Experimental and numerical investigations on the shock wave attenuation performance of blast walls with a canopy on top

摘要

This paper presents experimental and numerical investigations on the performance of various blast wall configurations in attenuating the shock wave. The blast walls are composed of a gabion wall with a canopy made of metal sheets, which is mounted at the top of the gabion wall with different angles of inclination. Three experiments were conducted for each configuration. Numerical models are developed and validated against the experimental data. Due to the small width of blast walls in the experiments, besides the vertical air flow over the top of the wall, the horizontal air flow around the sides of the wall plays a great role in the overpressure distribution behind the wall. The interaction between these air flows causes an overpressure increase at the building facade. In order to prove the design concept of the canopy, the wall width in the forthcoming experiments should be so large that no horizontal air flow occurs. Using the validated numerical models, three observations arisen from the studies of blast walls having infinite width. Firstly, the canopies can further reduce the overpressure and impulse behind the blast wall. Secondly, configuration M3 (canopy arranged 45 degrees facing the charge) shows the best performance in shock wave attenuation among all three configurations. It offers an overpressure (impulse) reduction ranging from 51.7% to 88.0% (from 30.5% to 59.2%) at the gauges employed in the experiments, compared to the free field scenario. Thirdly, the optimal angle of inclination of the canopy, by which the blast wall achieves the best shock wave attenuation performance, lies between 105 degrees and 120 degrees (between 115 degrees and 125 degrees) for the overpressure (impulse) reduction.