Numerical investigation of the temperature field and frost damages of a frost-penetration tunnel considering turbulent convection heat transfer

Abstract

Accurate evaluation of tunnel temperature field plays an essential role in anti-freezing measures of cold-region tunnels. The aim of this study is to establish turbulence-based theoretical models for the temperature field of cold-region tunnels and to investigate the temperature field and frost damages of an actual cold-region tunnel with negative mean annual air temperature. A transient convection–conduction heat transfer model with turbulent flow and phase change was established. The proposed theoretical model was validated using model test results. The temperature field and frost damages of the Daban Mountain tunnel were investigated. The influence of global warming on the temperature field was also deeply discussed. The results indicate that for the Daban Mountain tunnel, the freezing circle develops to the radial surrounding rock and simultaneously develops along the longitudinal direction of the tunnel. Permafrost occurs at the tunnel entrance in the 7th year and along the whole tunnel in the 16th year. The formation rate and maximum freezing depth of permafrost is significantly influenced by the mean annual air temperature. The annual air temperature amplitude has significant effect on the formation rate of permafrost but little effect on the maximum freezing depth. Under global warming, the mean annual temperature of the surrounding rock decreases first and then increases. In the early years, the unfrozen surrounding rock freezes yearly and develops into permafrost. However, as the mean annual air temperature rises, the permafrost gradually degenerates into seasonally frozen rock and the maximum freezing depth decreases yearly.