Experimental study on fire characteristics of urban rectangular tunnels based on different slopes

Abstract To explore the combustion pattern and temperature distribution law of urban rectangular tunnels when a fire occurs. Considering the influence of variables such as different firepower, fire source spacing, and tunnel slope, the vertical and horizontal flame combustion patterns and tunnel temperature distribution of double fire sources under different slopes were studied by the indoor model experiment method. The results show that under the same conditions of the fire source spacing ratio μ, when the slope of a rectangular tunnel is between 0% and 3%, the influence of dual flames combustion morphology on tunnel slope is relatively small; When the tunnel slope is 4% to 5%, that has a significant impact on the combustion morphology of dual flames, and the flames are more dispersed and sparse than the tunnel slope is between 0% and 3%. As the tunnel slope increases, a high-temperature zone forms at the top of the tunnel and gradually moves towards the uphill direction of the tunnel, the high-temperature area gradually decreases as the slope increases with the same μ. The research results provide a theoretical basis for the fire protection design standards and fire prevention measures of urban rectangular tunnels.