Damage mechanism of asphalt mixtures induced by frost heave under cyclic temperature variations: A discrete element simulation study

To investigate the frost heave failure mechanism of asphalt mixtures under Cyclic Temperature Variations (CTV) cycles, this study employs the water-ice particle phase transition coupled expansion method based on discrete element theory. Using PFC2D software, the CTV cycles process of asphalt mixtures is simulated, with the accuracy of the simulation results validated through laboratory testing. Simultaneously, a pore water particle frost heave evaluation index ( φ v ) was defined, establishing a functional relationship between φ v and the number of CTV cycles events to quantitatively characterize the extent of pore water frost heave. Furthermore, leveraging the superior visualization capabilities of the discrete element software, analyses were conducted on the internal stress field, displacement field, velocity vectors, and microcrack damage within the specimens during CTV cycles. Results indicate: (1) Repeated CTV cycles induce locally high stresses within specimens, which rapidly develop during loading, ultimately leading to internal structural failure and reduced compressive strength. (2) During CTV cycles, particles within specimens undergo three phases: “concentration-disorder-stabilization.” Velocity vectors eventually exhibit a roughly symmetrical distribution extending from the center toward both upper and lower sides. (3) During the mid-stage of CTV cycles, ‘through-crack propagation’ occurs within the specimen. As the number of CTV cycles increases, this phenomenon intensifies, with crack propagation exhibiting a distinct directional tendency. This study provides a novel approach and methodology for investigating the frost-heave failure mechanism of asphalt mixtures during CTV cycles.