| The fatigue cracking of asphalt concrete pavement is one of the main failure types of the asphalt pavement, is also the important reason causeing other diseases of the asphalt pavement. The asphalt mixture is a kind of the heterogeneous compound materials, which contains lots of pores and defects, and its performance is related with the composition of materials, also impacted by the temperature condition significantly.All these factors above makes the fatigue the problem of asphalt pavement is always a difficult and hot research in the field of road engineering.Research on the fatigue life of asphalt pavement at present, which can be divided into experimental study and theoretical analysis.The method of experimental study based on the experimental data builds relevant model between the fatigue life and stress or strain under the Pavement structural layerDamage mechanics and fracture mechanics method is the main content of theoretical analysis, the damage mechanics method is commonly used in the current to study asphalt pavement fatigue crack formation stage life, and the fracture mechanics method is used to calculated fatigue crack development stage life,and rarely combined to calculate the whole life of asphalt pavement. In this paper, we study the mechanism of fatigue failure of asphalt pavement, using the nonlinear damage cumulative theory and Paris formula total fatigue life model to establish the whole fatigue life modle,and using the fatigue test to validate the feasibility and effectiveness. The research content of this paper mainly in the following aspects.First, select cross concentrated force beam as research model is derived based on the nonlinear cumulative damage model for fatigue crack formation life analytical solution, and the combination of containing the Paris formula of crack length factor to establish fatigue life model.A nonlinear damage accumulation theory using of crack formation on the relationship between the damage degree and the number of cyclic loading, damage degree and residual fatigue crack forming life relationship.Second, comparative analysis of the advantages and disadvantages of different fatigue test scheme, selection of neutral point bending fatigue test, often force loading pattern, carrying the asphalt mixing material trabecular specimens of bending pull strength test and fatigue test at- 10℃, 5℃, 0℃, 5℃and 15℃.Third, the study on the change law of the fatigue life of asphalt mixture under the different temperature and stress ratio conditions. The study found that with the increase of temperature, the asphalt mixed material fatigue life of small beam specimens decreased gradually; under the condition of the same temperature, asphalt mixing material beam test of fatigue life decreases with increasing stress ratio; when the temperature is high, the asphalt pavement fatigue development stages of life in the fatigue life of the pavement structure accounted for a higher proportion of, under the condition of low temperature of asphalt pavement fatigue development stage of life is small.Fourth, using Origin Software to deal with experimental data,determining the fatigue damage parameter a * and P value at the- 10℃, 5℃, 0℃, 5℃ and 15℃,according to the test data by regression analysis respectively, fitting the a * and P and t(temperature); studying law bettween the crack expansion rate and the variation of the stress intensity factor values,determined Paris formula parameters a and N values under the conditons of 15℃, 0.5,0.6,0.8 three stress ratio. Compared the values of whole life fatigue model to the test, validate the feasibility and effectiveness of the established fatigue life model.Fifth, using ABAQUS software to establish the finite element model of two-dimensional asphalt pavement, combined with the establishment of fatigue life model calculation of fatigue life of the asphalt pavement, the amount of damage and Research on pavement fatigue life changes with the layer thickness and modulus of elasticity. |
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