Study On Fatigue Characterization Of Asphalt Pavement Under Vehicle Loads

Asphalt concrete layer is predominantly used as a construction material for flexible pavements (surface layer) today because of its high quality engineering performance such as elasticity, durability, and water resistance; Running vehicles on the high class road are one of mainly reasons which caused road failure, such as fatigue failure, rutting, cracking and so on. Therefore, the behavior of asphalt layer under traffic loading is being always concerned by scientists and engineers.In thesis, the auther focuses on the item that fatigue characteristic of asphalt concrete layer under vehicle loads.Vehicle loading, include axle loads, tire pressure, and vehicle's style, is one of the main direct influence factors to made asphalt concrete damage. There are studied by the dissertation with traffic investigation and statistics theory. The distributions of axle loads and tire pressure at present cross the nation are closed to Gauss's Distribution, but the distribution of vehicle style model is not so, which has no clearly distribution modle.The tendency high-speed orientation and accelerat heavy of truck make dynamic loading more and more be pay attention now. By usage of computer simulation, the influence of vehicle's parameters and its application are discussed, treatment method of dynamic loading in stress analysis is given too in the dissertation. At the same time, range of parameters selection is list in the essay.Stresses field is foundation and a useful tool to deal with engineering project. The set approach and explicit express are given by use of numerical method in this thesis. It is shown that stresses field of asphalt surface layer under vehicle loads is a multi-axial stress field and more complicated than we thought before. It can be said that stress state in asphalt concrete layer is in multi-axial state. Another important item is that it is unreasonable to design road with maximum tensile stress or strain at bottom of asphalt concrete layer as the calculation parameter, and stress range composed by tensile strain and pressure strainDamage prediction and life evaluation of structure are handled with use of load spectrum (stress spectrum or strain spectrum). In other words, load spectrum is basis and very important for damage and life prediction. Base on computer simulation, the strain spectrum of asphalt concrete layer under axle loads in chapter 4.Experiment is very important to science and technology, and fatigue strength is a subject which combined theory analysis with experimental research. Fatigue strength experiment of asphalt mixture is done, its fracture surface is analyzed, and its characteristic is analysis too by the paper. The results show that fatigue behavior at negative stress ratio is different with positive state.Fatigue life of asphalt concrete is affected by the healing., and it can be improved by pressure stresses; the accuracy of evaluation of fatigue life of asphalt concrete under axle loads is discussed too.The proposed approach of fatigue design for asphalt concrete under axle loads list at the end of the dissertation.