Research on seepage and stability of embankment slopes under coupled rainfall-vehicle loading

China has an extensive network of rural roads, which generally lack reinforcement/support measures or other slope-face protection designs. Consequently, during rainfall events, these roads pose considerable safety risks under the combined effects of vehicular loading and rainfall. In this study, a series of embankment-slope model tests was conducted using a self-developed rainfall simulation system and a RAW-200Z loading system to investigate the coupled effects of vehicle loads and different rainfall patterns. The seepage characteristics of the slope were examined by analyzing the temporal and spatial distributions of water content and pore water pressure within the slope. Subsequently, a finite-element model with the same geometry as the experimental setup was established in COMSOL Multiphysics for verification and analysis. The measured pore water pressure data were fitted and imported into the model, and the strength reduction method was adopted to quantitatively evaluate slope stability under the various coupled conditions. The results indicate that, compared with slopes subjected to rainfall alone, rainfall-vehicle coupling significantly alters the seepage behavior, leading to higher water content and pore water pressure than in the rainfall-only scenario. Moreover, the seepage characteristics vary markedly among rainfall patterns and are positively correlated with rainfall intensity and total rainfall amount. The stability analysis further shows that, when the fitted experimental pore water pressure data are used, the reduction in the factor of safety is greater than that predicted by conventional simulations. These findings confirm the detrimental effect of coupled rainfall and vehicular loading on slope stability and provide a theoretical basis for stability assessment of low embankment slopes under com-plex loading conditions.