Investigation of temperature and humidity impact on thermal comfort in deep underground tunnel during construction in hot climate: A case study in an underground hydropower station

Abstract

This study investigates the thermal and humidity conditions and their impact on workers’ thermal comfort during the construction of underground tunnels in hot climates. Wall temperature, air temperature, and humidity were measured within an underground hydropower station tunnel. The wall temperature at the tunnel entrance and bottom end was found to be 4 °C higher than in the middle section. Air temperature stabilized at 450 m from the entrance, while humidity stabilized at 1450 m from the entrance. A Computational Fluid Dynamics (CFD) model was employed to simulate these conditions, with results demonstrating good agreement with on-site measurements for both air temperature and humidity. Simulation outcomes revealed a vertical temperature difference of up to 20 °C near heat sources, underscoring the potential of increased ventilation rates as a viable solution to mitigate high temperatures at tunnel ends. Evaluations based on PMV (Predicted Mean Vote) and WBGT (Wet Bulb Globe Temperature) criteria indicated that areas adjacent to heat sources do not meet thermal comfort standards, highlighting that reliance on dry bulb temperature alone is insufficient for assessing thermal comfort during underground tunnel construction activities. These findings can inform the optimal design of ventilation and air conditioning systems throughout the construction of underground tunnels.