A Simple Approximate Simulation Using Coupled Eulerian–Lagrangian (CEL) Simulation in Investigating Effects of Internal Blast in Rock Tunnel

The need for faster and safer means of land transportation has increased due to scarcity of land. The number of terror attacks on the underground metro tunnels has increased in the past couple of decades. These events have presented the increased need for blast resistant design of metro tunnels. The stability of underground metro tunnels constructed in the different rocks has been analysed in the present paper. The analysis of impact loading has been carried out using nonlinear finite element technique. The coupled Eulerian–Lagrangian which is an advanced method of modelling for trinitrotoluene (TNT) and air inside the tunnel has been used. The explosive charge has been assumed at the centre of the tunnel having 100 kg mass, and the analysis is carried out for 30 ms of duration. The nonlinear behaviour of TNT has been simulated by using Jones–Wilkins–Lee material model of the equation of state. The nonlinear behaviour of the different rocks, i.e. Quartzite, Quartz-Schist, Sandstone, Shale and Dolomite, has been considered through the Mohr–Coulomb constitutive model. The rock model has 30 m × 30 m × 35 m dimension having an opening of 5 m at the centre of the model. The tunnel has 12.5 m of the depth of overburden and tunnel lining has 0.35 m of thickness. The tunnel lining has been reinforced with steel bars of Fe415 steel grade, and concrete has M30 grade. The rock tunnel constructed in Shale is susceptible to a higher magnitude of damage as compared to other rocks in this paper when exposed to internal blast loading. The Quartzite rock tunnel is the most suitable choice for constructing the blast-resistant tunnel. It has been concluded that Quartzite has higher safety against an internal blast loading caused by 100 kg TNT explosive charge. Heaving has been observed for all the cases on the ground above the location of TNT.