Experimental and Theoretical Investigation of Longitudinal Temperature Attenuation and Smoke Movement in Urban Utility Tunnel Fires

The urban utility tunnel is an indispensable part of modern engineering construction. However, the fire risk cannot be ignored due to the narrow space and limited ventilation of the utility tunnel. A study of smoke filling is performed in a 1/8-scaled utility tunnel (25 m × 0.5 m × 0.45 m). Five heat release rates (5, 10, 15, 20 and 25 kW) and four positions of fire sources are used for tests. The initial position of the one-dimensional smoke movement of strong plume is determined. Based on the traditional model, the longitudinal temperature attenuation model of tunnel smoke is established with consideration of radiation and convection heat losses. The theoretical value of the longitudinal temperature rise of smoke is in good agreement with the experimental value. A one-dimensional spreading velocity model is established that coincides well with the experimental value, and the relative error is less than 20%. The spreading velocity of smoke is increased by the heat release rate. The velocity of the smoke spreading at the near end is smaller than that at the center, due to the long spreading route. The current conclusions disclosed in this study provide important guidance for the ventilation design of utility tunnels for fire smoke scenarios.