Abstract: To investigate the effect of the crosssectional shape of a submerged floating tunnel(SFT) on its structural response and impact resistance under underwater explosion conditions, the LSDYNA finite element software is used to establish numerical models for circular, elliptical, and rectangular SFT crosssections. This enables the simulation and analysis of their dynamic responses. A comparative analysis is conducted on the three tunnel crosssections during explosions, focusing on tube displacement, pressure, and effective stress response characteristics. The results are summarized as follows. (1) The circular section of the SFT is impacted by explosions over the smallest range, exhibiting the lowest values for displacement, pressure, and effective stress peaks, along with the highest safety factor and shock wave resistance. (2) The elliptical and rectangular sections show a higher tendency to experience local stress concentrations. In particular, the rectangular section exhibits higher pressure and effective stress peak values than the circular and elliptical sections, indicating poorer impact resistance. (3) The vertical displacement of the elliptical section is larger than that of the rectangular section; meanwhile, the displacement and deformation of the rectangular section are notably distorted. In summary, the comprehensive analysis reveals that the circular SFT section offers better blast resistance than the elliptical and rectangular sections.

Key words: submerged floating tunnel; underwater explosion, crosssection form, LS-DYNA finite element software, structural response, explosive resistance performance