Abstract
Investigating the temperature field evolution in high-geothermal tunnels is crucial for optimizing thermal control strategies. Field monitoring obtained the spatiotemporal distributions of rock temperature (Tr), environmental temperature (Te), and air flow velocity (Wv), while laboratory experiments quantified the temperature-dependent response characteristics of thermal parameters for surrounding rock and lining materials. A transient heat transfer model based on tunnel ventilation was established, which incorporates the time-temperature effect (TTE) of material thermal parameters and was validated through numerical simulation. The study found: (1) Compared with the constant material thermophysical parameter model, the proposed TTE model reduced the temperature prediction error by 17.6% during the secondary lining construction process. (2) The variation characteristics of tunnel peak temperature, heat dissipation peak, and temperature difference between the center and edge of the secondary lining under various influencing factors were investigated. (3) The thermal insulation structure caused a substantial increase in concrete peak temperature (15.6°C) during the early stage of secondary lining construction, which is detrimental to its early strength development; however, after the completion of hydration heat release, the sandwich-type thermal insulation structure helped reduce the temperature of the entire secondary lining. (4) A multivariate prediction model coupling Tr, Te, and Wv was established, capable of accurately estimating extreme temperatures and heat dissipation rates at various construction stages.
Full Text
Temperature field evolution characteristics in the high geothermal tunnel considering thermo-temporal effect (TTE) of material thermal properties
Xinrong Liu1,2, Yan Wang1, Xianhan Zhou1,2
1 School of Civil Engineering, Chongqing University, Chongqing 400045, China
2 Key Laboratory of New Technology for Construction of Cities in Mountain Area of the Ministry of Education, Chongqing University, Chongqing 400045, China
Abstract
Understanding temperature field evolution in high geothermal tunnels is crucial for optimizing thermal control strategies. This study employed field monitoring to capture the spatiotemporal distribution of rock temperature (Tr), ambient temperature (Te), and air flow velocity (Wv), while laboratory experiments quantified the temperature-dependent response characteristics of thermal parameters for both surrounding rock and lining materials. A transient heat transfer model based on tunnel ventilation was developed, incorporating the thermo-temporal effect (TTE) of material thermal properties, and validated through numerical simulation.
The research yielded four key findings. First, compared with models assuming constant thermal properties, the proposed TTE model reduced temperature prediction errors by 17.6% during secondary lining construction. Second, the study systematically investigated variation characteristics of tunnel temperature peaks, heat dissipation peaks, and temperature differentials between the center and edge of the secondary lining under various influencing factors. Third, although insulation structures increased peak concrete temperature by 15.6°C during the early construction stage of the secondary lining—potentially impairing early strength development—sandwich insulation structures proved effective in reducing overall lining temperatures after hydration heat release subsided. Fourth, a multivariate prediction model coupling Tr, Te, and Wv was established to accurately estimate extreme temperatures and heat dissipation rates across different construction stages.
Keywords: high geothermal tunnel; unsteady thermal properties; temperature field evolution; sandwich insulation structure