Nonlinear evolution and influencing mechanism of rutting in asphalt pavement under coupled high-temperature and heavy-load conditions

To investigate the nonlinear evolution and mechanism of rutting in asphalt pavement incorporating steel slag under coupled high-temperature and heavy-load conditions, a three-dimensional finite element model was established in ABAQUS based on a typical semi-rigid base asphalt pavement structure. Steel slag was used to replace 30% of the natural coarse aggregate by mass. The Bailey–Norton creep model was adopted to characterize the high-temperature mechanical behavior of the asphalt mixtures, and the model was validated using laboratory rutting tests. On this basis, coupled working conditions involving multiple temperatures and load levels were established. The rut depth at 60 min was used as the primary evaluation index, and a coupling influence coefficient was introduced to quantitatively characterize the interaction between temperature and contact pressure. The results show that rut depth increased nonlinearly with increasing temperature and contact pressure. The coupling influence coefficient remained close to unity under a contact pressure of 1.0 MPa, whereas it increased to 1.09 and 1.15 at 65 °C and 70 °C, respectively, under 1.2 MPa, indicating an evident synergistic amplification under severe high-temperature and heavy-load conditions. Mechanistic analysis indicates that high temperature reduces the modulus and shear resistance of the asphalt mixtures, while heavy loading increases the internal stress level. Their combined action increases the shear stress ratio and promotes the accumulation of shear-related viscoplastic deformation. The AC-20 layer remained the main contributor to rutting, while the contribution of AC-13 increased with temperature. The findings provide a reference for the rutting performance evaluation and pavement design of asphalt mixtures incorporating steel slag under high-temperature and heavy-traffic conditions.