this presentation discusses the various monitoring and safety aspects associated with the underground structures, particularly tunnels.

1. MONITERING AND SAFETY
ASPECTS IN UNDERGROUND
STRUCTURES
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2. NECESSITYOFGEOTECHNICAL
INSTRUMENTATION
FINDING OUT THE ENGINEERING PROPERTIES OF THE
SOIL.
MODIFYING THE ENGINEERING PROPERTIES OF THE SOIL
TO THE DESIRED LEVEL.
DESIGN OF THE STRUCTURE BASED ON THE PROPERTIES.
MONITORING THE GEOTECHNICAL CONDITIONS OR
BEHAVIOR OF THE STRUCTURE DURING THE
CONSTRUCTION PROCESS.
CHANGES IN THE DESIGN BASED ON THE BEHAVIOR.
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3. IMPORTANCE OFMONITERING INSTRUMENTS
TO OBSERVE THE BEHAVIOR OF THE STRUCTURE
MONITORING INSTRUMENTS ARE REQUIRED .
INSTRUMENTATION IS A TOOL TO ASSIST WITH THESE
OBSERVATIONS. THEY ARE OUR EYES AND EARS INSIDE
THE ROCK.
INSTRUMENTATION IS USED TO MEASURE THE RESPONSE
(DEFORMATION, STRESS ETC.) OF SOIL OR ROCK TO
CHANGES IN LOADING OR SUPPORT ARRANGEMENTS,
AND FROM THE MEASUREMENTS TAKEN, THE NEED FOR
MODIFICATIONS TO THE LOADING OR SUPPORT
ARRANGEMENTS IS DETERMINED.
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4. PURPOSE OFGOOD INSTRUMENTATION
SITE INVESTIGATION.
DESIGN VERIFICATION
CONSTRUCTION CONTROL
SAFETY
LEGAL PROTECTION
PERFORMANCE
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5. SITE INVESTIGATION.
Instruments are used to characterize and determine initial site
conditions.
Common parameters of interest in a site investigation are pore
pressure, permeability of soil, slope stability etc.
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6. DESIGNVERIFICATION
Instruments are used to verify design assumptions.
Instrumentation data from the initial stage of a project may show the
need or provide the opportunity to modify the design in later stages.
For example, data obtained from NATM shotcrete cells in the initial
stretch of tunnel is used to revise the thickness of shotcrete in the
later stages.
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7. CONSTRUCTION CONTROL
Instruments are installed to monitor the effects of construction.
Instrument data helps the engineer to determine how fast construction
can proceed without adverse effects on the foundation soil and
construction materials used.
For example, in tunnel construction, the data obtained from the load
cells helps the geotechnical engineer to know if the stresses in the
excavated tunnel have been stabilized and how fast he can proceed
with further excavation.
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8. SAFETY
Instruments can provide early warning of impending failure.
In case of metro railway tunnels instruments provide early
warning through real time monitoring systems available on the
internet for any excessive and undue ground movements
affecting the adjoining premises, structure and utilities like the
railways, power lines, water lines etc.
within the zone of influence of the excavations or tunnels. This
allows for implementation of preventive remedial actions well
within time.
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9. LEGALPROTECTION
Instruments provide designers and contractors the basis of a
legal defence should resident and owners of adjacent properties
blame construction for damage to their property and life.
This aspect gains prominence in constructions in populated
areas such as for underground metro railways
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10. PERFORMANCE
Instruments are used to monitor the in-service performance of
a structure.
For example, monitoring leakage, pore water pressure and
deformation can provide an indication of the perform bolts and
movements within a tunnel can provide an indication of the
stability of tunnel.
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11. MONITERING EQUIPMENTS
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12. ROOF TO FLOOR CONVERGENCE MEASUREMENT
Used to measure deformation in tunnels by measuring contraction ( or elongation )
Procedure : Measurements are taken by simply stretching the telescopic rod
between the reference points, and reading the graduations on the rod. These
indicators are useful for understanding the roof to floor closure in the advance
galleries at various stages of extraction.
TELESCOPIC
CONVERGENCE ROD
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13. Chart Type Convergence
Recorder
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14. REMOTE CONVERGENCE
INDICATOR
• For monitoring convergence in
roof
• Sensor – Vibrating wire type or
Potentiometric type
• Needs laying of wire from
instrument location to
measurement site
• Fails immediately with the
failure of immediate roof
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15. STRATAMONITORING BYTELLTALES
• Tell tale is strata – extensometer.
• It provides pre-emptive warning of roof-falling.
• The dual-height tell tale provides an immediate visible
warning, distinguishing between movement above and below
rock-bolted height.
TYPES
• Single height tell tale
• Dual height tell tale
• Three point tell tale
• Four point tell tale
• Rotary tell tale
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16. SINGLE HEIGHTTELLTALE
• It comprises a strata movement indicator usually with color
bands and/or graduations.
• a mechanical tell tale consists of a strata movement indicator
positioned in the mouth of a drilled hole and attached to an
anchor installed up the hole
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17. Dual height tell tale
• Dual Height tell tale is
designed to be installed
for monitoring the
bolted strata.
• They have two
versions – one for dry
drill holes and the
other for watery drill
holes.
• This is designed to be
installed following the
installation of roof bolt
reinforcement.
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18. SAFETYMONITORING
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19. ACTION LEVELS
• GREEN 0 - 25 mm
• YELLOW 25 - 50 mm
• RED 50 mm +
ACTIONS
• GREEN No action required, continue routine monitoring
• YELLOW Identify height of softening [HOS].
If HOS is above bolts, install longer
reinforcement.
If below top of bolts, install additional standard
length reinforcement to increase density of
support.
• RED Restrict access.
Investigate.
Install longer reinforcement
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20. RotaryTell tale Extensometer
• It is useful where the conventional method of Roof support system is
not convenient or possible.
• Movement of the strata is indicated with a magnification of 1:15.
• It gives visual indication to a workman regarding the status of Roof
stability.
• Rapid and simple to install.
• Rotary type are useful for variable depth.
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21. MAGNETEXTENSOMETER
• The Magnet
Extensometer consists of
a series of magnets that
are installed with an
access pipe.
• The magnets are
anchored at specified
depths.
• Measurements are taken
by lowering a probe
through the access pipe
to detect the depth of the
magnets.
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22. VIBRATING WIRE LOAD CELLS
• The load cell is a transducer working
on vibrating-wire principle.
• It has three stretched wires housed in
a metal cylinder, which are plucked
by an electric pulse of high energy.
• Changes in the load exerted on the
cell cause changes in the length of the
wire, resulting in variations of
frequency of vibration of the wire.
• As the load increases the frequency
decreases accordingly and vice-versa.
• This frequency is measured by a
digital read-out unit, and is converted
into load using calibration charts.
Efficacy and adequacy of the support
system can be inferred on the basis of
these load cells.
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23. ROCKBOLTLOAD CELL
• The load cell is a transducer working on vibrating-wire
principle.
• The load cells should be installed under the roof bolts using
specially prepared steel seating arrangement .
• The load cells should be installed at the junctions to understand
the change in load over the roof bolt during the operation.
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24. Mechanical Load Cell
• Load cell consists of an elastic disc element sandwiched
between two plates.
• The disc deflects under load and changes distance between
plates.
• The deflection is measured with a dial gauge or suitable
electronic transduced.
• It has limited application due to nonlinear calibration curve
and restricted application.
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25. STRESS CELL
• Principle : These are used for measuring unidirectional stress
change in the pillar. It consists essentially of a wire tensioned
across a steel cylinder (38 mm diameter). As the stress within
the rock/coal changes, the cylinder deforms, causing tension in
the wire to change.
• Procedure : A bore hole of 38 mm diameter is required for
installing the stress meters, preferably at mid height of the
pillar either horizontally or slightly rising/dipping according to
dip of the seam. The stress meter along with wedge and platen
assembly is set in the borehole with the help of special
installation tools, at a depth of about 4 to 9 m.
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26. Safety aspects
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27. Scope and application
The rule applies to construction of underground tunnels, shafts,
chambers, and passageways. It also applies to cut-and-cover
excavations, both those physically connected to tunnels and those that
create conditions characteristic of underground construction. Hazards
common to such work include reduced natural ventilation and light,
difficult or limited access and egress, exposure to air contaminants,
fire, and explosion
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28. Provisions of the
standard
• The standard gives employers the flexibility to select from a variety
of appropriate and effective methods of controlling workplace
hazards
• In underground construction. It includes a safety program focusing
on instructing workers in topics appropriate to specific jobsites
• And it gives specific duties and responsibilities to a “competent
person.”
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29. Competent person
• A “competent person” is one capable of identifying existing and
predictable workplace hazards who is authorized to take corrective
• action to eliminate them
• Duties of competent person
• Monitoring air
• Inspecting the work area for ground stability
• Inspecting all drilling equipment prior to each use
• Inspecting hauling equipment before each shift and visually
checking all hoisting machinery, equipment, anchorages, and rope at
the beginning of each shift and during hoisting
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30. Safety instruction
• Employers must ensure that workers are instructed on
the recognition
• and avoidance of hazards associated with underground
construction.
• Instruction must include the following topics that are
appropriate to
• each jobsite:
• Air monitoring
• Ventilation and illumination
• Communications
• Flood control
• Mechanical and personal protective equipment
• Explosives: fire prevention and protection
• Emergency procedures: evacuation plans and check-
in/check- out procedures
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31. Access and egress
• Employers must provide safe access to and egress from all
workstations and prevent unauthorized underground entry. Completed
• Unused sections of an underground work area must be barricaded.
• Unused openings must be covered, fenced off, or posted with warning
• signs indicating “Keep Out” or other appropriate language
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32. Check-in/check-out
• Employers must maintain a check-in/check-out procedure that
ensures above-ground personnel can maintain an accurate
count of people who are underground, in case of an
emergency. At least one
• Designated person must be on duty at the surface whenever
anyone is working underground. That person is responsible for
securing
• Immediate aid in case of an emergency
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33. Gassy operations
• • Using more-stringent ventilation requirements
• • Using only diesel equipment approved for use in gassy operations
• • Posting each entrance with warning signs and prohibiting smoking
and personal sources of ignition
• • Maintaining a fire watch when hot work is performed
• • Suspending all operations in the affected area until all special
requirements are met or the operation is declassified
• Additional air monitoring is also required during gassy conditions
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34. SPECIALAIRMONITORING
REQUIREMENTS
• The employer must assign a "competent person" to perform air
monitoring. If this individual determines that air contaminants may
present a danger to life at any time, the employer must
immediately take all necessary precautions and post a notice at all
entrances to the underground site about the hazardous condition
and his responsible for checking air quality
test for oxygen first
testing for methane and other flammable gases
hydrogen sulfide levels
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35. Illumination
• As in all construction operations, the rule requires that proper
illumination be provided during tunneling operations, as
specified
• When explosives are being handled, acceptable portable
lighting equipment must be used within 50 feet of any
underground heading
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36. Fire prevention and control
• open flames and fires are prohibited in all underground
construction activities, except for hot-work operations.
• Smoking is allowed only in areas free of fire and explosion hazards.
• Employers must post signs prohibiting smoking and open flames
where such hazards exist
• Gases such as acetylene, liquefied petroleum, and methyl acetylene
propadiene (stabilized), may be used underground only for hot-
work operations.
• Leaks and spills of flammable or combustible fluids must be cleaned
up immediately.
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37. Safety provisions
• —IS: 4756:- 1978 – Safety Code for Tunnelling work
• —IS: 3764 –1966 – Safety Code for Excavation work
• —IS: 4081-1986 – Safety Code for Blasting and Related drilling
operations
• —IS: 4138-1977 – Safety Code for Working on Compressed Air
• —IS: 7293-1974 – Safety Code for Working with Construction
Machinery
• —IS: 5878 (Various parts) – Codes of practices relating to
tunnelling and underground excavations
• —Indian Explosive Act -1988
• —Indian Explosive Rules -1983
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38. Lighting:
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39. • Minimum 50 lux at headings during drilling, mucking 70 m.
and scaling.
• Minimum 30 lux for trolley track working area.
• Minimum 10 lux for other areas inside the tunnel or on
approach cut/roads.
• Emergency lights (battery operated) at the working faces and
at regular interval along the tunnel.
• Proper earthling and grounding of all electrical apparatus.
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40. Medical facilities:
• First Aid box with experienced first aid attendant with his
distinguishing badge on each shift.
• Stretchers in every shift at portal.
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41. Protective wear:
• Helmet, steel tow safety shop, gum boots for each worker.
• Sign boards 1x1.5m in size to be displayed at the approach
“Construction AREA, HELMET required beyond this point”
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42. Notices and signs:
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43. Telephone System:
• For communication between control locations inside tunnel
and portal (when more than 500m)
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44. Ventilation
• Essential to make working space safe for workers by keeping
the air fresh and repairable and by eliminating harmful and
obnoxious dust, dynamite fumes and other gases. Mechanical
ventilation must be used for long tunnels.
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45. • It is essential to ensure
• Temp < 40 C dry and < 29 C wet at the working place.
• Concentration of gases in side the tunnel by volume
a) Oxygen not less than 19.5%
b) Carbon monoxide not more than 0.005%
c) Carbon Dioxide not more than 0.5%
d) Hydrogen Sulphide not more than 0.001%
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46. Sanitation and Drinking
Water
• Sanitation - Unless the worksite is within 500 m of the portal of
the tunnel, sanitation facilities shall be provided close by.
• Drinking Water- Drinking water, at least 5 litre per person
employed in the shift, shall he provided near the portal and
also inside the longer tunnels.
• Washing and cleaning facilities shall be provided for all
workers near the portal.
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47. Risk register
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48. Emergency Planning &
Mitigation of Risk
• to ensure safety of tunnel workers and other stakeholders
• A culture of safety can be enhanced by in-house training,
communication through toolbox meetings and display of
procedures and escape plans on notice boards.
• table top exercise and regular drills shall be conducted once in
every six months.
• Accountability for safety performance must be appropriately
allocated through the entire safety management process, in
particular to the emergency plan
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51. Safety measures for blasting
• Based on IS :4081- 1986.
• No metals except approved metal truck bodies shall be
allowed to come in contact with cases of explosives.
• Blasting caps, electric blasting caps or primers shall not be
stored in the same box, container or room with other
explosives.
• Smoking shall be prohibited in the storage area of explosives
and in its vicinity.
• Packages containing explosives shall not be allowed to remain
in the sun.
• Explosives shall not be carried in the pockets or folds of
clothing by any person.
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52. • All electrical wiring and equipment of storage area shall be
adequately insulated and protected against mechanical
damage to prevent short-circuiting.
• Children and unauthorized or unnecessary persons shall not
be present where explosives are being handled or used.
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53. Safety measures for drilling
• No drilling shall be started until previous holes in the blasted
area are flushed with air and water.
• While planning drilling operations for blasting purposes,
consideration must be given to the nature of stratum and the
overburden with a view to avoiding the possibilities of land-
slides after blasting.
• The position of all holes to be drilled shall be marked out with
white paint.
• The face of rock shall be carefully examined before drilling, to
determine the possible presence of unfired explosive.
• The diameter of the bore of each hole shall be greater than
the outside diameter of the cartridges of explosive.
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54. • explosives shall not be forced down a bore hole or on
obstruction in a bore hole.
• A bore hole near another hole loaded with explosives shall
not be sprung.
• No holes shall be loaded except those to be fired on the next
round of blasting and after blasting.
• Drilling shall not be resumed after blasts have been fired until
a thorough examination has been made.
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