Experimental study on smoke propagation characteristics in dead-end tunnel networks during construction stage based on a small-scale model

This study investigates smoke propagation in Dead-end tunnel networks during the construction phase using a 1:30 small-scale physical model based on the Tianshan Victory Tunnel. The model consists of two main tunnels, a central service tunnel, and two cross passages, with 62 temperature measurement points. Experiments were performed under various fire source locations, fire sizes, and ventilation conditions, focusing on three factors: longitudinal temperature decay, lateral diversion at cross passages, and smoke propagation time. Results show that temperature in the main tunnel exhibits an exponential decay along the tunnel's length, with higher temperatures near the fire source. Cross passages significantly alter smoke flow, causing lateral diversion at node locations. Mechanical ventilation was found to be more effective than natural ventilation in controlling smoke and temperature distribution. The study highlights how fire source location and ventilation mode influence smoke behavior and temperature attenuation. These findings provide experimental data for optimizing fire safety and ventilation strategies in ultra-long tunnels during the construction phase. The study emphasizes the importance of effective ventilation in controlling smoke and preventing excessive heat buildup, which can reduce fire risks and ensure the safety of workers and tunnel users. The results also underscore the need for detailed modeling of smoke and fire behavior in the design and operation of multi-tunnel systems. This research contributes to fire safety science, offering practical insights into thermal dynamics and ventilation control in dead-end tunnel systems, and provides recommendations for improving fire prevention measures during tunnel construction and operation.