Discrete element analysis on progressive damage mechanism of phase change material-mixed clay with freeze-thaw cycles

Phase-change-material-mixed clay (PCM-clay) effectively regulates temperature fluctuations and prevents freezing in the core walls of dams, canals, embankments, and pavements in cold regions. Despite the potential of PCM-clay, limited research has conducted on its damage mechanisms when subjected to freeze-thaw (F-T) cycles. In this study, discrete element method (DEM) was established to numerically simulate and analyze the progressive damage mechanism of PCM-clay during F-T cycles. Fundamental assumptions, were made regarding filling configurations, and contact model selection. Laboratory experiments were conducted to calibrate the model parameters and evaluate simulation accuracy. The progression of crack development, force chain networks, and particle displacement throughout the entire F-T cycle are examined and discussed. The results indicate high accuracy of the model, with an efficiency of 0.82 and 0.78 for untreated soil and PCM-clay, respectively. Compared to untreated soil, the F-T-induced cracks in the PCM-clay model were mainly tensile and more evenly distributed across the PCM-clay sample. Post-cycle analysis revealed a relatively continuous internal force chain network and minimal particle displacement, while maintaining structural integrity. This study elucidates the mesoscopic behavior and mechanism underlying F-T damage in PCM-clay, thereby contributing to a clearer understanding of its performance and functional principles in cold-region engineering applications.