Abstract
Traditional embankment is widely used in the permafrost regions along the Qinghai‐Tibet Railway (QTR) because of its simple construction and lower cost. However, this form of embankment has insufficient ability to resist external thermal disturbance. To clarify the thermal characteristics of traditional embankment under climate warming, the ground temperature change process of section K1068 + 750 of the QTR was analysed in this study. Based on the field monitoring data from 2006 to 2019 and the established heat transfer model, the past and future changes of permafrost thermal regime under the embankment were analysed. The results show that the degradation of permafrost under the embankment is faster than that under the undisturbed site due to the combined of embankment construction and climate warming. The sunny‐shady slope effect related to embankment orientation makes the distribution of permafrost temperature under embankment asymmetric. In the long term, permafrost degrades both under the undisturbed site and embankment. The continuous degradation of permafrost causes the settlement and deformation of embankment, especially the asymmetric degradation of permafrost on sunny side and shady side will cause longitudinal cracks on the embankment. Therefore, timely application of strengthening measures which can slow down the degradation of permafrost and adjust the uneven ground temperature on the sunny and shady sides under the embankment is of great significance to the safety of the traditional embankment.
Highlights
Introduction e Golmud-Lhasa section of the Qinghai-Tibet Railway (QTR) with a length of 1142 km was completed and started operation in 2006 [1]. It covers 550 km of continuous permafrost regions, 50% of which belong to warm permafrost areas with the mean annual ground temperature (MAGT) higher than −1°C [2]. e high thermal sensitivity of warm permafrost makes the stability of embankment in these areas significantly affected by changes in the external environment temperature [3]
Many studies based on field monitoring have shown that with the climate warming and the change of land-surface energy balance caused by the construction of embankment, the permafrost along the QTR has been extensively degraded, especially under the traditional embankment [4,5,6,7]. e degradation of permafrost has caused the settlement deformation of the embankment, which reduces the smoothness of the railway track and poses a threat to the safe operation of the train [8,9,10,11]
Since 2006, the ground temperature on the sunny side has been higher than that on the shady side at the same depth. e most representative one is the depth of permafrost table (PT) on the sunny side that is more than 5 m, which is deeper than that on the shady side
Summary
Lhasa section of the Qinghai-Tibet Railway (QTR) with a length of 1142 km was completed and started operation in 2006 [1] It covers 550 km of continuous permafrost regions, 50% of which belong to warm permafrost areas with the mean annual ground temperature (MAGT) higher than −1°C [2]. Many studies based on field monitoring have shown that with the climate warming and the change of land-surface energy balance caused by the construction of embankment, the permafrost along the QTR has been extensively degraded, especially under the traditional embankment [4,5,6,7]. Based on ground temperature and deformation data, the researchers analysed the thermal response of permafrost under the embankment to climate and human activity [15,16,17]. For some new forms of embankment, the stability can be determined by establishing a suitable mathematical model before the embankment construction [21,22,23,24]. e numerical simulation can be used to analyse the degradation progress of permafrost under the embankment and the embankment deformation in the future under climate change, so as to find the embankment that needs to be strengthened in time [25,26,27]. e simultaneous use of field monitoring and numerical simulation in the study helps to solve more engineering problems, and improves the accuracy of the conclusions
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