Blast responses of polyurea retrofitted utility tunnel reinforced with basalt fibre reinforced polymer bars

Polyurea coating and carbon fibre reinforced polymer reinforcing techniques were applied to retrofit a severely damaged urban utility tunnel (UUT). The blast responses of the retrofitted UUT were investigated through in-filed explosion experimental tests, and the displacements, strains, accelerations, and damage were compared. The retrofitted UUT exhibited comparable or even better blast resistance than the intact UUT. Although the polyurea coating was flexible, it exhibited excellent performance in improving the blast resistance of the damaged UUT. As the UUT reinforced with basalt fibre reinforce polymer (BFRP) bars has smaller damage compared with the UUT reinforced with steel bars, its retrofitting is simple, and the cost is low. The roof was simplified as an elastically simple support one-way slab. Euler beam theory was adopted to analyse the dynamic responses of UUT roof considering the interaction between soil and structure, which agree well with the experiments in the first three cases.