The two-phase seepage fluid (i.e., air and water) behaviors in undisturbed granite residual soil (U-GRS) have not been comprehensively studied due to a lack of accurate and representative models of its internal pore structure. By leveraging X-ray computed tomography (CT) along with the lattice Boltzmann method (LBM) enhanced by the Shan–Chen model, this study simulates the impact of internal pore characteristics of U-GRS on the water–gas two-phase seepage flow behaviors. Our findings reveal that the fluid demonstrates a preference for larger and straighter channels for seepage, and as seepage progresses, the volume fraction of the water/gas phases exhibits an initial increase/decrease trend, eventually stabilizing. The results show the dependence of two-phase seepage velocity on porosity, while the local seepage velocity is influenced by the distribution and complexity of the pore structure. This emphasizes the need to consider pore distribution and connectivity when studying two-phase flow in undisturbed soil. It is observed that the residual gas phase persists within the pore space, primarily localized at the pore margins and dead spaces. Furthermore, the study identifies that hydrophobic walls repel adjacent fluids, thereby accelerating fluid movement, whereas hydrophilic walls attract fluids, inducing a viscous effect that decelerates fluid flow. Consequently, the two-phase flow rate is found to increase with then-enhanced hydrophobicity. The apex of the water-phase volume fraction is observed under hydrophobic wall conditions, reaching up to 96.40%, with the residual gas-phase constituting 3.60%. The hydrophilic wall retains more residual gas-phase volume fraction than the neutral wall, followed by the hydrophobic wall. Conclusively, the investigations using X-ray CT and LBM demonstrate that the pore structure characteristics and the wettability of the pore walls significantly influence the two-phase seepage process.

Workability of asphalt is crucial for pavement construction and quality assurance. The macroscopic and mesoscopic mixing workability of different base and polymer-modified asphalt mixtures was evaluated using a modified testing device and simulated by the three-dimensional discrete element method via the three-dimensional Particle Flow Code, respectively. The experimental results demonstrate that polymer-modified asphalt mixtures exhibited inferior mixing workability compared with base asphalt mixtures, consistent with their higher binder viscosity. The mixing workability decreased with the elevated nominal maximum aggregate size, and the open-graded mixtures showed inferior mixing ability compared with those of continuous and gap-graded mixtures. The sensitivity analysis demonstrates that temperature appeared to be the most significant influencing factor of the mixing workability, followed by gradation and asphalt binder type. The denser contact force chains of mixtures under lower temperatures observed by the numerical simulation provided evidence of the decreased mixing workability. The gradation appeared to only provide a path for load transfer without influencing the contact force properties. These findings provide a theoretical basis for understanding the mixing behaviors of asphalt mixtures.