ارزيابي عددي ميزان تأثيرپذيري ايستگاه‌هاي متروي تهران تحت انفجار سطحي قوي

Numerical Assessment of the Impact rates of Metro Stations under Strong Surface Explosion (case study of Tehran metro station)

سازه‌هاي زيرزميني از جمله ايستگاه‌هاي مترو حين حملات تروريستي، يك سازه‌ي امن و راهبردي هستند. در پژوهش حاضر سعي شده است ميزان تأثيرپذيري ايستگاه‌هاي خط 7 متروي تهران تحت انفجار قوي سطحي به كمك نرم‌افزار اجزاء محدود L‌S-D‌Y‌N‌A مطالعه شود. با توجه به تغييرشكل‌هاي بزرگ، كه در مدل به وجود مي‌آيد، از روش A‌L‌E (A‌r‌b‌i‌t‌r‌a‌r‌y L‌a‌g‌r‌a‌n‌g‌i‌a‌n E‌u‌l‌a‌r‌i‌a‌n) استفاده شده است. در ابتدا، يك مدل خاك بدون مقطع ايستگاه تحت انفجار سطحي مطالعه شده و مقادير به دست آمده از نرم‌افزار با توصيه‌نامه‌ي 1−855−5T‌M جهت صحت‌سنجي مقايسه شده است. در ادامه، به مطالعه‌ي چاله‌ي ايجاد شده در اثر انفجارهاي 3، 7 و 11 تن پرداخته شده و پاسخ ايستگاه‌هاي مترو تحت انفجار 11 تن T‌N‌T، كه قدرت معادل قوي‌ترين موشك غيرهسته‌يي حاضر است، در عمق‌هاي مختلف بررسي شده است. نتايج مطالعات نشان مي‌دهند ايستگاه‌هايي كه در عمق بيشتري از 19 متر قرار گرفته‌اند، بدون آسيب و امن هستند.

The increasing number of worldwide terrorist attacks in recent years and danger of enemy air attacks highlights the significance of the secure design of urban structures and explosion mechanics as the passive defense. Iran is no exception from these external threats considering its position in the Middle East. Subway stations are considered as the safe and strategic structures during terrorist operations since they provide 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 are more likely to occur due to the difficulty of detecting and preventing their threat. The present study was carried out in 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 performance of Tehran metro stations in response to a surface explosion of 11ton TNT, equivalent to the explosive power of the most potent non-nuclear missile, was evaluated. The results from validation model analysis indicated that the pressure waves propagated into the soil as the hemispherical waves as well as the peak pressure values closely matched the predicted values of the technical design manual TM5-855-1. The results also showed that the depths of the crater created by the detonation of 3, 7, and, 11 tons of TNT were 6.5, 9, and 12 m, respectively, for the surface detonation of 11 tons of TNT charge. The affected region of the soil was about 18 m beneath the ground surface, and the duration was almost 0.4 seconds. In addition, although the safety of stations with depths of less than 19 m against the 11-ton explosive charge was not guaranteed, that of the stations deeper than 19 m could be quite ensured.