The Influence of Explosive Loads on the Strength of Shallow Underground Bomb Shelters

Abstract

This study investigates the impact of explosive loads on the strength of shallow underground bomb shelters under the detonation of a kamikaze drone warhead with a 90 kg TNT equivalent. A numerical modeling methodology is proposed, employing the finite element method in the ABAQUS software with a coupled Eulerian-Lagrangian approach. The JWL equation of state is used to describe the behavior of explosives, the Concrete Damaged Plasticity model accounts for damage and degradation in concrete, and the Johnson-Cook model simulates the nonlinear elastic-plastic properties and failure of steel. The stress-strain state of the shelter’s structures and soil base is analyzed, alongside pressure changes in the soil and the dimensions of the resulting crater. The numerical results are validated by comparison with empirical relationships derived from field tests, including those by Gould and Cooper. It is found that the shelter’s entrance groups facilitate blast wave penetration, leading to localized damage and failure of load-bearing structures, particularly near entrances. A modified shelter design is proposed, with entrance groups separated from the main structure and a damping soil backfill, significantly reducing the blast wave’s impact and preserving structural integrity. To enhance resilience, it is recommended to position entrance groups at a maximum distance from the shelter, incorporating a system of two to three airlock chambers with hermetic armored doors, aligning with Swiss standards. Future research will involve full-scale tests to calibrate model parameters and refine finite element removal algorithms for more accurate simulation of physical processes.