page_title: Submerged floating tunnel
section_title: Construction
hierarchical_section_title: Submerged floating tunnel / Construction
caption_attribution_description: English: Two types of submerged floating tunnels
context_page_description: A submerged floating tunnel, also known as submerged floating tube bridge, suspended tunnel, or Archimedes bridge, is a proposed design for a tunnel that floats in water, supported by its buoyancy.
  The tube would be placed underwater, deep enough to avoid water traffic and weather, but not so deep that high water pressure needs to be dealt with—usually 20–50 m is sufficient. Cables either anchored to the seabed or to pontoons on the surface would prevent it from floating to the surface or submerging, respectively.
context_section_description: The concept of submerged floating tunnels is based on well-known technology applied to floating bridges and offshore structures, but the construction is mostly similar to that of immersed tunnels: One way is to build the tube in sections in a dry dock; then float these to the construction site and sink them into place, while sealed; and, when the sections are fixed to each other, the seals are broken. Another possibility is to build the sections unsealed, and after welding them together, pump the water out.
  The ballast used is calculated so that the structure has approximate hydrostatic equilibrium (that is, the tunnel is roughly the same overall density as water), whereas immersed tube tunnels are ballasted more to weight them down to the sea bed. This, of course, means that a submerged floating tunnel must be anchored to the ground or to the water surface to keep it in place (which of these depends on which side of the equilibrium point the tunnel is).
caption: Two types of submerged floating tunnels
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