Study on Fire Smoke Distribution Characteristics in Mountain Spiral Highway Tunnels

In previous studies on tunnel fires, researchers primarily focus on the impact of a single factor on smoke dispersion characteristics in tunnels, neglecting the combined effects of multiple influencing factors and their mutual interactions. Based the theory of smoke dispersion, a series of numerical simulations were performed using a fire dynamics simulator to reveal smoke distribution characteristics in mountain spiral highway tunnels. The results indicated that the radius of curvature, altitude, and slope gradient predominantly govern tunnel fire distribution in spiral tunnels. Specifically, the impact of the radius of curvature on smoke dispersion patterns is independent, whereas altitude and slope gradient exhibit interactive effects. Notably, increased altitude intensifies the chimney effect induced by a slope due to faster smoke dispersion in tunnels with higher altitude. Conversely, an enlarged slope mitigates the thickening of the smoke layer caused by the altitude, as it reduces the layer thickness in tunnels with steeper slopes. The results can play a role for further elucidating the numerical smoke distribution patterns in spiral tunnels.