Numerical simulation on the performance of thermosyphon adopted to mitigate thaw settlement of embankment in sandy permafrost zone

Desertification and climate warming have affected the stability of the crushed-rock interlayer embankment of the Qinghai-Tibet Railway (QTR) in the permafrost zone. The two-phase closed thermosyphon (TPCT) is adopted to mitigate the problem in sandy permafrost zone. A composite heat transfer model, including air convection in the crushed-rock interlayer, the air-TPCT-soil coupled heat transfer for TPCTs system and the heat conduction with phase change in the soil layers, is developed based on the equivalent thermal resistance for the TPCf. And an increase in average air temperature by 0.04 degrees C a(-1) was also simulated. The numerical results indicate that TPCTs play rapidly a cooling effect and approach a thermal balance state after 10 years of construction. TPCfs installed at the embankment slope effectively ease the underlying permafrost degeneration and cool down permafrost. However, the cooling scope and magnitude of TPCTs largely depends on working duration after installation. If the mean average air temperature is still lower than -3.5 degrees C after considering climate warming, TPCTs installed at the 10th year of QTR operation can mitigate the negative effect of climate warming and sand accumulation in the sandy permafrost zone of the Qinghai Tibet Corridor. (C) 2017 Elsevier Ltd. All rights reserved.