عنوان مقاله [English]
The increasing number of worldwide terrorist attacks in recent years and the danger of enemy air attacks indicate the importance of the secure design of urban structures and explosion mechanics as passive defense. Our country, Iran, is no exception from these external threats considering its position in the Middle East.
Subway stations are considered a safe and strategic structure during terrorist operations as they serve as a safe route for the transfer of power and equipment. Tunnel structures can be exposed to internal or external explosions. The internal explosions are less likely to occur because it is hard to get an explosive material inside a tunnel due to modern security and control systems inside subway tunnels. However, external blasts because of the difficulties of detecting and preventing their threat are more likely to occur.
The present study is carried out with the finite element software LS-DYNA using the ALE (Arbitrary_Lagrangian _Eulerian) technique to simulate and monitor the propagation of the blast pressure waves into the soil. Furthermore, the response of Tehran metro stations caused by a surface explosion of 11ton TNT that is equivalent to the explosive power of the most potent non-nuclear missile is evaluated. The results of validation indicated that the pressure waves propagated into the soil as hemispherical waves and the peak pressure values closely matched the predicted values of the technical design manual TM5-855-1. The results indicate that the depth of the crater created by the detonation of 3, 7, and 11 ton TNT is 6.5, 9, and 12 m respectively, for the surface detonation of 11 ton TNT charge. The affected region of the soil is about 18 m beneath the ground surface, and the duration is around 0.4 seconds. Additionally, although the stations above 19 meters of depth do not have enough safety against the 11-ton explosive charge, the stations deeper than this depth are safe.