The submerged floating tunnel is an innovative concept for crossing waterways. It is a tunnel that floats in water, supported by its buoyancy, self-weight, and constraint forces resulted from the cable system. It utilizes the law of buoyancy to support the structure at a moderate and convenient depth. It gives new opportunities to the society for regional growth and protects the environment.
It is a tube-like structure made of steel and concrete. As the tunnel is situated at a depth of almost 30m, it should be perfectly watertight, and secondly, it should withstand hydraulic forces coming on it. It is made of 4 layers-Outer most layer is constructed of aluminum to resist the water. The second and third layer is made of the foam to float the tunnel easily in water. The fourth layer is concrete which gives strength to the tunnel.
STRUCTURAL COMPONENTS OF SUBMERGED FLOATING TUNNEL
The structural components provide strength and stiffness against the various forces acting under the water surface. The 3 basic structural components are-
1]Tube:-It should accommodate the traffic lanes and equipment. It may be constructed of steel or concrete, and its shape can be circular or elliptical.
2]Anchoring:-It is of 4 types. a]SFT with pontoons-It is independent of water depth; the system is sensitive to wind, waves, and currents. b]SFT supported on column-It is an underwater bridge with a foundation on the bottom. c]SFT with tethers to the bottom-It is based on tethers being in tension in all future situations. d]SFT unanchored-It is interesting as it has no anchoring .
3]Shore Conection:-The connections to the shore require appropriate interface elements to couple the flexible water tube with the much more rigid tunnel bored in the ground.
CONSTRUCTION OF SUBMERGED FLOATING TUNNEL
At first, dreading is done. Dreading is a technology used to remove a wide variety of materials underwater without adverse effects on the waterway environment. The construction steps are-
1]Pre casting-Huge tunnel sections are constructed on dry dock. The dry dock is flooded, and the panels are transported to their respective places.
2]Construction of joints-After the submersion of different panels in water, they are connected by using a rubber gasket.
3]Construction of foundations-A hollow chamber is penetrated down the sea bed, which evacuates the water trapped inside it by a valve present on its top surface.
4]Anchoring of cables-After the foundation work is completed, the cables are anchored to the floating tunnel, which will avoid its movement and place it firmly in alignment. Finally, the tunnel will be in position and ready to use.
EXAMPLES
1]Seikan tunnel-World's longest undersea railway tunnel.
2]Tokyo Bay Aqua line-World's longest undersea portion road tunnel.
ADVANTAGES
1]Allows construction of a tunnel in intense water.
2]Construction activities are less harmful to aquatic life.
3]No harmful environmental effects.
The submerged floating tunnels will set up new trends in transportation engineering and which shows with the advances in technology that will reduce the time required for traveling. Benefits can be obtained concerning less energy consumption, air pollution, and reduce noise emission. It provides new opportunities for improvement of communication and regional development.
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