Indian National Committee on Large Dams. Design and Construction Features of Selected Dams in India

FIGURE

l8:

Photograph

showing

the

view

of

the

completed

tunnel

with

lining

etc.

curved

segments

were

fixed,

as

the

excavation

proceed_

ed,

and

a

little

extra

excavation

was

done

at

the

footings

9f

this partial

rib. Wti.n

u

reach

of

about

lJlt

ts-0

ft)

was

ready.-ir

was

i-;.ai;;iy

-"o.,.r"t.

rneo

wrth

oumpcrete.

under

the

protection

of

this

457.20

mm

i

eog.O0

;-

(lS;

.x24

in.)

thick

concrete

arch,

furrher

excavarion

*u,

ca.riea

;;;,;;il;-

ipto

tt,.

invert.

.

Liniyg

of-the

Tunnels:

Concreting

of

the

arch

was

done rvith

the

help

of

pumpcrere-s

using

3g

mm (lf

in.)

maximum

:lzg

aggregate.

The

,tdogtn

-oi

the

concrete

was

219.8q

kgpersq

cm

(3000"pound

per

sq in.).

concrete

in

the

r=nvert

*ut

piacecl

i,itr,

maxi-

mum

aggregate

of

76.2

mrn (3

in.)

(frigure

tg).

3.2

Diversion

of

the

River

-

The

diversion

of

the

suttej

River

was

undertaken

immediately

afrer

the

rainy'r.uron

of

1954,

i.e.,

in

44

September-October

lg54

in

low

water.

Large

quan-

tities

of

excavated

materiars,

consisting

oJ ri.t

and

e,arth,

\,vere

lying

on

both

rid",

of

the

river

and

at

tne

oqportune

time

the

muck

rvas

buil-dozed

into

the

river

frorn

both

the

banks

and

the

river

brocked

across.

As

the,gap

started

narrowing

down.

tfre

no*;;;

olverreo

towards

the

two

tunners.

The

top

of

this

initial

bund

or

the

.pilot

Coffer

dam,

lvas

kept

9!ly

a

few

feet

above

the

water_lerjel,

i.e.,

about

El. 356.62

m

grl70

ft).

It

was,

then raised

and

strengthened

to,El.

365.76

m

(1200

ft).

fo

.ri;ri

wirtr,

there was

considera_bre

r..pug.

through'-trris-

emuant<-

ment.

This

was

checked

^by"

dumpiig

clay

over

the

upstream

slope

and

by.placing_earrhfil[d

girnny

bags

at

the dorvnstream

toe

lFigurJD).

A

f;;'

ffi;i

were

also

improvised

-to

gaitrel

this

seepage

in

order

to

have

a

dry

area

in

the

location

of

ttri-trench-L*.uuu-

t19lt

required

for

the

core

of

the

main

.ofl..

dam.

This pilot

bund

,ltimatery

formed p"it

or iLL

main

coffer

dam's

rockfiil

zone.

A

similaf

tr";

uuoa

,u,

*1i,;iFi

*H

FIGURE

19

: Photograph

showing

the

vierv

of upstream

coffer

dam under

construction.

also

put

in

at the

downstream

end of

the

dam area

near

the

tunnel

outlets

so

as

not

to allorv

anv

back-

water

into

the

working pit.

Thus, the

entire

area

required

was

enclosed,

and

excavations for

the two

coffer

dam

key

trenches

were

started at

both

the

sites

simultaneously.

The water

seeping

into

the

area from

both

the upstream

and

downstream

bunds

was

handled

expeditiously by

having

two

local

open

pits

in the

river bed

which r,vere

always

being

dredged

out to

keep

them

a ferv

feet lower than

the

rest

of the area

under excavation.

Thus,

all

surface

and sub-surface

water

got

collected

in

these sumps

and rvas pumped

out

continuously.

About 0.57

cumecs

(20

cusecs)

of

continuousipumping

was required

at this

stage

oi

the

rvork.

The

main

coffer

dams were

constructed

with

all

the

care

TQuired

for

a

rockfill

dam

and rvere

comple-

ted

to full

heighrs

before

the

monsoons

of 1955

(Figure

20).

3.3

Excrvation

for

the

Dam

and

the

Left

power

House

A

total

of about

seven

to

eight million

cu

nr

(ten

million

cu

yd)

of excavation

was

involved

in

the

construction

of

the

dam

and

appurtenant

rvorks.

In

November

1954,,

the

Sutlej

Rivef

was

diverted

through

the

right

tunnel. Before

this,

excavation

for

the

dan-r

had been

necessarily

restricted

to stripping

the

canyon walls.

Stripping

of

the left

abutm6nt

was

45

FIGURE

20

:

Photograph

showing the

view

of

coffer

iam

completed.

started

in

November

1953,

and that of

the

right

abutlnent

in

May

1954.

On

both

abutments,

hydrarllic

sluicing

was

don-e

to clear the

canyon

wafli

of over-

burden

and

loose

rock. Water

irom

the river

was

p.lT-peq.by

high-pressure

pumps

to

above El.

457.21

m

(1,500

f0

and

then

diretted-

onto

the

overburden

under

-a -pressure

of

21.09 kg

per

sq cm

(300 p.s.i.)

t$rough

hydraulic

monitors.

The

high-pressure

jet

sluiced

considerable

amount

of

loose-miterial

down

the

canyon

slopes

and into

the

river below, whence

it

was

washed

away

by

high

floods.

Sp^ecial

blasting gelatin,

75

percent

strength,

was

used

for

excavation.

-Ttre

varioui

rows

of

ho-les were

delayed

by

millisecond

detonators

so that

the

rolvs

will

follow

one

another

and

the

sound

rock

will

not

be

disturbed.

At

the

peak

of

excavation,

l

power

shovels with

46

?

total.capugitl

-of

30

dipper

yards

were

employed

tor

loading

the

blasted

rock

into

a

total

of 4i

eno-

d.grp

trucks

-

20

of

20.3

tonnes

(20

tons)

capa_

city

and

27

of

15.2

tonnes (15

tons)'

.apaciiv.

The

muck

was

hauled

for

about

t.bt trn

(oo.'*it.)

along

the

river

and

spread

there

by bulldozeis.

The

excavation

of

the

upstream

clay

band posed

special

problems.

F9r

the

safety

and the

ituuitity

or

tn.

dam the

up-stream

c-lay

band,

a-bout

30

m

(gg.4i0

*iJ",

had

to

!e

dugout

down

to,a

depth

of

60 m

tf

g6.S

fti

below

the

river

bund

(see

section

of the

oamj.

As the

sandstone

was

dippirig

downstream,

the

sandstone

bands would

sag

ana

iollapse

as

soon

as

the

cray

stone

support

was

removed.

To

overcome

this

diffi--

991!I

excavation

was

done

for

a depth

of

about

18.29

m-

(60

ft)

and backfilled

with

conlrete.

Harches

were

left

at

convenient

intervals

in

the

concrete.

Balance

of

the

excavation

was

done

through

these

FTGURE

2l

(a)

: Photograph

showing

the

view

of

cement

unloading

shed.

hatches

by

mining

methods

and

cavities

were

backfilled

with

concrete.

ftre

work

was

very

difficuit

and

had

to^

be

completed

in

a

few

monthi

before

the

onset

of

the

monioon.

3.4

Excavation

of

penstock

Tunnels

iameter

6.10

m

(20

ft)

were

,

sccornffiodate

the

4.57

m

liners

leaving

a space

ofl

lund

for

concrete

encase-

with

their

centre

line

at

stream

were

raid

r,oriro'fi;'"i#":fir?''n:,l3:l;

and

thereafter

i_nclined

suitably

to

reach

the centre

line

elevation

of

428.24

nr

1r,405

rt)

aoove

-.un sea

level

at

the

upsrream

end'

at

the

axis

or inl dam.

9pfl

cut

excavation

rvas

done

upto

elevation

352.04 m

(1,155

ft)

above

mean

sea levei

near

the

do*nrtr.u-

portal

of

the

tunnels,

before

the

actual

excavation

for

boring

the

tunnels

was

started.

Full

face-.*"uuu-

tion

*'as

done

i'the

entire

horrzontar

porti"n

leaving

3.5

Cement

Handling

and

Storage

47

FIGURE

2l

(b)

:

Photograph

showing

cement

storage

silos.

about

457.20

m

(

1,500

ft) downstream

of the

dam

site.

The

cement

handling

system

consisted

of

four

operations

:

(l)

Pumping

of

cement

from

collecting

hoppers

to

storage

silos

at elevation

396.24 rrr(1,300

ft)

above

mean

sea level.

48

(2)

Conveyance

of

cement

from

storage

silos

to

the

transfer

silos

at

elevation

457.20"m

(1,500

ft)

above

mean

sea

level.

(3)

Feeding

of the

first

stage

and

second

stage

batching

and

mixing

planti

frorn

this

transfir

silo.

(4)

Cement

refining

air

separator

plant.

The

structural

parts

of

the

prant

were

locaily

fabricated.

There

weie

six

cernent

storage

silos

eabh

of

5,000

barrel

.

cap-acity

(a

barrer

is

."quui

to

375

pounds

or

170.10

kilograms).

The

.quip-ent

was

designed

ro

handle

32i

B.B.L.

per

hour.

The

rift

flom.storage

silos

to

transfer

silo

hid

been

so

arranged

that

it

u'as practically

the

same

as

from

trunif.,

silo

to

s.econd

srage

batching

and

mixing

plant.

The pumps

qg

the

unloading

docks

iould

pu*p'

in.

..-"ri

ro

a

distance

of 243.84

m

(800

ft)

rvhereas

those

at

storage

gilqr

could

do

so

up

to

a

distance

of

5lg.t6 m

(1,700

ft).

The pipe

iines

from

the unloading

docks

to

the

six

storage

silos

were provided

with

two-way

diverting

valves

1nd so laid

ttrat

cement

could bi

pumped

to

any

one of the six

silos.

storage

silos.

power.

3.6

Aggregate

Recovery

The

main

sources

of

aggregates

were

deposits

at

Neilla

and Fatehwal,

situated

5 and

g

km

downstream

of

the

dam

respectively.

The

Fatehwal

deposits

had

thick

beds

of

aggregare,

which

were

excavated

up

to

depths

of

7.6

i\25

ftl,

some

of

it

under

water.

Ma-ximum

size

of coarse

^ ^Jh"

aggregate

at

Fatehwal

was

recovered

by one

3.82

cu

m

(5

cu

yd)

electric

shovel

and

two

l.9l

cu

m

(2+

cu

yd)

draglines

for

excavation

under

water.

At

Neilla

,!. proccdure

for

ag_qregate

recovery

was

similar

to

that

at Fatehwal.

The

equipment

con-

sisted

of

one

2.68

cu

m

(3+

cu

yd)

shovel'and

one

2.29

cu

m

(3

cu

yd)

dragline.

. _A_egregate

from

the

surge

pile

at Fatehwal,

or

right

bank

of

the

river

*as

first

conveved

to

the

49

TIT-

'-

-rl:r*=:::-:

-T---

-.

:i.,,lT:,,

FTGURE

22

: view

of

bert conveyor

system

at

Neilla

showing

scalping plant,

etc.

50

Belt

conveyors

were

widely

used

at

Bhakra

Dam

on

account

of

the

huge

quantity

of

material

to

bi

handled,

the

rugge.d-

-terrain,

tle

limitid

working

area,

and

the

considerabre

difference

in

elevatioi

l-.,ly:r:r

the.aSqregate.

quarry

and

the

batching

and

mlxrng plant.

For

these

reasons

conveyors

were

the most

efficient

and

economicar

-.ittoo'

oi

t.urrr-

portation.

In

order

to

-avoid

interruption

in

concrete

produc-

tion

a

stock

of

about

152,916

cu

m

tZOO,00dcu

Vd)

of raw

ag€regate

was

maintained

near

in. ti""r.-ouinp

hopper.

The

material

from

this

,to.t

;;;

drawn

gnly

when

it

was

lot

possible

to t

aut

u!gr.gu,.

ftgf

long

9_istances-

during

the

heavy

-onr"oi'r.

One

1.91

cu

m

(28

cu

yd)

shovil

was

assigh.O

ioit

ir

u.ru.

TABLE

I

Conveyor

No.

Max.

Lump

Size mm

(in.)

Belt

width

mm

(in.)

Capacity

Tonnes

(Tons)

per

hour

Speed

metres.(ft)

per

mln.

Horizontal

length

metres

(ft)

Max.

lift

metres

(ft)

approx.

l.

2.

2A,.

3.

4.

5.

6.

7.

8.

9.

+

177.8

(+21

+

177.8

(+21

+

177.8

(+t1

r77.8

(7)

177.8

(7)

177.8

(7)

177.8

(7)

r77.8

(7)

177.8

(7)

l9.l

(314)

177.9

(7)

t77.8

(7)

177.8

(7)

177.8

(7)

r77.8

(7)

t77.8

(7)

177.8

(7)

r77.8

(7)

177.8

.

(7)

r77.8

(7)

177.8

(7)

177.8

(7)

1066.8

(42)

1066.8

(42)

762

(30)

762

(30)

762

(30)

762

(30)

762

(30)

762

(30)

762

(30)

762

(30)

762

(30)

914

(36)

914

(36)

914

(36)

9t4

(36)

914

(36)

9t4

(36)

914

(36)

914

(36)

914

(36)

914

(36)

1066.8

(42)

914.3

(e0o)

914.3

(e0o)

76.2

(7s)

609.6

(600)

609.6

(600)

609.6

(600)

609.6

(600)

609.6

(600)

609.6

(600)

304,9

(300)

507.9

(sOo)

763.9

(750)

763.9

(7s0)

763.9

(7s0)

763.9

(7s0)

763.9

(750)

763.9

(7so)

763.9

(750)

'763.9

(750)

763.9

(750)

763.9

(750)

965.0

(es0)

t3l.l

(430)

|

3l.l

(430)

76.2

(250)

r49.3

(4e0)

r49.3

(4e0)

r43.3

(470)

149.3

(4eo)

155.4

(sl0)

143.3

(470)

82.3

(27o)

r34.1

-(440)

146.3

(480)

r49.3

(4e0)

r52.4

(500)

146.3

(480)

|

43.3

(47o)

149.3

(4eo)

149.3

(4eo)

r49.3

(4e0)

149.3

(4eo)

146.3

(480)

152.4

(s00)

209.7

(688)

I

15.8

(380)

100.6

(330)

505.4

(16s8)

580.9

(te06)

336.8

(r

r05)

6rt.4

(2006)

88.4

(2e0)

71.6

(23s)

4g.g

(160)

100.6

(330)

367.6

(r206)

234.1

(768)

877.2

(2878)

605.3

(1e86)

t

95.1

(640)

224.9

(738)

9r.4

(

+

rool

195

(

+

64r)

76.2

(

+

2so)

76.2

(

+

zso;

r82.9

(600)

+

28.9

(*

Ps)

29.6

(e7)

r2.2

(40)

-

4;6

(-

t5)

2.4

(8)

-

5.2

(

--

17)

7.9

(26)

17.7

(56)

l

g.0

(5e)

I1.9

(3e)

25.9

(8s)

2r.3

(70)

36.3

(l

le)

-

42.7

(

-

t40)

10.1

(33)

I

r.0

(36)

3l.I

(102)

r0.7

(35)

42.4

(13e)

_

5.8

(_le)

l7.l

(56)

32.0

(105)

10.

11.

12.

13.

t4.

15.

r6.

t7.

17

A.

l7B.

18.

19.

5l

----

FIGURE

23:

Photograph

showing

the

general

view

of

aggregate

classification

plant

at

Bhakra.

3.7

Aggregate

Classification

and

processing

plant

Tl:

:r::,ing

point

of

classificarion

plant

operarion

was

20,320

ronnes

(20,000

tons)

fiu,i

iiorug'.

,r.g.

52

pile

which

received

raw

aggregate

from

Fatehwar

and

Neilla

through

g63.6

tJf;rr.'r.

(SS!

tonrl'-Ol,

hour,

:d

earlier..

The

surge'pile

*uJ

ression-

whereas

the

a'a;oiniog

ty

457

.20

m

(

1,500

ft)

Iong

and

to

200

ft)

wide

iocatdd

at

00

ft)

above

mean

sea

level

:enins

plant,

classified

aggre-

gate

storage.

piles.

and

sand

piies,

etc.

The

rvorking

of

plant

rvas

divid.l

jlto^rwo'

operarions

fil

eggregare

_

classification,

and (ii)

Sand.Lu'riin.utl;"..'r

'Lt

A

ggrega

te

Cl

as

sificatio

n

was

reclaimed

Ay a-TSAS.ZS

1,066.8

mm

(42

in.)

wide

b

was fed

by

trvo

1,066.g

mm

electro-ma_enetic

vibratir

remote-controlled

from

the

contror

centre

rocated

near

the.top

o-f

the

screen

house.

The

;;;;.)^;;"\o.

tg

discharged

into

a

20.32

tonnes

(r0

i";;i,

.lp"u"itv

surse

$.

ii+,.*

FIGURE 24

:

Photograph

shouing the view

of aggregate;classification plant.

bin

rvhich

helped

in regulating

feed to the

screens.

Under

the

surge bin were

two

vibrating

feeders of

the

same

type

as installed

in the

reclamation

tunnel

under

surge

pile

described

above.

These

feeders

regulated

the

feed

to

1.83

mx 3.66

m

(6

ftx 12

ft)

vibrating

screens

(Nos.

I

and 2)

each

of

which

was

with

double

deck

having

76.2mm (3

in.) square

openings

on

top deck

and 38.1

mrn

(

l*

in.)

square openings

on

the botrom

deck.

These

decks

respectivety

*aihed

and separated

177.80

mm-76.20

mm

(7

in. 3

in.) and

76.20

mm-

38.10

mm

(3

in.-

l$

in.)

gravels.

The

classified material

bottom

deck

19.05 mm-4.76

mm

(3i

4

in.-3l

l6

in.)

Screens

: The

screens were

of

suspended

type with

inclinatiorr

kept

adjusted

to

around

20o

-to

give

optimum

.screening_

efficiency,

i.e.,

maximum

output

with

minimum

undersize

going

with

the

retained

material.

All these screens were

for wet

screening

and

spray

bars

were

fixed on

both

the

decks.

Watei

was

sprayed

at

pressure

of

3.52

kg/cm2 (50

lblsq

in.)

and

bronze deflectors were

used

for

breaking

the

u'ater

into

a

powerfu!

spray.

It

was

noticed

that

the

classified aggregate,

especially the bigger sizes

broke

into

smaller

sizes

due

to fall from the belt

conveyor

to the

piles.

Rock

ladders

were,

therefore,

provided

for all sizes

except

pea

_sravel

19.05 mm

to

4.76

mm

Qla

h.

to 3/16 in.).-

53

Indian National Committee on Large Dams. Design and Construction Features of Selected Dams in India

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