| Relying on the advantages of fast construction,low engineering cost and long service period,thin-layer overlay as a preventive maintenance technology has been more and more widely used in recent years.However,the application time of thin overlays is shorter,especially for thin-layer overlays with a thickness of 1 to 2 cm.At present,there is a lack of investigations on diseases of thin-layer including various working conditions,so that the current researches of thin overlays are mainly carried out based on engineering experience.Only by clarifying the main diseases and treating the symptoms can the key technical problems of thin overlays be determined and solved.Based on this,this article conducted an in-depth investigation and research on common diseases of thin overlays in China,and found that aggregate stripping was one of the main disease types of thin overlays.The discrete element model of pavement structure was established to study the mechanical response of pavement structure under different layer thickness conditions,and the meso-mechanical response of thin overlays asphalt mixture under different layer thickness,gradation type and surface modulus conditions were studied.The results showed that the forces were uneven and not completely continuous within 1cm of the thin overlays surface,and the mechanical responses of the pavement structures were not distributed axially symmetrically along the central section of the load.With the decrease of the thickness of the thin layer and the increase of the modulus of the surface layer,the maximum and average values of particle contact normal pressure,normal tension and tangential force gradually increased,which made the aggregate more prone to spalling.In addition,compared with AC-5 overlay,OGFC-5 overlay aggregates were easier to stripping.Through Shear Gyratory Compaction(SGC)test,the compaction characteristics of thin overlays asphalt mixture under different gradation types,specimen sizes,compaction parameters and methods were studied.The results showed that the smaller the target compaction height,the more compaction times needed to reach the target compaction height.When the target height was lower than a certain value,no matter what compaction parameters were used,the specimen could not be compacted to the target height,and the air voids of the specimen were much higher than the target air voids.In addition,based on the discrete element simulation results of rotating compaction,the smaller the forming height,the more significant the distribution of the strong force chain inside the specimen,which indicated that it was more difficult for the pressure to diffuse and transfer adequately inside the specimen.The particles in the weak force chain area could not move and rotate sufficiently,resulting in the specimen compacted difficultly.Using CT and image processing technology,the mesoscopic structure of the specimens molded under different molding methods,gradation types,and target heights were studied.The results showed that for AC-5 asphalt mixture,the smaller the forming thickness,the greater the number of radial cross-section voids,while the opposite trend was for OGFC-5 asphalt mixture.Under different types and different molding conditions,compared with 63.5mm specimens,when the molding height was15mm,the uniformity of the void along the height direction was better,the average equivalent diameter of the void was larger,the gap roundness_was smaller,and the void roundness was worse.It showed that the ineffective compaction was not caused by uneven compaction,but due to insufficient compaction when the thickness was thinner,and insufficient displacement between the aggregates.In addition,the fractal dimension of 15mm OGFC-5 specimens were greater than 63.5mm specimens,reflecting the poor compaction performance when the thickness was thinner.When AC-5 asphalt mixture was molded into 63.5mm specimens,there was uneven compaction,which caused its fractal dimension to be larger.The size and shape parameters of the void gradation distribution function of OGFC specimens were larger than those of AC specimens,indicating that the void area of OGFC specimens had a larger value range,but the degree of concentration was higher.Compared with the63.5mm specimens,the size parameters of the target thickness 15mm specimens were larger,the void area had a larger value range,and the proportion of large voids were larger.A bitumen-aggregate sweep test was proposed to evaluate the adhesion of asphalt and aggregates.Steel brush was recommended as the type of sweeping brush.The amount of asphalt was 0.5 kg/m~2,the curing temperature was 70°C,and the curing time was 4 hours.Besides,the adhesion test results test between different asphalt and aggregates were distinguishable.The three types of high-viscosity asphalt had the best adhesion performance,and rubber asphalt performed worst.The adhesion of limestone aggregate to asphalt was better than that of basalt.The anti-stripping sweeping test was established to evaluate the anti-stripping performance of asphalt mixture.The recommended curing temperature for high-viscosity asphalt and other asphalts was 75°C and 70°C,respectively,The curing time was 4h,and the sweeping time was 10min.The quality loss of the mixture was taken as the evaluation index.The failure development of asphalt mixture during anti-stripping sweeping test were put forward and divided into six stages.The anti-stripping sweeping test were used to evaluate effect of asphalt,aggregates,fibers and mixes gradations on the anti-stripping performance.The results showed that the mixes sweeping test had significant distinguishing characteristics for different asphalts.The results of the mixes sweeping test were compared with the cantabro test results and60℃dynamic viscosities.The results of the cantabro test result and the 60℃dynamic viscosities could not effectively characterize the anti-stripping performance of the asphalt mixture. 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