Analysis On Design Axle Load Of Heavy-loaded Perpetual Asphalt Pavement

Along with the rapid development of highways, the widespread premature failure and decreasing service life have become one of the key factors which restrict the further development of asphalt pavements. Foreign practices have proved that constructing perpetual pavement is an effective approach to solve premature failure and increase the service life of asphalt pavement. However, there is few domestic research and practice on perpetual pavements.In this thesis, mechanical response analysis about typical structures was performed using mechanic theories with BISAR program according to the traffic features of heavy and overloaded vehicles. Then, the relationships between failures and loads were discussed and the axle load conversion equations fitting for heavy-loaded perpetual pavement were established. On the basis of the axle load distribution model, the applicability of using the foreign common 80kN as design axle load was verified and the reasonable design axle load to heavy-duty perpetual pavement was selected with consideration of the cumulative fatigue effect.Computations and analyses show that, compressive strains of the subgrade and tensile strains of the asphalt layer would substantially increase under heavy loads and permanent deformations and fatigue cracks may occur consequently. The exponent 4 can not be adequate for the relationship between failures and loads and should be increased greater in degree for heavy-loaded perpetual pavement. The theoretic recommended values are 4.33 to compressive strains of the subgrade and 5.75 to tensile strains of the asphalt layer respectively. In addition, the use of common 80kN as design axle load can not be satisfactory to the 40 years design period for the traffic features of heavy and overloaded vehicles and the cumulative 80kN axle loads are only 49 millions and can last for 10.1 years for an example pavement. The design axle load for heavily loaded perpetual pavements is related to traffic composition and should take the fatigue effect of the load into account. Taking the fatigue effect into account results in a design axle load of 115kN corresponding to required 40 years for the example pavement, which is greater than foreign design axle load 80kN.