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Damages caused by the multi-axles load on the pavement are more complex, due to the interaction between axles. To investigate influences of the multi-axles load on the bottom-up crack of the flexible pavement, the equivalent factor (EF) that represents damage ratios of multi-axles to single-axle based on the viscoelastic continuum damage model was proposed. Through the finite element method, influences of temperature, pavement thickness, and axle configuration on the EFwere analyzed. Results suggest that the asphalt mixture with smaller m-value is more likely to have smaller EF. With the increase of temperature and asphalt layer thickness, EFof dual-axles load increases but EFof triple-axles load decreases. Besides, the wheelbase is the only factor of the axle configuration that has remarkable impacts on the EF. Making the distance between the maximum compressive and tensile stress close to the wheelbase can reduce the damage of multi-axle load.

Semi-analytical finite element method has great advantages in computational efficiency compared with three-dimensional, because it only requires a two-dimensional mesh in the cross-section by incorporating the Fourier series along the third dimension. This study utilised the method to analyse pavement responses induced by moving vehicles. Combined with the structural property of pavement, the method is improved in terms of meshing and boundary conditions based on existing research. Using the Fourier series to represent loading functions along the driving direction, the load motion can be expressed as the translation of trigonometric functions. Spring element is applied at bottom to simulate the soil support, and viscous element is applied at vertical boundary to control the interference of reflected wave. The whole algorithm was realised by MATLAB programming. This algorithm was first used to analyse a layered structure under a rectangular load. Its accuracy and efficiency were verified by comparing it with a three-dimensional finite element model in ABAQUS. Then this algorithm was utilised to simulate a test road under a moving truck. The material assembly used the parameters calibrated by several nondestructive tests. Analysis results were compared with the field monitor of sensors for verification. This study also has some reference value about applying semi-analytical finite element method in pavement engineering.