The Research On Site Condition And Greening Strategy Of Shaded Green Space Under Viaduct

In order to relieve the increasingly serious problems of urban traffic,the major cities in China are under the trend of viaduct construction.And the environmental problems,especially the shaded green space under viaduct,arises along with the rapid development of urban viaduct construction.However,relevant researches are lag behind significantly,and the pratice study appear to be rigid and invariable.As a result,the scientific planning guidance of the shaded green space under viaduct is becoming the primary research content of the utilization of urban viaduct space.In this paper,the author take the form of shaded space under viaduct and the characteristics of green site condition as the point of penetration.Based on the related forein literatures and domestic practical researches,the study summarizes the constitute form and environment characteristics of the shaded green space under viaduct.Select the main urban region of Wuhan city as the object of study,the thesis focusing on systematically measuring and simulating on the environmental factors of shaded green site condition: Using the TES-1336 A illuminance meter and the DAVIS Vantage Vue weather station,the light,humiture and wind speed of each sample are monitored by a fixed point and real-time data.Simulate the different light conditions of the sample by using Ecotect Analysis software.The type and sorting of the pollutant are determined by the experiments which on the stormwater runoff sampling of the bridge’s surface.The status of shaded soil under the viaduct is tested by taking use of the soil texture by finger-feeling and observation.Combined with the results of the simulation analysis,this paper found that there are six major problems in the site condition of the shaded green space under viaduct,such as weak light,water shortage,pollution,poor soil,traffic barrier and lack of maintenance and management,and specific embodiment of these problems are as follows:(1)The light of viaduct shade is mainly affected by four aspects: the trend of the viaduct body,B/H,the surrounding environment and the light guide.Generally speaking,during the plant growth,light of the north-south orientation viaduct space is superior to the east-west orientation.At the same time,compared with the east-west orientation,the light of the north-south shaded viaduct space can be more effectively improved by the same B/H rangeability.In addition,the smaller the B/H,the better the light environment.And the daily average PAR index showed a good correlation with B/H.Moreover,the light guide can faintly enhance the light environment of the middle part of shaded viaduct space.(2)During the day,the temperature and humidity of shaded viaduct space(inner space)are lower than that of the outer space,while the wind speed of inner space is higher than outer space,which is mainly due to the barrier of the viaduct to the sun heat transfer and the life activities of the plants under the viaduct.(3)The main types of pollutants in the viaduct stormwater runoff are COD,SS,TN,TP,and the concentrations of Zn,Cu,Cr,Pb,Cd and other heavy metal are less content.Among these pollutants,COD,SS,TN,are the most harmful pollutants to green space environment,next is TP,and five kinds of heavy metal(Zn,Cu,Cr,Pb,Cd)is harmless to the green environment.(4)The soil of shaded green viaduct space is the construction of backfill,which have many problems such as unstable structure,barren,lack of water,impurities and weak water retention capacity.These problems are more prominent in the viaduct which is short of post-maintenance and management.According to the site environment characteristics of Wuhan urban viaduct,this article recommend about 130 kinds of light adapted plants,90 kinds of hydrophilous plants,and 47 kinds of pollution resistant plants,which can be used in Wuhan and other cities with similar climate and plant resources.Subsequently,this paper systematically expounds the basic strategy of plantscape design to adapt to the light and water,then this paper put forward the method of combining plant with water,small garden ornaments and city image.On this basis,this paper also introduces the outstanding cases of different strategies,and propose the greening patterns of shaded green space under viaduct in the urban region of Wuhan.The paper summarizes the problems of the site condition of the shaded green space under viaduct in our country,and puts forward a series of greening strategies in order to provide a theoretical reference for the practice of all the domestic cities.In the end,the author made an outlook on the measurement of the environmental factors and the plant test of the suitable plant species in shaded green space under viaduct.