Research On Fatigue Damage Behavior Of Asphalt Pavement Based On Gradient Aging

During the service of asphalt pavement,the asphalt will gradually deteriorate due to the influence of the external environment,and the distribution of asphalt aging in the pavement is uneven and has a certain gradient.Aging will cause the performance of asphalt mixtures to change,which will have an impact on pavement forces.Therefore,based on the premise of gradient aging,this paper studies the stress characteristics and fatigue damage characteristics of common semi-rigid base asphalt pavements,the long-term fatigue damage development law of semi-rigid base asphalt pavements is also explored.Firstly,the constitutive relationship of asphalt mixture is studied in this paper.A viscoelastic constitutive model with temperature adjustment coefficient is derived from the viscoelasticity of asphalt mixture,a damage constitutive model is derived based on the pseudo-strain theory,and a numerical implementation is carried out in the finite element subroutine UMAT.Secondly,the parameters of the constitutive model were obtained by means of dynamic modulus test and four-point bending fatigue test.Then the experiments were simulated in the finite element method.The results show that the simulation results in this paper have a good correlation with the test results,and can reflect the stress characteristics of asphalt mixture.Subsequently,the temperature field was calculated in the finite element and compared with other data to verify the accuracy.The results show that the temperature field calculation method used in this paper is consistent with the actual measurement results and can reflect the temperature distribution inside the asphalt pavement.Finally,based on the temperature field,this paper studies the stress characteristics of semi-rigid base asphalt pavement,and the long-term development law of asphalt pavement with semi-rigid base is summarized.The study found that the maximum horizontal tensile stress at the bottom of the asphalt surface layer of the semi-rigid base asphalt pavement increases with the decrease of the base modulus,and the deepening of the aging degree also increases the tensile stress at the bottom of the surface layer to some extent.During the process of moving load,the stress and strain at the bottom of the asphalt surface layer will go through the transition stage of “compression-tension-compression”,the horizontal stress at the center of the two-wheel load will also change from compression to tension as the depth increases.The influence of external factors on fatigue damage is different.Temperature can change the distribution of stress in the pavement.Increasing the tire pressure will also increase the stress and strain at the bottom of the asphalt layer.Neither can be ignored in the research.