2. 2
CONTENTS
Introduction
Some shapes of the tunnel
Factors to be considered in Tunnel construction
Selection of tunnelling methods
Case studies
Conclusions
References
3. 3
Introduction
• The underground structures provides the scope for humans to protect themselves from the
natural disasters (hurricanes), to hide from the enemies.
• Tunnels are underground passage structures and are enclosed by the concrete lining.
• Tunnels also cut short the distance between two points.
• Therefore there were many applications of the under ground construction in defence sector ,
transportation sector ( for roadways and railways) and in laying waste water pipelines under the
road surface.
• In olden days, the tunnels are used as secret ways, to escape from enemies and now there are
used to save the time in transportation.
• There were many construction techniques used for building underground structures such as cut
and cover method, Conventional methods and using Tunnel Boring machine.
Source:- https://www.engineeringcivil.com/underground-construction-techniques.html
5. 5
Some shapes of the tunnel
Source:- Mobaraki, B., and M. Vaghefi. 2015. “Numerical study of the depth and cross-sectional shape of tunnel under surface explosion.” Tunnelling and
Underground Space Technology, 47: 114–122. Elsevier Ltd. https://doi.org/10.1016/j.tust.2015.01.003.
6. 6
Factors to be considered in Tunnel construction
1. Collapse
• Based on the type of soil strata, the measures are to be taken against the collapse of
tunnel.
• If it is hard rocky is present, no support is provided (self supported) and in case of
loose soil, external supports are provided (steel meshes).
• We should overcome huge overburden pressure, while constructing the tunnels under
the mountains and steel arches are used to bear the pressure.
Source:- Li, J. C., H. B. Li, G. W. Ma, and Y. X. Zhou. 2013. “Assessment of underground tunnel stability to adjacent tunnel explosion.” Tunnelling and
Underground Space Technology, 35: 227–234.
7. 7
2. Ventilation
• We must provide proper inflow and outflow of air into tunnel for workers, so they work
comfortably at depths.
• As we go deep into the earth, the temperatures rises and make the workers inconvenient
to work, so use the water as coolant.
• It was much required for the workers working in mines.
• The exhaust gases from vehicles are to be pumped out of the tunnel.
Source:- Porras-Amores, C., F. R. Mazarrón, I. Cañas, and P. Villoría Sáez. 2019. “Natural ventilation analysis in an underground construction: CFD
simulation and experimental validation.” Tunnelling and Underground Space Technology, 90: 162–173. Elsevier Ltd.
9. 9
3. Precision
• We must study about the soil strata completely over the construction place and should plan
the path for the Boring machine to travel along the particular strata.
• For example, it is economical for the boring machine to travel through the chalk strata than
travelling through the hard rocky strata.
• In some projects, they use two tunnel boring machines to fast up the construction process,
therefore the meeting point of two TBM’s must meet at one common point.
• Therefore the usage of laser guided device is used in order to coordinate with planned path.
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4. Safety
• In conventional technique, we use drilling and blasting operations to construct a tunnel,
it releases toxic gases like co, in to the tunnel.
• These gases are deadly for the worker in the tunnel and it is necessary to remove them
out of the tunnel.
• It is necessary to build underground stations with enough supplies, so it can be used in
case of emergencies.
• The workers in coal mines are exposed to methane gas, if this is inhaled in larger
quantity the worker may lose his life.
• In case of aerial attacks, tunnels offer better protection than bridges.
Source:- Flammability Testing of Materials Used in Construction, Transport and Mining 2006, Pages 231-274
11. 11
Selection of Tunnelling Methods
Depends on the
• Ground conditions
• Level of Water table
• Length and diameter of the tunnel
• Depth of the tunnel
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES
WITH DIFFERENT TUNNELLING METHODS.
12. 12
Tunnelling Shield method
• It is a protective structure used during the excavation of large
man-made tunnels.
• It is used to excavate the soft soil strata of the earth surface and tunneling shield can
be used as a temporary support structure.
Source:- https://en.wikipedia.org/wiki/Tunnelling_shield
13. 13
Conventional Method
• Conventional method is the construction of underground openings of any
shape with a cyclic construction process, such as
o Excavation (using drilling and blasting or mechanical excavators)
o Mucking (removing the debris and waste)
o Placement of the primary support elements such as Steel ribs,
meshes, shotcrete.
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES
WITH DIFFERENT TUNNELLING METHODS.
14. 14
• Conventional tunnelling provides with the wide variety of construction methods
that allow engineers to make the most appropriate choice to achieve safe tunnel
construction.
• It provides great variability in shape of the cross section and opted when the
strata of earth continuously changing. This flexibility makes conventional
tunnelling method the most advantageous tunnelling method in many projects.
• Generally it was preferred for short tunnels and in some complicated sections of
long tunnels such as fault lines in the earth.
• Incase of fault lines the section of the tunnel is to be cement grouted and then
drilled through it.
Conventional Method
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES
WITH DIFFERENT TUNNELLING METHODS.
15. 15
TBM Method
Based on the geological conditions, TBM’s are classified in to following types
1. Hard rock TBM’s
• These excavate the rocks with disc cutter mounted in the cutter head.
• It provides no shield, allowing the rock for self support.
2. Soft ground TBM’s
• In soft ground, the tunnel excavated may result in collapse due to cohesion forces.
• It provides shielding layer by stabilizing the layer using steel meshes and shotcrete.
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES
WITH DIFFERENT TUNNELLING METHODS.
17. 17
TBM Method
• Tunnelling by TBM is used for the excavation of underground openings of normally
circular shape under many types of geological condition, varying from hard rock to
very soft sedimentary layers.
• The length of the TBM used in Gotthard Base Tunnel is of four football fields and
span of TBM cutter head is of 10 meters and the ideal speed of the TBM is around
14 meters per day.
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES
WITH DIFFERENT TUNNELLING METHODS.
18. Working of TBM
• The cutter head of the TBM consists of tough iron teeth in form of
gears that rips off the rocks easily.
• Debris are collected and are passed out through the conveyor belt
behind the cutter head.
• Mechanical arm arranges protective steel mesh over the freshly
excavated surface of the tunnel.
• The robot present behind, then cements the mesh with shotcrete.
• Hydraulic fleets shunt the machine to move forward.
• Later, the workers lay concrete platform for road/railway purposes.
18
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES
WITH DIFFERENT TUNNELLING METHODS.
19. 19
1. Gotthard Base Tunnel
• It was the tunnel built across the Alps mountain Range in
Switzerland with total length of 57 Km (longest railway tunnel).
Case studies
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES WITH
DIFFERENT TUNNELLING METHODS.
20. 20
• Two methods were used in the construction of Gotthard tunnel
1. Conventional Method (35%)
2. Tunnel Boring Machine (TBM) Method (65%)
Source:- Ehrbar, H. n.d. Gotthard Base Tunnel, Switzerland, experiences with different tunneling methods GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES WITH
DIFFERENT TUNNELLING METHODS.
21. 21
2. Bolu Tunnel
• Bolu Tunnel was built across the Mount Bolu in Turkey with the length
of 3.1 kilometers used for road ways.
• It was built by using NATM (New Austrian Tunneling Method).
• NATM is not a tunneling method, but an approach covering all general
principles of tunneling.
• Based on the principle, it is to maximize the capacity of ground to
sustain its own weight and balancing of overburden pressures.
Source:- Aygar, E. B. 2020. “Evaluation of new Austrian tunnelling method applied to Bolu tunnel’s weak rocks.” Journal of Rock Mechanics and
Geotechnical Engineering, 12 (3): 541–556. Chinese Academy of Sciences. https://doi.org/10.1016/j.jrmge.2019.12.011.
22. 22
Source:- Aygar, E. B. 2020. “Evaluation of new Austrian tunnelling method applied to Bolu tunnel’s weak rocks.” Journal of Rock Mechanics and Geotechnical
Engineering, 12 (3): 541–556. Chinese Academy of Sciences. https://doi.org/10.1016/j.jrmge.2019.12.011.
23. 23
Conclusion
• In areas where the available space for constructing transportation structures is
scarce, we can go with tunnels for effective utilization of space (urban places).
• Sometimes it is better to use mixture of construction methods to construct the
tunnels in the point of economical view.
• The application of tunnels in our life is quite often for the utility pipes (sewage,
gas pipes), hence new technologies should be developed to ease the construction
pace at small scale works also.
24. 24
References
• Mobaraki, B., and M. Vaghefi. 2015. “Numerical study of the depth and cross-sectional shape of tunnel
under surface explosion.” Tunnelling and Underground Space Technology, 47: 114–122. Elsevier Ltd.
• Li, J. C., H. B. Li, G. W. Ma, and Y. X. Zhou. 2013. “Assessment of underground tunnel stability to
adjacent tunnel explosion.” Tunnelling and Underground Space Technology, 35: 227–234.
• Porras-Amores, C., F. R. Mazarrón, I. Cañas, and P. Villoría Sáez. 2019. “Natural ventilation analysis in an
underground construction: CFD simulation and experimental validation.” Tunnelling and Underground
Space Technology, 90: 162–173. Elsevier Ltd.
• Flammability Testing of Materials Used in Construction, Transport and Mining 2006, Pages 231-274
• Ehrbar, H. n.d. Gotthard Base Tunnel, Swizerland, experiences with different tunneling methods
GOTTHARD BASE TUNNEL, SWITZERLAND EXPERIENCES WITH DIFFERENT TUNNELLING METHODS.
• Aygar, E. B. 2020. “Evaluation of new Austrian tunnelling method applied to Bolu tunnel’s weak rocks.”
Journal of Rock Mechanics and Geotechnical Engineering, 12 (3): 541–556. Chinese Academy of
Sciences.
