Studying Bump at Bridge Approach of Short Subgrade with Oblique Prestressed Concrete Overlaying Asphalt Layer

The differential settlement of short subgrade between two highway structures (bridges, tunnels, culverts, etc.) is significantly greater than that of the other subgrade for the insufficient compaction of short subgrade owing to limited construction site. This paper aims to establish the control criteria to prevent bump at bridge approach for differential settlement of short subgrade with oblique prestressed concrete overlying asphalt layer (AC + OPC) composite pavement. In this work, the short subgrade and AC + OPC composite pavement were defined. Meanwhile, the driving comfort was analysed and the control criteria for differential settlement of short subgrade with different lengths were obtained based on the driving comfort using the driving comfort test. Finally, the effects of different layer parameters on stress and deflection were investigated and the control criteria for differential settlement of short subgrade were established based on the void area beneath the slab using the finite element software ANSYS. Results show that the length of short subgrade between two highway structures is defined to be less than 200 m. The vehicle speed and longitudinal slope have significant effects on the vertical acceleration. The asphalt layer modulus, OPC layer thickness and modulus, base layer thickness and modulus, and foundation modulus have effects on the flexural stress and deflection, especially the OPC layer thickness. The relationship between the additional stress and void area beneath the slab is derived. In addition, the control criteria for differential settlement of short subgrade with different lengths are put forward based on the void area beneath the slab and driving comfort. The application of AC + OPC composite pavement can prevent bump at bridge approach of short subgrade effectively. The results of this paper can provide guidance for the application of AC + OPC composite pavement.