Based　on　the　explicit　finite　element　method　(FEM)　code　LS-DYNA3D　and　the　viscous-spring　boundary,　the　3D　elastic-viscous-plastic　dynamic　response　model　composed　of　explosion　cavity,　an　underground　structure,　a　shock　isolation　material　and　geological　backfills　were　established.　The　empirical　relation　was　used　during　the　simulation　of　the　explosion　cavity.　By　comparing　with　the　results　of　the　empirical　relation　of　technical　manuals　TM5-855-1　of　the　USA　Army,　it　can　be　seen　that　the　proposed　model　and　method　are　reasonable.　The　shock　isolation　effect　of　the　crushable　backpacking　was　also　discussed.