Experimental Study on Multi-Layer Composite Confinement Structures with Different Energy-Absorbing Layers Subjected to Internal Explosion

Traditional single-layer reinforced concrete (RC) internal blast containment structures face challenges in blast resistance, crack control, and sealing integrity. Multi-layer composite configurations leveraging energy-absorbing interlayers have emerged as a promising alternative. However, the coupled wave-attenuation mechanisms, dynamic load-transfer pathways, and strain-to-damage evolution in such systems remain insufficiently quantified. To address this gap, this study designed and fabricated two multi-layer composite confinement structures with energy-absorbing layers made of foamed concrete and dense sandy soil, respectively. A series of internal explosion tests with varying TNT charge masses (0.15 kg to 0.80 kg) was conducted. The magnitude and distribution of the load acting on the inner wall of the structure during internal explosion were analyzed, and the deformation characteristics and mechanical mechanisms of the multi-layer composite confinement structure under internal blast loading were investigated. The results indicate that the foamed concrete layer possesses superior blast wave attenuation and energy absorption performance. For instance, under the 0.8 kg charge, the peak contact pressure transferred to the outer layer was approximately 23% lower, and the peak hoop strain in the outer layer was about 7% less compared to the structure with the sandy soil layer. The test results can provide a basis for theoretical analysis and numerical calculation.