Critical velocity and backlayering distance in tunnel fires with longitudinal ventilation taking thermal properties of wall materials into consideration.

A set of tunnel fire experiments using a 1:20 scale model tunnel was conducted taking into account the scaling of heat conduction through the tunnel walls. The critical velocity and backlayering distance measured in the tunnel fire experiments were compared with other reference data to examine the effect of the thermal properties of the tunnel walls on these two parameters. In this paper, we present new correlations for estimating the critical velocity and backlayering distance, and discuss the difference between our correlations and the previous ones from the viewpoint of the thermal properties of the tunnel wall materials. [ABSTRACT FROM AUTHOR]