Full-scale experimental study on fire characteristics induced by double fire sources in a two-lane road tunnel

The vehicle collisions, intense heat radiation and convection from flame and high-temperature smoke can easily cause double-source fire disasters in tunnels. In this paper, four full-scale fire experiments were performed in Jiangpu road tunnel to investigate the characteristics of double fire sources. The whole process of the ventilation velocity, heat release rate, longitudinal ceiling temperature, vertical temperature, carbon monoxide and flame deflection angle are analyzed. The results indicate that the interaction between the double fire sources affects the heat release rate and flame deflection angle and other parameters of each fire source. The ventilation and the fire source spacing can change the coupling state of thermal feedback mechanism and the shielding and entrainment effect of double fire sources. The fire source spacing affects the interaction mechanism and the smoke flow state between the ceiling jets of the double fire sources, which leads to the difference in the longitudinal ceiling temperature distribution between the double fire sources. According to the characteristics of smoke movement between double fire sources, the schematic diagrams of ceiling jets between double fire sources are established. The longitudinal ceiling temperature rise of double fire sources is analyzed from the perspective of steady state and unsteady state. The longitudinal ceiling temperature data of full-scale fire tests is compared with the pre-diction models proposed by other researchers. The "barrier effect" phenomenon was also observed in the double -source fire tests, especially in the vertical smoke temperature. The findings contribute to deepening the un-derstanding of the fire characteristics of the double-source fire disasters.