014 Blast loading of concrete pipes using C-4 charges

The E39 coastal highway route in Norway is envisioned a future without ferries. A submerged floating tunnel built in concrete has been suggested as a means of crossing wide and deep fjords. Blast loading against this type of structure could have disastrous consequences, and potentially cause the collapse of the entire structure. To investigate the response of tubular concrete structures subjected to blast loading, standard off-the-shelf unreinforced concrete pipes were tested using live explosives. A plastic explosive was used to generate the load, and the tests were filmed by two synchronised high-speed cameras. Three pressure sensors equidistant from the charge position logged the pressure. Further, three different positions for the charges were used to investigate the effect of charge position. The charge size was varied for each position to find the amount of explosives needed to breach the pipe. It was found that a contact charge detonated from the outside requires almost twice the explosive amount to breach the pipe than a contact charge detonated from the inside, suggesting a significant confinement effect. Numerical simulations using finite elements produced good qualitative results.