The response of underground structures subjected to blast loading is generally discussed in protective engineering. Usually example structures are box shaped concrete structures, partially or fully buried in soil medium. The loading and response of the underground structure involves different mechanisms as compared to the above-ground structures. The response of an underground structure to a Blast Loading is investigated in this paper, neglecting the effect of structure-soil interaction (SSI). In this paper an attempt is made to use the easily available FEM software STAAD and ANSYS, instead of latest software programs such as LSDYNA/AUTODYN for the Smooth Particle Hydrodynamics (SPH) technique, which is superior in modeling large deformation zone with relatively simple geometry, with the Lagrange finite elements (FE) which are more effective in modeling complex structures. Soil is a continuum of millions of particles assembled in a close proximity with the voids between these particles normally filled with air and/or water. In this paper, two phase soil model is considered consisting of saturated soil in the ratio of 70:30 of solid and water, respectively. Three cases of the FEM Models are considered; in Case-1 soil is considered a 3D solid linear element connected through nodes; in Case-2 soil is considered a 3D element divided into solid and water; and in Case-3 soil is considered a Non-linear 3D Element. Blast Load is applied as a transient load in the form of a nodal load spike for 5 milliseconds and the Dynamic response is calculated for the three cases. Two types of Response are provided in this paper, Displacement and Stresses.
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