Multi-dimensional assessment of parameters governing the thermal-humidity environment in high-geothermal tunnels during operation

The excessive heat and humidity in high-geothermal tunnels present significant challenges to personnel safety and structural stability. This study aimed to explore how geological and ventilation parameters influence thermal–humidity control performance of a tunnel during operation. To clarify the influence pathways, a multi-dimensional thermal–humidity environmental assessment framework was established to evaluate six key parameters and quantify their contributions using the Taguchi analysis of variance method. An orthogonal test L27(3 6 ) was designed, incorporating three evaluation indices: the maximum temperature variation in the tunnel ( T D − v ), the heat index ( HI ), and the necessary ventilation duration ( t s ). The results indicate that the surrounding rock temperature exerts the most significant effect on T D − v , with a percentage contribution of 69.32%. The dominant parameter for the HI was found to be the air temperature, accounting for 81.83% of the variation. Regarding the t s index, both air temperature and surrounding rock temperature were identified as critical parameters, with contribution rates of 35.14% and 55.69%, respectively. Considering three indices, the significance of the parameters ranks is as follows: surrounding rock temperature, air temperature, surrounding rock thermal conductivity, ventilation time, fan speed, and relative humidity. The analysis yielded an optimal operational strategy with T D − v (5.35 °C), HI (12.79 °C), and t s (1 day).