Abstract: The model-scale experiment method was used to study the fire smoke diffusion and temperature distribution under the ceiling in an inclined tunnel with the upper or lower portal sealed, considering different sealing conditions, heat release rates and tunnel slopes. The results show that when the lower portal is sealed, the smoke layer is approximately parallel to the tunnel floor, and the slope has little effect on the maximum temperature rise. When the upper portal is sealed, the smoke layer interface is almost parallel, and the maximum temperature rise increases with the tunnel slope. The longitudinal temperature distribution under the ceiling in inclined tunnel fires exhibits exponential decay under different sealing conditions. The tunnel slope has a great influence on the temperature decay under the ceiling in upper-portal-sealed tunnels. On the contrary, the slope has little influence on the longitudinal temperature decay in lower-portal-sealed tunnels. Finally, some comprehensive empirical formulas are established to estimate the ceiling maximum temperature rise and the temperature decay taking sealing conditions, heat release rates and tunnel slopes into consideration.

Key words: tunnel fire, sealing condition, tunnel slope, smoke diffusion, temperature distribution