Study On Fatigue Performance Of Asphalt Mixture Under Dynamic Load

With the increase of traffic volume,fatigue diseases of asphalt pavement occur frequently and earlier than the design service life.Predicting the fatigue resistance of asphalt mixture can reduce the waste of resources and pollution caused by maintenance and reconstruction of asphalt pavement.At present,research on the fatigue resistance test of asphalt mixture is being conducted both domestically and internationally.The triaxial repeated creep test is widely used due to its specification for fatigue failure conditions,and the small accelerated loading test is also receiving significant attention due to its high reducibility and authenticity.However,the definition of fatigue failure in the small-scale accelerated loading test is not uniform.Therefore,it is necessary to clarify the failure conditions of the small-scale accelerated loading test through the triaxial repeated creep test,evaluate the fatigue performance of asphalt mixture,and reveal the influence of gradation design on the fatigue performance of asphalt mixture.In this thesis,90# petroleum asphalt is used as the matrix asphalt,and gradation designs of AC-16 and AC-20 are conducted to meet the requirements of the specification for road performance.The fatigue failure criterion of the asphalt mixture is proposed through the triaxial repeated creep test,and the small accelerated loading test is conducted based on the conditions of the triaxial repeated creep test to clarify the failure criterion and basis of the small accelerated loading test.The discrete element simulation software PFC3 D is employed to reveal the difference in fatigue performance among different gradations,predict the fatigue performance of the asphalt mixture,and establish the relationship between the triaxial repeated creep test and the small accelerated loading test.The specific research conclusions are as follows:(1)By calculating the resilient modulus of the triaxial repeated creep test under different conditions,the fatigue failure criterion of the resilient modulus is proposed,and the PD(permanent deformation)model is established to predict the permanent deformation of the asphalt mixture.(2)In the small accelerated loading test,the fatigue failure criterion of the resilient modulus is verified by utilizing the test conditions provided by the triaxial repeated creep test.The grey correlation method reveals that the fatigue resistance of the asphalt mixture is primarily affected by the porosity of the gradation design.(3)Based on the phenomenological method,the triaxial repeated creep test and the small accelerated loading test are correlated.The fatigue life and temperature equivalent curve of the triaxial repeated creep test affected by temperature are established,and the failure condition of the small accelerated loading test is defined.(4)In combination with the resilient modulus fatigue failure criterion,the logarithmic model of the time step and creep strain of PFC3 D simulation for the triaxial repeated creep test is established to evaluate the fatigue performance of the asphalt mixture.A small accelerated loading test model is established,and the relationship between the simulation time step and the actual load cycle times is determined by utilizing the change of strain and resilient modulus to predict the fatigue life of the asphalt mixture.(5)By conducting the clump(cluster model)simulation of triaxial repeated creep test and small accelerated loading test specimens,the influence of the coarse aggregate skeleton structure on the fatigue resistance of the asphalt mixture is explained.It is noted that the fatigue resistance is better when the aggregate skeleton is dense,and vice versa.The results of this thesis can provide scientific data for determining the stop condition of fatigue failure in the small accelerated loading test,offer a theoretical basis for the study of fatigue performance of asphalt mixture,and establish a foundation for the application of the PFC3 D software in the study of fatigue performance of asphalt mixture.