Tunnel anti-freezing defence method based on daily temperature cycle

At present, anti-freezing fortification of tunnels in cold regions mostly takes the annual temperature fluctuation as a reference for analysis, thus ignoring the phenomenon of the daily cycle temperature. A method for using the daily temperature cycle was developed to analyse the anti-freezing fortification method. The temperature field of a tunnel was analysed through numerical simulations, corresponding anti-freezing fortification measures were proposed and suggestions for frost damage fortification zoning were devised. It was found that, as the radial depth from the lining surface increases, the phenomenon of alternating positive and negative temperatures gradually disappears. The temperature variation trend at the back of the insulation layer was consistent with that at the lower surface, and the temperature variation at the back lagged behind that at the lower surface. With an increase in the longitudinal distance of the tunnel, the phenomenon of significant temperature fluctuations gradually disappeared and the temperature of the lining surface increased. The difference between the formula developed in this work and the formula proposed by China Railways in terms of the frost-resistant fortification length of tunnels in cold regions was found to be only related to environmental impact.