tunnels

1. PREPARED BY:-
Husain Jamali-07

2. INTRODUCTION
WHY TUNNELS ARE CONSTRUCTED
HISTORY OF TUNNELS
CLASSIFICATION OF TUNNEL
SHAPE OF TUNNEL
PROCESS FOR CONSTRUCTION OF TUNNEL
TUNNEL CONSTRUCTION METHODS
ADVANTAGES

3. Tunnels are underground or underwater
passageway, excavated through the
surrounding soil/earth/rock enclosed
except for entry and exit, commonly at
each end.
A tunnel may be used for foot or vehicular
road traffic, rail traffic, or for a canal.
Secret tunnels are constructed for military
purpose.
Special tunnels, such as wildlife crossings,
are built to allow wildlife to cross human
made barriers safely.

4. To provide the shortest route through an obstacle.
To provide the rapid or timely provision of facilities.
To reduce the steep gradients especially while climbing up and then
climbing down rapidly i.e. in short distance.
To avoid the expensive acquisition of valuable commercial land.
To avoid the damage of built urban facilities, roads, pavements, etc.
When the depth of ground cutting exceeds 20 m.
To avoid the expensive maintenance cost in open cut area in sliding
lands, sinking or unstable grounds, snow-drifting grounds, ponding,
marshy, soaked, etc areas.

5. The first ever tunnels were made by
cavemen.
About 2180B.C., Babylonia tunnel was
built under Euphrates river. It was 900m
long, 3600mm wide and 4500mm high.
The largest tunnel built in ancient times
was 1470m long, 7600mm wide and
9000mm high between Naples and
Pozzuoli in 36B.C.
HISTORY OF TUNNELS

6. CLASSIFIED BY EXAMPLE OF TUNNELS
• Purpose Railway tunnels, metro system,
highway tunnels, pedestrian tunnels,
water tunnels, sewage tunnels, services
tunnels, storage tunnels.
• Geological location / condition Rock tunnels, earth tunnels, and
submerged tunnels.
• Cross-sectional shapes Rectangular shape, circular shape,
elliptical shape, egg shape, horse shoe
shape, and segmental shape.

7. The shapes of tunnel are usually determined by
their purpose, ground conditions, construction
method and/or lining materials.
There are four shapes of tunnel:-
Circular shape tunnel
Elliptical shape tunnel
Horseshoe shape tunnel
Oval/Egg shape tunnel

8.  This type of section offers greater
resistance to external pressure.
 If ground is highly unstable, such as
soft clay or sand, it is necessary to use
circular section.
 For carrying water and sewerage
circular shape tunnels are used e.g.
Aqueduct

10.  They are used in grounds compare
to rock.
 These tunnel serve as water sewage
condition.
 The smaller cross section at the
bottom maintains the flow at the
required self cleaning velocity.
 Because of their narrow base they
are not used as traffic tunnels.

11.  These section have narrow cross-
sections at bottom. They are best
suited for carrying sewage.
 They maintain self-cleansing velocity
of flow of sewage both in dry and
rainy seasons.
 They resist external as well as internal
pressure due to their circular walls.
 These section of tunnels are difficult
to construct

12.  They are commonly used for rock tunnelling.
 These shape consist of horizontal roof
together with arched sides and a curved
invert.
 It has the advantage of utilising the
compressive strength of concrete in resisting
the loading by means of arch action and the
base is wide enough for traffic.
 They are most popular as traffic tunnels for
road and railway routes.
 They are also difficult to construct.

13. The tunneling survey is an underground survey done for constructing a
tunnel
The survey done can be divided into 3 methods:-
Surface survey
Transferring the alignment underground
Levels in tunnels

14.  Surface survey connects points representing each portal of a tunnel.
 A traverse connecting the portal points determines the azimuth, distance & differences in
elevation of each end of the proposed tunnel.
 Based on the local conditions and proposed length of the tunnel the methods of working
are adopted.
 It is always advisable that the survey is based on the suitable local coordinate system.
 The alignment is permanently referenced by a system of monuments within an area
outside each tunnel portal.

15. A long tunnel excavation is carried inward from both ends. But vertical shafts are also sunk
up to the required depth along the alignment of the tunnel at intermediate locations along
the routes. The vertical alignment can be done by:-
• Plumb bob
• Optical collimator
• Laser
A heavy plumb bob (5 to 10 kg) is suspended on either a wire of heavy twine. Oscillations
of the bob can be controlled by suspending it in a pot with high viscosity oil. The bob is
suspended from a removable bracket attached to the surface side of the shaft.
Optical plumbing becomes important with the increase in depth of internal shaft.
A Laser equipment can be used to provide a vertical line of sight. The laser generates a
light beam of high intensity and of low angular divergence and can be projected over long
distances since the spread of the beam is very small to provide a visible line for constant
reference.

16. Laser Equipment

17.  In transferring levels underground, little
difficulty is encountered at the ends of the
tunnel, but at the shaft use is made of
• Steel tape
• Chain
• Constructed rods
• Steel wires
 Now a days EDMI is also used. But in all cases
the main idea is to deduct the height of the
shaft measured from the top of a benchmark of
known value.
Depth measured by EDM
Depth measured by Steel tape

18. Classical method
Cut and Cover method
Drill and Blast method
Immersed Tube method
Sequential Excavation Method (SEM)
Tunnel Boring Machines(TBM)
Shield tunneling method
New Austrian tunneling method

19. Supports are predominantly timber, and transportation
of muck is done on cars on narrow gauge tracks
powered by steam.
Progress is typically in multiple stages i.e. progress in
one drift, then support, then in another drift and so on.
The lining would be of brickwork.
These craft-based methods are no longer applicable,
although some of their principles have been used in
combination up to present day.
Some of the great tunnels were built with this method.
In this method excavation is done by hand or simple
drilling equipment.

21. Cut and cover tunnelling is a common and well-
proven technique for constructing shallow
tunnels.
In this method trench is excavated and roofed
over with an overhead support system strong
enough to carry the load of what is to be built
above the tunnel.
• Step one: Construction of diaphragm walls, piles,
and decking.
• Step two: Excavation within the diaphragm
walls, installing struts as work progresses.
• Step three: Construction of permanent floor
slabs and walls.
• Step four: Fitting out the internal structures,
backfilling, and reinstating the surface
structures.

22. This tunnelling method involves the use
of explosives.
Drilling rigs are used to bore blast holes
on the proposed tunnel surface to a
designated depth for blasting.
Explosives and timed detonators are
then placed in the blast holes.
Once blasting is carried out, waste rocks
and soils are transported out of the
tunnel before further blasting.

23. CUT AND COVER METHOD

24. When a canal, channel, river, etc., needs
to be crossed, this method is often used.
A trench is dug at the water bottom and
prefabricated tunnel segments are made
water tight and sunken into position
where they are connected to the other
segments.
Afterward, the trench may be backfilled
with earth to cover and protect the
tunnel from the water-borne traffic, e.g.,
ships, barges, and boats.

25. Soil in certain tunnels may have sufficient
strength such that excavation of the soil
face by equipment in small increments is
possible without direct support. This
excavation method is called the sequential
excavation method.
Once excavated, the soil face is then
supported using shotcrete and the
excavation is continued for the next
segment.
The cohesion of the rock or soil can be
increased by injecting grouts into the
ground prior to excavation of that
segment.

27. A tunnel boring machine (TBM), also known as a "mole", is a
machine used to excavate tunnels with a circular cross section
through a variety of soil and rock strata.
The TBM is designed to support the adjacent soil until temporary or
permanent linings are installed.

28. Tunnel Boring Machine

30.  In New Austrian Tunnelling Method (NATM) a flexible lining is employed.
 It transforms the rock or soil surrounding the tunnel profile from a load exerting
system into a load-carrying one.
 This is achieved through monitoring the behaviour of underground excavations and
the revision of support to obtain the most stable and economical lining.

32. Construction Methods For Different tunnel shapes
Methods Circular Horseshoe Rectangular Elliptical
Cut and Cover 
Shield Driven 
Bored 
Drill and Blast  
Immersed Tube  
Sequential Excavation 
Jacked Tunnel  

33. FACTORS AFFECTING SELECTION OF
TUNNELING METHOD
Geological and Hydrological condition
Cross-section and length of continuous tunnel
Local experience and Time/Cost consideration
Shape of tunnel
Managing the risk of variations in ground quality
Limits of surface disturbance

35. Linings are required in most tunnels, always in soft ground and
frequently in rock.
They are required for two purposes: structurally to retain the earth and
water pressure, and operationally to provide an internal surface
appropriate to the function of the tunnel.
The principal materials for permanent lining of bored tunnels are:
1. Brickwork, blockwork and masonry
2. Insitu concrete
3. Preformed segments
4. Sprayed Concrete

36. Tunnel ventilation systems can be categorized into four main types.
The four types are as follows:-
• Natural Ventilation
• Longitudinal Ventilation
• Semi-Transverse Ventilation
• Full-Transverse Ventilation

37. A naturally ventilated tunnel is as simple as
the name implies. The movement of air is
controlled by meteorological conditions and
the piston effect created by moving traffic
pushing the stale air through the tunnel.
This effect is minimized when bi-directional
traffic is present.
The meteorological conditions include
elevation and temperature differences
between the two portals, and wind blowing
into the tunnel.
Another configuration would be to add a
centre shaft that allows for one more portal
by which air can enter or exit the tunnel.
Many naturally ventilated tunnels over 180
m (600 ft) in length have mechanical fans
installed for use during a fire emergency.

38. Longitudinal ventilation is similar to natural
ventilation with the addition of mechanical
fans, either in the portal buildings, the center
shaft, or mounted inside the tunnel.
Longitudinal ventilation is often used inside
rectangular-shaped tunnels that do not have
the extra space above the ceiling or below the
roadway for ductwork.
Also, shorter circular tunnels may use the
longitudinal system since there is less air to
replace; therefore, the need for even
distribution of air through ductwork is not
necessary.
The fans can be reversible and are used to
move air into or out of the tunnel.

39. Semi-transverse ventilation also makes
use of mechanical fans for movement of
air, but it does not use the roadway
envelope itself as the ductwork.
A separate plenum or ductwork is added
either above or below the tunnel with
flues that allow for uniform distribution
of air into or out of the tunnel.
This plenum or ductwork is typically
located above a suspended ceiling or
below a structural slab within a tunnel
with a circular cross-section.

40. Full-transverse ventilation uses the same
components as semi-transverse ventilation,
but it incorporates supply air and exhaust
air together over the same length of tunnel.
This method is used primarily for longer
tunnels that have large amounts of air that
need to be replaced or for heavily traveled
tunnels that produce high levels of
contaminants.
The presence of supply and exhaust ducts
allows for a pressure difference between
the roadway and the ceiling; therefore, the
air flows transverse to the tunnel length and
is circulated more frequently.
This system may also incorporate supply or
exhaust ductwork along both sides of the
tunnel instead of at the top and bottom.

41. Tunnels are more economical than open cuts beyond certain depths.
Tunnels avoid disturbing or interfering with surface life and traffic
during construction.
Tunnels prove to be cheaper than bridges or open cuts to carry public
utility services like water, sewer and gas.
If tunnels are provided with easy gradients, the cost of hauling is
decreased.
In case of aerial warfare and bombing of cities, the tunnels would
grant better protection as compared to bridges.

42. MONITOR-MERRIMAC MEMORIAL TUNNEL BRIDGE

43. Project details:-
Project name-- Monitor-Merrimac Memorial
tunnel-bridge
Client- Common wealth transportation board
(formerly state highway and transportation
board)
Contractor – Virginia department of
transportation
Distance between portals – 1.463 km
Time required - 7 years (1985 to 1992)
Method of construction – Immersed tube
method
Total cost of project – 400 million dollars
Location – Hampton roads Northfolk and
partly in Suffolk
Qty. of materials – 40,800 Tons of Concrete
21,800 Tons of Steel
3 Million of Tiles

44. • Traffic lanes -13 feet wide, 2.5-foot-wide ledges on either side of the roadway
• Vertical clearance -16.5 feet (road to ceiling)
• Uniqueness – Radio signals does not break

45. Project Detail:
Client: Indian Railway
Executing Agency: IRCON (Indian Railway
Construction Company Limited)
Contractor: HCC (IRCON being the Client for
HCC)
Project Location: Jammu & Kashmir
Construction Period: 2005-2013
Length of the Tunnel: 10.96 Km
Project Cost: 1150 Crore
No. Of tracks: 1 (Broad Gauge)
Need of this Project: To reduce the travel time
and to sustain connectivity between Quazigund
(Kashmir) and Banhihal (Jammu)

46.  TECHNICAL SPECIFICATION
•Width: 8.4 meters
•Height: 7.9 meters
 CONSTRUCTION TECHNIQUES
• New Austrian Tunnelling Method (NATM)
• Drill & Blast
• Road Header (relatively new machinery to
the Indian construction market)
 UNIQUENESS
• Tunnel is open throughout the year.
• Underground drainage system to avoid
seepage in tunnel.
• 3 m wide road in tunnel for maintenance,
emergency rescue & relief.
• Mobile connectivity inside the tunnel.

47. Challenges faced:-
•Presence of Soft geology.
•Presence of fairly populated village above the alignment.

48. Project Details :
Client : Norwegian government
Contractor : Norwegian Public Roads
administration
Consultants : Foundation for Scientific and
Industrial Research
Construction Period : 1995-2000
Tunnel Length : 24.5 km
Tunnel Width : 9 m (30ft)
Route : Aurdal – Laerdal (Norway)
Project Cost : 1082 Million Norwegian krone
No. of lanes : 2
Location : Sognog Fjordane, Norway

49. THANK YOU
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