Permafrost-Related Embankment Deformations along the Qinghai-Tibet Railway.

The Qinghai-Tibet Railway traverses 550 km of permafrost region. After embankment construction in 2003, considerable detrimental permafrost-related embankment deformations developed along the railway. Based on field monitoring data collected from 2005 to 2012, typical embankment deformations, as well as their mechanisms along the railway were analyzed, taking into account the thermal regime and ice content of the subgrade soil layers. Results showed that frost heave of the embankment was slight and only occurred on a few in-cut roadbeds and air convection crushed rock embankments (ACCEs) in colder permafrost regions (< -1.5 °C). It mainly developed with upward movement of the permafrost table under the roadbed during the first 3-4 years after embankment construction. Settlement of embankments was significant, and some already threaten the railway's safe operation. As ACCEs successfully cooled the shallow subgrade and underlying permafrost, embankment settlement was relatively slight and acceptable. Settlement of traditional sand gravel embankments (TSGEs) was generally greater than that of ACCEs. In warmer permafrost regions (> -0.7 °C), thaw consolidation of the underlying permafrost resulted in significant settlement on TSGEs, some of which reached 40 cm. [ABSTRACT FROM AUTHOR]