Experimental study on temperature distribution beneath tunnel ceiling under the condition of transverse double fire sources

•Transverse double fire experiments in a scaling tunnel were carried out.•Effects of HRR and fire space on the ceiling transverse temperature were analyzed.•New ceiling maximum and transverse temperature distribution models were proposed. The maximum ceiling temperature and transverse temperature distribution under the condition of transverse double fire sources are experimentally and theoretically studied. A series of experiments were carried out in a scaling tunnel (1:20) to investigate the effects of heat release rates (HRR) and distance of the two fire sources (S) on the maximum temperature and the transverse temperature distribution beneath tunnel ceiling. Results shown that when the fire sources were set close to each side of the wall, the location of the maximum temperature was found at the middle ceiling of the tunnel. A inverted “N” shape ceiling temperature distribution, with the ceiling temperature firstly decreased and increased and then decreased, was found along the half-cross section of the tunnel. New maximum and transverse ceiling temperature models were developed with considering the distance and heat release rate of the two fire sources, and considering the air entrainment restrictions by the sidewall. New findings of this work can provide a significant reference for the risk assessment of tunnel fires with two transverse fire sources.