Experimental Studies on Mitigating Local Damage and Fragments of Unreinforced Masonry Wall under Close-in Explosions

Abstract

Debris hazard causes most of the casualties and injuries in terrorist or accidental explosions. It is defined as high-velocity fragments originating from structural components and building envelope systems induced by a blast wave. Unreinforced masonry (URM) walls, which are commonly used as a building envelope system, tend to break into sharp fragments under blast loading, especially when the explosion is at close range. Therefore, it is of great significance to develop effective protective techniques to mitigate the local damage and fragments of URM walls under close-in explosions. In this paper, a new method of utilizing a dry-suspended stone slab system as a protective measure for mitigating local damage to and fragmentation of URM walls under close-in explosions was proposed. The proposed method uses the dry-suspended stone slab system as a blast wave stopper to reduce the blast load acting on the URM wall through the blast wave interaction with the stone slab and blast-induced fragments, thus mitigating the local damage and fragments of URM wall. In order to investigate the effectiveness of the dry-suspended stone slab system, four experiments were carried out to study the local damage and fragments of URM walls protected by the dry-suspended stone slab system and a commercial blast-resistant panel under different close-in blast scenarios. The experimental results were compared with each other and with results of previous tests of unprotected URM walls under the same blast scenarios. The results showed that both the dry-suspended stone slab system and the commercial blast-resistant panel are effective in mitigating local damage to and fragmentation of URM walls under close-in explosions. When the trinitrotoluene (TNT) charge increased from 1 to 6 kg with the standoff distance unchanged (400 mm), the dry-suspended stone slab system performed much better than the commercial blast-resistant panel in decreasing the crushing or spalling damage of the URM wall, indicating that the proposed dry-suspended stone slab system can be used as a protective measure to mitigate the local damage to and fragmentation of URM walls under close-in explosions.