Experimental Study On The Mechanism Of Permeability Attenuation Of Permeable Asphalt Pavement Under The Combined Action Of Multiple Factors

Permeable asphalt pavement,as an important component of sponge cities,has a high porosity structure that can effectively reduce surface rainwater runoff,ensure driving safety,and its connectivity gap can also absorb sound and noise,improve road service quality,have good ecological functions,adjust surface temperature and humidity,and slow down the urban heat island effect.However,its structural characteristics also make it susceptible to the dual effects of cyclic traffic load compaction and the blockage of particles carried by runoff,resulting in a decrease in the effective porosity of the permeable asphalt pavement.The functional advantage of the permeable asphalt pavement gradually weakens,and the decrease in porosity also leads to a significant reduction in its service life.This study starts from the mix design of permeable asphalt pavement in highway engineering,and sets up in-situ blockage tests on actual permeable asphalt pavement to study the impact of different blockage conditions on the permeability performance of permeable asphalt pavement.During a certain road service period,the permeability coefficient at different positions on the road cross-section is tested to study the attenuation characteristics of the permeability performance of actual permeable asphalt pavement.In order to study the impact of vehicle load on permeability performance,accelerated loading tests were conducted under different load conditions.On this basis,the conditions of clogging particles and rainwater erosion were added to study the mechanism of permeability degradation of permeable asphalt pavement under the combined action of multiple factors.While studying the mechanism of permeability attenuation,in order to obtain a permeable asphalt pavement structure that can effectively alleviate permeability attenuation,multi factor coupled accelerated loading tests were conducted on asphalt mixtures with different porosity and aggregate particle sizes.On the basis of the above,combined with industrial CT scanning technology,the pore characteristics of permeable asphalt mixtures with different particle sizes of aggregates are studied from a microscopic perspective,and their permeability performance is analyzed.At the same time,the pore characteristics of different graded blocked sand after accelerated loading tests are analyzed.According to the results of in-situ blockage test and permeability coefficient measurement,it was found that fully mixed particles have the most severe blockage effect on permeable asphalt pavement,followed by coarse particles and fine particles;The greater the rainfall intensity,the lower the degree of blockage of permeable asphalt pavement;The more times the erosion occurs,the degree of blockage gradually recovers.The service time of permeable asphalt pavement is relatively short,and the overall trend of the development of pavement permeability from the middle belt to the green belt is that the permeability is becoming lower and lower.According to the accelerated loading test,it was found that with the increase of loading times and axial load,the permeability gradually decreases;As the loading speed increases,the loss of permeability gradually decreases;The presence of water environment results in more severe attenuation of permeability and greater rutting depth;Blocking particles can alleviate the aggravation of rutting to a certain extent;Under the joint action of multiple factors,the fully integrated sand distribution has the greatest contribution to the permeability attenuation of permeable asphalt pavement;The lower the porosity,the smaller the attenuation of permeability;When the porosity is the same,the permeability retention of PAC-16 is the highest.Based on CT scanning technology and analysis results,it was found that the larger the maximum nominal particle size,the lower the proportion of connected voids,the more uneven the distribution of two-dimensional voids,and the smaller the overall number of pores.The porosity structure of PAC-13 has a higher coordination number,and the permeability is optimal under the same design porosity.Full set sand mixing has the greatest effect on reducing the porosity of permeable asphalt pavement.The blocking particles of coarse sand are mainly concentrated on the surface of permeable asphalt pavement,while fine sand can cause deeper structural blockages.