In the modern world, the demand for bunkers has grown significantly as a vital means of protection against blast loads. This study investigates the structural response of underground bunkers subjected to surface blast loads using finite element (FE) analysis in ABAQUS/Explicit. The model uses the Mohr-Coulomb model for soil, Concrete Damage Plasticity (CDP) for the bunker liner, and Johnson-Cook for steel and aluminum. Five dome curvatures (flat, D/8, D/4, 3D/8, and D/2) were analyzed under a 1000 kg TNT explosion. Results show higher stress, deformation, and tension damage with increasing curvature, especially for D/2. Organic sandy clay caused maximum stress and deformation. Two mitigation strategies were proposed: upgrading concrete from M40 to M50 and adding an aluminum 2024-T3 liner. M50 concrete reduced stress by 19.23%, deformation by 5.09%, and damage by 2.63%, while the aluminum liner provided greater protection, reducing stress by 83.12%, deformation by 58.03%, and damage by 67.07%.

In this work, a novel multi-layer composite structure has been proposed for its application in the design of protective shelters. The proposed work investigates the dynamic behaviour of a multi-layer composite under the action of single and multiple projectile impact loading. The target consists of soil, reinforced concrete, steel plate, high-density polyethylene and boulder-mixed cement mortar. It has been subjected to the projectile impact (single and multiple) of a 2.3 kg ogive-nose hard cylindrical projectile having a 50.80 mm diameter. The mechanical performance in terms of the velocity profile of the projectile, residual velocity, penetration depth, ballistic limit velocity, energy absorption and damage of the target has been quantified through a numerical framework. Further, equations have been formulated to determine the fracture material parameters associated with the Riedel-Hiermaier-Thoma (RHT) model to cater for varying strengths of concrete or similar materials. The proposed composite target has demonstrated enhanced penetration resistance and lesser damage compared to its reinforced concrete monolayer counterpart. The interaction between shock waves and the target's material characteristics lead to projectile ricocheting in multiple projectile impacts. Further, an analytical model has been developed to predict the forces transmitted to the lowest layer, which are essential for design purposes. The model has been proposed from the fundamentals using the concepts of impedance. The result derived from the theoretical formulation is in good agreement with the numerical results. Finally, the damage has been quantified to assess the extent of structural deterioration in multi-layer targets, emphasizing the relationship between energy absorption ratio and damage.

While in recent times a considerable amount of research has addressed World War I's impact on France's archaeological heritage, the effects of the battles waged on French soil during World War II have garnered only limited attention, and the few studies that exist have essentially dealt with the damage done in urban contexts. These observations prompt several questions. How did the destruction of archaeological heritage wrought by the war occur, and where did it occur? What kinds of archaeological sites were affected? Did the destruction have an impact on post-war archaeological research? This essay attempts to offer a global assessment and focuses on both Allied bombings and the construction of the French (Maginot Line) and German (Atlantic Wall) defensive positions.