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

96

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right

side non-overflow

dam.

y

of 9 vents

of

size 3.05

m x

ft)

designed

to discharge

595

//-

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--ltt

-

la

169'l6m

vinl

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oir

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O

lO

20 30 mrlrrt

B'i-eft

po.wer

block

Right

conol heod

sluice

btock

FIGURE 9

:

Sections

of

left

power

block

and right

canal

head

sluice

block.

chute

sluice

was

ovided with

a

3.05

m

x

7.62 m

(I0

ft

x

25

ft) sizC

xed wheel

gate

operated

by

a

rope

drum

hoist

shaft

ar

EL

175.56

ituated

at the top

of

the

gate

is

25

tonnes

(

(576

f0.

The weight

of

each

6l

tons)

and the

hoist

capacity

).

These

gates

were

also

supplied

the horizontal

apgog.provided

for

a

length

af

29.41

m

(9^6

ft__6

in.)

at

El.

144.49

m

@74

ft),

wiih

an

end

siu

of

1.52-m

(5

f0

height

and

crest

at

El.

146.00

m

(479

tt).

The

bellmouth

entrance provided

for

each

sluice

consists

of

the roof

confirming

io

an

elliptical

curve

^X2Y!

oI

equatron

-in..

*

4.

:

1

and

the

trvo

sides

to

that

of

equation

#*#

-

t.

Hydraulic

modet

experiments

were

conducted

to

study

the

formation

of

hydraulic

jump

and

to

determine

the optimum

length

of the apron

and

optimur'

height

of

the

end

sill,

ih.

position

of the rraining

walls,

ihe

discharge

capacity

of

the

sluices

and

the

efficiency

of

the

bellmouth

entry

-provided

for

the

sluices.

As

the

hydraulic

jump

was

found

to

form inside

the

sluice

barrel

for

certain reservoir

levels

and

discharges,

the

piers

of

the

sluice

barrel were

extended

beyond

the to^e

of

the

dam section

.which

ensured

the

formation

of

hvdrauric

jump

outside the

sluice

barrel

for

all

conditions of

flow:

The

sluice barrel

floor

also

is made

horizontal

pp

10

the outlet,

followed

by

a 18.90

m

(6}ft)

long

horizontal

apron

beyond,

at

the same

elevaiion,

up

to

which

the

piers

are extended

and

the

differencb

jn

sill level

of the sluice

barrel

and

the

canal bed

level

is-negotiated

by

I in 3

slope,

without

the

provision

of any cistern

or raised

end

sill. The portibn

of

the

lO mclrcr

rf

West

Germany.

An emergency

ype

and

of

size

3.96 m

x

9.46

m

(13

ft

x

31.03

fO

of the

dam.

s

provided

on the

upstream

face

6.4

Right

Canal

Hefd

Sluice

(Figure

9)

The

head

sluice

blocks

7 3

to

75

of t

for

the ri-eht

canal

is

located

in

46

tonnes

(45.28

ton

by

Messrs

M.A.N.

gate

of

fixed

wheel

It

consists

of

a batt

4.57

m

(10

ft x

I

sluices

is

kept

at

bed level

and

full

su

cumecs (21,000

c

)

at

the

minimum

drawdou'n

level

of

*

155.45

m

+

510

ft).

The

sill level

of the

149..05 m

(

+

489

ft\,

while

the

of

the

canal

below

ply

level

of

the

deep

cut section

are

at

+143.26

m

(

1470

tt)

+

504.5 f0 respectively.

The

d for

the sluice barrel

floor to

from

the

axis

of

the

length

of 8.38 m (27

ft 6

in.)

dam

and

conform

to a

parabolic

curve

of

equation,

:

400

f.

A circular

curve of

connects the

parabolic

curve to

15.24

m

(50

ft)

radiu

+

153'92rn

sluice

beyond the

shutter line

is provided

with

a

semi-circular

roof.

The

sluice

vents

are

provided

with

fixed

wheel

gates,

electrically

operated

through

gate

shafts,

by

rope drum

hoists located at

El. 179.83 m

(590

ft).- As

these

are regulating

gates,

slide

plates

are

provided on

the upstream side

of

the

gate

shaft

to ensure

the effectiveness of the

seals

throughout

the

regulating range

of

the

gates.

The

gates were

manufactured

and

supplied by Messrs

Tungabhadra Steel

Products

Ltd.,

and

hydraulic

rnodel

studies

were

carried

out by

their

consultants,

Messrs

Neyrpic of

France in

their

laboratories.

Provision

is made

for

an

emergency

gate

operated

by

a

gantry

crane

moving

on top

of

dam.

7. Design

of Power Waterways

(Figure

9)

7.1

8

penstock

pipes

of

4.88

m

(16

ft)

diameter

with

centre line

at

El. 123.4

m

(405

ft), are

embedded in the

power

dam

blocks

16 to 23 at

the

left

flank, for

pur-

poses

of

porver

development.

Releases

through

these

penstocks

will

be

let into the

river below,

after

power

development, which

will

be

picked

up at

Prakasam

Barrage

as

Vijayawada

for

irrigation

requirements

of

Krishna

delta.

In addition,

3

power

sluices of size

4.57 m

x

11.58

m

(15ft

x 38 ft)withsill

atEl. 146m

{479

ft),

are

provided

in

the

right

non-overflow

section

of dam adjacent

to

the right canal

head sluices

to develop

hydro-power

with the

waters

that

will

be

drawn

into

the right canal

below

for irrigation.

7,2 The

penstocks

are embedded

horizontally

in

the

power

dam,

unlike

the

common

practice

of embed-

ding the

pipes

in an

inclined

way. This

method

facilitated

raising

the

power

dam

with

ease

up to

the

sill

level of

the

penstock

pipes.

The

other

advanta-ees

are that

the

length

of

pipe

embedded

irr

8. ConstructionContractAdministration

8.1

)[ajor

Corttracts

There

\\

ere

no

major

contracts

on

the

contruc-

tiorr of the dam

proper,

viz.,

placement

of

maso-

nry and concrete.

The

only major contracts engaged

on

the

construction were

for the

fabrication

and

erection

of

gates

and

hoists

for

the various outlets

provided

in

the dam.

The

spillway

crest

gates

and

the

dam

masonry

is

smaller

resulting

in reduction

in

the

immediate

cost

involved

and thlt the

extension

The

intakes

are

controlled

by

high

head

gates

of

!I.d

wheel

type

of size 4.04

m

x

lit

m

({iq

n x

25.30 ft)

on

the-upstre.am

face

of

the

dam,

operated

by hydraulic hoists.

These

gates

are intended-

to

be

quick

acting type with provision

for

remote

Control

from the

power

house. The gates

and hoists

were

lupplied

by

Messrs

M.

A.N.

of West

Germany.

Each

gate

weighs

about

50 tonnes

(49.21tons)

aria

the

hoist is

designed

for

a maximum

normal

capa-

city of

70

tonnes

(68;9

tons).

The

hoist is

also

checked

lowered into

position

by

means

of

a

travelling

7l.Iz

tonnes

(70

tons)

gantry

crane.

provided

on

top of

darn.

Purt

lll-Construetion

hoists

were

furnished

by

Messrs

Jessop

&

Co. of

Calcutta.

The

penstock

gates

and hoists, the

chute

sluice

gates

and hoists'

and

the irrigation-cum-diver-

sion

tunnel

gates

and

hoists

were suppiied

by

Messrs

M.A.N.

of

West

Germany

through

Messrs

Escorts

Ltd.,

Delhi.

The right

canal

head

sluice

gates and

hoists

were

furnished by Messrs Tungabhadra

Steel

Products Ltd.,

in

collaboration with

Messrs

Neyrpic

of

France.

The

prestressed

concrete

bridge

built

across

the river

below the

dam

line

is

another

.esd.f

'"-j^4'

97

structure

that

was

constructed

on

a major

contract

by

Messrs

Andhra

Cement

Construction

Company,

Madras.

8.2 Minor

Contracts

negotiation

stage,

the

mukhaddams

would

further

reduce

their

already

competitive

rates. The lowest

negotiated

and accepted

rate

was offered

to

all

the

other

mukhaddams

as

well

and

the

work

distributed

to

all

of

them.

In

this

way,

the work

was

carried

out

quickly

at

economical

rates.

This

system of

negotiation

and

distribution of

work among

all the

bidders was particularly

adopted

in road

work, quar-

rying of

rubble

and loading of sand

into

lorries,

etc.

Considerable

economy was

achieved

by adopting this

method

as the

rates

were very competitive

and

reasonable

and

the

work

at the

same

time

was

got

done earlier

than

one could

expect

of a

regular

con-

tractor.

8.3 Government

and Contractor's

Organisation

'

The damsite lay

in a

hilly tract

of

thorn

scrub

jungle

in the interior

and

was a haunting

ground

for

tigers

and other

wild

animals.

The nearest town,

Macherla, was

2t

km

(13

miles)

away.

The

first

and

foremost

tasks

involved

before

taking up

work

on

the

dam

were

the

formation

of approach roads

and

bridges,

etc.,

to

the

damsite,

construction

of

camp

buildings

providing

protected water supply

and

electric supply,

and

setting

up of

medical,

public

health.

educational,

banking,

postal

and

telephone

98

truction

sluices,

drilling

and

grouting,

laying of

masonry,

R.C.C.

work

forgalleriesand

fbundltion of

left earth

dam,

in

addition

to

excavation

of founda-

tions. The

services

circle

looked

after construction of

earth

dam

also.

As

the

dam

rose

in height, trestle

bridge

and

monotower

cranes

were

erected

on the

dam.

In addition

to laying

of

masonry,

new works included

embedment

of

penstock

pipes

and erection

of trash-

rack

_

structures,

borin_e

of

irrigation-cum-diversion

tunnel,

construction

of

various

sluices in

the

dam,

laying

concrete

for

spillway,

bucket

and

sluices,

etc.,

and

erection

of

gates

for

various openings.

An

addi-

tional

mechanical

circle

was

formed in

the

year

l9G4

to

cope

up

with

all the

increasing

mechanical

works.

The

number

of supervisory technical

staff

engaged on

the

dam

construction

was

of

the order

of

650.

-

Medical

and Public

Health:

About 45,000

skilled

Labour

and

Lobour

Welfare

: All

the labour

engaged

on

various construction

activities

on the dam

and allied

works

was

accommodated

in

four labour

camps on

the

right bank

and

three

on the

left

bqlk, with

one more

at

the Bandlakarva

quarry

site,

a little

far

away

on

the

left

bank.

Medical

and

health

servrces,

community centres

and night

schools,

etc.,

were

established

for

ihem.

Other

facilities

provided

included

canteens,

first

aid

centres,

rest

sheds and

creches,

etc. A Labour

Officer

was

appointed

and the

labour

was

well

looked

after and

harmonious

relations

existed

between

the labour

and

the contractors

on

tion was

brought

to

completion

without

any major

trouble

or unrest.

Audit

and

Accoutlts

: To assist

the

eneineers in

dealing

with

the

financial, payment

and

a"ccounting

problems,

one

independent

pay

and

accounts

organi--

sation

was

constituted,

headed by

a

Financial

Adviser

and Chief

Accounts

Officer of

the

rank

of Accountant

General

and was

incharge

of

compilation

of

project

accounts

and payment

of

bills

after

pre-check.

The

project

accounts

were

made

available

for concurrent

audit to

the Accountant

General

for

rvhich

separate

staff

headed

by

a

Deputy

Accountant

General

was

stationed

at the

damsite

alongside

the

accounts

staff.

With

the

introduction

of

this

pre-audit

system, the

Executive

Engineers

and the

Assistant

-

Engineers

were

relieved

of

the

duty

of issue

of cheques

and

Law

and

Order

and

Vigilance:

The

headquarters

of

the

Deputy

Superintendent

of

police

was iocated

at

the

damsite

with

adequate

staff

in

the

various

colonies. vigilance

Inspectors

working

under

a

vigilance

officer

checked

pilferage

and

theft

-of

materiaJs

not

only

from the variouJ

stores

but

also during

transit

u-nd

kept.

the

department

informed

of

any

unsocial

elements

in the

township.

8.4

Land

and Land

Rights

and

Rehabilitation

In order

to

bring

down

the

cost

of

land

acquisition,

the

ployisions

of

the

Nagarjunasagar

project

Land

Acquisition

Act,

1956,

freezing

the land

values

at

the

level

prevailing

on

1

July 1953

were

made

applicable

to

the

submergence

area

under

the

reservoii.

How-

e-ver, as a

generous

gesture

to

the landless

poor,

even

the encroachers

on

Government

lands

who

were in

continuous

possession

and

enjoyment

for three

years

were

given

compensation

at the

rate

of

one-third of

-the

market

value

of

the

land.

57

villages

including

hamlets and

thandas

convering

an

area

of more

than

12,140

ha

(30,000

acres)

with

a

population

of 24,500

were

subrnerged

under

the reservoir.

24 suitable com-

pact

blocks of

reserve

forest

areas measuring about

ll,290ha(27,000

acres) were

unreserved,

cleared

of

forest

growth

and

allotted

to

the

displaced families.

This

fresh area was

transferred,

free

of

cost, first

to

the

"+JtY#'"t+Sf

99

project

and

subsequentry

ro

the

Revenue

Department

subject,

however,

to

airy

revenue

deriveJ

fro,n

the

assignment

of

land

being

iredited

to the FoirJo.prii-

ment.

The

concession-s

granted

to

the

dispraced

famiries

are

enumerated

below

:

(d)

Free

transporr

to shift

the

families

and

their

belongings'

Those

who

shifted

uv-trr.rserves

were

paid

Rs.

1.09

per

km

(Rs.

l.?5 per

mile).

(ii)

Permission

to

take

the

building

materials

free

of

cost,

even

after

receiving

.J*prniutlon,

for

constructing

houses

at

the'rehabilitarion

centres.

(ttt)

Allotment

of 4

ares

(l0cents),

free

of

cost,

to

each

family

for

house

sire

at

ihe

rehabitituiion

centres.

(fr,)

An

ex

gratia

amount,

subject

to

a

maximum

of

Rs.

300.,

1o

eaglr^family

receiving

u .orp.nr"_

tion

of

Rs.

500

or

l-ess.

to mike

up-rhe

total

amount

to

Rs.

750.

(y)

A

free.grant

of 2.O2ha (5

acres)

of

dry land

or

l

.01

lt*

Q.i

acres)

of wet

land

to

every

displaced.famity

owning

land

of

g.09

-

ha

(20

acres)

or

less.

(vi)

A

loan

of

Rs.

100

and

a

grant

of

Rs.

r00

to

each

dispraced

family

havinf

ress

rhan

qo.+l

t

a

(l_00

acres),

ro

meei

the

cost

of

reclamation

of

the

agricurturar

rand

allotted

to

them

in

the

rehabilitation

centre.

(vif)

Pucca

drinking

warer

wells

in

the

rehabilita-

tion

centres

at

the

rate

of

one

foi

lvery

50

families.

(viii)

lnternal

roads

in

the

village

site,

approach

road

to

the

rehabilitation

centre

frbm

the

existin=q

main

road

and village

schools,

temples,

chavadies-cum-community

ientres

ana-

ottre,

common

facilities,

ifl

submerged

in

the

old

village,

at the

cost

of

the projeft.

(ix)

Pernrission

to

the

displaced

families

to

cultivate

their

lands

in

their

oid

viilages

tirr

trr.v

were

submerged

in

the

reservorr,

on

payment

of

Iease

amount

equivalent

to

land,.u!ni..

8.5

Constructiort

Support

Facilities

(l)

FecrLrrres

FoR

Suppr.y

op

MareRrALs

Cement

: A

new

cement

factory

was

erected

at

Macberla,

at

a

distance-"i

uuout

24

km (r5

miles)

from

the

damsite,

where gooOlln'estone

deposits

are

100

available.in

plenty

for

the

manufacture

of cement,

to

cater

ro

the

needs

of

the

project-

io-ru-ri.

-i*depart-

mental

metre galge

railw'ay'rin.

r"r-iuii

.onnriti"g

Macherla

to

the

Righl

Bank'on

Lanka

ffi;-Hlir

uni

cement

was

conveyed

in

60

bulk

""**i

wagons.

Arrangements

were-

made

ut

thr

railwav

terminus

to

unload

cement

direc-rly

into

uuit

";;;;;r"";;il;:

which,

in

turn.

conveved

the

cemeni-

to

the

various

batching

plants

on

righ1

-and

feft

-flanfcs.

These

bulk

cement

carriers

were

of

thorny

craft

ivp.

fuilv-

.quipp.A

*itf,

lir:9rnp-rglsgrs

capabte

of

tiftfig

cement

to

a

nJilUt-oT

22.86

y

(71_{t)

at

the

rate

of

ZO.1Z

tono.,

tZO

ilos)

p.,

hour.

In

addition,

rwo

silos

oilSl6

t;;;;r'?i,oooi"iil

,cgRacitv -each

yele built

near

the

roti

-ol'l'ie

ranka

Mgtg

Hill,

such

that

cement

-could

u.

u'roua.a

into

and

drawn

frory

these

sitos

into

trucks-bt

;;;;itv

and

conveyed

to

the

batching

plants,

in

"ise"ihe

bins

at

the

batching

plants

*ere

filt.

surkhi:

A.

ba,

milr

was

erected

at

the

damsite

to

manufacture

4n. .

grained

surkhl-;;;a;;-'i"

ttre

required

specification

ror

aomiiiur.'ii'.iii.ot'-ortar

and

cemenr

concrete,

from

the

clay;A;;illvailable

in

plenty

in

the

vicinity.

Sand

: Trvo

sources

of

sand

were

located,

one

in

ream

at

a

distance

of

about

eam

of

the

damline

and

the

Liver

at

a

distance

of

about

re

north

of

the

damsite.

In

of

the

high

masonry

coffer-

rsiderable

quantity

of

about

of

sand

was

depoiitea

on

the

of

about

4.90-km

(3

miles)

right

bank

and

this'deposit

approach

road

was

laid

t

the

right

bank

at

about

_

sand was

collected,

conveve

construction

of

dam.

Sir

with

regeneration

every

yeal

of

construction

of

the

dam

were

laid

to

the

site

for

transport

of

sand.

As

these

approach

roads

were

riabre

for

submersion

under

the

reservorr,

transport

of

sand

to

the

batching

plants

was

carried.out

by

means

of

ordinary

lorriesl'fn.

sand

-was

collected

at

one prace

by

means

of

a dozer

and

loaded

into

the

lorries

iranrarty

uy

means

.r

"r

Emco

loader.

A

fleet

ot

45

to

so

ioriiil;;t.il'rortn,

nt'

as

well

as by

the

contrac_

Lransport

about

1,640

cu

m

ay

working

round

the

clock.

nstruction

of

the dam,

rvhen

ised,-

the

peddavagu

sand

roach

road

were

submerged

sand

from

Haria

River

-J."il1'3,ltJnitji

:Hilft';ffi1

Another

approach,

road

rvas

raid

to

ihe

Haria

siie

for this

purpose

and

sand

conveyed

by

means

of

trucks. Road

transp.ort

was

preferred

to

the

othet

o,ooi.

of- ,t"or-

port

by

rail

or

rope

way

here

uiro,

in

view

of

economy

"+tH:tlitr&e-**.-

.*

ffi-

rn

cost, greater

flexibility

in

operation

and

facility

to

rncrease

the ourturn

by

entrusting

part

of

the woik

to

contractors

in

the

case

of

road

iransport.

Again,

mechanical

equipment

such

as

loaders,'

showels-and

belt

conveyo{s

could

not

be

used

for

toaoing

sana

into

the

trucks

inasmuch

as

the

regeneratio-n

of

sand

in

the river

fluctuated

very

wide)y

from yiur

to

y.u.

and was

spread

gveT

?

large

area.

Hence

toaift

operations-

were

carried

out

with

rn"nuil-lubour.

A

fleet of

about

40

trucks

was

utilised

to

ronu.y

1,416

cu m

(50,000

cu

ft)

of

sand

daily.

Rubble:

All

the

stone

required

in

the firsr

srage

construction

of

dam

was

obtained

from

the

islarid

quarry

situated

about

3.2

km

(2

miles)

upit.ea-

of

daglfe

Approach

roads

were

taid

by

tn.

O.jurument

and..the quarrying

and

conveyance

oi

stone

was

done

DJ

rneJob

work

contractors

engaged

for

the.construc_

tion of

masonry

with

_

the

mJrtir

suppried

ai

site

by

the department.

Tlg

dgpgtment

madi

some

arrange-

ments

.for

supply

of

jackhammers

and

comprisseO

air

tor

drrllrng

to

the contractors,

but

the labour

resorted

to the

old

methods

of

hand

driils

to

wbich

they

were

accustomed.

conveyan_ce

was

done

by

means

of

ord.inary

lorries.

A

fleet

of

over

76

loiii.,

was

maintained

by

the

contra

about

2,830

cu m

(1,00,000

the

day

shift

of 8

hours

witl

I,400

for quarrying.

Ar

submerged

on

raising

the

constnrction,

fresh quarries

were

tapped

at

Bandla-

karva

located

at

a distance

of

abouiit.z

to

rz.g

t,n

g

to

8 miles)

to

the north

of

the

damsiie.

About

50

percent

of

the total

work

involved

oo

irtr

dam

in

re

with

the

stone

obtained

arry.

There

was

sufficient

Iffi.'ilfff;

'liffff"J:

ror

operation

*ppried.

o;tl"'8#tff#3i::fff

t;

149

cu.m/m

(1,600

cf,m)

c-apacity

instalred

iru..nt.ur

pla,ce

in

the

area.

Blasting

*ir

donq

*itrr getutine

and

electric

detonators.

A

Jeparate

laboui

ca"mp

was

established

at site

ro

accommodate

the

labour

enlaged

on

this

quarry.

The

sqge

system

adopted

for

the

conveyance

of

sand

from

Halia

River

was

idopted

for

conveyance

of

stone

from

Bandlakarua

quarry

for

the

same

reasons.

A

fleet

of

over

100

Leyhnd

irucks

of

7.62

tonnes

(7+

tons)

capacity

was

ensased

for

conveyance-

Loading

and

unloading

of

thJvehicles

rvas

carried

out

by

manual

labour.

T6

keep

this

huge

fleet

of

lorries

in working.condition,-r

*o'.tiirop

*us

established

at

site

for

serviiing

and

repairs.

(2)

Fncnrurs

on

SroRss

In

order

to

ensure

prompt

and

regular

procurement

and

flow.of

supplies

to

the

variou,

uiit,

"f;h;

p.oje"t,

a

-

central

store

was

maintained.

About

30,00b

iiemi

of

materials

were procured

and

kept

in

rtot.r-

io

.ate,

to

the

needs

of

thb

severar

consurning

diuiiioni.

This

worth

about

Rs.

22

crores.

system

was

evolved

to cope

j"

?','*

1T::I;,

"

ll;

*?,1:

::

(3)

WonKSHop

Fncnrrrrs

r

concrete

and

bearings

for

9'

construction

of

Dam

and

Appurtenant

structures

(Figure

10)

9.1

Diversion

and

Care

of

River

(I)

Mesouny

ConrnRolu

(pnoro

l)

This

was

tf.

largest

cofferdam

ajtempted

on

any

project,

formed

ro

i

total

t"ngifi

oT-gil?i1,000

ft)

cove-ring

one-third

wicith

of

the

'ver

to

a

maximum

heighr

of

13.4

I .(4r

rt)

ano

in;i;id;Jui

ss,soo

cu

m

(2.1

M.

cu

ft)

of

masonry.

O.:o

"m

A

Fr)

rrrigt,

of

maso_nry

in

.the

foundation

was

built

in

cement

mortar

I

: 4

mix

and

the

rest

in

".-rni.ortar

t

:

g

mix.

The

entire

wail

was

constructed

in

a record

period

of

less

-thro

3

months-

The

unii

coit

of

the

masonry

ranged-

from

Rs.

19.07

to

2l.gg

pr.

.o

*

(54

to

62

per

100

cq

fr),

which

was

perh"p,

tf,,

Iowest

rate

for a

work

of

similar

nature

"u.ii.d

dut

anywrrere

in

the

country.

The

cofferdam

*;il

;;,

,hilted

to

one

of

the

hi_ghest

recorded

floods

*itn

u

iir"diarg.

or

about

25,490

cumecs

(9

rakh

cusecs)

soorl

after

its

construction

in

the year

1956,

but

lt

u.trau"o;.ry

:atisfactorily

and,

.except

for

a

day or

t*o

*ir"o

tt,

flood

level

was.at

its pe'ak,

the

work

within

the

coffer-

dam

area

continued

-unirterrupted

tt

iougt

out

the

whole

flood

season.

(2)

PruccrNc

oF

TsMponany

Rrven

SI-urces

The

six diversion

sruices

constructed

in

brocks

43,

4s

and

47 at

EJ

82.^3.m

(27oft);;;;iiouia.a*itr,

srlgle

steel

shutters

of size

4.gg

m

x

j.fj

,n-iro

rt

*

lTft

6

in.)

outsid.e

t_o

outside,

weighing-"ir,irt

6.r0

to^n1e1J6

tonp)-.

As

rhese gates

were

tesr!.'ea'io.

neaa

of

5.13.

m

.(17

ft

6 in.).'only

but

the water_level

was

:T.?::l:q 1? 99

up

beyond

Ei

s1.44 m

(roo

fij

au,ine

pruggrxg,

th€y

were

strengthened

to

withstand

a head

or I

z. r

9

m

(4U

tt)

and

the

weight

of each

gate

came

to

about

12.20

tonnes (12

tons)

uTt..

strengthening.

The

p.lugg^ing

operations

were

carried

;ri;;-l-;iu*-.r.

In

the,

frst

stage,..earth

bund

was

form.a

"p

io-8ilct

++

an.'

tne

flow

drverted

through

the

sluices

in

brocks

45

and

47.

As

the

seepage

was

ippreciaute,

u--r..Lnaury

101

-

t--€t'"'

1-

t

'Pn'

Power

dom

l2l.9m-

{;";"*,f:Jfil,-l=-.f

Non

over-flow

29.5rn

F-n6

---f.Spill-woy

471.0

m-

r

I

hi non

over-flow

553.cl

m--.<l

of rood-woy

tB+.40

m

3'O x 4.6

right

conol heod

sluices

9 nbs.

INDEX

184.40

180.o

t70.o

t60.o

t50.o

t40.o

t30.o

r20.o

roo.o

90.o

80.o

700

60.96

4.9m

5

o

L

t

o

e

E

oE

o o

o

3Fj:1""..,3"on

.o

xxF--

r'

r

i1960

-___-_

,t

s

il96l

606---

D

t'

"1962

,iiooxx

"

a

"t963

Progress

lo end

m

of

Jine

1964

Prooress

fo end

--'-'-of

Juno

1965

'

'Prooress

to eniJ

x-x-x-

of

J-une

l9b6

Progress

lq end

of

Jude 1967

Progress to eod

xxxxx'of

June'

'tg6g

i,rogress lo end

o

f

Jun'e

1969

M Monotower

cron€O

lO

?O 3Om

O tOO 2OOm

t-L--t-.|-.J

Vertlcol

Horlzonlol

FIGURE

10

: Progress

of

construction.

l02

PHOTO

I : Work

in

progress

in

the

masonry

cofferdam

area

on

the

left

flank.

PHOTO 2

:

Masonry

dam-left

side

blocks

under construction.

bund was also formed to

reduce

the

same

and

the

little

leakage

that

was

still there

was

let

out through

small

openings in

the

shutters

and

pipes provided

down-

stream. The

shutters

were then

lowered

in the

sluices

in

block 43 and

plugging of sluices

was done

for

a

length of 10.67

m

(35

fi)

out of a

total

length of 80 47

m

(264

ft).

The concreting

was done

in

two

bits,

first

up to

the centre

line

elevation

of the

sluice and

left

for curing

and

aeration for

one

day and

the balance thereafter.

ln

the

second stage,

the shutters

of

sluices

in blocks 45 and

47

were

closed

simultane-

ously

after the

flow was cutoff

by forming

a ring

bund

on

the upstream and

plugging

operations

carried

out,

as

in the case

of block

43.

While

plugging

the

two

sluices in

block 43, thefour

sluices

in blocks

45 and

47

could

discharge

85 cumecs

(3,000

cusecs)

with

the

water-level

at

El.

83.82

m

(275

ft).

While

plugging

the

other four

sluices in blocks

45

and 47,

however,

the

water-level

was.

steadily

building

up and the

plugging

completed

before

the

water-level

reached

El.9l.44m

(30Oft). Later on, after

completing

the

plugging,

the

water-level

was

allowed

to

build

up still

higher

and the

flon's

pass

through the

diversion

tunnel at

El. 91.44

m

(300

ft).

The third stage

concreting

of the

balance

length

of

the

sluice barrels

were

done in the

season. Contact

grouting

was done

later

on-

The

concrete

used

for

plugging was of rich

mix

of

281 kg/cme

(4,000

p.s.i.)

strength mixed

withwater-

proof

chemical, Acco

Proof.

The

pipes provided for

driving seepage

water

were

plugged

and

grouted

later

on.

(3)

DrvrRsroN-cuM-lRRrcATroN

TuNNel

Tunnelling :

Excavation

of

El.

91.44

m

(300

ft)

tunnel was

started

from both

upstream

and

down-

stream

sides

simultaneously.

Excavation was

done

in

two stages, the

top

8.2

m

(27

ft) first

and the

bottom

0.9

m

(3

ft) next. A

steel

structure,

called

Jumbo

moving

on

rails

was

erected in

the

tunnel

to drill

holes

in rock

over

the entire

cross-section

of

the

tunnel

simultaneously.

14

Nos.

of

jack

hammers

with

pushers

run on compressed

air and

mounted on the Jumbo

were used for

drilling.

The

length

of the

holes

drilled

was

3

m

(10

ft)

and

the diameter

varied

from

29

to

34

mm

(1.14

10

1.34 in.).

About

130

to

150 holes

were

drilled

for each

blast.

The

holes were

loaded

with'

gelatine

and half-a-second

short delay electric

detona-

rors

and

fired

after

pulling

out the

Jumbo

sufficiently

far

ofl.

The

foul

gases

emanating from

the

blast

were

removed

by

exhaust

ventilation.

One

duct

of 0.9

m

(3

ft)

diameter,

with

one

blower

of

566

cu

m/min

(20,000

cfm)

capacity

coupled to a 22.5

H.P.

motor

for

every

305 m

(1,000

ft) length of

duct,

was

used

in

103

PHOTO

3: Blaw-Knox

batching

plant.

the

tunnel.

Blasted

muck was loaded

by

a

1

cu m

(1;5

cu

yd)

loader

into

5 cu m

(7.5

cu

yd)

dumpers

and

brought

outside.

The

progress

made in tunnelling

was

about

2.5

m

(5.2

f0 in 16 hours. The

entire

tunnel

for

a length

of

786

m

(2,580

ft)

was

completed

in

about

9

months.

The

total

quantity

of rock

excavated

was

62,300

cu m

(22

lakh cu

fr). The

entire El.

+91.44

m

(300

ft) tunnel

rvas

bored through

good

granite

rock.

The

goose

neck tunnel

at

El. 121.92 m

(400

ft)

was

excavated through shales

in

the first 25 m

(82

f0

length.

In

this case, a

small

pilot

tunnei of

size

7.2

m

x

2.1

m

(4ft

x

7ft)wasexcavated first,

top

half

of the

tunnel

next in

short

lengths

and the

rock

in

the

roof supported with

heavy

steel sections

and

wedges.

Later otr,

the bottom

half

was

excavated.

A

number

of

perfo

bolts were dri.ren even in

the

El.

+

91.44

m

(300

ft) tunnel at

places

where it was

excavated

through

weak

granite

rock.

Concrete Lining:

The tunnel

was

lined with

minimurir

0.3

m

(1

f0

thick concrete

lining

with

nominal

reinforcement.

Invert

of the

tunnel

was

lined

first

for

the

full

length.

Then

prefabricated

steel

shuttering

for sides

and

arch

in standard

lengths of

'I2.2

m

(40

ft) was

erected

and concrete

pumped

by

means

of a

pneumatic

placy

of 0.76

cu m

(1

cu

yd)

capacity.

Concrete was

manufactured

outside and

conveyed

inside

the

tunnel

by

Letournou dumpers and

104

fed

into

the hopper

of

placy.

The progress

achieved

on

lining

including

tying

grills

was

IZZ m

1+OO

ft)

per

month. The

total

quantity

of concreting

involved

was

12,744

cu

m

(4.5

lakh

cu ft).

Plugging

of El. 91.44

m

(300

ft)

Tunnel

:

The iriga-

tion needs

of Krishna

delta

were

kept in

view

in

programming

the

plugging

operations.

Water

was

not

required in

the month of

May

but

it

should be

ensured

on lst

June

without

interruption.

On

29

April 1967,

when

the

reservoir

was

at

El. 100 rn

(330

ft),

gates

were

lowered,

work

on

plugging

taken

up

round

the clock

and

2,270

cu

m

(80,000

cu

ft)

of concrete laid

in the

zone

of

first

phase

of

plug

before 30 May

1967,leaving

a ventway

of

18.6

sq m

(200

sq

ft) belowthe

roof.

On

7

June

7967, the

gates

were

operated

to release

waters

to

Krishna

delta

through

the

vent

left

above the

partial

plug.

This was

continued

till

the reservoir was

built

up to El. 119

m

(390

ft), when the

gates

were

again

lowered

on

28

July

1967,

and

laying

of

concrete

in the

second

phase

of

plug

taken up

and

completed in less

than

7

days. By

this

time'

the reservoir rose

to El.

125

m

(410

f0 and

the

gates

of El.

122

m

(400

ft)

tunnel

were

operated to

release water

to

Krishna delta

on

4

August

1967.

This

was

continued

till

the waters

overflowed

the spillway

at

El.

160

m

(52-<

ft).

Later

on

the

gates

of

El. 122 m

(400

ft)

tunnel

were

lowered and

the

third and

last

phase

of

plug

was

completed

with

pHOTO

4 :

Thousands

of

labour

lifting

s_ton_e

and

mortar-by

head

loads over timbet

scaffoliling-a

stirrin!--sp"ttact"

harkinf

back

to

theancienttimesofTemplesof

Southlndiaand

PYramids

of EgYPt'

masonry

and

concrete.

The

concrete

mix

used

for

the

pfuggin!

was

of

210

Ag/cm2

(3.000

p's'i') strength'

bontacigrouting

was

also

done

later

on'

9.2

Construction

of

MasonrY

Dam

Almost

half the

mass

of

the

dam

lies

below

-r

106.68

m

(+350.00 ft)

level,

as

agains-t

t!9

average

tiu.t

bed

level

of

+74.68

m

(+245'00

ft)'

It

was

pottiUt. to construct

masonry

in

the

lower

half

of

itt"

du*

up

to

this

level

without

the

use of

heavy

equipment

bs

the

maximum

lift

involved

is

32

m

(tb5-

ft).

Hence

the

construction

programme

was

divided

into

two

stages.

The

first

stage

of

con_struction

in

the

lower

portioi up

to

*

106.68

to

*

115'82

m

(+350.00 to

*

380.00

ft)

level

was

carried

out

by

the

ivaitable

machinery

supplemented

by

enormous

local

f"U""i

(photo

2).

h6e^

iecond

stage

cornprising_the

balance

of

work

above

+106.6E

to

*115'82

m

i

ilso.o0

to

*380.00

ft)

levcl

required.special

equip-

*."t

for

lifting

stone

and

mortar

to

high

elevations.

This

rvas

calted-the

trestle

stage

as a

steel

trestle

bridge

with

monotorver

cranes

were

utilised

in

this

stage-

-o^f

conitruction

(Photo

7).

The

dam

was divided

into

79

blocks

of

approximately

18.29

m

(60

ft) length

each

and

each

block

entrusted

to

one

job

worker.

Mortar

was

manufactured

and

supplied

at site of work

depart-

mentally

and the

contractors were

required

to

build

the

masonry

with

their

own

stone

obtained

from

the

quarries.

This method of contruction

by

job

work

or

petty

contract

system

contributed,

to

a

great

extent,

to

keep

down

the

cost of construction.

For

mixing

mortar,

a

Blaw

Knox

batching

plant

(Photo

3)

equipped

with

12

numbers

of 0.76

cu

m

(

I

cu

yd)

mixers

and a

Winget batching

plant

with 4

numblrs

of

2.29

cu

m

(3

cu

yd)

mixers

were engaged

in

both

the

stages

of

construction of

dam. In

the

first stage,

mortar

was transported

to

the

damsite

by tipping

wagons'hauled

by diesel

locos

running 6n

metre

gld€-c

raif

line.

In

locations

where

rails could

not be

laid,

it

was

conveyed

by

tipper

lorries. Rubble

was

conve-

yed from

the

quarries

to the

damsite

with

ordi-nary

iorries.

The

mortar

and

rubble conveyed

to

the

dam-

site

were

lifted to

the

top of

dam

under construction

by

head

loads

and

jawalies

on a network

of

timber

scaf-

folding

erected

on the

rear face of the

dam

in

progress

(Photo

4).

The timber

scaffolding consists

of

an

inclined

105

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

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