tunneling techniques

1. Topic 4: Tunneling
by
Dr. Magudeaswaran Palanisamy
Professor of Civil Engineering
Adithya Institute of Technology
Coimbatore 641107
dr.magudeaswaran@gmail.com

2. 
Is an underground or underwater passageway, dug
through the surrounding soil/earth/rock and
enclosed except for entrance and exit, commonly
at each end. A pipeline is not a tunnel, though
some recent tunnels have used immersed tube
construction techniques rather than traditional
tunnel boring methods.
• Tunnel

3. 
A tunnel may be for foot or vehicular road traffic,
for rail traffic, or for a canal. The central portions
of a rapid transit network are usually in tunnel.
Some tunnels are aqueducts to supply water for
consumption or for hydroelectric stations or
sewers. Utility tunnels are used for routing steam,
chilled water ,electrical power or
telecommunication cables.
• Tunnel

4. 
• Parts of a tunnel

5. 

6. 

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8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 
 Hard Rock Tunnelling
 Soft Rock/Soil/Ground Tunnelling
• Two main types of
tunnelling

16. 
 In Scandinavian hard rock conditions, most tunnels are
excavated by drill & blast technique in softer rock, other
excavation methods such as road.
• Hard Rock Tunnelling

17. 
Bored Tunnelling Method (sometimes
called Tunnel Boring Method)
Drill and Blast Method
• Types of hard rock
tunnelling

18. 
 Workers generally use two basic techniques to advance a tunnel.
In the full-face method, they excavate the entire diameter of the
tunnel at the same time. This is most suitable for tunnels
passing through strong ground or for building smaller tunnels.
The second technique, shown in the diagram below, is the top-
heading-and-bench method. In this technique, workers dig a
smaller tunnel known as a heading. Once the top heading has
advanced some distance into the rock, workers begin excavating
immediately below the floor of the top heading; this is a bench.
One advantage of the top-heading-and-bench method is that
engineers can use the heading tunnel to gauge the stability of
the rock before moving forward with the project.
• Soft Rock/Soil/Ground
Tunnelling

19. 
 Cut and Cover Tunnelling Method
 Immersed Tube Tunnelling (for underwater tunnels)
 Shield Tunnelling
• Types of Soft Rock/Soil
/Ground Tunnelling

20. 
 Original purpose
 In Military
 In Sewers
 In Mining
 In Rail traffics
 In Hydroelectric station and etc.
• Purpose of a tunnel

21. 
 Cut-and-cover
 Drill and blast
 Tunnel boring machines ( TBM )
 Immersed tunnel
 Tunnel jacking
 Shield tunnel
 Other methods
• Tunnel Construction Method

22. 
Construction Methods
Circular Horseshoe Rectangular
Cut and Cover X
Shield Driven X
Bored X
Drill and Blast X X
Immersed Tube X X
Sequential Excavation X
Jacked Tunnel X X

23. 
 Simple method of
construction for shallow
tunnels where a 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.
 Two basic forms / methods
of cut-and-cover
tunnelling:
1. Bottom-up
2. Top-down
• Cut -and -Cover

24. 
 is a protective structure used
in the excavation
of tunnels through soil that
is too soft or fluid to remain
stable during the time that
it takes to line the tunnel
with a support structure of
concrete, cast iron, or steel.
In effect, the shield serves as
a temporary support structure
for the tunnel while it is being
excavated.
• Bored (tunnel boring machine )

25. 
 An alternative to using a
TBM in rock situations
would be to manually drill
and blast the rock and
remove it using conventional
conveyor techniques. This
method was commonly used
for older tunnels and is still
used when it is determined
cost effective or in difficult
ground conditions.
• Drill and Blast

26. 
 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.
• Immersed Tube

28. 
 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.
• Sequential Excavation Method (SEM)

29. 
 The method of jacking a
large tunnel underneath
certain obstructions
(highways, buildings, rail
lines, etc.) that prohibit the
use of typical cut-and-
cover techniques for
shallow tunnels has been
used successfully in recent
years.
• Jacked Tunnels

30. 
 This method uses one or two
shields (large metal cylinder) to
cut out a tunnel through the soft
ground. A rotating cutting wheel
is located at the front end of the
shield. Behind the cutting
wheel is a chamber where,
depending on the type of the
TBM, the excavated soil is
either mixed with slurry (called
slurry TBM) or left as is (earth
pressure balance or EPB shield).
Systems for removal of the soil
(or the soil mixed with slurry)
are also present.
• Shield Tunnelling

31. 
• Local tunnels
 Ternate-Nasugbu
Tunnel (Kaybiang
Tunnel)
 longest tunnel in the
Philippines (300 m);
constructed for 4
years.

33. 
• Local tunnels
 Malinta Tunnel (Corregidor)
 initially used as a bomb-proof storage, but later used
as a 1000-bed hospital; 831 feet (253 m) long, 24 feet
(7.3 m) wide and 18 feet (5.5 m) high. Branching off
from this main shaft are 13 lateral tunnels on the
north side and 11 lateral tunnels on the south side.

35. 
• Local tunnels
 Fort Bonifacio Tunnel (Bonifacio Global City, Taguig)
 The tunnel was initially used as a passageway for military
supplies and war materials. It was first constructed around
1936 with the help of Igorots. It stretches 2.24 kilometers
(1.39 mi) (from Pasig River to Villamor Airbase in Pasay)
at an average depth of 70 feet (21 m).

37. 
• Intact rock
 Intact rock contains neither
joints nor hair cracks, and
thus breaks across sound
rock. Spalling conditions,
which is when thin slabs of
rock fall off the roof or walls
of the tunnel, , and popping
conditions, where rock slabs
on the sides or roof of the
tunnel spontaneously and
violently detach, may occur
for several hours or days
after blasting.

38. 
• Stratified rock
 Stratified rock consists of
individual strata with little
or no resistance against
separation along strata
boundaries. Spalling
conditions are quite
common.

39. 
• Moderately jointed
rock
 Moderately jointed rock
contains joints and hair
cracks, but blocks between
the joints are locally
grown together or so
intimately interlocked that
vertical walls do not
require lateral support.
Again, spalling and
popping conditions may be
encountered.

40. 
• Blocky and seamy
rock
 This consists of chemically
intact or nearly intact rock
fragments which are
entirely separated from
each other and imperfectly
interlocked. The vertical
walls of the tunnel may
require support.

41. 
• Crushed rock
 Crushed rock is chemically
intact, but extensively
fractured. If the crushed
rock is small-grained and
below the water table, it
will exhibit the properties
of a water-bearing sand.

42. 
• Squeezing rock
 Squeezing rock slowly
advances into the tunnel
without a perceptible
volume increase. This
condition requires a very
high percentage of
microscopic and sub-
microscopic micaceous
minerals or clay minerals
with a low swelling
capacity.

43. 

44. 
Thank you for listening 
by
Dr. Magudeaswaran Palanisamy
 Professor of Civil Engineering
 Adithya Institute of Technology
 Coimbatore 641107
 dr.magudeaswaran@gmail.com