Research On Fatigue Damage Characteristic Of Asphalt Mixture Based On Accelerated Loading Test

Asphalt pavement is the main pavement type of high-grade highway.Fatigue cracking is one of main destruction forms of asphalt pavement.The study on the fatigue performance of asphalt mixture not only allows us to understand and master the mechanical properties of the asphalt mixture, fatigue damage law,but also improves the fatigue properties of asphalt mixture, pavement performance and service life. A majority of domestic and foreign scholars and researchers carried on in-depth studies on the fatigue properties of asphalt mixture,mainly on indoor small beam specimen fatigue test,such as tension- compression fatigue test,bending fatigue test, indirect tensile fatigue test.The fatigue test methods have some limitations,they can not simulate actual road working state.It will have a certain bias on the evaluation of the fatigue performance of asphalt mixture based on these fatigue test methods.Therefore,with the help of the small-scale accelerated loading test equipment,this article will establish the stiffness decay equation of asphalt mixture by testing resilient modulus under different loading times,and reveal fatigue damage law of asphalt mixture.The fatigue damage variable is defined by the modulus decay basing on the basic theory of damage mechanics. The stiffness decay equation was deduced,accelerated loading test was conducted on six different types of graded asphalt mixture.The accelerated loading test data was fitted and the model parameters were obtained by using the stiffness decay equation through the fitting software,the fitting results present a good correlation. Then,the stiffness decay equation of asphalt mixture are established based on accelerated loading test.Damage evolution law of asphalt mixture is analyzed during fatigue failure process.The evolution process of asphalt will undergo three stages,namely migration phase,stable phase,acceleration phase.Fatigue failure criterion is proposed, the maximum value of stiffness decay rate which is attained from the stable phase turning into fatigue damage stage is regarded as the fatigue failure point.The fatigue life obtained by using this criterion is consistent with the results,verifying the reasonableness of the proposed fatigue failure criterion.By contrast with interior specimen fatigue test,the small-scale accelerated loading test shows the scientificity and rationality in the study of fatigue performance of asphalt mixture.The research results can provide theoretical reference for the fatigue life forecast and fatigue damage characteristics research of asphalt mixture,and have reference value for improving design method and durability of asphalt pavement.