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NEELUM JHELUM HYDROELECTRIC PROJECT

JANDARBAIN NULLAH/ MAJHOI

By ATIF RAFIQ

ON GOING ACTIVITIES: Drill and Blast

Grouting

TBM

Lining & Invert Concreting

Above Ground Activities

NEELUM JHELUM HYDROELECTRIC PROJECT

Excavation and support work is being carried out in a

cycle of following activities:

Survey

Drilling for blast

Charging

Blasting

Ventilation

Mucking

Scaling

Mapping

Rock Mass Categorization

Support work and Fixtures Installation

1st Layer Shotcrete

Rock Bolts (Fully Grouted Dowels, Swellex,

Anchor bolts)

2nd Layer of Shotcrete

TUNNEL EXCAVATION AND SUPPORT SYSTEM

SURVEY

Marking points around the face periphery to

keep the tunnel aligned as per designed

elevation and coordinates using surveying

equipment.


DRILLING FOR BLAST Drilling for blast is done with hand held air pusher leg drill

or drilling jumbo machine 2~4 m deep inside tunnel face

according to engineer s’ approved blast design.


Drilling with

CHARGING AND BLAST It involves charging of explosive cartridge inside cleaned

drilled holes and firing with NONEL ( Non Electric)

method.


Explosive Cartridge

Detonating

Cord

VENTILATION

Dilution of dust ,noxious fumes and toxic gases

produced after blast is carried out by ventilation

system.


MUCKNG OF BLASTED MATERIAL

Mucking involves transportation of blasted

material in dumping truck after loading with loader

toward spoil deposit.


SCALING

Scaling is the removal of loose rock parts

mechanically & manually by excavator bucket ,

jack hammer and scaling bar.


7-GEOLOGICAL MAPPING

Geological Mapping is an important component during

tunnel excavation. The discontinuities (bedding & major

joints , joints sets ,fault , shears etc. and lithological

contacts) and lithology from exposed faces, crown ,

walls are mapped and supports recommendation are

made after evaluation of rock mass characteristics

using Q – system.


SPECIMEN OF GEOLOGICAL MAPPING OF

EXCAVATED FACE OF TUNNEL

Rock Mass Quality Classification:

During excavation of rock, a rock mass quality

classification will be performed by the engineer/Geologist

after each blast. To facilitate the work the rock mass

quality will be grouped into five classes, Q1 – Q5 as

defined.

Q1 “Very Good” (Q > 40) : Massive to low joint frequency, Jv < 5/m², tight

joints, unaltered strong rock and insignificant stress

slabbing.


Q2 “Good” (Q = 11 to 40) : Low to moderate joint frequency, 5/m² < Jv < 10/m².

Strong rock with none or Insignificant alteration and with

coating on some joints. Low to moderate stress

Slabbing.

Q3 “Fair” (Q = 5 to 10) : Moderate to high joint frequency, 10/m² < Jv <

20/m². Moderately strong to strong Rock generally with

coated joints and with some seems and some minor

weakness

Zones. The rock mass may be slightly weathered. Also

applies Q1 and Q2 class with Moderatre to high intensity

stress slabbing and to medium to low strength rock

subjected to low medium Stresses causing plastic

deformations.

Q4 “Poor” (Q = 01 to 04) : High joint frequency, Jv > 20/m², Clay seams (Fault

zones, swelling clays) in moderately strong rock. Also applies to

moderately weathered strong rock and high to very high

intensity stress stabbing in Q1 and Q2 class rock mass and to

low Strength rock subjected to medium to high stresses

causing plastic deformation.

Q5 “Extremely Poor” (Q < 01) : Completely crushed rock containing a significant

amount of secondary clay minerals as in major fault zones.

Smectite clays may lead to significant swelling and squeezing.

Also applies to highly weathered rock and to low strength rock

Mass subjected to high stresses causing plastic deformation.

In addition to the rock mass quality ( the Q-value), two other factors

are decisive for the support design in tunnels and caverns. These factors are

safety considerations and the dimensions i.e. the span width of the tunnel or

the height if the walls are being considered. Generally there will be an

increasing need for support with increasing span width and increasing wall

height. To express safety considerations, a factor called ESR ( Excavation

Support Ratio) is used.

A low ESR value indicates the need for a high level of safety while

higher values indicate that a lower level of safety will be acceptable.

A. For temporary openings, Vertical shafts ESR values are 2-5.

B. For permanent mine openings, water tunnels for hydropower (Exclude

high pressure penstocks) the ESR used is 1.6.

C. For power stations, storage rooms, railway tunnels, under ground nuclear

power stations, public facilities etc. the ESR ranges from 0.5 to 1.3.

ESR together with span width (or wall height) give the equivalent

Dimension in the following way:

Equivalent Dimension = Span width or height in m / ESR

Support work Classification

1st LAYER OF SHOTCRTE (SRF)

Spraying of 6 cm thick 1st layer of Fiber Reinforced

Shotcrete by shotcrete Jumbo / machine / robot after

flushing the surface with pressurized air and water.


DRILLING FOR ROCK BOLT

Drilling for rock bolts is being carried out with Hand Held

Air Pusher Leg Machine or Drilling Jumbo to drill holes

ф = 42 mm & 3.9 ~4.9 m long.


INSTALLATION OF ROCK BOLTS

1-Installation involves grouting of clean drilled holes with

cement –sand grout (1:1) then inserting rock bolt ф =25

mm , 4~7 m long (10 cm outside).

2- Installation of Swellex Friction Bolts in weak rockmass

with continuous water pressure at 250 bar.

3- Installation of Rock Anchor ф =32mm , 7 ~12 m long

with cement-water grout.



INSERTION OF GROUT

MATERIAL IN HOLE


INSERTION OF FULLY CEMENT

GROUTED BOLT


INSTALLATION OF ROCK ANCHOR(ANCHOR BAR)

12 m LONG


INSTALLATION OF EXPANSION

SHELL BOLT

FIXING OF WIREMESH,STEEL RIBS,LATTICE

GIRDERS

Fixing of welded wiremesh (6x100x100 mm ),

Steel ribs (distribution bar) ф=10 mm @ 40~50 cm to

keep the main bar ф =16 mm @10~20 cm in position

and Lattice Girders 1~2 m spacing.



FIXING OF WIRE

MESH


FIXING OF STEEL RIBS

DISTRIBUTION BAR MAIN BAR


FIXING OF LATTICE

GIRDERS

TIGHTENING OF ROCK BOLTS

Tightening of rock bolts is carried out after grout has

achieved 2 Mpa strength (approxi) after 6-8 hrs of

installation with specified Torque Wrench.


TIGHTENING OF ROCK BOLTS


2nd LAYER OF SHOTCRETE

Spraying of 8~10 cm thick 2nd layer of SRF ( in case of no

w/mesh , steel ribs) & plain shotcrete (in case of w/mesh

, steel ribs) with shotcrete jumbo/machine after flushing

the surface pressurized air and water.


2nd LAYER OF SHOTCRETE



Tunnel Lining under progress


TUNNEL AFTER CONCRETE LINNING

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