Study on the Characteristics of Environmental Temperature Distribution and Optimization of Ventilation Parameters in High-Temperature Tunnels During Construction Period

A field investigation was conducted on the temperature distribution of the high-temperature tunnel environment during the construction period, and a three-dimensional numerical model for single-head ventilation of the high-temperature tunnel during the construction period was established after quantifying the heat source based on the construction conditions. After verifying the reliability of the numerical model, a study was conducted on the distribution characteristics of tunnel temperature and optimization of ventilation parameters. The results show that: (1) The environmental temperature distribution along the tunnel can be divided into two sections. Within the first 20 meters from the heading face, there is a sudden increase followed by a decreasing trend, while from 20 meters beyond the heading face to the tunnel entrance, there is a trend of initial increase, followed by a decrease, and then a continuous increase with decreasing inlet air temperature or increasing airflow; (2) Decreasing inlet air temperature leads to a linear decrease in the peak environmental temperature within the tunnel, while increasing airflow results in a quadratic decrease in the peak environmental temperature, indicating that inlet air temperature has a more significant impact on the peak environmental temperature within the tunnel compared to airflow; (3) Utilizing a multivariate function, we established a predictive model for tunnel environmental temperature considering the coupling effects of airflow and inlet air temperature. The model suggests that when the inlet air temperature is ≤15 ℃, an airflow rate of >40 m³/s is sufficient to meet the construction requirements for the tunnel environment. However, when the inlet air temperature exceeds 20 ℃, additional cooling measures are necessary.