A Full Coupled Numerical Method for Dynamic Response of Metro Tunnel Subjected to Surface Explosion

Terrorist blast attacks have increased in recent years. Hand bombs are one of the means for terrorist operations because of their dangerous progressive damages. In this paper, a full coupled numerical method is adopted to study the dynamic response of a metro tunnel in the sandy loam. The numerical model is developed using LS-DYNA and will be able to present a realistic behavior for the physics of this phenomenon. In the current study, the ALE method has been used. The air, explosive charge, and soil are considered as ALE’s parts; while, the structure of the tunnel has Lagrangian mesh. Two paths have been studied in the longitudinal and the circular directions for assessing tunnel lining safety. In the free-field state, the accuracy of the model is verified by comparing the peak pressure and acceleration in the soil with the empirical predictions available in the literature. The safety assessment has been done according to blast vibration criteria. The tunnel would not be safe, as per the PPV standard, under the condition of w=500kg and R=4m. Tunnel crowns are the most vulnerable areas while the peak particle velocity is 19cm/s with maximum permanent vertical deformation.