DEM study on the thaw settlement mechanism of permafrost embankments based on phase-transition thermo-mechanical coupling

This study presents a novel discrete element method (DEM) model that explicitly accounts for the ice–water phase transition to investigate thaw settlement behavior in highway embankments built on permafrost. The model simulates heat transfer from the asphalt pavement into the embankment under solar radiation, capturing the dynamic process of ice melting as temperatures exceed 0 °C. This phase change weakens the soil structure and subsequently induces settlement. To improve long term predictive capability, seasonal variations in solar exposure duration are also incorporated. Through systematic parametric analysis, the influences of ice content, embankment geometry (width and height), and the thermal differential between sunny and shady slopes on settlement behavior and thaw bowl evolution are quantitatively evaluated. The results indicate that higher ice content and wider embankments markedly increase settlement, whereas greater embankment height effectively reduces it by extending the heat conduction path. Thermal asymmetry between the sunny and shady slopes is identified as a critical driver of asymmetric settlement and thaw bowl development. Although it is a two-dimensional model that omits traffic loading, seasonal air temperature variations, and detailed ice-lensing effects, this research offers a mesoscale perspective on thaw-induced deformation and provides practical insights for the design and maintenance of transportation infrastructure in cold regions.