Asymmetric Thermal Effects of Thermokarst Lake and High Sunny Slope on Permafrost Subgrade

Sunny-shady slope and thermokarst lake are widely distributed along the Qinghai-Tibet highway, the lateral thermal erosion of which will induce serious subgrade diseases and affect long-term stability of the highway. In this paper, four numerical models were established to analyze the coupling thermal influence of thermokarst lake and high sunny slope on permafrost subgrade. Lateral single and composite thermal disturbances induced by 80m width lake and 5.3m height sunny slope had been investigated and the thermal influence weight of above two factors was also calculated by pixel method. The results show that: 1) High sunny slope leads to more serious lateral thermal erosion, and the melting depth is larger than that of the common subgrade, which also causes the lateral deviation of the temperature field of the subgrade. 2) Thermal erosion of roadside thermokarst lake mainly affects the permafrost below the lake bottom. Lateral thermal erosion of the lake has little effect on the morphology of thawing plate of subgrade permafrost, and it can melt the deep permafrost under the subgrade which results in a thickness decrease of the underlying permafrost layer. 3) With increase of servicing time, the weight of thermokarst lake lateral thermal erosion on the permafrost subgrade gradually decreases, and corresponding thermal impact of high sunny slope takes the dominant position.