Experimental Study On Clogging And Cleaning Behavior Of Porous Asphalt Mixture

Permeable asphalt mixture is an environment-friendly asphalt mixture with connectivity voids formed according to specific gradation,which has certain strength and water permeability.Permeable asphalt mixture has been widely used in road engineering,municipal engineering and garden engineering,and has achieved good social,environmental and ecological benefits.However,the voids in the road construction paved with permeable asphalt mixture are easy to be filled by sand and gravel and other substances,resulting in blockage problems and a decrease in water permeability.In order to alleviate this problem and further promote the application of permeable asphalt mixture,scholars from various countries have studied the cleaning methods of blocked mixture.In this paper,firstly,the rotary compaction method is selected as the molding method of permeable asphalt mixture,and the distribution characteristics of void ratio in permeable asphalt mixture are explored.A set of blockage device for permeable asphalt mixture was developed using dewatering head to measure the permeability coefficient of permeable asphalt mixture,and uses normal water head to realize the blockage of permeable asphalt mixture.Through comparison,waterproof putty is smeared around the top of the mixture as the method to prevent side leakage.The permeability coefficient measured by the device conforms to the theoretical value and the test result is stable.Then,plugging experiments are carried out on permeable asphalt mixtures with different void ratios to explore the influence of void ratios on plugging results.High-pressure flushing was selected as the experimental cleaning method,and the mechanism of high-pressure cleaning was preliminarily explored.Finally,three cleaning thresholds representing different blockage degrees of the mixture,0.3 mm/s,0.5 k0,0.25 k0 are selected.It is stipulated that high-pressure cleaning measures should be taken when the permeability coefficient of permeable asphalt mixture decreases to the cleaning threshold.A set of experimental procedures are designed to simulate the blockage and maintenance process of permeable asphalt mixture,and high-pressure cleaning is carried out on the mixture with target void ratios of 15%,20% and 25% by high-pressure water gun.It is found that the permeable asphalt mixture formed by rotary compaction has more voids at both ends and less voids in the middle,and most of the blockages accumulate in the upper part of the permeable asphalt mixture.High pressure cleaning can wash away the blockages in the upper part of the mixture and maintain the connectivity of the voids again.In addition,the recovery effect of high-pressure cleaning decreases with the increase of blockage process.Compared with permeable asphalt mixture with low porosity,higher porosity has slower permeability coefficient attenuation,better anti-blockage performance and better recovery effect after high-pressure cleaning.In a word,exploring the blockage and cleaning process of permeable asphalt mixture can provide scientific and effective basis for the formulation of cleaning measures of permeable asphalt mixture and the design of permeable asphalt mixture.