Numerical Analysis of Top-Down Crack in AC Layer of Continuous Reinforced Composite Pavement under Multifactor Coupling

Top-down crack is a typical disease of composite pavement, its occurrence and expansion adversely affect the life of continuous reinforced composite pavement (CRCP). In order to explore the formation mechanism and propagation rule of top-down cracks in CRCP, based on the theory of linear elastic fracture mechanics, a 3D finite element model of pre-nstalled cracks on the top of AC layer is established. According to the main stress parameters that affect the formation of top-down cracks, the most unfavorable load position and the most unfavorable point corresponding to the stress parameters are determined. On this basis, the stress intensity factor of the crack tip under multi-factor coupling is calculated by contour integration. The variance analysis of the multifactor crack tip stress intensity factor is carried out through the orthogonal test method, and the main factors affecting the formation and development of top-down cracks are determined. At the same time, the single-factor sensitivity analysis on these influencing factors is carried out, thus the: formation and expansion rule of top-down cracks in continuous reinforced composite pavement is revealed. The result shows that (1) for the top-down cracks in continuous reinforced composite pavement, the most unfavorable load position is the loading position on the lateral crack side of the CRC layer, the unfavorable point of the longitudinal top-down crack is the loading position on the lateral crack side of the CRC layer at the inner edge of the proximal double wheels, while the unfavorable point on the transverse top-down crack is the loading line on the lateral crack side of the CRC layer; (2) the transverse top-down cracks is a comprehensive cracking mode with K2 type (sliding type) as the dominant type and K1 type (opening type) as the supplement, and AC layer thickness and crack load transfer capacity are the main influencing factors; (3) the cracking mode of longitudinal top-down cracks is dominated by K1 type, AC layer thickness, crack load transfer capacity, crack spacing and instantaneous temperature difference are the main influencing factors for its formation and propagation.