Study On The Fatigue Damage Performance Of Asphalt Mixture With Considering Loading History

Fatigue damage is one of the main failure types of asphalt pavement, so the fatigue performance of asphalt mixture has become a focus recently. The exiting trabecular fatigue test is under the condition of constant stress amplitude or constant strain amplitude, this loading way is continuous and different from the actual load which asphalt pavement suffer.In fact, there is time interval between vehicles and load size of vechiles is different.Therefore, by improving the strain-controlled fatigue test, this paper studied the impact of the factors above on asphalt mixture, and the main results are as follows:First, by the test, this paper analyzed the influence of temperature, strain size and frequency on the fatigue performance of asphalt mixture, including fatigue life, cumulative dissipated energy, initial stiffness and phase angle. With different stiffness damage criterias and prediction models, fatigue equations were established and parameters are analyzed.Secondly, in order to study the restoration status of stiffness and cumulative dissipated energy of asphalt mixture between different loading cycles, fixed loading times were setted as termination conditions and eaqual restoration time was considered, the effect of test conditions such as restoration methods, temperature and strain size were also analyzed.By comparing the variation law of D=N/N₁ curve of commonly used fatigue damage models, the appropriate model which adapted to strain-controlled fatigue test was selected. The effect of different temperature, strain size and frequency on unit cycle dissipated energy was studied. Based on the mechanics of material, trabecular model was built to simulate the strain-controlled fatigue test, the attenuation law of stiffness with damage propagation was analyzed and different stiffness injury criterias were considered.Variable amplitude fatigue test under strain-controlled mode was conducted to study the effect of loading sequence and loading amplitude on the fatigue performance of asphalt mixture with emphasis on the influence of high-low and low-high sequence on the stiffness and phase angle. Unliner fatigue damage was verified by the cumulative dissipated energy.Based on the Burgers model, the variable strain was written in the form of continuous function by the unit-step function, laplace transform and ilaplace transform were carried on to slove the stress under the condition of variable constant strain. The effect of loading sequence, loading amplitude and variation of viscoelastic parameters on stress were analyzed.The viscoelastic model under variable alternating strain was established and the stress was solved. The theoretical solution and the experimental were compared.