Mechenic Analysis And Research On The Performance And Loading-response Of AC Overlay On Exsiting PCC Pavement

With the effect of vehicle loading and environmental influence, the performance of PCC pavement declined gradually. It wasn't the time for AC overlay repaving until the service performance(toughness, skid-resistance and bearing-capacity et.) of PCC pavement degraded down to a specific level, or the existing pavement cannot satisfied the future transportation. The standard method of extending a pavement's service life is to lay a new AC overlay over the old PCC. According to the unique structure of overlay composite pavement, the finite element methods and multi-layer system theory are adopted in the dissertation, which associated with deep research in damage theory, mechanic analysis and life-prediction mold of AC overlay on old PCC pavement. Here are mainly aspects in the study: (1)AC overlay pavement reflective-crack damage molds and theories. The initiating and propagating mechanism of reflective cracking is analyzed, and the influence of traffic loading and temperature variation were studied; (2)Mechanic analysis of AC overlay under the traffic-loading stress, thermal stress and the coupled stress. 3D FEM is used to analyze the AC stress in response to different structure parameters, through which the tendency of different parameters and relationships were illustrated The loading stress, thermal stress, and coupled stress in AC structures are emphatically analyzed considering the overlay structure with different interlay materials, which can greatly release the respond-stress of AC layer. (3)Crack analysis and life prediction mold of AC overlay. With fracture mechanic theory, the intensity factor K_â… , K_â…¡in joints tip of AC pavement, are used to calculate expansion angle and equivalent intensity factor K_e, which were inputted into prediction mold of the fatigue life of asphalt overlay. After cracking-propagatation analysis, the reflective crack speed in different periods and fatigue life were obtained.(4)Lab experiments with asphalt concrete rutting test devices were applied to conduct fatigue reflective-cracking experiments, with comparison among different interlay materials in AC overlay structures. Rutting loading was used to simulate traffic-loading conditions, by which the initiating and propagating process of traffic-loading reflective cracking were simulated and further confirmate the theory calculations.