چكيده به لاتين
In this study, the numerical modeling of mitigation of blast waves on underground structures with the use of LS-DYNA program was investigated.
Most recently, lots of terrorist attacks have been occurred all over the world and so many researchers have been encouraged working in this field. There are different ways to reduce blast effects on underground structures. Vibration isolation with wave barriers is one of them. Wave barriers can be placed near explosive or near underground structures which respectly named active and passive isolation.
Results show that there are two distinct loading mechanisms. The first, resulting directly from the propagation of stress waves and the second due to inertial loading from soil located between the crater and the structure.
To validate the numerical model, Davies centrifuge tests is used. After validation of results, parametric studies were conducted in three sections. In the first section, the effect of barriers materials on the vibration isolation efficiency was investigated. Barriers made up of concrete, foam with different densities, steel sheet pile wall and a composite one (foam-barrier) were modeled. The numerical results were corresponded well with the results obtained from centrifuge tests. The composite barrier made up of concrete and foam, showed the best performance in reducing pressure, strain and acceleration. The rusults also show that the foam barrier can only mitigate blast-indued shock waves while concrete wall is effective in reducing the inertial loading. Sheet pile wall shows a similar trend to concrete wall.
In the second part, the effect of barriers location on the vibration isolation efficiency was studied. Generally, the greater the distance of barrier from explosive, the higher vibration isolation efficiency.
In the third section, the effect of barriers shape was investigated. Of the four cases examined, composite (foam-concrete) cube-shaped barrier had the best performance. After that, they were cylindrical-shaped, cube-shaped and linear-shaped barrier, respectively. It should be noted that the last three barriers were all made of concrete.
Keywords: Blast, Underground structures, Vibration isolation, LS-DYNA software.
