The Formation Mechanism Of Top-Down Crack In Asphalt Pavement

Fatigue cracking is one of the major modes of premature distresses in asphaltpavements. Cracks of asphalt pavements appeared like microcracks but later propagate inwhole highway. The knowledge and understanding of the mechanism of crack initiationand propagation processes are very essential to enhance the resistance crackingperformance of asphalt pavement structure, to select optimum asphalt mixtures and toimprove the present design methods.The fatigue cracks, fatigue life and crack propagation path of the pre-sawed asphaltconcrete beam(half circle) have been researched by the bending fatigue test. The result ofthe test and simulation shows that, the fatigue life ascends with the addition of the distancebetween the loading point and the sawed crack. And the fatigue life descends with theincrease of the stress level. In general, the crack propagation path abides certain rule. Andthe test demonstrates that the path propagates along the boundary of the aggregate nearlynot splits the particles.According to the Top-Down cracks, considering the visco-elasticity of asphaltmixture，depending on the theory of mixture asphalt crack propagation as the index ofdissipate creep strain energy, coupling method combining the element free Galerkinmethod(EFGM) and the finite element method(FEM),Establishing the simulated model ofthe emerging and extending of Top-Down crack, researching the mechanism of Top-Downcrack in asphalt pavement. Under the analysis of the pavement parameters, restricting thepavement propagation by the Top-Down crack during the designed life period of thehighway, providing the theory of selecting the asphalt mixture and choosing the properoverlay thickness for the long-life asphalt pavement.