The lateral thermal erosion of thermokarst lake would in a certain extent influence the stability of the roadbed neighboring the lake-edge. In this study we developed a heat transfer model with phase change under the cylindrical coordinates and then predicted the changes of ground temperature regime beneath the roadbed and possible subgrade defects caused by the thermokarst lake. The results show that the annual mean lake-bottom temperature (AMLT) and the horizontal distance from the roadbed to lake-edge (HDRL) become two mainly factors that determine whether the thermokarst lake can influence the permafrost roadbed and how about the degree. Supposing the lake area is constant, the thermokarst lake with a higher AMLT usually damages the permafrost roadbed more seriously than the one with a lower AMLT. In additional, the thermal effect is also more obvious with the decreasing of the HDRL. Under the influence of the thermokarst lake, the ground temperature has been gradually warming and the talik area has been rapidly expanding beneath the roadbed. However, the most of the thermokarst lakes have been experiencing a process of area expansion. If this factor is considered, the actual increments of ground temperature and talik area are more than the predicted values and the damage would be more serious.
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