Dynamic Response of Underground Tunnel in Soft Soil under Surface and Subsurface Explosion

Response of underground structures to buried explosion is very complex involving multiple phenomena occurring simultaneously. Studies focusing on this topic have gained momentum on account of increased terrorist threats involving explosives. However, due to multiple reasons experimental data are scarcely available. Computational modeling presents as a suitable alternative. Responses of tunnels subjected to subsurface and surface explosion are numerically investigated using LS-DYNA version R10.1.0. The interaction of blast loading with tunnels and damage mechanisms are studied considering the two burst cases. The location of explosive is further changed with respect to tunnel and its effect on damage response is studied. Three subcases designed based on location variation are side-burst, oblique side-burst, and overhead burst. Additional parametric study is performed with factors like stand-off distance and compressibility of soil. Soil compressibility is controlled by the hydrostatic compression curve, and the effect of both loading and unloading path on response of tunnel structure is investigated. A multimaterial arbitrary Lagrangian-Eulerian (MM-ALE) approach is used to model the problem, wherein soil is modeled in two parts (i.e., Lagrangian and Eulerian) to avoid numerical issues. Lastly, a solution to avoid numerical instability caused by the excessive mesh deformation at the Lagrangian-Eulerian interface of soil domain is suggested. (C) 2021 American Society of Civil Engineers.