Viscoelastic Mechanical Response Analysis Of Asphalt Mixture And Asphalt Pavement Under Dynamic And Static Loads

As an important part of highway,the asphalt pavement has an important impact on the safety,comfort and durability of highway service.Asphalt mixtures has the typical viscoelastic properties that are closely related to loading time,loading frequency,load type,and environmental temperature.In order to analyze the viscoelastic mechanical response of asphalt mixtures and asphalt pavement under dynamic and static loading modes and the effect of temperature shrinkage stress on asphalt mechanics,the following work is carried out according to the National Natural Science Foundation project:(1)AC-13,SMA-13,SUP-13,and OGFC-13 graded asphalt mixtures were prepared by the Superpave gyratory compactor and using the rubber modified asphalt as the binder.Subsequently,the uniaxial compression creep tests are applied to test the static creep characteristics of four graded asphalt mixtures under multiple temperatures,and the creep master curves of four graded asphalt mixtures are obtained and plotted by using timetemperature equivalent principle.In addition,Burgers model and modified Burgers model are used to analyze the creep characteristics.Furthermore,in order to comprehensively analyze the relaxation properties of the four graded asphalt mixtures,the relaxation modulus of the four graded asphalt mixtures is deduced by the convolution integral,Laplace transformation and Simpson quadrature formula.The second-order generalized Maxwell model and Scott-Blair model are adopted to analyze the influence of different temperatures and gradation on the relaxation characteristics of asphalt mixture.(2)The dynamic modulus of four graded asphalt mixtures under dynamic load at 10?,20?and 30? are obtained by dynamic modulus tests,and the dynamic modulus master curves of the asphalt mixtures at 20? are calculated by time temperature equivalent principle.The dynamic modulus and phase angle of four graded asphalt mixtures are fitted and analyzed by improving sigmoid model.Then,according to the time-frequency conversion principle and the static relaxation modulus data,the dynamic modulus of four graded asphalt mixtures is obtained,and the difference between the dynamic modulus data measured directly and the dynamic modulus data derived from derivation are compared and analyzed,and the functional relationship between the dynamic modulus obtained from the test and the derived dynamic modulus is established.The results show that there is a good linear relationship between them,and the derived dynamic modulus is about 7-10 times of the dynamic modulus obtained from the test.(3)According to ABAQUS finite element software,the three-dimensional finite element model of asphalt mixture indoor tests(uniaxial compression creep test,dynamic modulus test)is established,and the viscoelastic mechanical response of asphalt mixture specimens under dynamic and static load is studied through finite element simulation.Then,according to WLF equation and temperature shrinkage coefficient of asphalt mixtures,the numerical model of temperature shrinkage test of four kinds of graded asphalt mixtures is established,the temperature shrinkage characteristics of four kinds of graded asphalt mixture are analyzed,and the cracking temperature of four kinds of asphalt mixture under different cooling rate is proposed.The results show that the indoor test results are close to the numerical calculation results,and the average error is less than 10.35%.Under the same cooling rate,AC mixture has the lowest crack initiation temperature.(4)The three-dimensional numerical model of asphalt pavement constructed by four kinds of graded asphalt mixture is established by using ABAQUS finite element software,and the variation characteristics of internal stress,strain and deflection of each structural layer with loading and unloading time under static load are analyzed by finite element software.The influence of gradation type and vehicle speed on the internal stress-strain response of each structural layer of asphalt pavement is analyzed by applying moving load with different speed.The results show that: due to the viscoelastic properties of asphalt mixture,the asphalt pavement will still have some residual deformation after unloading;the rutting deformation caused by long-term static load is much higher than that caused by high-speed dynamic load.