Abstract:

In order to reveal the critical velocity in an underground interchange tunnel with the longitudinal ventilation, two types of Y- shaped tunnels, the merging type and the diverging type, were studied. 30 MW heat release rate was setted，and the critical velocity in each ramp of Y- shaped tunnels was compared with the normal single-slope tunnel. In addition, the longitudinal temperature distribution at 2 m and 6.2 m in the ramp was analyzed. The results showed that, in the unfired ramp of the Y-shaped tunnel, the critical velocity is equivalent to the theoretical value of critical ventilation in the single- slope tunnel. For the fired ramp, the critical velocity of the merging type is less than the theoretical value, on the contrary, the critical velocity of the diverging type is greater than the theoretical value in the single-slope tunnel.  

Key words:

Y-shaped tunnel；longitudinal ventilation；slope；numerical study；critical velocity  ,