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| Study on fire resistance range and fire protection of tunnels with side concentrated smoke exhaust |
| Zhu Hangkai1,2
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1. China Railway Siyuan Survey and Design Group Co., Ltd., Wuhan 430063, Hubei, China;
2. National &
Local Joint Engineering Research Center of Underwater Tunnel Technology, Wuhan 430063, Hubei, China |
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Abstract The structural fire protection scope for a double-deck shield tunnel with side-focused smoke exhaust was determined.The fire heat release rates corresponding to the temperature-time curve specified in the German Guidelines for the Equipment and Operation of Road Tunnels(richtlinien für die ausstattung und den betrieb von straßentunneln, RABT)were inversely determined as 35 MW for the upper tunnel and 30 MW for the lower tunnel. A numerical tunnel model was established using fire dynamics simulation software(fire dynamics simulator, FDS), and multiple scenarios were simulated, including a 15 MW conventional fire, standard fires, and effective and failed smoke exhaust conditions. The fire-induced temperature fields and zones reaching the fire-resistance limit were investigated.The results showed that the maximum area of the fire-resistance-limit zone at the vault of the upper tunnel was 512 m2. Fire protection was therefore required over a transverse width of 10 m and a vertical extent of 2 m downward from the vault, whereas no overtemperature zone was observed on the sidewalls. For the lower tunnel, the maximum area of the fire-resistance-limit zone on the roof slab was 498 m2. Under the most unfavorable condition, the overtemperature zone on the sidewalls extended 2.5 m downward from the roof slab. Accordingly, fire protection was required over a transverse width of 10 m on the roof slab and a vertical extent of 2.5 m on the sidewalls. These findings provided a quantitative basis for the fire-resistant design of similar double-deck shield tunnels employing a side-focused smoke exhaust mode.
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Published: 12 October 2026
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