Comparative Study On Fatigue Characteristics Of Asphalt Mixture Under Uniaxial Tensile And Four-Point Bending Loading Mode

With the increasing improvement of the national transportation system,most of the domestic pavement structure adopts asphalt pavement with the advantages of good flatness and driving comfort,but with the increasing service period of asphalt pavement,asphalt pavement will occur in various forms of damage,fatigue damage is one of the most important forms of damage.At present,there are many test methods for predicting the fatigue life of asphalt mixtures,but the test data obtained by each fatigue test are quite different and do not have high comparison.Therefore,this paper will compare the fatigue characteristics of asphalt mixture through two fatigue tests,uniaxial tensile fatigue test and four-point bending fatigue test,so as to provide reference for asphalt pavement structure design.In this paper,the uniaxial tensile fatigue test and four-point bending fatigue test of four different types of asphalt mixture were carried out at three strain levels,the initial dynamic modulus of the material and its corresponding loading cycle times under different fatigue test methods were determined,and the dynamic modulus change law of the whole stage under different strain levels was analyzed,the fatigue life results of asphalt mixture were analyzed,and the fatigue life estimation model of the relationship between the number of loading cycles,strain level and dynamic modulus was established.The fatigue characteristics of asphalt mixture under different loading modes and the correlation between the two fatigue tests were compared.Bisar3.0 software is used to calculate the mechanical response in the structure of asphalt pavement of flexible base layer,so as to obtain the tensile strain data of the bottom of the asphalt layer,and the fatigue life estimation model of asphalt mixture under different test specifications is used to estimate its fatigue life.The experimental results show that the initial dynamic modulus obtained by the four-point bending fatigue test and the uniaxial tensile fatigue test is not much different,and the dynamic modulus change law of asphalt mixture in the whole stage under the two fatigue tests is divided into three stages.The four-point flexural fatigue test has a good correlation with the uniaxial tensile fatigue test,and can convert the four-point flexural fatigue data and the uniaxial tensile fatigue data equivalently.The fatigue life estimation model based on different specifications has a good correlation with the fatigue life estimated by the estimation model based on uniaxial tensile fatigue test,so that the fatigue life estimation model based on uniaxial tensile fatigue test can be used in the design of asphalt pavement structure.