Damage Behavior of Porous Asphalt Concrete under Load–Pore Pressure Effects

Due to the large void ratio of porous asphalt pavement, rainwater is more likely to infiltrate through surface voids and affect the internal structure, leading to pavement damage. The objective of this study was to investigate the variation of mixture damage under different load levels and dynamic water pore pressure levels. Based on a microscopic finite-element damage model for porous asphalt concretes, the effects of repeated loadings and dynamic water pressure were introduced. Finite-element simulation models were established to analyze the pavement damage variation under loadings and the coupled effect of loadings and dynamic water pressure. The study examined the changing patterns of mixture damage under stress and revealed the mechanism of damage development in porous asphalt concretes. It was found that the damage of asphalt mastic is concentrated in the aggregate skeleton force transfer path. As the number of load cycles increase, the damage develops rapidly within 1,000 load cycles, and the damage development rate slows down. The degree of mortar damage finally stabilizes at approximately 30%. An escalation in load from 0.7 to 0.8 MPa leads to a sharp increase in damage and the mixture’s failure. With the increase of water pressure level, the change in the damage level of the model is relatively small. However, the degree of element damage increases exponentially with the increase of dynamic water pressure. Elevated dynamic water pressure intensifies the development of cracks surrounding internal voids, ultimately contributing to mixture cracking.