Mechanical Behaviors Of Flexible Base Asphalt Pavement Structure Under Nonuniform Vertical Tire Contact Stresses

With the development of flexible base asphalt pavement in developed country, combined with domestic situation and environment, relevant organizations have applied this kind of pavement structure in high-grade highways. Nowadays asphalt pavement design criterions of domestic and overseas adopt circular uniform load to simulate the acting force from vehicle to pavement structure, with the assumption of complete continuity in each structure layer. However, the distribution law of wheel load is extremely complicated, contact shape is not circular, but is nearly elliptical, rectangle,its acting force presents obvious heterogeneity. There is differences between material property, construction procedure, construction quality control of each structure layer of asphalt pavement, leading to weak cohere of each layer, which cant contribute to ideal complete continuity.Based on the assumption of wheel load in traditional asphalt pavement design theory, combined with influence factors of tire contact pressure and relevant field test results, the numerical simplification is carried out on the distribution of tire contact pressure. On account of research means used by this thesis, three-dimensional finite element numerical simulation software EverStressFE is analyzed in detail. Both theoretical analysis mentioned above are steppingstone to relevant research.For the purpose of describing wheel load non-uniformity, three dimensions simulation finite element analysis software EverStressFE is used to establish the finite element-infinite element coupling numerical model of flexible base asphalt pavement structure under non-uniform vertical wheel load. Contrastive analysis is conducted between structure pavement surface deflection, pavement structure shear strain, the bending tensile strain of asphalt layer bottom, the differences of soil vertical compressive strain at the top of the base caused by different wheel load distribution patterns. It is discussed about the design life control-index of flexible base asphalt pavement under the influence of non-uniform vertical wheel load. The conclusion shows that non-uniform wheel load locally affects the deflection on the surface and the shearing strain of pavement structure, while makes little contribution to soil vertical compressive strain at the top of the base. The maximum flexural-tensile strain of the bottom of the asphalt layer in traveling direction is bigger than that in the lateral direction. The design life of pavement structure is controlled by permanent deformation.Based on the non-uniform effect of wheel load, for the purpose of studying the influence caused by bonding conditions of surface-basement, basement-subbase layers on flexible base asphalt pavement structure, three dimensions simulation finite element analysis software EverStressFE is used to analyze the mechanical response under two extreme layer bonding conditions, complete continuity and complete discontinuity, as well as dynamic evolution laws of the pavement structure life in different bonding conditions of layers. The result shows that, bonding conditions of layers affect the deflection on the surface, the shearing strain and the flexural-tensile strain of pavement structure, soil vertical compressive strain at the top of the base in different extent. The fatigue life of pavement structure and permanent deformation of life present nonlinear damping in the situation that bonding condition of layers deteriorate. In this situation, damage mode of pavement structure transform between permanent deformation and fatigue cracking, which increases the difficulty of design, construction and maintenance. The influence of bonding conditions of layers on flexible base asphalt pavement structure is greater than non-uniform load, while they are relatively independent.