Research On Fatigue Damage Of Semi-rigid Material And Structure Of Asphalt Pavement

Semi-rigid base is mainly adopted in high-grade highway asphalt concrete pavement.However, fatigue failure of asphalt concrete pavement with semi-rigid layer is serious dueto heavy traffic coupled with environmental effect. To break through the bottleneck of thedesign idea of long-term pavement structure for semi-rigid base asphalt concrete pavement,research must be conducted on the fatigue damage model and the relative parameter alongwith simulation of material and structure damage. The kernel of pavement structure designis the model of fatigue damage for semi-rigid materials. And its establishment along withapplying is the general key technology of asphalt concrete pavement with semi-rigid base.The project begins with study on the fatigue damage model of semi-rigid basematerials. And then research on verify the structure damage of semi-rigid base materials byALF and actual engineering research. From the research, A fatigue damage model whichreflects the actual damage status of pavement structure was established.The fatigue testing method that based on flexural strength (FS) determined by thebeam specimen sawed the geometric symmetry position from a larger beam is developedaimed at solving the problem of large discreteness and variability of the fatigue test results.The flexural stiffness modulus test method is developed by measuring the maximumdeflection difference between the middle third of the specimen, which has solved theproblem of the nonuniformity of flexural stiffness along the specimen subjected to repeatedload. The model of modulus attenuation that related to stress ratio is found for the first timebased on fatigue test and continuum damage mechanics. The simulating of the damageprocess of material and structure applying finite element and analysis method is done basedon model of modulus attenuation.To determine the modulus parameter in mechanical response analysis, the method ofcompressive elastic modulus test is developed by measuring the deformation of the middlethird part of the cylindrical specimen when subjected to determined load, which hasimproved the reliability of test results. The effective modulus magnitude of semi-rigidmaterials at the end of the design life is determined based on theoretical analysis andin-situ detection, which has provided basis for parameter input in damage analysis. Thefatigue damage model of semi-rigid base materials and structure was firstly investigatedand verified by the combination of heavy load ALF and mechanical response sensorssystems, the damage phases and the corresponding characteristics of semi-rigid base weredeterminded and the relationship between time of fatigue damage fist phase and secondphase was provided.