Experimental investigations on explosive breaching mechanisms for exterior metal doors and explosive effects on room occupants

Door breaching represents a tactical procedure employed by security and civil protection forces to rapidly gain access to the interior of a structure by overcoming physical barriers using specialized methods and equipment. While metal door breaching techniques are primarily utilized by special intervention units, their application to residential metal doors remains limited due to an insufficient understanding of the breaching mechanics and the critical need to ensure personnel safety. This study presents experimental results on the breaching of residential metal doors using push-type explosive devices strategically positioned over locking mechanisms. The investigation focused on assessing the influence of the core material—polystyrene, polyurethane foam, and mineral wool—on the deformation of the door leaf and the overall breaching process. The experiments were conducted on both full-scale doors fabricated under controlled laboratory conditions and commercially available residential metal doors acquired from the local market. Additionally, the study analyzed the impact of the door leaf composition (steel sheets of 0.5 mm and 1.0 mm thickness and medium-density fiberboard (MDF)) and the role of the locking configurations, including the number of locking bolts and multi-lock points, on the breaching efficiency. Furthermore, the study investigated the spatial positioning of the explosive device on the door leaf, the effect of a 25 ms detonation delay between multiple explosive devices and the role of a Kevlar fabric in facilitating the uniform distribution of the water jet charge. Moreover, the research assessed the impact of the shock wave on intervention personnel, as well as the potential risk posed by door fragments to room occupants. Experimental findings indicate that explosive charges placed directly over the locking mechanisms effectively breach metal doors irrespective of door leaf composition. However, this breaching approach may generate significant risks to room occupants, highlighting the need for further analysis of mitigation strategies to enhance operational safety.