Application verification of blast mitigation through the use of thuja hedges

Abstract

Nowadays, large gatherings of people, such as open-air concerts, outdoor-sport events, trade fairs, etc., are often attracted by the terrorists. Recently, an interesting passive alternative way of securing such events against terrorist threats appeared in the scientific literature, in which the tree hedges mitigation potential against blast waves were studied. Despite comprehensive studies regarding selected species of hedge trees, the real application outlines were reported to be still missing for those barriers. Our study verified the mitigation potential of thuja in field tests for (i) several distances behind the hedge and for (ii) several positions along the hedge wall. The explosives of 5 kg trinitrotoluene with a rectangular shape were used in four detonations. Six pressure pencil gauges were registering the overpressure histories. A high-speed camera was recording the in-plane deformation of the hedge wall, the motion of selected points on the height of the wall was plotted. For each position, the reduction of overpressure peak and overpressure impulse were obtained in reference to their counterparts for the position without a hedge. The maximal overpressure peak reductions obtained were 14% for case (i) (differing distances from the explosive) and 22% for case (ii) (differing positions along the hedge wall). The experiments' outcomes showed the safest position behind the thuja wall and the actual benefit from using them in the public application if the terrorist acts would happen.