Study On Modification Of Fatigue Performance And Life Prediction Model Of Asphalt Mixture During Service Period

In the long-term service environment,asphalt pavement should not only bear the internal damage caused by vehicle load repetition,but also consider the influence of temperature change on asphalt mixture.When the fatigue damage occurs to the asphalt pavement structure,the performance of the material also decreases.Fatigue cracking still occurs frequently on asphalt pavement in service.Scholars pay more and more attention to the assessment of residual carrying capacity and residual life of asphalt pavement in service period.Therefore,it is of great significance to the reconstruction design,construction and maintenance of old asphalt pavement to study the fatigue damage law of asphalt mixture under the action of multiple factors and establish the prediction model of the corresponding fatigue life.According to the test road cut of graded gravel base asphalt pavement which has been loaded more than 9 million times of standard axle load and the road cut of Ji-Qing expressway which has been in service for 25 years.The three-point loading four-point bending fatigue test in strain control mode was carried out with universal material testing machine 810,and the accelerated loading test was combined with the field test road.The fatigue performance and life prediction model of asphalt mixture in service period are further studied.The main contents are as follows:Firstly,a second-order equation with curvature was obtained by multiple regression analysis of strain,temperature,speed and other influencing factors and their response values by response surface method.The significance of each factor to initial stiffness modulus,fatigue number,phase angle and dissipated energy was determined by variance analysis of regression equation.The influence degree of multi-factor interaction on response value was analyzed by contour diagram and three-dimensional diagram,and the optimal scheme of four-point bending test of asphalt mixture was proposed.Secondly,based on the four-point bending fatigue test data of asphalt mixture cutting parts during service period,the fatigue damage evolution law of asphalt mixture during service period under the action of single factor was analyzed,and the applicability of the indoor fatigue life prediction model in "Research on Design Indexes and Parameters of Asphalt Pavement" to asphalt mixture during service period was verified.The fatigue life prediction model of asphalt mixture used for accelerated loading modification is determined.Thirdly,based on the paved graded gravel base asphalt pavement test road,the fatigue loading test at 15℃ was carried out with the help of full-temperature domain scaling accelerated loading testing machine S100.The mechanical response data of pavement under different times of wheel load were collected,and the attenuation law of pavement fatigue performance was analyzed.The static and dynamic strain and FWD strain of asphalt mixture layer under heavy load were obtained.Based on FWD bending detection and reverse calculation of asphalt mixture modulus at different damage stages,the reverse calculation modulus and bending modulus of asphalt mixture with loading times were analyzed,and the reverse calculation modulus and temperature correction model of asphalt mixture was established.Conscription was established by Sigmoidal function fitting residual modulus of asphalt mixture ratio and loading times,the relationship between modulus of asphalt mixture is constructed nonlinear damage evolution model of attenuation,and analyzed the pavement structure strength and bearing capacity with the number of wheel load and the change of environment,reveals the attenuation law of fatigue performance of asphalt mixture.Finally,combined with loading mode coefficient,field correction coefficient,transverse distribution correction coefficient and standard axle load conversion coefficient,the APT test road asphalt mixture fatigue life prediction correction model is established,which provides a basis for asphalt mixture residual bearing capacity evaluation and asphalt pavement life prediction.