| In China, the asphalt pavement was a typical pavement structure, but the rutting phenomenon always happened only after a few years operating, which was harmful to the pavement performance. In America, The full depth pavement was a very common pavement structure, but the rutting phenomenon was relatively rare. Therefore, the paper adopted the method of energy analysis to analyze the effect of asphalt layer thickness on the permanent deformation, which was based on the energy dissipation, and used the relationship between the plastic dissipation and the thickness of asphalt layer to determine the minimum thickness of asphalt layer. The main contents of this paper included: analyzing the energy distribution during the loading process, establishing the finite element model, establishing the method to determine the minimum thickness of asphalt layer, analyzing the effect factors and the changing rule of the permanent deformation.From the perspective of theory, the paper analyzed the pavement energy conversion during the load process. Before the analysis of the energy distribution, the paper set up some hypothesis, including the thermal energy and kinetic energy were not produced during the loading process, the boundary conditions and the interface contact conditions between the pavement layers. According to the basic formula, the external work energy was deduced under the action of vertical load and horizontal load, then the paper deduced the energy absorbed by the pavement structure, which was transformed from the deformation of pavement structure layer. Finally the paper introduced the method to calculate the stress, strain and displacement of pavement structure layer.The paper used ABAQUS to establishing the finite element model: selecting the type of pavement structure, material parameters, loads, loading time, pavement structure geometry model, boundary conditions, mesh division method and finite element model validation. Secondly the paper calculated the changing rule of energy and permanent deformation of asphalt pavement with the time increasing under one load cycle, analysed the relationship between the dissipation energy and the permanent deformation, made the conclusion that the creep dissipation energy and plastic dissipation energy had a direct influence on the permanent deformation of asphalt pavement. The next part, the paper calculated the changing rule of the energy and permanent deformation under different thickness of asphalt layer. Finally the creep dissipation energy and permanent deformation were calculated with the changing of the thickness of asphalt layer, under the situation that plastic deformation of asphalt pavement dosen’t appear.The paper established the method to determine the minimum thickness of asphalt layer: On the basis of the finite element model, the paper used the relationship between the thickness of asphalt layer and the plastic dissipation, to determine the minimum thickness of asphalt layer and introduce the method to determine the minimum thickness. According to the relationship between plastic dissipation energy and the modulus of asphalt layer, the paper determined the reasonable modulus of asphalt layer under the limited pavement thickness. According to the relationship between the permanent deformation and the modulus of base layer, the paper determined the reasonable modulus of base layer under repeated load cycles. The final part analyzed the effect factors(including the structural layer modulus, temperature, overload, horizontal load coefficient and driving speed) and the changing rule of the permanent deformation. |
