Study On The Design Criteria Of The Asphalt Pavement

The deflection method has been using for the asphalt pavement design in China for several decade years. Though the deflection criterion has the apparent advantage that can be easily measured in the field, pavement failure are caused by excessive stresses and strain instead of deflections, so there are a lot of criticism for it. On the other hand, deflection criteria are not compatible with stress or strain criteria, it means that deflection cannot possibly be a criteria with the stress or strain criterion at the same time.In this paper, the rationality of deflection is analyzed in detail first. Based on the analysis, the paper then discusses the relationship between deflection as design criterion of asphalt pavement structure and damage of asphalt pavement is not direct or inevitable. Under the condition of supposing that various damage of asphalt pavement is lead by insufficient whole intensity of the structure of the asphalt pavement, the deflection criteria is adopted in current asphalt pavement specification as design criterion, in fact the idea is mistake, because it inverts cause and effect. At the same time, the deflection is not used to control elastic strain and plastic strain of the subgrade. so that it is unreasonable to use deflection as design criterion of asphalt pavement continuously.The paper analyzes that no matter semi-rigid base or flexible base that surface layer of asphalt pavement is pressed, under the condition that the contact between the layers of the asphalt pavement is full friction. At the same time, for the semi-rigid asphalt pavement, the fatigue life of asphalt layer is longer than semi-rigid base in despite of the contact is full or not. So it is not necessary to calculate the stress under the surface layer of the asphalt pavement.In order to make up valid design criterion, the paper analyzes main damage forms of the asphalt pavement, then put forward new design criterion system, including design criteria to control permanent deformation of surface layer and subgrade, design criteria to control tired damage and design criteria to control surface layer to be tired at low temperature. At the same time, the paper analyzes deflection is useful in new design system, and an example is given.