Study On The Cracking Mechanism And Prevention Measures Of Top-Down Crack On Flexible Base Asphalt Pavement In Seasonal Frozen Area

In recent years，since the functional and structural damage of semi-rigid base asphaltpavement seriously affect the life of road, while the flexible base asphalt pavement in foreignhighways performs well, the domestic researchers make some early investigations on theflexible base asphalt pavement. However, a Top-Down crack is liable to initiate from the roadsurface of flexible base asphalt pavement during its practical application. Although wideinvestigations have been conducted on this problem, the mechanism and the preventionmeasures of Top-Down crack have not been clearly clarified yet. Therefore, in thisdissertation, considering the typical climate and traffic conditions in Jilin province, thecracking mechanism of Top-Down crack and its prevention measures for seasonal frozen areahas been systematically studied, and the research results will play significant effect on thefurther application of flexible base asphalt pavement in seasonal frozen area of the wholecountry.In this study, the traffic conditions of Jilin Province was firstly investigated, andthree-dimensional contact stresses in the pavement-tire contact area for roads with smooth icefilm, compacted snow and dry pavement conditions in seasonal frozen area were respectivelyinvestigated by constructing a finite element model of pavement structure ofTonghua-Dandong highway with ABAQUS. Secondly, the distribution of the road surfacetransverse stress, shear stress along the traffic direction and shear stress along the depthdirection in the road-wheel tracks area is analyzed, and the initiation location of Top-Downcrack is confirmed. Based on these results, a cohsive zone model is adopted to analyze thedamage of pavement surface area under different ultimate shear strengths and tire pressures.According to the climatic characteristics of Jilin province, the temperature field model wasestablished, and the damage induced by different magnitudes of cooling rate and couplingeffects of temperature and traffic load for the pavement surface area is investigated by usingcohesive elements. Thirdly, the fracture mechanics theory is used to analyze the variationaltrends of the stress intensity factor at crack tip under different thicknesses and modulus of thesurface and the base layers, modulus of soil base, loading conditions, crack depths, cooling rates, three pavement structures paved in Tonghua-Dandong highway. Based on above results,the cracking mechanism and prevention measures of Top-Down cracks in flexible base asphaltpavement are finally proposed for seasonal frozen area.