Analysis Meso-Mechanical Behavior Of Asphalt Pavement Structure Based On Tire-Road Coupling Effect

The transformation of asphalt pavement structure design from static to dynamic has become a hot topic in the field of road engineering worldwide.When uniformly distributed static loads are used as the load form and the macroscopic homogeneity of the pavement structure materials is considered in pavement design,it inevitably leads to a disconnection between the design and service stages.To address these issues,this study is based on tire-road coupling dynamics and considers the non-uniform characteristics of tire loads.Through a combined simulation approach using numerical calculations and finite element analysis,a refined representation of tire load input is achieved.A microstructure model is established based on image processing techniques to analyze the mechanical behavior of the pavement structure at the microscale,taking into account the macroscopic loading characteristics and the connection with the microstructure of the asphalt pavement.The primary research work conducted can be summarized as follows:(1)A quarter-vehicle road-terrain coupled dynamic model is constructed based on the nonlinear Euler-Bernoulli foundation beam.The parameters of the pavement structure are pre-defined,and the influence of different speeds and vehicle dynamic loads is taken into account to obtain the vehicle dynamic loads under uneven road excitation.By integrating the measured tire parameters,the non-uniform characteristics of tire loads are accurately represented using the Uni-tire theory model.(2)Considering the viscoelastic properties of asphalt mixtures,a finite element model of the asphalt pavement layer system under non-uniform loading is established based on experimental sections.Through a combined simulation approach,accurate external loads are obtained to analyze the influence of different loading conditions and the superposition effect of multiple-wheel axles on the dynamic response of the pavement structure.The functional characteristics of different layers in the asphalt pavement are determined based on the dynamic response at different depths.The results indicate that the influence of non-uniform dynamic loads on various response indicators of asphalt pavement structures accounts for more than 15%,while the vehicle-pavement coupling effect contributes to approximately 3% of the dynamic response.For multiple axle loading configurations,with a 27.2% superposition effect on the vertical stress between the middle and rear axles.(3)Based on image processing techniques,the relationship between the twodimensional and three-dimensional microstructures of asphalt mixtures is established.Industrial computed tomography(CT)scanning is used to obtain microstructure images of asphalt mixtures,and image processing techniques are employed to extract two-dimensional microstructure parameters.Volumetric calculations based on various assumptions of regular bodies are utilized to convert between two-dimensional and three-dimensional microstructure parameters.Considering the spatial structure of the specimens,a symmetric spatial extraction method is used,and it is found that a minimum of five images are required to establish the three-dimensional equivalent two-dimensional model of asphalt mixtures,providing a basis and method for the establishment of microstructure models.(4)A microstructure finite element model considering cohesive zone model(CZM)theory and image processing techniques is developed to incorporate cohesiveadhesive forces.Based on the macro-micro cross-scale model and analysis methods,the microscale loading characteristics of different layers in the asphalt pavement structure are analyzed.Indicators representing the stress distribution of the microstructure are proposed,and the influence of non-uniform loading on the microstructure is clarified.The results show that under non-uniform loading,the peak stresses in the microstructure can reach 1.5 to 4 times those under macroscopic loads.Compared to the stress distribution under uniformly distributed loads,the vertical stresses in both mortar and aggregate increase by more than 40%,while the maximum increase in the transverse stress is 34.8% for aggregate and 94.3% for mortar.The stress distribution inside the microstructure under uniformly distributed dynamic loads is more uniform compared to non-uniform loading,which leads to significant uneven internal stress distribution in the microstructure under non-uniform loading.