Performance of soft porous media wave barriers in ground shock reduction

Abstract

The mitigation of blast-induced ground shock is an important issue in the protection engineering. Soft porous materials are usually used to form an isolation layer as wave barrier around buried structures for vibration absorption. Experimental and numerical investigations on vibration isolation have been carried out in the past few decades. However, these wave barriers have not been well evaluated in either field trials or numerical simulations when subjected to close-in blast impact. This paper reports our field trial and numerical evaluations on the performance of soft porous media wave barriers in ground shock reduction, including First, ground shock reductions through mixed soil walls are reported in a 5T TNT surface explosion field trial in Woomera Australia. The mixed soil walls were formed by mixing in-situ soils with expanded polystyrene (EPS) particles. Three pits (two mixed soil walls and one open trench) were designed at the scaled distance of approximately 2 m/kg 1/3. Their performances were measured and evaluated. Second, the performances of six wave barriers (open trench, inundated water trench, in-filled geofoam with three densities, and concrete wall) were numerically evaluated through a large-scale numerical model. This model had two steel boxes symmetrically placed at two sides of the charge, one box without protection (unprotected) and the other behind a wave barrier (protected). Numerical simulations showed that both open trench and geofoam barriers can effectively reduce blast-induced stress waves, but inundated water trench and concrete wall have almost no effect on the reduction of ground shock. Their performances are all charge-weight dependent. These results are in good agreement with the above-mentioned field trial observations. Therefore, geofoam barrier is more practicable in the reduction of ground shock in soil mass.