Strength theories and structure-failure characteristics of asphalt pavements

To evaluate and verify the failure modes and characteristics of asphalt pavements under complex stress states, the distribution characteristics of equivalent stress within the pavement structure were analyzed by using the classical five strength theories and the unified strength theory. Three typical pavement structure schemes, namely semi-rigid base asphalt pavement, flexible base asphalt pavement, and inverted asphalt pavement, were considered. The failure modes of pavement structures characterized by various strength theories were analyzed through numerical calculations. Research results indicate that structural failure modes and failure layers of a specific pavement characterized by various strength theories are different. For the semi-rigid base asphalt pavement, the first, second, and Mohr's strength theories mainly characterize the bending and tensile failure at the bottom of the base layer, while the third and fourth strength theories mainly characterize the shear yield failure of the asphalt surface layer. The unified strength theory mainly characterizes the tensile and shear combined cracking failure of the surface layer and base layer, and the maximum equivalent stress occurs within the asphalt surface layer, which can reach 0.8 MPa. A specific strength theory may be characterized as differential failure modes in different pavement structures. The fourth strength theory mainly characterizes the shear yield failure of the asphalt surface layer in the semi-rigid base asphalt pavement, and the shear cracking failure of the asphalt surface layer in the flexible base asphalt pavement. The fourth strength theory and the unified strength theory suggest more reasonable characteristics of pavement structure failure and reflect richer information on pavement structure failure. The combination of these two strength theories can characterize common distresses such as cracking in base and surface layers and rutting in surface layer, thus comprehensively controlling the load-type fatigue failure of pavement structures. The unified strength theory reveals the mechanical mechanism of surface layer preferentially cracking and failure, providing a new theoretical explanation mechanism for common pavement distresses such as top-down cracking and longitudinal cracking in practical engineering and proposing an optional strength verification index for independent control of surface layer cracking failure.