Abstract: simulation. The results showed that: With the increase of leakage time, the volume of combustible gas leaking from small holes is increasing, while which from larger hole reaches the peak value first, and then decreases. Based on the explosion simulation of leakage gas cloud, it was found that the overpressure increases with the increase of axial distance from the explosion source, and the more combustible gas, the more serious the explosion, and the overpressure is up to 143.838 kPa; Between the mitigation measures, the replacement of tunnel portal is effective to alleviate the explosion consequence in most of scene, and the overpressure can be reduced by more than 44.45%; While the addition of filler is more suitable for mitigating the explosion of small combustible gas cloud, and the overpressure can be reduced by 57.72%.

Key words: tunnel, natural gas, leakage, vapor cloud explosion