Damage evolution and stress-relief mechanism for airport pavement structures under high-frequency impact load

To address the cumulative damage of rigid airport pavements induced by aircraft takeoff and landing, this study proposes the incorporation of a cement asphalt (CA) mortar stress-relief layer to enhance its impact resistance. Taking the B737-800 aircraft as an example, a three-dimensional finite element model of rigid airport pavement was established in ABAQUS. Combined with the concrete damage plasticity (CDP) model, random impact loading conditions were implemented using the Vexternaldb and Vdload subroutines. The effects of slab flexural strength and thickness, stress-relief layer thickness, aircraft vertical sinking velocity, and loading position on pavement damage were systematically analyzed. The damage evolution characteristics under repeated impacts, as well as the mitigation mechanism of the stress-relief layer were revealed. The results indicate that pavement damage is dominated by tensile failure under repeated impacts, while compressive damage is negligible. Increasing the flexural strength and slab thickness can delay initial damage to some extent, but is insufficient to effectively suppress damage accumulation induced by repeated impacts. The incorporation of CA mortar stress-relief layer can significantly mitigate early-stage damage progression, reducing viscous dissipation energy by more than 90%. Under hard landing conditions, increasing the thickness of the stress-relief layer from 2 cm to 6 cm reduces plastic dissipation energy by 95%. However, an excessively thin layer (1-2 cm) tends to undergo tensile failure prior to the slab. A thickness of 3-4 cm is recommended for the stress-relief layer based on comprehensive evaluation. This recommendation is derived under the current model parameters and ideal interfacial bonding conditions. The aircraft vertical sinking velocity has a significant influence on energy dissipation, while the inclusion of the stress-relief layer markedly reduces both the degree and rate of stiffness degradation of the pavement. The stress-relief layer is effective in suppressing damage accumulation, reducing energy dissipation, and delaying stiffness degradation, providing a theoretical basis and technical reference for the structural design of airport pavements with high impact resistance.