The Cracking Mechanism Of Top-Down Cracking In The Asphalt Pavement

Top-Down cracking is harmer failure mode for asphalt pavement than the traditionalfatigue cracking, which has a greater influence on the later performance characteristics andservice term of the asphalt pavement. At present there is little research for Top-Down crackingin the domestic, design index of controlling the disease is lack in the design code. In this case,it is very necessary to study cracking mechanism of the Top-Down cracking and thusdetermine the failure criteria.In order to study Top-Down cracking’s cracking and expand mechanism of the asphaltpavement, the paper uses AI method gets the temperature field of pavement structure, andobtains the dynamic modulus after aging according to asphalt aging prediction model in thecase of temperatures, aging life, porosity and depth. The paper sets up a new tire-pavementcontact model through combing horizontal force and contact pressure distribution. Analysepavement structure’s stress response under the combined effect of the modulus gradient,traffic loads, cooling by using the ABAQUS finite element software. At last it determines thecracking criterion and mechanism of Top-Down cracking.Cracking mechanism of Top-Down cracking is that: When pavement is unaged, theanalysis shows that shear stress under wheel load is the major reason that caused Top-Downcracking. After aging or cooling, the maximum tensile stress significantly increased. Themaximum tensile stress that greater than the asphalt mixture tensile strength caused cracking.Considering the existance of micro-cracks, when the stress intensity factor on the direction ofthe maximum circumferential tensile stress reaches the fracture toughness, the micro-cracksbegan to expand in I+II compound fractures.