The numerical study on the ventilated embankment in permafrost regions in Qinghai–Tibet railway

Ventilated duct system is widely used to prevent the degradation of the permafrost. For the ventilated embankment in high-temperature frozen soil region in the Qinghai–Tibet railway project, numerical analysis of temperature field under different layouts of ventilated duct system, such as the duct span, duct diameter, buried depth of the ducts and the height of embankment are systematically considered and optimized design of the ventilated duct system is proposed. The main results are as follows. (1) With an artificial regulation of the boundary condition of the ducts, the mean annual ground temperature of the permafrost drops to about 1.0–2.0 °C. (2) With the same ratio of the span to the diameter of the ducts, the layout with the smaller diameter ducts can get a relative better cooling effect. (3) Considering the ducts traversing the embankment, the stability of the ducts and the roadbed is also analyzed under the load cases of initial stress, the dead load of the soil, the trainsʹ load and the frost heaving. (4) The differential deformation made by frost heaving under the proposed layout of the ducts and embankment cause larger tensile stress on the ducts than ordinary loads, especially on those ducts with larger diameter, which should be paid more attentions by the engineers.