Investigation of nonlinear heat transfer mechanisms in high geotemperature tunnels considering construction hydration heat effects

To address the problem of temperature-induced cracks in high-temperature tunnel lining structures, which are susceptible to the coupling effects of support timing and hydration heat, this study establishes a transient numerical calculation model of the radial temperature field for tunnels under construction using the finite difference method. The primary focus is to analyze the influence of support parameters and environmental factors on the lining temperature field, with the goal of optimizing thermal management of tunnel linings to prevent temperature-induced structural issues. The main conclusions are as follows: (1) Hydration heat has a pronounced impact on the temperature distribution within tunnel linings, leading to a maximum temperature variance of 51.52 °C between the interior and exterior surfaces. (2) In standard lining structures, ambient temperature is linearly related to both the Maximum temperature difference within the secondary lining and the stabilized temperature at the outer surface. Return air velocity influences these temperature metrics through exponential relationships, characterized by upward and downward convex curves. Similarly, the time interval between the construction of initial support and secondary lining shows an exponential correlation with these temperature metrics, exhibiting downward convex curves. (3) For sandwich-type lining structures, the thickness of the insulation layer impacts the Maximum temperature difference and stabilized surface temperature through exponential relationships, resulting in upward and downward convex curve patterns, respectively.