Submerged Floating Tunnel
A submerged floating tunnel, also known as submerged floating tube bridge, suspended tunnel, or Archimedes bridge, is a design for a tunnel that floats in water, supported by its buoyancy, self-weight, and constraint forces resulted from cable system and thus submerged to a certain depth underwater. It is a tube-like structure made of steel and concrete placed deep underwater to avoid water traffic and weather. It is designed to accommodate road or rail traffic.
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. Huge tunnel sections are prefabricated in a dry dock and the sections are moved to the site. The sections are then sealed, sunk into place while being sealed, and, when the sections are fixed to each other, the seals are broken. The tunnel is made of 4 layers-: outermost layer is made of aluminium to resists corrosion, inner two layers made of foam to float the tunnel easily and the innermost layer is made of concrete which gives strength
1. Submerged floating tubes allow construction of a tunnel in extremely deep water, where conventional bridges or tunnels are technically difficult or prohibitively expensive
2. They would be able to deal with seismic disturbances and weather events easily, as they have some degree of freedom in regards to movement, and their structural performance is independent of length.
3. Construction process has less harmful effects to aquatic life.
4. It reserves the landscape for other purposes.
5. It reduces air pollution as all the emissions collected at one end of the tunnel.
6. Reduces noise emission and consumes less energy.
Despite all these benefits SFTs have some drawbacks. Swell, vortex shedding and slowly varying internal waves due to layers of different salinity present a hazard of significant dynamic oscillations. Also, some common accidental situations have to be solved including fire, sinking ships, falling anchors as well as sudden massive water ingress into the tube. However research is going on for its improvement and definitely, the submerged floating tunnel will set up new developments in transportation engineering. Benefits can be obtained like less energy consumption, air pollution and reduced noise emission. Also, this may the best way of transportation to the islands. The SFT will usher in a new era of transportation technology.
WRITTEN BY: Biswajit Sahoo & Pradeep Kumar Behera