Pulsatile saturated seepage in asphalt mixtures using the multi-relaxation time lattice Boltzmann method

Moisture-induced damage caused by water seepage is a major factor in asphalt pavement deterioration. When vehicles pass over the water-covered pavements, the surface water forms a dynamic pressure layer between the tyres and pavement. To investigate the seepage behaviour of this tyre-induced dynamic pressure water within compacted asphalt mixtures, four two-dimensional pore-structure models with varying air void contents were reconstructed using digital image processing. A computational framework combining the large Eddy simulation model with the multi-relaxation-time lattice Boltzmann method was employed to simulate the turbulent flow under high-pressure gradients. The effects of air void content, vehicular speed, load power exponent, and rest time on key hydro-mechanical parameters were analysed. Results indicate that increasing air voids enhances pressure, velocity, and permeability, while shear stress exhibits a non-monotonic response at 12.4% voids. Higher vehicular speeds may amplify all parameters, with permeability reaching its maximum at 60 km/h. Conversely, larger power exponents reduce seepage velocity and shear stress, and extended rest periods alter seepage direction and shear stress behaviour. The highest pore-water pressure and shear stress were concentrated within 15 mm of the surface, offering quantitative insight into early-stage moisture damage and guidance for improved asphalt mixture design and pavement construction.