Abstract: The temperature field in tunnels with high ground temperatures is influenced by multiple factors during their construction, and the field evolution mechanism is complex. To understand this phenomenon, the distribution characteristics of the rock temperature, surrounding temperature, and wind speed in a tunnel are investigated; additionally, laboratory experiments are conducted to examine the change rules of the thermophysical parameters of the surrounding rock, primary support, and secondary lining materials under different temperatures. Subsequently, an unstable mathematical model is implemented using the COMSOL numerical simulation software. This model examines the evolution law of the temperature field throughout the tunnel excavation process, including primary support and secondary lining construction. Finally, a prediction model for the maximum temperature of the primary support and secondary lining during the construction period is established through multiple function regression analysis. Results reveal the following key insights: (1) With increasing temperature in the tunnel, the thermal diffusion coefficient of surrounding rock exhibits a quadratic decreasing trend, specific heat capacity demonstrates a quadratic increasing trend, and thermal conductivity decreases following an upward concave quadratic function. (2) The thermal diffusion coefficients of the primary support and secondary lining materials show a quadratic decreasing pattern. Meanwhile, the specific heat capacity of these materials initially increases and then decreases with rising temperature, indicating the nonlinear behavior of their thermal energy storage characteristics. (3) When the maximum temperature in the primary support and secondary lining of the tunnel is used as the characteristic points, the increasing rock and surrounding temperature in the tunnel linearly increases the maximum temperature in primary support and secondary lining. Meanwhile, an increase in the return air speed effectively lowers the temperature quickly at first and then slowly.

Key words: tunnels with high ground temperature, unstable heat transfer, temperature field evolution, thermophysical parameters