| Fatigue cracking is a main form of structural damage of asphalt pavements (chiefly including asphalt pavement with half rigid base course and AC overlay on portland cement concrete pavement). Virtually, it is a process that the AC material gradually deteriorates and forms cracks under the traffic loads. Traditional fatigue mechanics only represents the stage before fatigue cracking of the AC layer. But, for the reflective cracking of asphalt pavement with half rigid base course and the cracking of the AC overlay above joints (cracks) in existing PCC pavement, the results of research show that the fatigue life of AC layer is mainly the life of the crack propagating stage. So the theory and method of fatigue destructive mechanics (fatigue fracture mechanics and fatigue damage mechanics) should be used to study and design the pavement structures instead of traditional fatigue mechanics. As a new branch of destructive mechanics, fatigue damage mechanics can comprehensively represent the total process of forming fatigue cracks and the crack propagating in materials and structures. Applying the theory and method of fatigue damage mechanics to the research on the fatigue cracking of asphalt pavement is conducive to reveal the mechanisms of asphalt pavement fatigue cracking and measures anti-cracking (such as reinforcing) and then the design method of anti-cracking can be put forward. In this paper, the theory and method of fatigue damage mechanics are adopted to study the fatigue damage behavior of asphalt mixture and the fatigue failure of asphalt pavement and predict the fatigue life of AC overlay on existed PCC pavement.In the first part of the paper, rational models of asphalt mixture fatigue damage are established, and practical and effective computational methods for these models are set up.Firstly, one conventional model of fatigue damage and classical damage mechanics theory are used to analyze the fatigue behavior of asphalt mixture specimens in fatigue tests including direct tension, cantilever beam bending, three point bending and wheel tracking byAsphalt Pavement Analyzer (APA). For every type of tests, corresponding fatigue damage model and computational method are set up. Comparing the results of fatigue damage analysis with the test, the rationality and validity of the fatigue damage model suggested are proved. At the same time, the values of parameters in the asphalt mixture fatigue damage model are obtained.The results of analyzing the fatigue behavior of the specimens in direct tension test, cantilever beam bending test, three point bending test and wheel tracking test by APA show that the fatigue failure regularities of specimens in different tests are different. It is mainly the difference between the proportions of fatigue life at the fatigue cracking stage and crack propagating stage in the total fatigue life of specimens. In spite of that, the cracks propagate stably in specimens for all types of tests. Thus the Paris formula can be used to describe the fatigue crack propagation, and the values of fatigue fracture parameters in the Paris formula are regressed by using the results of fatigue damage and stress intensity factors computation.Wheel tracking test on asphalt concrete beam under several levels of load is carried out by APA to study the fatigue behavior of asphalt concrete material and compare the reinforcing effects of geotextile with that of glass fiber geogrid. The results of tests show that these reinforcing measures can prolong the fatigue life of the specimen to more than twice times. It is found there exists one arch effect in the specimen owing to the lateral restraint, and it makes the phenomenon of APA specimen cracking indistinct.In the second part of the paper, the bridging effect of reinforcement and factors influencing it as the crack in half rigid base course propagates into the asphalt layer are explored deeply.The influences of interfacial condition and reinforcement on the asphalt pavement behavior under symmetrical, eccentric loads or loads with...
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