Study on fire behavior of cable in utility tunnel under different initial oxygen concentrations

In this study, a series of experiments was carried out in a circular utility tunnel, and the characteristics of cable fires at different locations and different initial oxygen concentrations were investigated. The results show that at a low initial oxygen concentration, there is a smoldering phase after the flame disappears and multiple local re-burns occur with the fire-induced flow which is affected by the initial oxygen concentration and the location of the fire source. At low initial oxygen concentrations, the mass loss rate is more affected by the oxygen concentration than by the location of the fire source. Based on the entrainment theory of pool fire, a new model for estimating the flame length of cable fire at different initial oxygen concentrations was established. This study provides a reference for fire prevention design, fire risk assessment, and post-disaster reconstruction of utility tunnels.