Numerical investigation on temperature–humidity field under mechanical ventilation in the construction period of hot-humid tunnel along the Sichuan–Tibet Railway

High temperature–humidity environment is one of the severe challenges in constructing Sichuan–Tibet railway tunnels.For enhancing construction efficiency and guaranteeing tunnel worker safety,addressing the high temperature–humidity environment has irreplaceable significance.This study innovatively investigated the distribution law and evolution process of the thermal–humidity coupling field dur-ing tunnel construction.Besides,the corresponding ventilation measures were proposed based on the evaluation heat index(HI).If the initial temperature of the surrounding rock is constant,the distance between the ventilation duct outlet and the tunnel working face should not be greater than 30 m.Otherwise,the cooling performance of ventilation will be significantly weakened;If this temperature ranges in 65–85℃,the recommended ventilation velocity is 10–25 m/s,and the ventilation distance should not exceed 20 m.The con-clusions in this study are beneficial to better understand the high temperature–humidity environment in tunnel construction and can be a guideline for practical engineering application.