On the internal blast loading of submerged floating tunnels in concrete with circular and rectangular cross-sections

The Norwegian Public Roads Administration has initiated a large research project on a potential ferry-free coastal highway route E39 on the west coast of Norway. For the wide and deep fjords, a submerged floating tunnel (SFT) in reinforced concrete has been suggested as a possible solution. A potential hazard for such a structure is internal blast loading, which can be devastating to its structural integrity. To assess the blast performance of concrete structures, a shock tube has been used to generate blast loading against concrete slabs with and without reinforcement. The shock tube tests were filmed with high-speed cameras, and digital image correlation was used to measure the out-of-plane deformations. A finite element model using input from material tests was set up in ABAQUS/Explicit to recreate the slab experiments. Based on the models validated by the shock tube experiments, full-scale numerical simulations of blast loaded SFTs with circular and rectangular cross-sections were run. The results were used to assess the qualitative performance of each cross-section geometry with respect to blast loading, where the circular cross-section indicated a superiour behaviour.