Abstract: Based on the pavement technical condition of the test highway S120, a three-dimensional model of the thicker asphalt layers overlaying on the existing concrete cement pavement (CCP) is established by the finite element software ABAQUS, which considers the interlayer contact between the existing CCP and overlay layers and the joints in CCP. First, the temperature field of the structure is calculated and analyzed, and then the influence of the thickness of adjustment layer on the mechanical response of the structure under the coupling action of temperature and traffic load is studied. At last the functional requirements of each structural layer are analyzed. The following conclusions are drawn:under the local typical high temperature, the temperature in the top surface is higher than 55℃, and the temperature field varies greatly between 0~30 cm; increasing the thickness of the overlay layers reduces the temperature stress caused by the existing CCP. The overlay layers are subjected to larger vertical displacement and the upper surface layer and adjustment layer are subjected to larger tensile stress, which is the main causes of Surface-down cracking and Bottom-up fatigue cracking. The upper surface layer is subjected to large compressive and shear stresses, while the lower surface layer and adjustment layer are also subjected to large shear stresses; as the thickness of adjustment layer increases, the tensile, compressive and shear stress of adjustment layer can be effectively reduced, and the required tensile strength of the old CCP structure can be greatly reduced, which enhances the anti-reflective crack ability and anti-fatigue ability of structure; according to the mechanical analysis, the proposals of the Mix Designing of the overlaying layers are given. The research results providing a theoretical basis for improving the design of road materials and improving the durability of overlay structures.

Key words: highway engineering, overlay thick asphalt layer, cement concrete pavement, mechanical analysis