Study On Vegetation Construction And Influence On Traffic Noise In Ji-Qing Highway Of Zibo Section

Highway construction brought about some negative impact on ecological environment and vegetation resources along the line, especially serious noise pollution by the strong radiation of traffic noise. Therefore, vegetation rehabilitation was an important part of highway construction. Based on field investigation and data processing of regressive analysis, canonical correlation analysis, principal components analysis, etc., a systematic research was conducted on the traffic noise attenuation effect of shelterbelt forest, using Zibo section of Ji-Qing Highway as study object. It showed that:(1) In view of different afforested demand, different types of vegetation establishment were carried out in central partition, subgrade slope, road side, intercommunication area, service area,etc, which took a great role to environmental protection and the landscape beautification. Louver type dizziness preventing planting pattern was designed in central partition, wall-to-wall grass planting pattern was conducted in slope, and zonal companion planting pattern was developed in sheltbelt. Considering artistic vision effects, planting pattern was unitary, thus, the biodiversity had relatively lower level and larger fluctuation in the different road section.(2) The highway traffic noise pollution was extremely serious. With the 24-hour equivalent sound level 76.2 dB(A), it was beyond the standard extremely. And traffic noise was obviously affected by driving condition, such as vehicle flow, vehicle type, vehicle speed, load, maintenance condition, etc... Regression analysis showed that power exponential equation Y=49.5930X^0.06 was the optimal model to reveal the relationship between traffic noise and vehicle flow. Among them, small vehicle had extremely significant correlation with traffic noise, whose correlation coefficient was 0.5595, and the next were large vehicles.(3) Based on the traffic noise contrasting monitor in the forest land and bare land, it indicated thatα=0.38, f=1000Hz, k=0.12 were suitable in FHWA prediction model, American forest attenuation model and forest belt attenuation experience model, all of those had a high confidence level.(4) Different forest belts had different effects on traffic noise attenuation, which were much better than no-forest land. Experiment results indicated that through a sheltbelt with a width of 125m, noise attenuations may reach above 6dB(A), for 18.7%～26.7% being cut down. Concerning with each branch-leaves characteristics, the noise attenuation ability of Sabina chinensis was superior to Canadensis Moench, Populus, and Sorphora japonica.(5) The width of forest belt was a key attenuations factor. In order to revael the relationship of them, manifold regression analysis models using monitor data were established, such as linear model, quadratic polynomial model, compound model, growth model, logarithmic model, exponential model, cubic polynomial model, logisstic model, inverse model, power exponent model, S curve model. It was obtained that Y=b₀+b₁x+b₂x² +x³ was the optimum model. And traffic noise attenuation may achieve a relatively stable state after 100m belt.(6) The effects of forest belts on noise attenuation changed much with the seasons. The reduction effect was of significant difference between the winter and the autumn, the winter and the summer, the spring and the summer. And there was the most remarkable difference between the winter and the summer. Thus, a great attention should be payed to the allocation of evergreen species and deciduous species.(7) Planting spacing, tree height, clear bole height, DBH, crown width, canopy density, porosity, species diversity were screened out as the effective forest attenuation parameters. There were closer relativity of noise reduction with tree height, crown width, canopy density, porosity and species diversity , especially with tree crown width.