Process and mechanism analysis of typical permafrost area surface deformation at two sites along the Qinghai-Tibet highway based on long-term leveling observation

Surface deformation indicates permafrost changes and multi-year surveys can reflect its characteristics and causes. In this study, surface deformations in Wudaoliang (WDL) and Xidatan (XDT) were determined based on long-term leveling measurements, hydrothermal data, precipitation and soil sampling. In-situ observations can be used to study the influence of hydrothermal changes in the active layer on the surface. The amplitude and onset date of seasonal deformation are different due to the soil moisture (SM) and soil texture in the two permafrost regions. High SM and fine-grained soils can cause significant seasonal surface deformation. A good correlation existed between the freeze-thaw front migration rate and deformation in the active layer with a uniform distribution of SM. The inter-annual subsidence rate in the WDL was higher than in the XDT, owing to the different rates of ground ice thawing near the permafrost table. The long-term subsidence rate positively correlates with the increased seasonal deformation amplitude, especially in fine-grained soils. Schematic diagram of permafrost surface deformation. [Display omitted] •Soil moisture and texture affect the amplitude and onset date of seasonal deformation, especially in shallow soil.•Ground ice thawing impacts inter-annual subsidence, reflecting the permafrost degradation with high ice content.•Long-term subsidence is positively correlated with seasonal deformation increased, especially in fine-grained soils.