Investigating the Evolution of arch temperature and prediction model for temperature rise of fire Smoke: Model testing of an Extra-Long highway tunnel with vertical shaft

Abstract

In order to investigate the characteristics of the arch temperature distribution of extra-long highway tunnel fire under the action of vertical shaft mechanical smoke exhaust, relying on the Yunshan Tunnel in Shanxi Province to carry out the physical model test of tunnel fire scaling under the vertical shaft mechanical smoke exhaust, to explore the influence of the vertical shaft structural parameters on the longitudinal temperature distribution of the tunnel, as well as the characteristics of the upstream and downstream tunnel smoke outlet attenuation of the temperature of the arch in the conditions of the different fire power and fire position, the results show that: the diameter of the shaft and the height of the smoke outlet upstream temperature has less influence on the temperature of the tunnel smoke outlet. The results show that the diameter and height of the shaft have less influence on the upstream temperature of the smoke outlet. For the downstream of the smoke outlet, the larger the diameter of the shaft, the faster the arch temperature decreases; the higher the height of the shaft, the lower the arch temperature at the downstream measurement points. The arch temperature upstream of the smoke outlet shows a significant exponential attenuation trend for different fire power and location, and the influence of smoke exhaust speed on the temperature attenuation is extremely small when the fire source is far away from the smoke outlet. On the contrary, the temperature attenuation of the arch downstream of the smoke outlet was significantly affected by the smoke exhaust speed and was not sensitive to the change of the distance between the fire source and the smoke outlet. At low wind speeds (≤13 m/s), the downstream temperature followed an exponential attenuation; while at high wind speeds (15 m/s), the attenuation pattern shifted to linear. Predictive equations for the temperature rise in the upstream and downstream arches of the smoke outlet were fitted for 94.9 kW and 158.1 kW fire power, which provided a theoretical basis for fire safety assessment.