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)

1. Presented by:-G.MANI KANTA
14L41A0119

2. INTRODUCTION
 Submerged floating tunnel is basically making a
tunnel to float underwater which is balanced by its
buoyancy, self weight and constraint forces resulted
from cable system and thus submerged to a certain
depth underwater.
 It is basically tube like structure floating at some depth
below water surface and fixed against excessive
movements. The tube is designed to accommodate
road and or rail traffic.

3. “ARCHIMEDES PRINCIPLE”
 Any object wholly or partially immersed in an fluid, is
buoyed up by a force equal to the weight of the fluid
displaced by the object.
 this means if more surface area exposed to water
surface more are the chances of floating it.
 Ships, submarines, offshore oil rigs etc. work on this
principle.
 Research shows that the buoyancy to weight ratio for
the tunnel to float should be less than one and
between 0.5 to 0.8

4. MATERIAL USED:-
 As the tunnel is situated at a depth of 30m, it should
be perfectly water tight and secondly it should resist
the salty sea water and thirdly it should be withstand
against hydrostatic forces coming on it.
 It is made of 4 layers. Outermost layer is constructed
of aluminium to resist the salty sea water. Second and
third layer is made of the foam to float the tunnel
easily in water. Fourth layer is of concrete which gives
strength to the tunnel.

5. PRESENT SCENARIO
 A simple submerged tunnel have been used as a means
of transport for about 100 years.
 They are considered to built when the underneath
ground surface is shallow and the tunnel can be placed
directly on sea bed and can be covered by sand and
backfill material so as to avoid their movement.

6. Sydney Harbour Tunnel(2.8 km)

7. Seikan Tunnel (53.9 km)- world's
longest undersea railway tunnel

8. Channel Tunnel( 37.9 km)-the tube rail between
ENGLAND & FRANCE world's longest undersea
portion railway tunnel

9. Marmaray (ISTANBUL) connecting
Asia and Europe

10. NEED FOR SUBMERGED FLOATING
TUNNEL
 A “SFT” is considered when the depth of sea or ocean
is too deep so that no tunnel or any solid body could
sustain the pressure acting on it at such a deep level.
 In that case the tunnel is lifted up such as about 30 to
100m deep from the sea surface where the water
pressure is comparatively lower than what is at the
bottom depth.

11. PARAMETERS OF AN “SFT”
An SFT basically consists of four parts
1) The tunnel structure which is made of different
segments
2) The shore connection structure which connects it to
shores.
3) The cable systems which are anchored to the
waterbeds to balance net buoyancy.
4) The foundation structure which are constructed at
waterbed to install cable system.

12. Step by step procedure
1) Construction of tunnel segments on dry dock.
2) Transporting the tunnel segments to their final
places and placing them underwater.
3) Joining of different tunnel segments by using rubber
gasket.
4) Anchoring the tunnel to the cables.

13. STEP ONE{PRECASTING}:-
 Huge tunnel sections are constructed on dry dock.
 The procedure consists same as that of precast
construction.
 Dry dock is flooded and the panels are transported to
their respective places.
 Sinking of the panel is controlled by the use of ballast
tank as in case of submarines.

14. STEP TWO{JOINTS}:-
 After the submersion of different panels in water they
are connected with one another by using a rubber
gasket.
 Another procedure includes trapping of water between
the joints and then removing it afterwards.

15. STEP THREE{FOUNDATIONS}:-
 The application consists same as that of in caisson
foundation.
 A hollow chamber is penetrated down the sea bed as
shown which evacuates the water trapped inside it by a
valve present on its top surface.
 Such type of foundations are been used for the
offshore oil rig plants.

16. STEP FOUR{ANCHORING OF
CABLES}
 After the foundation work is completed the cables are
anchored to the floating tunnel which will avoid its
movement and will place it firmly in alignment.
 This operation can be carried out by divers.
 Finally the tunnel will be in position and ready to use.

17. Advantages of “SFT”
 Allows construction of tunnel in extremely deep water,
where conventional bridges or tunnels are technically
difficult or prohibitively expensive.
 Any type of cross sectional area can be provided since
being prefabricated.
 No obstruction to navigational routes as compared to
conventional bridges since all of the tunnel being
placed underwater.
 Construction activities has less harmful effects on
aquatic life.

18.  No harmful environmental effects such as fog or storm
since the whole structure is covered and is present
inside the water.
 Low energy consumption due to more gentle gradient.
 Vehicular emission can be collected at one end of the
tunnel thus reducing the air pollution.
 Tremendous speed for trains could be obtained by
creating a vacuum inside the tunnel since it will result
in negligible air resistance.

19. TRANSATLANTIC TUNNEL
 AIM- to join north America to west Europe via a
submerged floating tunnel present in the Atlantic
ocean.
 Will require 54000 prefabricated tunnel segments.
 Use of maglev trains for fast travel.
 Maintaining perfect vacuum to avoid air resistance.
 Could travel from New York to London within 54
minutes with a tremendous speed of 8000km/h.

20. CONCLUSION:-
The submerged floating tunnel will set up new trends in
transportation engineering and which shows with the advances in
technology that will reduce the time required for travelling. And
make the transportation more effective by hiding the traffic under
water by which the beauty of landscape is maintained and valuable
land is available for other purposes. Benefits can be obtained with
respect to less energy consumption, air pollution and reduced
noise emmission.For wide and deep crossings the submerged
floating tunnel may be the only feasible fix link, replacing present
day ferries and providing local communities with new
opportunities for improved communication and regional
development.

21. REFRENCES:-
1. Forum Of European
National Highway
Research
Laboratories (1996), Analy
sis of the submerged floating
tunnel concept, Transport
Research Laboratory
Crowthrone,Berkshire,RG45
6AU.
2. Havard Ostlid (2010),
When is SFT
competitive, Procedia
Engineering, 4, 3–11
3.http://dsc.discovery.com/c
onvergence/engineering/tra
nsatlantictunnel/interactive/
interactive.html
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