Physical and Numerical Modeling to Study Effects of an Underwater Explosion on a Buried Tunnel

Abstract

The effects of an underwater explosion on a tunnel buried below submerged ground were studied through a combination of physical model tests, utilizing a geotechnical centrifuge, and numerical model analyses, using an explicit dynamic hydrocode program. Centrifuge tests conducted at 70g on reduced-scale physical models were used to assess the effects of 0.9 t of explosives on a 5.5-m-diameter prototype tunnel. The numerical model was subject to a two-stage validation process to compare the pressures in water and strains on the tunnel by comparing with theoretical and experimental results, respectively. The strains in the tunnel were found to increase with water level above the ground surface; this continued up to a certain point, after which the strains remained constant. The point after which the strains remained constant was found to depend on the mass of explosives. As expected, the strains were found to increase with reduction of soil cover above the crown. This approach may be useful in designing new underwater tunnels and in evaluating mitigation measures for existing tunnels.