3. Context
Introduction
Materials used
Principle used for Construction an (SFT)
Need for Submerged Floating Tunnels (SFT)
Parameters of an SFT
Construction procedure
Advantages
Transatlantic Tunnels
Conclusion
4. 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.
5. 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.
6. “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
7. PRESENT SCENARIO
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.
8. 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.
9. 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.
10. 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.
11. 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.
12. 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.
13. 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.
14. 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.
15. 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.
16. 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.
Advantages of “SFT”
17. 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.
18. 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.
