Viscoelastic Analysis Of The Saturated Asphalt Pavement

The moisture damage of asphalt concrete pavement is the most common disease. It will cause many quality problems of the asphalt pavement, and affected the pavement performance and reduces the durability. Therefore the moiture damage of asphalt pavement has caused wide concern. It has become the important subject of scientific research and engineering practice. In this paper the saturated asphalt pavement is done viscoelastic dynamic, static response through the theoretical analysis and the numerical simulation. Complete the following content:Firstly, in the spatial axisymmetric coordinate Biot consolidation equations and the continuity equation of flow were solved by using differential constitutive relations of the viscoelastic body and the integral translation method. Explicit equations of stresses and displacements were derived.Secondly, explicit equations of stresses and displacements of the axial symmetry semi-infinite body were derived by using boundary conditions of the surface and the infinity. The inversion of the Hankel transform can be taken by using the complex Simpson integral method. In the inversion of the Laplace transform, the F. Durbin method is used. A numetical analysis is developed with Burgers model. By analyzing asphalt concretes with different fiber contents, results show that when the fibers content is0.20%, the asphalt concrete has many excellences, such as the small excess pore pressure, the big vertical stress, the small vertical displacement. So it can avoid the moisture damage better.Thirdly, by using the layer theory, boundary draining conditions and interlayer contact conditions, explicit equations of stresses, displacements, excess pore-water pressure and water velocity of the two-layer continuous viscoelatic system and two-layer sliding viscoleastic system were derived. The results of the present theory is in contrast with the results of finite element analysis, and verify that the formula of this article is correct. Kelvin model is able to demonstrate the viscoelastic properties of the asphalt concrete. The excess pore water pressure of four double pavement structures is calculated. By comparing the calculated results, influents of boundary drainage conditions and interlayer contact conditions on the excess pore-water pressure are revealed.Fourthly, based on the layer theory and continuous contact conditions, explicit equations of stresses and displacements of multilayered viscoelastic system were derived. A numetical analysis is developed with Kelvin model. The excess pore-water pressure on the symmetric axis was computed. The results show that values of the excess pore water pressure under undrained conditions were significantly greater than values under drained conditions.Finally, the viscoelastic constitutive relation of asphalt mixture was established by using the data of the creep test. The viscoelastic dynamic response analysis of multi-layer saturated pavement structure is done by the finite element method. The results show that (1) the vertical displacement of the pavement surface did not recover completely after vehicle loads disappeared, and most of the vertical displacement stayed as the permanent displacement;(2) because the recovering rate of strain of asphalt surface course (viscoelastic body) was less than that of base course (elastic body), residual stresses stayed in the asphalt pavement.