Study On Two Stage Design Method Of The Semi-Rigid Asphalt Pavement

For its high strengths good stability,great bearing ability and good economy benefit,the semi-rigid base asphalt pavement is the most common pavement structure in China presently. But recently along with the economic development,the semi-rigid base asphalt pavement exposes more and more problems, for example the early damage phenomenon and the lower pavement life. So the pavement design theory and design methods should be reviewed in response to a large number of revealed problems, so as to raise new design methods.In this paper, firstly contrast the condition of service about the semi-rigid base asphalt pavement at home and abroad, to make clear that the main problems of the semi-rigid base asphalt pavement presently, to definite the research methods and studying route.Then compare the design methods at home and abroad and point out the insufficiency in current criteria. In the design indexes, because the pavement is a multilayer composite structure and the surface deflection is a synthetical index that can not reflect the diversity of the damage types about pavement structure, so the surface deflection can not be the unique (important) design index.; In the material parameters, based on the modulus deterioration of semi-rigid materials, the influence of the modulus towards fatigue life of pavements is analyzed, it advises to adopt two-stage modulus.Then analyze the stress characteristic of the typical semi-rigid base asphalt pavement structure that is acted on by loads to utilize the finite element software ANSYS. Point out that the characteristics of semi-rigid base asphalt pavement are quite strong load distribution ability and bearing capacity, small permanent deformation, less ruts, more bending damages of the base course and the subbase course, and reveal the unreasonability of some design indexes in current criteria.Analyze the main damage form, and definite the critical damage state and the design index system of the semi-rigid base asphalt pavement.Then based on the Palmgren-Miner Criterion on the Fatigue Damage Accumulation the two-stage fatigue life about the semi-rigid base asphalt pavement is raised up, and analyze the influence of the thickness of the asphalt surface course and the base course towards the fatigue life of the pavement. The paper advised that properly increasing the thickness of the asphalt surface and reducing the thickness of the base course should be done in order to raise the proportion of the residual fatigue life of the asphalt surface accounting for the total fatigue life of the pavement structure.Finallly, on the basis of the above analysis and the new design idea, the two-stage design method of semi-rigid base asphalt pavement is proposed for.