Study On Dynamic Modulus And Crack Propagation Of The Asphalt Pavement

The dynamic modulus of asphalt pavement and various cracks in pavement are the hot spot of the current research, whether it is the basic theory or the engineering practice.To comprehensive grasp of asphalt pavement dynamic modulus variation and correct understanding of the internal crack of asphalt pavement expansion mechanism, the road workers were able to have a further understanding of the mechanical behavior of the asphalt pavement. This will facilitate and improve the design and maintenance of asphalt pavement.In this paper, the dynamic response of Asphalt Pavement Based on dynamic modulus and the expansion of pavement fatigue crack are studied. Those problems are discussed by means of experimental study and numerical analysis. The main work and conclusions are as follows:(1)Four kinds of asphalt mixture(SMA-13, AC-20, AC-25 and ATB-25) are tested by the asphalt mixed material testing instrument(SPT) to study on dynamic modulus. The changing rule of dynamic modulus and phase angle under the influence of temperature, load frequency were analyzed. Introducing the fractional order derivative viscoelastic model to describe the dynamic properties of asphalt mixture which is based on the theory of fractional order calculus theory, then study on the dynamic viscoelastic of asphalt mixture by using the three-element model of fractional order derivative, and analyzed the fitting effects. The result shows that the three-element model of fractional order derivative by using few experiment parameters to describe the dynamic behavior of asphalt mixture, and have better fitting effects.The fitting parameter “r” have certain physical meanings which can reflect the viscoelastic properties of asphalt mixture ratio. For asphalt mixture, the value of parameter r is generally between 0.30 and 0.50.(2)Study on the mechanical responses of asphalt pavement structure under different speed and temperature which were based on the dynamic modulus parameters by the established dynamic modulus master curves of asphalt mixture. the mechanical responses of road surface deflection, the bottom tensile strain of asphalt layer and the top compressive strain of soil base under different conditions were analyzed and compared with the mechanical responses of the asphalt pavement structure which were based current spectification by the static compression rebound modulus; The mechanical properties ofasphalt mixture under the driving speed were determined based on the theory of fracture mechanics by the finite element method which using dynamic modulus master curve and the temperature conversion factor.Then the dynamic characteristics of asphalt pavement with more crack under moving lode mode, driving speed, load and temperature conditions were analyzed.(3)On the basis of the finite-cover-based element-free method with the constructed shape function by the way of the improved moving least-square which made this method could be used to deal with continuous and discontinuity problems, and through the numerical example showed the feasibility of this method.(4)Through the program to simulate propagation of the three point bending specimen with crack. To compare with the existing research results, the results show that this method can be better simulated the propagation of the mixture. The experimental results and the simulation results were compared, the results showed that the crack propagation path for the test specimen were basically the same, the crack tip stress concentration could be accurately simulated from this program, and the correct stress intensity factor could be calculated. So this program can be used to simulate crack propagation.(5) The crack propagation path in asphalt pavement structure was simulated by the finite-cover-based element-free method. Detailed evaluation the crack propagation under the influence factors such as the thickness of pavement, designed modulus, and traffic load. By using the gray relational advantage analysis method to analyze the size of the influence factors on the parameter KI、 KⅡand θ. The pavement structure(thickness and modulus) and load combined with each other differently are the main factors influencing the crack propagation of the asphalt pavement. As the growth of the crack propagation, the direction of crack propagation will change.