Mechanical response and blast resistance evaluation of prefabricated frame tunnels with steel box joints under internal explosion

The disaster assessment and mitigation of urban infrastructure under explosion loads is a research focus. Prefabricated tunnels are usually connected by joints, and their mechanical properties under explosion loads are of concern. To evaluate the dynamic response characteristics of prefabricated frame tunnels with steel box joints under explosive loads, an anti-explosion strategy was proposed in this study. A three-dimensional refined numerical model of the dynamic response of prefabricated frame tunnels was established, and the reliability of the modelling method was validated by full-scale explosion test results. The deformation characteristics, structural stress, damage evolution, and failure mode of these tunnels under vehicle explosion loads were explored. The influences of the thickness, stirrup spacing, and reinforcement ratio on the anti-explosion ability of the middle partition wall were evaluated. The results show that the displacement response of the tunnel partition wall changed in three stages and that the displacement increased significantly when the TNT equivalent explosive force reached 227 kg. The joint of the middle partition wall underwent the most deformation, and the degree of damage of the tunnel corner and the joint was higher than that of other parts. Under the influence of the Mach effect caused by the overpressure shock wave, cracks were generated in the middle partition wall of the tunnel, and obvious tension and compression areas formed. At Z <= 0.8, the failure mode of section S5 of the middle partition wall was mainly a seismic collapse failure and combined bending and shear failure. An increase in the thickness of the middle wall and a reduction in the stirrup spacing helped to improve the anti-explosion performance of the middle wall in this tunnel.