Study on thermal performance of novel asymmetric crushed-rock-based embankment on the Qinghai-Tibet Railway in permafrost region

Abstract Railway embankments in permafrost regions are often affected by serious thaw settlement diseases resulting from permafrost degradation. For this reason, a novel, asymmetric crushed-rock-based embankment (ACBE) structure was employed in the construction of the Qinghai-Tibet Railway in Beiluhe, China, in order to increase cooling capacity and protect the transverse thermal stability of the tracks. This study developed a heat transfer model which accounts for heat conduction occurring in the soil layers and the air convection occurring in its crushed-rock layers. The model helped to reveal the forced convection mechanism of air within the crushed-rock layer. The thermal characteristics of the ACBE for different soil layers were analyzed using ten years of measured data, and its long-term thermal regime was predicted by numerical model. Results indicate that novel ACBE plays a positive role in lifting the permafrost table (PT), lowering the ground temperature surrounding the PT, and maintaining the embankment's temperature distribution symmetry. Novel ACBE is thus an effective, active cooling measure which can mitigate permafrost degradation and transverse non-uniform deformation. These findings provide important guidance for future embankment construction in permafrost regions.