Numerical study of fence type blast walls for blast load mitigation

A new fence type blast wall consisting of steel poles was recently proposed based on the idea that the blast wave-obstacle interaction could generate wave reflection, diffraction and out-of-phase interference to reduce the wave energy. The effectiveness of this kind of new blast wall in mitigating blast loading was investigated through 2D numerical simulations and field blasting tests. In this study, 3D numerical simulations are carried out as an extension of the previous studies for a more comprehensive understanding of the effectiveness of fence blast wall. The simulations are performed by using an explicit dynamic finite element analysis software AUTODYN 3D with validated material models. Responses of a reinforced concrete (RC) wall under blast load are also calculated for comparison. Influences of different parameters of the fence wall, including the cross-sectional shape of the steel poles, spacing between poles, number of fence layers and spacing between layers, on its effectiveness in mitigating the blast loadings are investigated. The peak overpressure, impulse and overpressure-time histories behind the fence and RC blast wall are compared with those in free field for evaluation. It is found that the fence blast wall, if properly arranged, could perform equally or even better than the RC wall in mitigating overpressure and impulse of blast wave. Moreover, fence blast wall is less likely to generate the secondary debris hazards associated with the RC and other solid walls when close-in explosion occurs. Therefore, it is an excellent alternative blast barrier in protecting critical structures in urban areas.