Damage assessment of multi-layered concrete under internal explosion: A coupled numerical approach

The damage response of multi-layered concrete (MLC) structures under internal explosions is critical for damage effects and protective engineering. Traditional Arbitrary Lagrangian-Eulerian Finite Element Method (ALE-FEM) coupled models (AF) face limitations in capturing discreteness, damage evolution, and energy transfer in cement-stabilized macadam (CSM) layers. This study proposes a novel Structured Arbitrary Lagrangian Eulerian-Discrete Element Method-Finite Element Method (S-ALE-DEM-FEM) coupling method (SDF), where concrete, CSM, and soil/explosive/air domains are modeled via FEM, DEM, and S-ALE methods, respectively. Field tests reveal the SDF model achieves high accuracy (errors <10 %) in simulating cratering, swelling, and hidden damage morphologies, while the AF model shows poor robustness (max error 83.72 %). Parametric analysis indicates MLC damage becomes highly sensitive to CSM strength when scaled burial depth exceeds 0.292. Optimal blast resistance can be achieved with concrete strength >C60 (60 MPa) while maintaining the CSM strength above 1/4 of the concrete strength. This work establishes a validated computational model for damage evaluation and blast-resistant design of MLC systems.