Experimental analysis and machine learning research on tunnel carriage fire spread and temperature evolution

Abstract

Tunnel fire has become a major public safety concern with the development of tunnel construction. In this work, the behavior of carriage flame propagation, evolutionary mechanism and internal temperature distributioncaused by carriage fire in a 1/8 model tunnel were experimentally investigated. The effect of heat release rates (HRRs), longitudinal wind speeds and opening sizes on tunnel safety were comprehensively considered. The overall energy balance leads to the steady gas temperatures inside the carriage. The facade flame height and the flame horizontal extending distance are crucial for assessing the tunnel fire hazard. It is found that the height of facade flame decrease with relative lower longitudinal wind speeds to a threshold and then remains unchanged with increasing relatively strong longitudinal wind speeds increase. And, the horizontal extending distance of the facade flame increases with growing longitudinal wind speeds in the relatively lower range to a threshold and decreases with increasing longitudinal wind speeds increase in the relative strong range. Two new non-dimensional correlations based on model were proposed, taking into account all phase and longitudinal speeds for flame geometry features including, all fundamental physical factors included ventilation factor, inertia force, Froude number, thermal buoyancy and dimensionless HRR. Quantitative data and a basic introduction of the flame geometry at longitudinal speeds induced by carriage fires in a simulated tunnel, which is essentially different from other previously reported tunnel fires, are presented in this study. Furthermore, to perform fast calculation and contribute to fast operational tunnel management, machine learning methods, for example, BP neural network, were adopted to derive HRRs from the tunnel fire monitoring system by video data. The results of this paper can demonstrate the potential for tunnel fire safety engineering applications.