| Urban heat island effect is a phenomenon that the annual temperature of urban near-surface atmosphere is higher than that of suburban area.Among all the influence factors,the urban surface condition is an important one.With the development of social economy,the scale of the city is expanded,which has intensified the urban heat island effect.The environmental problems caused by global warming,air pollution and urban smog are becoming more and more prominent.As an important part of the urban surface,urban roads have a significant impact on the near-surface atmospheric temperature with its special thermal properties.Pavement,as a kind of road surface structure,is a direct carrier for urban roads to affect the near-Earth atmosphere in the form of thermal scattering.Therefore,the influence of urban road pavement on urban heat island effect was studied.In this study,the temperature field of road pavement and its influencing factors were analyzed.Then,the evaluation indexes of urban heat island based on the urban road pavement were established.The conclusion obtained by this study can be regarded as a reference in road construction to alleviate the urban heat island effect.The effect of urban road pavement on the urban heat island was verified through analysis on the generation and developing factors of the urban heat island,combined with the analysis on the relationship between near-surface atmospheric temperature and road surface temperature based on the field test.in Xi'an.In order to further clarify the influencing factors of road pavement temperature,the finite element models of asphalt pavement and cement pavement temperature field were established.The reliability of the finite element models was verified by field test.Based on this,the temperature distribution at the characteristic points of asphalt and cement pavement was analyzed.The results show that the variation of asphalt pavement temperature is similar to that of cement pavement.The temperature variation at the specific point of each pavement is consistent with the near-surface atmospheric temperature,both show a sinusoidal change trend.But the temperature change period of cement pavement is longer than that of asphalt pavement.At the same time,the external factors affecting the pavement temperature field was determined,which were temperature,solar radiation and wind speed.The internal factors are paving material properties and paving structure.The distribution of the temperature field was studied by changing the values of influence factors in the finite element model.The results show that the pavement temperature is positively correlated with solar radiation value,near-surface atmospheric temperature and pavement absorption rate,wind speed and pavement thermal conductivity.While,the specific heat capacity,emissivity,water content,void ratio and thickness are negatively correlated.Further analysis of the sensitivity of internal factors shows that the thermal property sensitivity of pavement materials from high to low is: absorption rate> emissivity> thermal conductivity> specific heat capacity.The sensitivity of pavement structure from high to low is: water content> Void ratio> thickness.According to the different sensitivity of each factor,combined with the actual pavement situation,the evaluation indexes of urban heat island effect were established from the perspective of urban road pavement,which were thermal conductivity,specific heat capacity,absorptivity and emissivity of pavement materials,void ratio and water content in pavement structure.The impact weight and evaluation criteria of each index were determined through the analytic hierarchy process,and the fuzzy evaluation method was selected to comprehensively evaluate the urban heat island effect.Four road paving schemes were randomly selected for comparison by fuzzy evaluation method and an optimum scheme was then determined.The optimality of the selected scheme was verified by the pavement temperature field model. |
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