Evaluation of blast-resistant ability of shallow-buried reinforced concrete urban utility tunnel

Abstract

To check the protective performance of shallow-buried steel bars reinforced concrete urban utility tunnel (UUT) under accidental explosion, a scaled shallow-buried UUT was designed, constructed and tested. In-field explosion experiments were carried out on this UUT. Dynamic responses, damage evolutions and failure styles of the UUT were revealed by the experiments. The tunnel roof is the most vulnerable component with longitudinal main cracks developing along the tunnel. When the scaled distance was larger than 1.10 m/kg1/3, no cracks appeared and the UUT was intact. When the scaled distance was reduced, the damage degree became more and more serious with longitudinal crack number developing from one at 1.000 m/kg1/3, two at 0.881 m/kg1/3, to three at 0.800 m/kg1/3. At 0.557 m/kg1/3 the width of the central crack abruptly increased to 11.2 mm and the UUT was seriously damaged. Damage level can be classified by the mid-span displacements of the roof, the width and number of the roof cracks, the accelerations and the maximum strains. The roof was simplified as an elastically restrained one-way slab. The Euler beam theory was adopted to analyze the dynamic responses, which are in agreement with the experiments in the first three cases.