Simulating the thermal regime of a railway embankment structure on the Tibetan Plateau under climate change

Abstract

With global warming and its amplified effect on the Tibetan Plateau, the permafrost on the Tibetan Plateau has been significantly degraded, manifested by decreased permafrost thickness, increased active layer thickness, thermokarst, and surface subsidence, causing severe damage to infrastructure. To better understand and assess the future stability of the Qinghai-Tibet Railway, we used a laterally coupled version of the one-dimensional CryoGrid3 land surface model to simulate the thermal regimes of the railway subgrade under current climate conditions. By modeling ground subsidence (i.e., by simulating the melting of excess ice) we provide estimates of future subgrade stability under low (Representative Concentration Pathway 2.6 [RCP2.6]) and high (RCP8.5) climate warming scenarios. Our modeled results reveal satisfactory performance with respect to the comparison of measured and modeled ground thermal regimes. Under current climate conditions, we infer that mostly thaw-stable conditions as maximum thaw depths do not reach the embankment base. The sunny side of the embankment (southeast-facing) reveals being more vulnerable to suffering from thaw settlement or thermal erosion than the shady side (northwest-facing). The extent of future railway failure due to thawing permafrost will depend on the magnitude of the warming. For conditions typical of Beiluhe (situated on continuous permafrost in the central Tibetan Plateau), the railway embankment might largely maintain safe operation until the end of the century under a scenario of climate stabilization. In contrast, under strong warming the railway subgrade is likely to destabilize from the 2030s onwards and embankment subsidence is initiated at mid-century through the melting of excess ice.