Research On Durability Of Drained Asphalt Pavement Based On Asphalt Aggregate Interface Theory Under Dynamic Water Pressure

After rain infiltration,dynamic water pressure will be generated in the pavement structure under the load of the vehicle.Repeated scouring will cause the deterioration of the asphalt mixture’s bonding performance and early water damage.In this paper,multi-scale simulation and laboratory test were combined through finite element macro simulation of saturated asphalt pavement,laboratory test of asphalt aggregate interface,and meso-mechanism simulation of porous asphalt concrete.Based on the dynamic water pressure and the asphalt aggregate interface theory,relevant research on the durability of the drainage asphalt pavement was carried out.Firstly,based on the theory of porous media,a three-dimensional finite element model of fluid-solid coupling under dynamic load was established using COMSOL Multiphysics(?)software.The effects of pore water pressure amplitude and distribution in different asphalt pavement structures,drainage layer thickness and different parameters on pore water pressure in the structure were compared and analyzed.The study found that the number of drainage layers increases and the pore water pressure decreases.The positive pore water pressure peak of dense graded asphalt pavement is about 3 times of the negative direction,and the positive pore water pressure peak of the drainage asphalt pavement is about 1～2 times.From the comprehensive simulation results,the sensitivity of each parameter of the pore water pressure of the single-layer drainage asphalt pavement from large to small is in turn the permeability coefficient,peak wheel load,and vehicle speed.Secondly,the changes of pore water pressure in different seepage stages were analyzed.The spatial distribution of pore water pressure,the influence of vehicle speed and wheel load,and the dynamic response of the drainage asphalt pavement structure under arch vertical moving load were explored.The results showed that with the development of seepage,the amplitude of pore water pressure decreases slightly.The pore water pressure in the pavement structure is concentrated near the wheel track,and the positive and negative pore water pressure alternately appear in accordance with the movement characteristics of the vehicle load.The vehicle speed and wheel load are linearly related to the pore water pressure in the structure.Asphalt mixture permeability and stress distribution affect the pressure gradient and seepage flow velocity in all directions.The pore water pressure in the longitudinal direction of the pavement has a greater impact.The three-dimensional stress and strain in the pavement structure are more complicated,but the stress distribution conforms to the characteristics of vehicle movement.Thirdly,The SBS modified asphalts with different viscosities were obtained by a high-speed shear meter.The correlation between the adhesion properties of asphalt-aggregate and the viscosity of asphalt was explored by the bond strength test of the asphalt-aggregate interface.The test results showed that when the SBS content is higher than 6%,the asphalt viscosity increases significantly.The higher the asphalt viscosity,the greater the critical temperature of the interface failure form transition of the asphalt-aggregate bonding test.The 30°C bitumen viscosity can be used as the optimal temperature for the test.The viscosity of asphalt has a high power exponential relationship with the bond strength of asphalt-aggregate.Lastly,based on the cohesive zone modeling and ABAQUS software,through CT technology,digital image processing and Matlab programming,a real meso-structure2D model was established,and the meso-mechanical behavior of asphalt concrete was studied.The research results showed that the cracking path of porous asphalt concrete,along the weak points with large voids,its damage cracking evolution mainly includes four stages:damage,crack initiation,micro crack growth and complete cracking.The bond strength of asphalt aggregates caused by dynamic water erosion is reduced.The potential anti-cracking performance of porous asphalt concrete under dynamic water damage can be evaluated through the definition of different asphalt aggregate interface material parameters.This paper started with the cause of early water damage on the drainage asphalt pavement.Through the macroscopic simulation of the dynamic water pressure inside the asphalt pavement structure,the mechanism of dynamic water damage was clarified.Through laboratory tests,the correlation between the viscosity and strength of asphalt aggregates was established,and the adhesive properties of asphalts with different viscosities were quantitatively evaluated.Combining the meso-scale mechanics analysis of the relationship between asphalt aggregate interface failure and bond strength was of great value for improving the strength of porous asphalt mixture and the durability of drainage asphalt pavement.