In this paper, we investigate the behaviour of concrete subway tunnels subjected to internal blast loading using Explicit Finite Element analysis. Tunnels, being a lifeline to any metro systems in the world are vulnerable to explosions due to accidents and terrorist attacks. Considering this immense risk, there is a need to address this problem, and overcome the complications involved in the analysis. A typical metro rail system with two tunnels of 5 m diameter running parallel to each other is considered. The centre-to-centre distance of tunnels is 8.0 m and it is embedded at a depth of 9.0 m below the ground level. The tunnel-soil interaction was also considered in this numerical model. Parametric studies have been carried out to study the significance of surrounding soil and explosive characteristics on the lining response. It is found that the concrete tunnel suffers severe damage when embedded in a clayey stratum than in a strong rock.