The Research On Particulate Characteristics And Landscape Improvement Measures Of Shaded Space Under Viaduct

A large number of viaducts in China have occupied urban space and land use,resulting in a lot of negative bridge space.In cities with insufficient public activity space,many bridges and yin spaces are being used spontaneously by people to carry out activities such as leisure,gatherings,and even morning exercises under the bridge.The pollution of particulate matter under the bridge will cause great health hazards to the active people,but different bridges and surrounding environment can have different effects on the particles in the bridge space.This paper screens 6 qualified sample viaducts in Wuhan,and selects14 representative bridges and cathode space standard sections as measured samples.In summer and winter typical weather,the concentration of particulate matter(PM_1.0,PM_2.5,PM₁₀,TSP)is carried out,the moving point of temperature and humidity in bridge space,synchronous monitoring at fixed point,to explore the distribution of different forms of particulate matter in bridge space and the influence of nine environmental factors on the concentration of particulate matter in bridge space,which may be an active activity for bridge safety.Urban public space provides a reference for landscape construction strategies based on the reduction of particles of viaduct shadow space.Firstly,the distribution characteristics of the bridge space in the different cross-sectional space forms（full-cover,central green belt,and green belt on both sides）in summer and winter,and the relationship between particles with different particle sizes are analyzed.Secondly,choose the temperature,humidity,greening width and area of the bridge space,and the outer space of the bridge（the range of the standard section of the viaduct is 50m outward）.The green area,building area,building distance and opening degree,and the aspect ratio of the viaduct.9 kinds of environmental factors,respectively,and the regression analysis of single factor and comprehensive factors of the particle concentration of the bridge and the space,and explore the influence of each environmental element on the concentration of the bridge.Finally,taking the typical monthly climate parameters and typical viaduct model of Wuhan as an example,combined with ENVI-met software,a three-dimensional model of roof greening,four kinds of human-car separation greening modes,four building heights and three water body areas is established.This paper compares and analyzes the variation of particulate matter concentration in bridge space,and combines the previous literature research to propose a particle improvement strategy for some of the available space under the bridge from the aspects of greening,building and space occlusion,water body and material application.The analysis found that:（1）the center position of the full-coverage and the central sub-strip type bridge space has a certain degree of particulate matter concentration lower than the position on both sides of the bridge and the bridge.The influence of particle concentration distribution is weak.（2）The concentration of Qiaoyin particulate matter is significantly higher than that in summer,and the summer concentration is lower than the spatial concentration outside the bridge.In winter,the opposite is true.（3）There is a linear relationship between the particle size of each particle size in the bridge space.The closer the particle size is,the more obvious the linear relationship is.The R² of PM_1.0 and PM_2.5 in summer is close to 1,and the fitness is the highest.（4）The determination coefficient of all environmental elements in multiple regression is higher than the simple correlation determination coefficient.The influence of the concentration of bridge-yin particles on the interaction is obviously increased.（5）The influence of temperature and humidity on the concentration of fine particles is large,and it is more obvious in summer than in winter.The influence of surrounding environmental factors on coarse particles is greater,and the winter is more obvious than in summer(6 Among the four particle size particles,PM₁₀concentration is more susceptible to these nine environmental factors,followed by TSP,PM_2.5 and PM_1.0 concentrations are most affected by environmental factors other than temperature and humidity..Combined with ENVI-met simulation,it summarizes the suggestions for improving the particulate matter of the bridge and the space from the aspects of greening,building and space shielding,water and material application:（1）Try not to plant trees in the bridge space,and combine the shade-resistant and pollution-resistant herbs with the shrubs.The planting is good;the surrounding space is dominated by deciduous trees,with appropriate matching of evergreen trees,and the spacing between trees is increased to reduce the barrier to the spread of particulate matter;the separation of human or low shrubs in the separation zone of people and vehicles on the diffusion of particulate matter in the bridge More favorable（2）The increase of the height of the buildings on both sides of the viaduct will increase the particulate matter in the bridge space.When planning the construction of the viaduct,the aspect ratio of the entire valley should be properly controlled.Increasing and reducing the spatial occlusion at different locations is also affected.Important means of particle concentration in the bridge space（3）Different types of water bodies are set in the bridge space.Reasonable use of underlying surface materials and special adsorptive materials at different locations is also beneficial to improve the particulate matter in the bridge and cathode space.