Research On The Influence Of Mixture Internal Fissure On Fatigue Performance Of Asphalt Pavement

Asphalt mixture is the most widely used pavement material for high-grade highways in my country,and it is also the preferred form of pavement surface structure in my country today.At present,the traffic tends to be heavily loaded,resulting in different cracks on the asphalt pavement.Scholars at home and abroad have carried out related researches on different cracks and interface cracks of asphalt concrete pavement,and analyzed the influence of cracks on the structural mechanics and fatigue characteristics of asphalt concrete pavement under different working conditions.The road performance of asphalt pavement is greatly affected by the internal structure such as void ratio.In the actual construction process,due to segregation of asphalt mixture,cracks may be generated in the asphalt mixture.Therefore,the existence of internal crack defects on the pavement The impact of the structure is significant.This paper obtains the influence of the internal cracks of the asphalt mixture on the fatigue life of the asphalt pavement through fatigue test and simulation analysis.The main research work is as follows:Analyze the possibility and reason of internal crack formation of asphalt mixture in combination with the actual project,define the internal cracks of the mixture,introduce the internal crack coefficient of the mixture as the index of quantitative analysis,and use the foil paper to wrap different quality products through theoretical analysis and related calculations.The machine-made sand realizes different internal crack coefficients,and carries out the design of the AC-13 asphalt mixture mix ratio.Preset the asphalt mixture specimens with different internal crack coefficients.Through the three-point bending test and the shear strength test,the two mechanical performance tests are used to study the impact of internal cracks on the mechanical properties of asphalt pavement,and analyze the impact of internal cracks on the mechanical properties of the pavement.the reason.The test results show that as the internal crack coefficient increases,the flexural tensile strength and shear strength of the specimen gradually decrease,and the time it takes for the specimen to be destroyed also decreases;the internal fissures of the mixture have an effect on the flexural tensile strength of the asphalt pavement.The influence of strength is more obvious,and the influence of shear strength is weak.The existence of internal cracks reduces the mechanical strength of the structure and reduces its mechanical properties.The rutting test and low-temperature bending test are used to analyze the influence of internal cracks on the road performance.The rutting test results show that when the internal cracks increase,the dynamic stability is not significantly reduced,and the internal cracks have a weaker effect on the high-temperature stability;With the increase of internal cracks,the low-temperature crack resistance is continuously reduced and is very obvious.Comparing the two tests,the internal cracks have a more obvious impact on the low-temperature performance of the road surface.Through the four-point bending fatigue test of small beam specimens with the same internal crack coefficient at three strain levels of 750με,1000με and 1250με,the effect of internal cracks on the fatigue performance of asphalt pavement was studied.The research results show that the existence of internal cracks reduces the fatigue life of the structure.With the increase of the internal crack coefficient,the fatigue life of the structure is lower;the greater the strain of the specimen with the same internal crack,the lower the fatigue life.The influence of internal cracks on the fatigue performance of the structure is preliminarily studied through four-point bending fatigue test,and the correlation between the internal crack coefficient λ and the parameter K in the stress fatigue equation is analyzed,and the fatigue with the internal crack coefficient is obtained by optimizing the corresponding variable fatigue equation.equation.Based on the theory of fracture mechanics,with the help of ANSYS finite element software,a two-dimensional structural model of asphalt pavement with internal cracks is established to study the numerical law of the stress intensity factor at the end of the internal crack in the upper layer of the asphalt pavement under dynamic load,and its fatigue life Perform calculation analysis.At the same time,the numerical simulation results and the four-point bending fatigue test data are compared and analyzed.The study found that under the combined action of tensile stress and shear stress,the expansion of internal cracks behaves as a composite expansion mode of open and shear.The analysis of fatigue life using Paris formula shows that the fatigue life of the structure decreases with the increase of internal cracks.The fatigue test law is basically the same as the simulation law,so it is believed that the influence of internal cracks on the fatigue performance of asphalt mixture has the above law.