3D simulations of large blast loads above underground tunnels

Underground spaces are ideal for public shelter and defensive infrastructure. The analysis of the response of these spaces to weapons attack is a significant challenge due to the complex interplay between multiple physical phenomena. This paper presents 3D simulations of large fully coupled blasts above tunnels in rock with the multi-physics program LS-DYNA. For increased computational efficiency, the modeling procedure is decoupled and divided into two steps: (1) a 2D Euler mesh is used for assessment of the blast load, and (2) the blast load is applied to 3D Lagrangian models that simulate the tunnel response. The MAT_CSCM and MAT_WINFRITH material models, originally developed for concrete, are used for simulating the rock medium. In order to examine modelling validity, numerical results are compared to findings from extensive field tests conducted by the Engineering Research Associates (ERA) between 1948 and 1952 and various other empirical data. Our comparative analysis confirms that the adopted modeling procedure yields reliable results of peak particle velocity, thus allowing for the interpretation of structural response. The proposed modeling procedure can be extended for the analysis of specific scenarios, thereby contributing to the field of protective design of underground space.