Connecting opposite shores of a lake, sea or river, has always been one of the major tasks to be faced by Civil Engineering, it being a fundamental need for the development of the areas surrounding a waterway. Nowadays, this issue is still topical and of great importance, as it is proved by the numerous large infrastructures which have been built or planned to be built in the last years all over the world, such as, for instance the Channel Tunnel, linking the shores of France with the ones of the United Kingdom, the Immersed Tunnel under construction in the Bosporus Strait (Turkey) or the Suspension Bridge designed to connect Calabria and Sicily in the Messina Strait (Italy). Numerous other important and noticeable cases could be mentioned, however the aforementioned ones probably represent the most advanced examples of the structural solutions which are traditionally most widely used to link areas divided by the presence of waterways: Cable Supported Bridges (i.e. Suspension or Cable stayed Bridges), Underground Tunnels and Immersed Tunnels. An underwater tunnel is a passage, gallery, or roadway beneath a body of water. Underwater tunnels are used for highway traffic, railroads, and subways; to transport water, sewage, oil, and gas; to divert rivers around dam sites while the dam is being built; and for military and civil defence purposes. Modern underwater tunnelling begins by constructing an immersed tube within a pre-dug trench on the river or sea floor. To do this, pre-fabricated sections of steel tube are floated into position and strategically sunk into the trench. The complexity of the design issues related to these classic technological solutions, increases as the distance to be covered grows up, so that the crossing of long span waterways can be, in many cases, very difficult and sometimes impossible. Moreover, the traditional systems feature some disadvantages which in some cases are of great importance, leading to the necessity to find alternative technical solutions.

1. SUBMERGED TUNNEL
UNDERWATER TUNNELING
BY
RIJWI GHOSH
1EW10CV060
Under the Guidance of
Mr. Nagaraja Gupta MS
Associate Professor
Dept. of Civil Engineering
East West Institute of
Technology
Bangalore-560091

2. UNDER WATER TUNNELLING
 An underwater tunnel is a passage, gallery, or roadway
beneath a body of water. Underwater tunnels are used
for highway traffic, railroads, and subways; to
transport water, sewage, oil, and gas; to divert rivers
around dam sites while the dam is being built; and for
military and civil defence purposes.
 Modern underwater tunnelling begins by constructing
an immersed tube within a pre-dug trench on the river
or sea floor. To do this, prefabricated sections of steel
tube are floated into position and strategically sunk
into the trench.

3. Types of Underwater Tunnels

4. Soft Ground Tunnel or Bored
Tunnel

5. Immersed Tunnels or Submerged
Tunnels

6. Submerged Floating Tunnels

7. Overview of forces acting on each
type:

8. What is a SUBMERGED TUNNEL???What is a SUBMERGED TUNNEL???
A Submerged Tunnel is a tunnel that
floats in water, supported by
its buoyancy(specifically, by employing
the hydrostatic thrust, or Archimedes'
Principle).
The tube is 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 (60–150 ft.) is
sufficient. Cables either anchored to
the Earth
or to pontoons at the surface
prevent it from floating to the surface
or submerging, respectively.

9. Why this ?Why this ?
 The big advantage of a floating submerged tunnel compared to a
bridge is the lightly loaded constructionlightly loaded construction.. Under water a weight
reduction takes place which lowers the loads to be carried by the
tunnel.
 Flexible submerged tunnel has much less problems with less problems with
earthquakesearthquakes which can happen in this area.
 Floating tunnel can be built fast from both shores having no no
problems with wind or high seasproblems with wind or high seas.
 Another possible advantage is space: the downward ramp leading
to a tunnel leaves a smaller footprint compared to the upward
ramps required by most bridges.
 Moreover traffic can run very fast through this tunnel compared to
ferry link.
 Due to lesser contact with the sea bed it has lesser possibilities of
chemical reaction with the construction material & the sea bad soil
strata.

10. Submerged tunnels can be placed immediately beneath a
waterway. In contrast, a bored tunnel is usually only
stable if its roof is at least its own diameter beneath the
water. This allows Submerged tunnel approaches to be
shorter and/or approach gradients to be flatter - an
advantage for all tunnels, but especially so for railways.

11. How this is constructed…….
 A trench is dredged in the bed of the water channel.
DREDGING
Dredging technology has
improved considerably in
recent years, and it is now
possible to remove a wide
variety of material
underwater without adverse
effects on the environment of
the waterway.

12.  Tunnel elements are constructed in the dry, for exampleTunnel elements are constructed in the dry, for example
in a casting basin, a fabrication yard, on a ship-liftin a casting basin, a fabrication yard, on a ship-lift
platform or in a factory unit.platform or in a factory unit.
casting basin fabrication yard
ship-lift platform factory unit

13. Materials used:
As the tunnel is situated at a depth of 20-50m, 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 super-buoyant foam to float the tunnel
easily in water. Fourth layer is of concrete which gives
strength to the tunnel.

14. After Casting…..After Casting…..
∗ After casting the ends of the element are then temporarily sealed
with bulkheads.
∗ Each tunnel element is transported to the tunnel site - usually
floating, occasionally on a barge, or assisted by cranes.

15. The immersion of the tunnel element is carried
out after the tunnel element has been moved
and the element has been ballasted as
necessary to provide adequate loads in the
immersion tackles.

16. The tunnel element is lowered to its final place
on the bottom of the dredged trench.

17. The new element is placed against the previous element
under water. Water is then pumped out of the space
between the bulkheads.
Water pressure on the free end of the new element
compresses the rubber seal between the two elements,
closing the joint.

18. Backfill
material is
placed beside
and over the
tunnel to fill
the trench and
permanently
bury the
tunnel, as
illustrated in
the figures.

19. Approach structures can be built on the
banks before, after or concurrently with
the Submerged tunnel, to suit local
circumstances.

20.  Submerged tunnels are sometimes perceived by
newcomers to the technology as "difficult" due
to the presence of marine operations.
 In reality though, the technique is often less risky
than bored tunneling and construction can be
better controlled. The marine operations, though
unfamiliar to many, pose no particular difficulties.

21. Case Study:
 Seikan Tunnel
 Channel Tunnel
 Tokyo Bay Aqua-Line
 Eiksund Tunnel

22. Seikan Tunnel (53.9 km)- world's longest
undersea railway tunnel, with a 23.3 km long portion
under the seabed. The track level is about 100 metres
below the seabed and 240 m below sea level. It connects
Aomori Prefecture on the main Japanese island of Honshu
with the northern island of Hokkaido.
The Operating speed is 140km/hrThe Operating speed is 140km/hr

23. Channel Tunnel( 37.9 km)-the tube rail between
ENGLAND & FRANCE world's longest undersea portion railway tunnel.
The tunnel carries high-speed Eurostar passenger trains,
the Eurotunnel Shuttle for road vehicles—the largest such transport
in the world —and international freight trains.
The Operating speed is 160km/hrThe Operating speed is 160km/hr

24. Tokyo Bay Aqua-Line (14 km) - With an
overall length of 14 km, it includes a 4.4 km bridge and 9.6 km
tunnel underneath the bay—the fourth-longest underwater
tunnel in the world & world's longest undersea portion road
tunnel

25. Eiksund Tunnel(7.7 km), world's deepest undersea
road tunnel, it reaches a depth of −287 metres

26. Regular vs. Underwater TunnelsRegular vs. Underwater Tunnels
Regular Underwater
Average CostsAverage Costs
$
787,500,000
$6,349,500,
000
Average LengthAverage Length
3.5 miles
= 5.63 km
4.5miles
= 7.24 km
Years BuildYears Build
1-3 3-6
http://www.eurotunnel.com/uk/

27.  Tunnels required for higher costs of security and construction than
bridges. This may mean that over short distances bridges may be
preferred rather than tunnels (for example Dartford Crossing).
 Bridges may not allow shipping to pass, so solutions such as the Oresund
Bridge have been constructed.
 Implementation of this project is very tough & requiring skilled labours &
heavy machinery & facing very adverse situations.

28. THANK YOUTHANK YOU