Deflection Equivalent Conversion of Overload Axle for Asphalt Pavement

Currently, the serious phenomenon of overload widely exists in the Chinese carrying trade. Those overload vehicles have been one of causes for pavement damage in severity. It is one of vital problems to pavement staff how to consider the effect of overload axle on pavement in the pavement design more effectively. According to the reduced formula of deflection ratio based on elastic-layer theory, the changing rules of deflection and axle load conversion index based on deflection equivalent are analyzed. The analysis was conducted using field survey result in the different combinatorial conditions of axle loads (100kN, 130kN, 150kN, 180kN, 200kN), tire pressures (O.7MPa, 0.9MPa, 1.1MPa) and pavement strength taking on standard deflection test truck, which has single rear axle with double tires each side. It is pointed out that the main factors to affect axle load conversion index are pavement structural strength (highway class) and axle load. The influence of tire pressure is not obvious and adopting axle load ratio for the axle conversion formula is more precise and convenient than adopting tire pressure ratio. An axle load conversion formula suitable to overload axle is regressed based on deflection equivalent for the asphalt pavement according to data collected in the field. The new formula reflects the overload axle load and pavement strength effect on axle load conversion and provides a basis for overload axle load conversion in the pavement design.