Abstract: In order to explore the characteristics of fire smoke transport in mountain tunnel, two typical fire source powers (20 MW and 50 MW) were selected by numerical simulation method to analyze the influence of fire source position on temperature distribution under tunnel roof, smoke transport rate and mass flow rate in shaft smoke under different longitudinal wind speeds. The results show that when the longitudinal wind speed is lower than 3 m/s, the temperature along the path of the upstream of the fire source decreases gradually with the increase of the longitudinal wind speed, while the temperature along the path of the downstream of the fire source shows an opposite trend with the increase of the longitudinal wind speed. When the fire source is near the shaft, the smoke spreading speed in the upstream and inside the shaft is higher than that in the far end of the shaft. When the fire source was far away from the shaft, the mass flow of smoke in the shaft reached the peak value of about 2 m/s with the longitudinal ventilation, while when the fire source was close to the shaft, the mass flow of smoke in the shaft reached a higher level when the longitudinal wind speed was low.

Key words: mountain tunnel; longitudinal ventilation; smoke movement; numerical simulation