Yongzhi Liu

The effect of permafrost changes on embankment stability along the Qinghai–Xizang Railway

After construction of the Qinghai–Xizang Railway, the resultant heat exchange between soil and atmosphere caused changes in the thermal and mechanical stability of permafrost beneath the railway embankment. Monitoring from 2005 to 2010 indicated 12 sections of embankment that experienced more than 5xa0cm of settlement, with three showing deformations of more than 10xa0cm and signs of continuing settlement. Embankment stability is closely related to permafrost changes beneath the embankment. Large-scale deformations have contributed to permafrost thaw and artificial permafrost table deepening, and this deformation has not stabilized over the short term. In contrast, small-scale deformations have contributed to a warming of the permafrost that has gradually stabilized as soil temperature decreases. Only three sections of the Qinghai–Xizang Railway have exhibited settlement deformation that exceeds 10xa0cm, through a deepening of the artificial permafrost table and a gradual increase in permafrost thawing result in embankment settlement deformation. However, with climate warming trends and the long-term operation of the railway, the long-term thermal and mechanical stability of the embankment needs to be carefully monitored to ensure the safe operation of the Qinghai–Xizang Railway.

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 ( −0.7 °C), thaw consolidation of the underlying permafrost resulted in significant settlement on TSGEs, some of which reached 40 cm.