Settlement trend of embankment-bridge transition section reinforced with thermosyphons in permafrost regions

Differential settlement of embankment-bridge transition section (EBTS) is easy to occur in permafrost regions, so it is necessary to carry out a long-term dynamic investigation, maintenance, and reinforcement on EBTS. In this study, settlement characteristics of two EBTSs reinforced by thermosyphons along the Qinghai-Tibet Railway (QTR) in 2010 were analyzed. In addition, the Pettitt test method was used to analyze the time when the thermosyphons showed a significant cooling effect after reinforcement, and the Verhulst model and exponential curve method were used to analyze the long-term settlement trend of an EBTS in the next 10 years. The results indicate that the accumulated settlements and settlement rates of monitoring EBTSs after reinforcement were obviously lower than the requirements of the design code for railway embankments in China. The fifth year after the completion of thermosyphon is the abrupt change point of the settlement data. The maximum difference between the change rate of the settlement rate before and after the abrupt change point is 78.5%. Thermosyphon will make the EBTSs close to the deformation stability after reinforcement for 10 years. Finally, according to the settlement evolution results, the accumulated settlements of the abutment of monitoring sites will be less than 50 mm in the 10 years after 2020. In general, thermosyphon, as a reinforcement measure, can significantly and rapidly slow down the settlement trend of the EBTSs and maintain its long-term stability. This study aims to deepen the understanding of the effect of EBTS reinforcement measures and provide a scientific basis for EBTS reinforcement in permafrost regions.