Modeling of Surface Blast Effects on Underground Structures

The effects of surface explosions on underground structures were studied through physical modeling, utilizing a geotechnical centrifuge. The types of structures considered in this study include tunnels and pipelines, located relatively close to the ground surface (within 5 m below ground surface). The use of the geotechnical centrifuge allows one to study the effects of large explosions on prototype scale, by using smaller explosives and scaled models of actual structures. This is explained by the centrifuge scaling law which states that the effects of an explosion will scale to the third power of the centrifuge acceleration (g) level. Controlled explosions were conducted in centrifuge experiments under 70 g gravity and strain measurements were recorded at different locations of the underground structures. The results of these experiments can be useful in designing new underground structures as well as for developing protective retrofits for existing structures. The influence of a compressible inclusion barrier immediately outside the structure was also studied. Depending on the thickness of cover between the source of explosion and the structure, the presence of the barrier may have a beneficial effect in reducing the impact of the blast.