Study on the coupling thermal effect of thermokarst lake and high sunny slope on permafrost embankment

Abstract

Sunny-shady slope and thermokarst lake are widely distributed along the Qinghai-Tibet highway (QTH), and their thermal influence on permafrost embankment can induce serious engineering diseases and affect its long-term service performance. This study aims to reveal the coupling thermal impact mechanism of roadside thermokarst lake and high sunny-slope on permafrost embankment. Firstly, an in-situ ground temperature monitoring site at K2952 + 300 section of QTH has been built and temperature distribution characteristic of observed embankment are investigated. Then, three numerical models are established and spatial–temporal characteristics of asymmetric temperature filed of permafrost embankment have also been analysed and compared. The results show that: (1) Permafrost artificial upper limit of observed embankment has a large fluctuation with the synergy of high sunny slope and thermokarst lake, and severe unilateral thermal erosion leads to the aggravation of subgrade disease despite heat pipes treatment has been adopted. (2) Thermalkarst lake has a certain degree of lateral thermal influence on permafrost embankment, while the magnitude of its thermal impact is related to the distance from embankment. (3) Significant endothermic effect of 5.3 m height sunny slope accelerates the melting depth of embankment underlying permafrost, and triggers off asymmetry morphology of permafrost temperature field. (4) Under the action of ipsilateral thermokarst lake and high sunny slope, the maximum melting depth and thawing plate deviation of embankment underlying permafrost can be exacerbated simultaneously, and the lateral thermal erosion caused by these two factors becomes more intensive as the thermokarst lake gradually approaches the roadbed.