Tunnelling
Introduction
&
Survey
HISTORY OF TUNNELLING
• Earlier history is traced through mining
started prior to 2000 BC
• Ancient tunnels were built for water supply
and escape route from Forts during wars
• Pioneer tunnel of canal age constructed in
1666-81 to connect Atlantic to Mediterranean
– Use of gun powder first time
• Due to importance of Water transport, canal
system developed in England & other
countries in 18th Century leading to
construction of no. of tunnels
HISTORY OF TUNNELLING (cont…)
• Brunel’s Thames Tunnel was constructed
between canal age and Railway age using
shield
• Enormous spread of Railways in Great
Britain in 19th Century brought no. of
tunnels.
• Alpine Railway tunnels between North
Europe & Italy involves new development
in drilling equipment and explosives
• Due to requirement of speedy construction
in longer tunnels/safety requirements
T.B.M. were developed which does not
involve normal drilling blasting.
PRIMARY FACTORS IN SELECTION
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Location/site of stations
Parameters of curve and gradient
Length of line
Balancing E/Work in Cutting & Bank
Stable sites for viaducts/Tunnels.
REQUIREMENT OF RAILWAY TUNNELS
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Tunnel cross-section
Drainage
Safety from loose falls
Refugis Trolley/Man
Ventilation
Lighting
TUNNEL CROSS SECTION
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Utility
SOD
Type of Rock/Soil
Method of Tunneling
Standardisation
SURVEYING
• Geological Investigation recommended at
preliminary survey stage itself.
• Geological Investigation
– Surface Mapping
– Electroresistivity tests
• Aerial Photogrammetry and Satellite
Images are recommended for Major
Projects
GEOTECHNICAL INFORMATION
REQUIRED
1) Geological Description with details of
lithology and variability
2) Location and Orientation of discontinuities
and planes of weakness
w.r.t. TUNNEL EXCAVATION
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BEDDING PLANES
JOINTS
FAULT/FOLDS
SHEAR ZONES
3) In Situ Stress
4) Geomechanical properties
5) Ground water
ROCK QUALITY DESIGNATION (RQD)
(BY DEERE 1964)
• RQD
(Percent)
Quantative
< 25
Very Poor
25-50
Poor
50-75
Fair
75-90
Good
90-100
Excellent
2.16” Dia double barrel diamond drill
equipment
ROCK QUALITY DESIGNATION (RQD)
(BY DEERE 1964) CONT….
• QUICK INEXPENSIVE
LIMITATIONS: By disregarding
- Jt. Orientation
- Tightness
- Gouge material
Topographical survey
• Initial corridors on maps 1:50,000 or 1:25,000
• Confirmation on maps 1:10,000 or 1:5,000
Ground survey
• Setting out alignment on ground
• Establishing relationship – Network
– Triangulation
– Traversing
– Trilateration
– Accuracy For short drives 1in 20,000 equals to 10 sec
– Accuracy For long drives & higher precision 1in
2,00,000
• Can be achieved with 1 sec theodolite but practically only 1 in
60,000 possible
Ground survey
• Levelling
– Accuracy of 2mm / Km
– Closing error of 3mm over 1 Km
– For large circuits square root of number of sights
– Back sight & Fore sight should be equal & of
moderate length i.e. not more than 35 m.
– Both scale of staff should be checked with
accuracy of 0.15 mm
Setting out & Control
• Setting out Base line at each working face
• Underground Survey
– Horizontal Alignment
– Vertical Alignment
Control of Tunnel Drive
• Initial survey for Setting out
• Primary control Survey
• Face control
– Control points at every 500 m & 100 m
Tunnel Profiling Methodes
• Regular spaced cross sections are taken
• Information is used for
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Estimation of clearances
Checking alignments
Determination of volumes of excavation
Determination of lining materials
Compilation of inventories and “As built”
drawings
– Monitoring changes
– Monitoring progress of projects
– Indication of structural failures
• Methods of tunnel profiling
– Contact methods
– Non-contact methods
• Manual
• automatic
• Contact methods
– Probe and proctor method
– Finger probe method
– Tape extensometers method
• Non-contact methods (manual)
– Theodolite / EDM Tachometer
– Optical Tachometer
– Laser Tachometer
– Photogrammetry
• Mono / stereo
– Light sectioning
• Non-contact methods (automatic)
– Reflectorless EDM
– Automated theodolites
– Railway gauging train
Light sectioning
Light sectioning cont.
• The light sectioning
method was developed
to quantify the
volumes of rock
involved. The
method makes use of a
radially projected then
beam of light.
Light sectioning cont.
• When projected in a
tunnel, and imaged
from a distance, the
beams highlights the
profile of this drift in a
Canadian mine.
Light sectioning cont.
• Image processing
techniques can be used
to calculate the
volume of excavated
material
Light sectioning cont.
• Image processing
techniques can be used to
measure overbreak, as in
this example from the
Mexican tunnels. The
measured tunnel profile is
overlain onto the design
profile. Overbreak (blue)
and underbreak (yellow)
are defined outside of the
of the specified tolerance
(green) of the design..
Reflectorless EDM
Major features
• Coaxial focusing system reflectorless EDM
• High-precision ±(5+3ppm x D)mm
reflectorless EDM
• 0.5 sec. high-speed tracking measurement
time
• Can be used with standard prisms and
reflector sheets
• Long distance measurement possible
(5km/16,400 ft. for a single prism)
• Offers powerful DTM-350 features, suitable
for a wide variety of surveying applications:
• Superior function on-board data recording
system (with 5,000-point data memory)
• Light, compact design
THANKS