Abstract: Abstract: In order to quantify the influence range of characteristic temperature after fire in tunnel, the characteristic temperature at eye height (70 ℃) and the characteristic temperature at ceiling height (334 ℃) are taken as key parameters of influence range. The temperature distribution rule of single and multiple fire sources in Yanhou tunnel accident was simulated by FDS numerical method. Results show that the influence range of temperature at eye feature height is smaller than that at the ceiling height, regardless of single or multiple fire sources. In the case of multiple fire sources, the superposition effect of the temperature obviously appears at the eye feature height between adjacent fire sources, while this phenomenon does not occur at the ceiling height. And, the temperature in the region is much higher than that at the eye feature height, the decay time is longer. In Yanhou tunnel with length of 464 m, the cars within 50 m from the first fire source has reached ignition temperature after 30 s, and the coal car 184 m from the first fire source does not temperature after 360 s. At the eye feature height, the temperature of smoke presents a highly unstable dynamic increase in superposition region, but the maximum temperature is lower than that at the ceiling. Outside the superposition area, the decay of temperature at the ceiling is slower than that at the eye feature height, but the influence region is still expanding in dependent of time consuming.

Key words: Key words: single fire source, multi-fire source, feature height, superposition region