Dynamic failure analysis of underground reinforced concrete dome bunkers subjected to external blast loading

This study investigates the dynamic failure mechanisms of underground reinforced concrete (RC) dome bunkers subjected to both surface and subsurface blast loading, addressing a gap in literature regarding 3D monolithic geometries. A high-fidelity numerical model was developed using the Coupled Eulerian-Lagrangian (CEL) method in Abaqus/Explicit, incorporating the Johnson-Holmquist II (JH-2) constitutive model for concrete and the Mohr-Coulomb model for soil. The framework was validated against numerical and experimental data, achieving less than 5% deviation in near-field peak pressures. Parametric investigations assessed the influence of burial depth, charge orientation, and shell thickness. Results reveal a critical “geometric vulnerability” to lateral blast vectors, where horizontal detonations induced 75% more concrete volume loss than equivalent overhead blasts due to the bypass of the dome’s compressive arching action. Furthermore, a counter-intuitive “Stiffness-Damage Paradox” was identified: increasing shell thickness from 0.5 m to 1.25 m exacerbated damage under specific impulsive loads. Analysis of internal energy histories indicates that rigid, thicker shells trap elastic strain energy, leading to brittle comminution, whereas compliant shells facilitate soil-structure interaction and plastic dissipation. These findings suggest that ductility and geometric efficiency, rather than pure mass, govern survivability in underground protective design. However, readers are cautioned that the manifestation of this stiffness-damage paradox is subjected to the specific structural compliance, soil acoustic impedance, and explosive conditions investigated herein, highlighting the critical need for coupled SSI analysis in protective design.