Investigating the seepage-thermal interaction process on the thermal stability of highway embankments in permafrost regions adjacent to thermokarst lakes

Abstract

The hydrological process of a thermokarst lake plays a pivotal role in the thermal stability of nearby embankments through its considerable influence on thermal in permafrost areas. However, simply treating a thermokarst lake as a heat source has hindered the understanding of the seepage effect during thermal erosion. Moreover, the mechanism by which the seepage process affects the thermal state of permafrost remains uncertain. Here, we conducted an investigation and collected monitoring data at an embankment–thermokarst lake comprehensive observation site on the Qinghai–Tibet Plateau. The monitoring data indicate that the geotemperature distribution in the embankment exhibited remarkable asymmetrical characteristics. Notably, the proximity of the ground to the thermokarst lake resulted in greater geotemperatures and higher water contents. A puzzling phenomenon was observed whereby the embankment away from the thermokarst lake exhibited a deeper permafrost table, demonstrating a deviated thawing bowl below the embankment. We employed a seepage–thermal coupling model to demonstrate that the seepage process profoundly affects the geotemperature distribution pattern. The simulation results reveal that the convection heat flux from water flow dominated the total flux, gradually causing a deeper permafrost table along the flow path. Hence, the permafrost table decreased during seepage, which is consistent with the monitoring data, generating a deviated thawing bowl away from the thermokarst lake. It is important to consider the seepage–thermal coupling effect to assess the thermal stability of embankments beyond thermokarst lakes accurately.