Permafrost warming under the earthen roadbed of the Qinghai–Tibet Railway

Abstract

This paper investigates the stability of the earthen roadbed built in the warm and ice-rich permafrost region. The varying thermal regime of the subgrade and the ongoing settlement of the roadbed were observed at field. The temperature data demonstrate that in warm and ice-rich permafrost regions, adoption of earthen roadbed results in warming of the underlying permafrost. It is primarily because the earthen roadbed traps the warm-season absorbed heat in the natural ground. In addition, the carried heat of the earthen roadbed that was constructed in warm season propagates downward to warm the underlying soil. The warming permafrost layer promotes the roadbed settlement, which was mostly linearly developed in the past five service years. A comprehensive analysis for the varying thermal regime and the ongoing settlement shows that the unfrozen water liberated from the warming, undrained layer experiences consolidation. The deformation of the undrained soils is mainly responsible for settlement of the roadbed. In comparison, the temperature variation of this warming permafrost layer is found to be less beneath roadbeds protected by thermosyphons or crushed rock revetments. The installation of thermosyphons into the earthen roadbed is recommended to prevent the further degradation of the underlying permafrost.

The Thermal and Settlement Characteristics of Crushed-Rock Structure Embankments of the Qinghai-Tibet Railway in Permafrost Regions Under Climate Warming

“…According to the location of occurrence, the sources of embankment settlement in permafrost regions are divided into four parts: embankment filling compression, active layer compression, permafrost thawing settlement and warm permafrost compression. The settlement in the first two parts mainly occurred in the first few cycles after the embankment was constructed, and the settlement during railway operation was mainly caused by compression and thawing consolidation of the underlying permafrost (Qi et al, 2007;Qin and Li, 2011). The permafrost beneath the UCRE and CRRE did not thaw (their APTs rose, as shown in Figure 6A) from 2006 to 2018, indicating that embankment settlement does not include thawing settlement in this study.…”

A heat-flux upper boundary for modeling temperature of soils under an embankment in permafrost region

“…Building embankment alters the thermal regimes such that the embankment absorbs more sunlight than the adjacent natural ground surface even if the surface materials are the same 36 . Plus the construction thermal disturbance, the permafrost underlain a roadway embankment has been found 0–1 °C warmer than the adjacent natural ground, especially in warm permafrost regions 37 . It has been observed that this temperature increment has caused 10–20 cm settlement to the embankment in warm permafrost region, and that the warming of permafrost still continues due to the global warming 38 .…”