Abstract：The 3D numerical simulation of underground explosion is of interest for the protection of underground structures under explosion. The energy of explosion is sufficient to vaporize the medium around the work point. The expansion of the vaporized gas displaces the medium further out，causing deformation and failure. So the radiation transport and details of the very-early-time dynamics in the explosion source region are not considered in numerical calculations，and the energy source is modeled as an initially uniform spherical region of the appropriate energy content. A simple approximation is used for the vaporized gas，where the gas is assumed to consist of Fe and isentropic expansion of the gas is calculated. The suggested model is performed as a material model of LS-DYNA3D through its user-defined material function. Attenuation of radial peak stress and radial peak particle velocity of explosion in granite and the wall load function for decoupled explosive are calculated by using this material model. The numerical results are in good agreement with the experimental and numerical data achieved by other scholars.
