Numerical analysis for critical height of railway embankment in permafrost regions of Qinghai-Tibetan plateau

In permafrost regions of Qinghai-Tibetan plateau, the critical embankment height must be considered in the process of the construction of railway, especially for the global climatic warming. In this paper, the two-dimensional numerical analysis for the critical embankment height (for coarse-grained soil) has been performed by using the finite element method. The mean annual air temperatures used in the calculation are −6.5, −6.0, −5.5, −5.0, 4.5 and −4.0 °C, respectively, and the value of temperature rise is taken as 1.10 °C in the coming 50 years. The minimum embankment heights derived from the analysis are 0.85, 0.92, 1.01, 1.18, 1.60 and 2.66 m for the different mean annual air temperatures, and the maximum embankment heights are 7.68, 7.55, 7.34, 7.00, 6.45 and 5.85 m, accordingly. On condition that the service life of railway embankment is 50 years, the critical value of the mean annual air temperature is −3.5 °C. Namely, in the areas where the mean annual air temperature is higher than −3.5 °C, the critical embankment height does not exist. Furthermore, by calculating, we can find that no matter whether high or low embankment is constructed, the ground temperature under the embankment will rise, and the permafrost will be in a degradation situation, which has been confirmed by the field observation data at Qinghai-Tibetan railway test sites.