Evaluation of Tunnel Fire Factors Under Combined Smoke Exhaust

Abstract

With the advancement of smart construction technologies, numerous high-altitude long road tunnels have been constructed in various countries in recent years. This has brought tunnel fire safety in special environments into focus as an important challenge. This study, using Pyrosim and Pathfinder software, focuses on the design parameters of personnel egress and smoke extraction systems in high-altitude tunnel fires. Through orthogonal experiments and numerical simulations, the key factors influencing available safe egress time (ASET) and required safe egress time (RSET) are systematically analyzed. In accordance with the fire safety egress principles for road tunnels, where ASET must be greater than RSET, the study proposes a set of optimal smoke extraction design parameter combinations for different altitudes. The results indicate that in natural smoke extraction mode, the influencing factors are ranked as follows: longitudinal ventilation velocity > smoke vent spacing > altitude > smoke vent area. In mechanical smoke extraction mode, the order of influence is as follows: smoke vent wind speed > smoke vent spacing > altitude > smoke vent area > longitudinal ventilation velocity. The study also finds that as altitude increases, the egress speed of personnel decreases, leading to longer egress times to safe areas for trapped individuals. Different types of evacuees also significantly affect egress speed. These findings provide valuable insights for the design and operational management of smoke extraction facilities in road tunnels.