Abstract: FDS numerical simulation software was used to study the smoke movement under the coupling effect of simulated slope and obstacle under natural ventilation condition, mainly analyzing the longitudinal smoke spreading characteristics under the tunnel roof, the plume characteristics in the obstacle area and the shaft smoke exhaust performance. The results show that: the height of the obstacle has a small effect on the maximum temperature of the roof, and the maximum temperature is mainly determined by the shaft height and slope, and gradually decreases with the increase of both and finally converges to a certain value. In the near fire, obstacles and slope will make the fire area flow field change, smoke plume length by the slope of the influence of the larger, the tunnel slope and shaft height to determine the efficiency of the shaft smoke exhaust, obstacles to its influence is small. In addition, the low shaft height will lead to the boundary layer separation phenomenon, which will not disappear with the increase of the slope, and there is always a vortex inside the shaft, when the shaft height reaches a certain value, the slope can effectively inhibit the smoke absorption through.

Key words:  tunnel fires, slope tunnel, obstructions, shaft smoke extraction, FDS