Thermal-deformation behavior of a crushed-rock embankment along a high-grade highway in permafrost regions

Numerous studies have been conducted to investigate the thermal stability of crushed rock embankments (CREs). In this study, we developed an automatic field monitoring system for a CRE during the construction of the Gonghe–Yushu High-grade Highway (GYHH) to explore both the convective cooling and the deformation controlling effect of the crushed rock layer (CRL). We evaluated the thermal-deformation performance of a the CRL based on the long-term field monitoring data. The results reveal that the upper peat layer could slow down the degradation of shallow permafrost. However, the heat absorbed by the black asphalt pavement significantly contributed to the degradation of the permafrost beneath the contrast embankment without the CRL. The CRL had an obvious cooling effect range for the shallow stratum, where an effective cooling zone formed (about 4 m deep in the 4th year after the construction of embankment). Nevertheless, deep permafrost beyond this effective cooling range continued to warm owing to the downward heat flux. Consequently, the total settlement of the CRE decreased by 23% compared with the contrast embankment in the 5th year. This work is expected to provide a reference for the design of the CREs in permafrost regions.