| In 2017,Gui’an New Area of Guiyang City implemented the Sponge city demonstration area in accordance with the suggestions on Sponge city construction put forward by the State Council,and built a series of LID(low impact development)facilities to optimize rainwater and flood management.With the rapid development of industrialization and urbanization,cities are facing a series of problems such as severe floods and waterlogging,rapid deterioration of water ecology,and intensified pollution of the water environment.Conventional LID facilities cannot meet the rainwater and flood management needs of cities,and innovative construction of high-performance and highly adaptable LID facilities is needed.Therefore,this article takes the construction project of Moon Lake Wetland Park in Gui’an New Area as the engineering background.Based on the hydrogeological problems of steep natural slopes,concentrated surface water collection,and low permeability soil in the southwest region,a regional and innovative sunken green space is designed by combining theoretical analysis,numerical simulation,on-site testing,and indoor experiments to solve the problems of large rainwater runoff and serious runoff pollution in the wetland park.The main contents of the study include:(1)Based on the comprehensive analysis of the runoff catchment patterns and pollutant transport characteristics of the underlying surface facilities in the region,and based on the hydrological regulation theory and solute transport mechanism of the underlying surface facilities,a new type of concave green space combination structure for runoff regulation experiments and model calculation indicators is proposed.(2)Based on the rainstorm intensity formula in the study area,the test rainfall runoff is designed.Analyze the permeability characteristics and material properties of red clay by examining the soil quality in the study area.Based on the monitoring system platform of Sponge city in Gui’an New Area,pollutants with representative concentrations in the local area are selected for design reference.(3)A new sunken green space structure composed of "overflow outlet+gravel drainage layer" is proposed,and a model test of the storage and drainage performance of the new structure under the design rainstorm condition is carried out.Utilizing control indicators such as surface runoff reduction rate,overflow interception rate,rainwater retention rate,peak delay rate,and pollutant removal rate,explore the hydrological performance and pollutant removal capacity of the new structure.(4)Based on the two-dimensional Richards and van Genuchten-Mualem flow control equations,the influence of various design parameters(overflow height,gravel drainage layer depth,red clay thickness,artificial fill layer thickness,and confluence area ratio)on the hydrological response of sunken green spaces under different rainfall intensity conditions was investigated using the Hydras-2D program.Normalize the design parameters using range(R)and weights to determine the most significant design parameters that affect the new composite structure.Based on these parameters,provide practical design parameter support and reference for low permeability soil areas with concentrated rainfall and high rainwater runoff(on sloping land)..(5)Using the HYDRUS-2D non equilibrium(dynamic)adsorption model,the two-dimensional convection dispersion equation is used to simulate the transport of pollutants.Based on the limited conditions of indoor experiments,this study investigates the effects of different hydraulic loads and matrix fillers on the removal efficiency of pollutants in new concave green spaces.Determine the optimal configuration for pollutant removal efficiency of sunken green spaces. |
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