Abstract: Thermosyphon is one of the important measures for thermal protection of the embankment in permafrost region. But the design method of the thermosyphon embankment is not provided in relevant standards. Therefore, the design of the existing embankments with thermosyphon mainly depends on the past engineering experience. Through field monitoring and theoretical calculation, the characteristics of heat exchange balance for the embankment in frozen soil region were analyzed. It was found that the embankment absorbs heat in warm season, but releases heat in cold season, and it was in the endothermic state for the whole year. The essential reason of the embankment thawing settlement is that the heat absorption is greater than heat release. A new design method of thermosyphon embankment was proposed based on the theory of heat balance. Its basic principle is to ensure the thermosyphon annual heat transmission capacity which is not less than the embankment net heat absorption. Taking the highway engineering in permafrost region of Qinghai-Tibet Plateau as an example, the design method proposed in this paper was verified by field test. The results show that the settlement of the thermosyphon embankment designed using the proposed method was significantly less than that of the ordinary ones. The thermosyphon embankment has improved the stability of the underlying permafrost and mitigated the settlement of the foundation permafrost. That verified the correctness and rationality of the method proposed in this paper. This method has clear theory, simple parameter acquisition and strong engineering application value, which can be widely used in design of the thermosyphon embankment in permafrost region.

Key words: embankment engineering, thermosyphon subgrade, heat balance, design method, field experiment