Using crushed-rock structures to improve the stability of embankment affected by thermokarst lakes in the warm permafrost region of Siberia

Thermokarst lakes are severely weakening the stability of embankments in the warm permafrost region of Siberia. To mitigate their adverse effects, two crushed-rock embankments and the filled thermokarst lakes with crushed rock are used to cool surrounding soil and prevent further thawing of permafrost. And a coupled model of airflow-heat-deformation was developed to simulate their thermal regime and settlement deformation based on the Tynda site. The results show that the thermokarst lake 10 m away from embankment toe, increases the geo-temperature by about 0.2 °C at 2.0-m depth below embankment center, causing the active layer thickness to increase by 0.63 m and an increase of the maximum settlement deformation from 44.93 cm to 51.16 cm in the 50th year. Both the crushed-rock interlayer embankment (CRIE) and U-shaped crushed-rock embankment (UCRE) exhibit effective cooling performance, with the latter performing better due to the enhanced convective heat transfer in revetment crushed-rock layers. The CRIE and UCRE decreases the corresponding settlement to 20.01 cm and 18.82 cm, respectively, but structural safety can’t be fully guaranteed. Only when thermokarst lake is 15 m or more away from embankment toe, can they be applicable with enough safety reserve. For enhanced safety, the filled thermokarst lakes with crushed rock further reduce the maximum settlement of CRIE and UCRE to 13.36 cm and 7.14 cm, respectively, effectively improving the structural stability. These results provide a valuable reference for the application of crushed-rock structures and embankment constructions in the warm permafrost region of Siberia.