Study On The Water-Retaining Behavior And Cooling Performance Of Urban Permeable Asphalt Pavement

The application of permeable pavement in urban road can effectively improve the water and temperature state of the urban underlying surface,realize the comprehensive utilization of rainwater,and inhibit the development of the urban heat island effect,which is an important part of the “sponge city” construction system under the concept of low impact development.The temperature change behavior of permeable pavement shows complex features under external hydrothermal environment.Scientifically analyzing and accurately grasping the hydrothermal change behavior of permeable pavement,which is conducive to improve the design and evaluation system of urban permeable pavement.In this study,the laboratory tests and numerical calculation methods were used to analyze the temperature change behavior of permeable pavement structures under water-retaining condition.The theoretical calculation models were established to analyze and evaluate the retained water's cooling mechanism and effect of permeable pavement.The road surface cooling effect of different types of permeable pavement structures was compared and analyzed by numerical calculation model,which provided the basis for the design and selection of watrer-retainning urban permeable pavement.Based on the porous media percolation theory under potential energy action,selected typical permeable pavement materials such as OGFC-13 asphalt mixture and graded gravel mixture.The water-retaining behavior of permeable pavement materials under different penetration conditions was analyzed,and the retained water evaluation indices were determined.The variation and influencing factors of permeable pavement materials' water-retaining effect under different penetration conditions were analyzed.The relational model of the water-retaining rate under the influence of material parameters was established,and the model reliability was verified.The heating test models for different types of the permeable pavement structures were established,the feasibility of the indoor model test was verified,and the accuracy and system error range were determined.Through the indoor test,the temperature change behavior of the permeable pavement under different heating and water-retaining conditions was simulated.The relationship between the pavement types,structural depth,water-retaining state,heating conditions,heating time and the temperature domain was analyzed.The predictive calculation model of the permeable pavement temperature variation was established,which provided the analysis reference for the the heating behavior of permeable pavement structures.Aimed at the water-retaining cooling behavior of permeable pavement,the time domain of the water cooling effect was divided.Based on the heat capacity variation and cumulative effect theory,the analysis method,evaluation indices and theoretical calculation models for the water cooling effect of permeable pavement were established.Based on this,the action mechanism of water cooling effect was revealed.From the perspective of the cooling effect and sustainability,the basic characteristics and influencing factors of permeable pavement's water-reataining cooling effect were analyzed.The ABAQUS finite element analysis software was used to establish the permeable pavement road surface temperature calculation model.The significant influence of the permeable pavement parameters,which were the layer thickness,specific heat capacity and thermal conductivity coefficient,on the road surface temperature were compared under the actual heating conditions.Based on this,the road surface temperature variation between non-permeable,surface permeable,base permeable and fully permeable pavement structures were compared under dry and water-retaining conditions,and the surface cooling effect of different pavement structures was compared.The cooling effect difference of permeable pavement road surface under water-retaining state was quantitatively analyzed.The short-term and long-term road surface cooling effect of permeable pavement was verified through actual urban road surface temperature observation tests.The above research provided the analysis basis and reference for the structural design and functional evaluation of water-retaining permeable pavement.