Asymmetric talik formation beneath the embankment of Qinghai-Tibet Highway triggered by the sunny-shady effect

Energy budget beneath the road embankment strongly impacts the permafrost thermal state and stability of the overlying infrastructure. However, magnitudes and rates of daily heat flux caused by the sunny-shady effect are poorly understood. Herein, we investigated the sunny-shady effect on heat flux characteristics of road embankments through long-term observations and numerical simulation. Simulated and observed soil temperatures at depth were in good agreement over the 2007–2012 period. Simulated results show that maximum differences in the annual heat budget were 19.8 MJ/m2, 61.3 MJ/m2, and 103.2 MJ/m2 for the cases with the mean annual near-surface ΔT of 1 °C, 3 °C, and 5 °C, respectively, in comparison to the reference case without the sunny and shady effect. These processes triggered the talik initiation and development on the sunny side and enlarged laterally and vertically. Talik area for the ΔT of 5 °C was more than 5 times larger than that of 1 °C. Finally, the sunny and shady effect can cause asymmetric road damage, such as uneven settlement and longitudinal cracking. The net finding is potentially helpful for better understanding differential embankment deformation, as well as for improving the design of the engineered mitigation measures.