion model of the lifting silt surface is given and theoretical analytical solution is solved.Using the model to solve the lifting silt problems of the 60 cm and 100 cm soil-planting green belts,the lifting silt depths are respective 9.66 cm and 10.19 cm,this recommended that the replacement depth on the surface of planting soil is 20 cm. |
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