Demonstration of a concept for blast barriers. Tests in model scale
Publish date: 2008-08-15
Report number: FOI-R--2522--SE
Pages: 17
Written in: Swedish
Keywords:
- blast waves
- protective barriers
- experiments
Abstract
The threat from IED (Improvised Explosive Device) has caused intensive efforts worldwide to develop protective structures. Different types of walls and barriers are built around sensitive structures like military camps, official buildings etc. Such barriers are often large and heavy constructions made of concrete or gravel and sand e.g. concertainers. The aesthetic aspect of such barriers is commonly neglected but in many cases, like long-term protection of sensitive structures in a city, a design that fits well in this environment could be of great value. The report deals with an idea for a fence-like structure made of steel with daylight openings that have almost the same blast reducing effect as a solid wall. The blast reduction was verified for an example of this type of structure, both experimentally and by hydrocode calculations. For the experiment, a scale model 1:4 of a barrier according to the concept was built. The barrier would measure 4 m by height in full scale. A test series with slight variations of the geometry of the structure was performed. TNT charges up to 2 kg (which corresponds to 128 kg in full scale) were detonated in front of the barrier. Pressure histories from gauges behind the barrier were captured and evaluated. In the test set-up, only some simple geometries of the modelled barrier were tested. A full-scale barrier would of course be given a somewhat different design with aesthetic aspects, the strength of the structure and production technique in mind. It is therefore important to do tests in full scale of a suggested final solution for this type of barrier. In short, the scale model tests indicate: The studied type of barrier performs better and better with increasing charge weights at shorter stand-off distances; the shock wave energy (i.e. the impulse density) behind the barrier then approaches the values from a solid barrier. The pressure values are somewhat higher than for a solid barrier, which means that the reflected impulse density, e.g. against a facade of a building, may be higher than with a solid barrier. For large charges at very short stand-off distances, an increased amount of shock wave energy leaks through the barrier near the ground level.