Study on temperature control and snow melting effects of a PCM-SHPs composite embankment structure

Highway embankments in cold regions face challenges, including the instability of permafrost and the driving hazards caused by snow and ice melt during winter, necessitating effective solutions. This study proposed a composite embankment structure integrating phase change material (PCM) and small heat pipes (SHPs) to enhance the stability of permafrost and meet snow-melting requirements in cold regions. By combining laboratory soil column experiments and numerical simulations, the effectiveness of the PCM-SHPs structure in promoting snow and ice melting on the pavement and mitigating permafrost thawing beneath the surface was systematically evaluated. Results show that: (1) Compared with the unmodified embankment, the PCM-SHPs embankment increases the number of days with above-freezing pavement temperatures by 83 days in the winter, significantly raising the pavement temperature and reducing snow and ice accumulation, thereby improving winter road passability; (2) The SHP system can significantly alleviate the thawing process of the underlying permafrost layer and promote the long-term stability of the embankment. At the 5th, 10th, 15th, and 20th highway operation years, the artificial upper limit of PCM-SHPs embankment exhibits uplift values of 0.89 m, 1.31 m, 1.29 m, and 0.93 m, respectively, relative to the unmodified embankment; (3) Optimization of PCM mixing ratio and layer placement indicates that a 15% mixing ratio with placement near the embankment base provides the best cooling performance; (4) The optimal SHP configuration is determined as a spacing of 9 m with a burial depth of 1.75 m below the pavement, enhancing temperature regulation and cooling efficiency.