Experimental investigation on the influence of ramp slope on fire behaviors in a bifurcated tunnel

Abstract

A series of scaled fire tests were conducted in a model bifurcated tunnel to investigate the influence of ramp slope on fire behaviors of ethanol pool fire under natural ventilation. Four ramp slopes of 0%, 3%, 6% and 9% with three fuel areas were varied. The maximum ceiling temperature in main tunnel and longitudinal temperature decay along the ceilings of horizontal main tunnel and ramp were measured and analyzed. Results show that the maximum ceiling temperature in the main tunnel increases as ramp slope increases, which is mainly due to the comprehensive effect of more ceiling flame caused by more air inflow, the increase of burning rate and the enhancement of heat accumulation. Furthermore, two modified models taking the influence of ramp slope into account are proposed based on current experimental results. The longitudinal temperature decay along ramp ceiling is influenced by slope, while the influence of ramp slope on the longitudinal temperature decay in main tunnel is relatively weak. In addition, empirical correlations are then proposed in accordance with an exponential function to include ramp slope factor for predicting the longitudinal temperature decay in the main tunnel and the ramp.