Performance, applicability, and optimization of a new slope cooling and protection structure for road embankment over warm permafrost

Abstract

How to deal with the issues that crushed-rock revetment embankments are facing, such as inadequate cooling, sand-filling, and rock-weathering, is of importance for the integrity and safe service of roadways built on warm permafrost (> −1.0 °C) in the Tibet Plateau. In this study, a new slope cooling and protection structure (SCPS) was developed and a field experiment was implemented in the plateau permafrost zone to examine its cooling effect on permafrost stratum. Numerical simulations were then conducted to evaluate its cooling applicability in different road embankments and to optimize the new structure for further application in highway embankments with a wider pavement based on a validated convection heat transfer model. The results indicate that the new SCPS can produce an effective cooling process on the embankment slopes and the underlying permafrost. This caused an evident decrease in permafrost temperature at the subgrade shoulders and a significant elevation of the permafrost table below it. The intensified convection cooling in winter and good thermal insulation in summer generate the excellent cooling of the SCPS. However, the cooling range of SCPS is limited for a wide highway embankment. The highly endothermic asphalt surface makes it difficult for the SCPS to cool the embankment core effectively. To enhance the cooling adaptability, an optimized structure combining insulation and the SCPS proved that it can significantly expand the cooling scope to the embankment core and further raise the permafrost table beneath a wider embankment. This study confirms the application of the new SCPS as a highly efficient technique for maintaining the integrity of narrow railway embankments, examines its possible utilization in wider highway embankments, and promotes the efficient use of the natural cold energy in the plateau permafrost zones.