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

KOYI\A

DAM

N.G.K.

MURTI

Formerly

Chief

Engineet

.

Goqternment

of Maharashftra

and

at

Bre$€nt

Consultant.13,

Vasant

Mahal'

C.

Road

Marine Drive,

Bornbay

V.R.

DEUSKAR

Secretary

to

Governrnent

of

t$aharashtra

tnigation

and

Fower

Departm$nt'

Bombay

P,M.

MANE

FormerlY

Chief

Engineer

Govern'nrent

of Mah'a

rashta

and

at

Present

Consulta

nt,

I a{rialya

nl

Feddar

Road,

BombaY

li

.stt"dJ*"r-f

I

'.

KoAnn

IDam

1.1

The

Koyna River is

a

tributary to the

Krishna

which

is

a

major

river

basin

in

peninsular

India,

draining

east

iito

the

Bay

of Bengal. The Krishna

basin drains an

area

of

about

2,59,000

sq

km

(1,00,000

sq

miles)

falling

in

the territorial

areas

of

Maharashtra,

Seetioi

n

I: f

ntro

d,untion

Karnataka

and Andhra

Pradesh

(as

linguistically

reorganised

in 1956). The 75

percent

dependable

yield

of

this

basin

has been assessed

to

be 57.3

thousand

million

cu

m

(2,060

thousand

million

cu f0 at

Vijaywada,

a

place

where the

Krishna

emerges

from

O

Moho

Osof

oro

t\

Scismogroph

slolion-

-

--

--O

Epiccnlr:s

of

corlh-lrcmorg

-f

Loke

spreod

orco-_

_ __GD

)

d..|

I

\

KoynoDom

FIGURE

1.1

: General

layout

of works,and

site

plan.

r19

the Eastern

Ghats

and

also

from

where

the delta

starts-Vijaywada

is

about

80.5

km

(SQ

mi-te-s)

from

the

sea altin!

the

river

course

(Figures

1.1 and

1.2).

catchment area

of about

891

sq

km

(344

sq

miles)-

This

area

though

small

receives

an

intense

rainfall

averaging aborlt

508

cm

(200

in-)

in a

4-month

monsoon

June

to

September, with a

low

coefficient

of

variation

(20 percent).

Consequently the

98

percent

dependable

yield

was

estimated

to

be

2.66TM cu

m

(94

TM cu ft),

i.e.,

roughly

Ul4th

the

98

percent

dependable

yield

of Krishna

from a catchment

area

U300th

of the basin

area

at

Vijaywada.

1.3

The

isohybts of annual rainfall

fall-off

so

rapidly

to

the

east

from Western

ridge or

continental

divide,

that

within

56.3

km

(35

milesl

from the

ridge the

averag€

annual

rainfall

is

about

50.8

cm

(20

in.)

(Figure

1.3).

All

this

makes it

evident

that

the

rivers

rising

in

the

Western

Ghats

offer themselves to

be easily

blocked

within

48.2

km

(30

miles)

from the dividing

ridge,

by

constructing

dams

to create

large

storages.

The

river

beds

vary from'El. 579

to

548.6 m

(1,900

to

1,800

ft)

,?

.)e

ro

76

/d+"'."

'-:

if

\-.-

rF

'l

.'"-8etuI+

"$"1

,'t^*d

?

.'-'t'-

,-

.J,

:

o

Ourg

?oo

$tg

t..

Fif

:.

-j

o

.9.,

20

€ti3*on,poorno

tgo

|rl#boloitrsor

o

l6

B

AY

OF

BENGAL

t6:

o

l4'

O 32

96

t6Okm

t*J

I

(t

or

(n

?

Map

of

Kristina

Basirii'and

adioining

area'

ffips

o

rO

(f)

I

oo

-J e

nd

prv€r---

j-->>\-

Heodquorter stot

e

tDistrict

e

O

Stote

boundOrY

- -/'*-'-'

r"

4'

-

Drstrrct

boundorY.--

-

---

---..

8o s

rr 1.......,..,,.,....,i

FIGURE

1.3

:

Isohyetal

map

of

Koyna

area'

121

-------"'/

1.4

This

favourable

combination of

hydrometeorological

conditions

and

topographical

features was

long

not'iced

and

exploited

by

the

House

of

Tatas

between

1905

to

1926

in

the

shane

of

hydroelectric

projects

at Khopoli,

Bhivpuri

anq

'Bhir;-'p;;Ji-fio,rr"r.

All

these

three

stations

used

up

a

diversion

of

about

r.ztiM

cu m

(42.6

t_M

cu

ft) on

an

average (excluding:

evuporation

l-o.sges) tg-

rhe source

end

-or

ine

itiuritaiiei

to

the

Bhima

River

which

in

itse

Krishna

on

its

left.

Koyna

w

but

it

had

to be

shelved

be,

power

already

created

could

and

because

of

the

financi

crisis

in

the world

during

the same

period.

1.5

Thyr -

Koyna

remained

to

be

exploited

after

India

glleO

Independence

in

lg47

and

-in

a

very

much

blgger

way

than

it

was

originally

contemplated.

El

Overburden

Sl Tuff

Breccio

.

Bore

lroles

s

Bosolt

630

585

540

495

450

4o^5

36cJ

315

27c^

225

r80

t35

90

45

6

8

122

FIGURE

1.4

:

Cross-section

of

Koyna Proiect

area to the left

for

about

15

km.

2.1

The

project

area

and

dam

lie

in the

Deccan trap

formations

(Basic

Basalt)

which

coverls nearly

the

whole

of

Maharashtra

from

the

coast

of

Arabian

Sea

upto &3.74

km

(400

miles) east and

along the

coast for

about another

643.74 km

(400

miles). The basalts

in

the

project

area

are believed

to be

2 to 4

km deep,

in

nearly

horizontal lava flows

with

breccia and

bole

sandwiched benween massive

lavas.

Geologically the

age

is said

to be not older

than upper

cretacious

nor much

younger

than

early Eocene

(Figures

2.1,2.2

and

2,3).

2.2 The

peninsular

shield,

and this trap

atea

in

particular,

was

believed

to be stable and

non-seismic.

TS

Subsequent

events

have

questioned

the

validity

of

Foundoli

linc

Koyno

Flivcr

{

,>

C

o

:

l

,

i,

Swtion

fl-Geological

antd,

Seism

ol,ogieal

differ

very

much.

They

are much

longer

and

less

predictable

in the

other areas.

Nevertheless

in

a

1,000-

year

period,

no

part

of the

globe

could be totally free

from

a shock.

Geological

ages are

much

longer

and

the

unit

is a

million

years.

664.46

656

3

608

L

o

=

Wit:i

r'ion6

overburden-__Ffil

Mossive bosoll--%

Tuff breccio---E

Bote

-

--E

536

t265

il45

lO:5

905

785

665

545

aE

.

Melrcs

FIGLJRE

2.1

:

Geological

section along the

axis

of

dam

anil

rough

longituilinal

profile

along

the

river.

A

rough

longitudinol

profile

olong

the rrwr

F,IGURE

2.2

: Geologicat

section

along

the

axis

of dam

and

rough

longitudinal

profile

along the

river.

r23

LUCKNOW

t",

lo

,

.'\\'

I

i-t

FIGURE 2.3:

Map

of

western India

showing Deccan volcanics

andfeatures

in

basement.

===

I.t

t

arl

'lltlrl

E

--l

:l

----=

r--

-l

c=_-l

tr

-x-r,-

j<,4

r24

In the

given

historical

background,

a

project

was

investigatedturing

1947

to

1950 and

prepared-in

195t

to construct

a dam

about 82.3

m

(270

ff)

above

the

gap

in-between.

treatment.

3.1 Choice

between

Rigid

Yersus

Flexible

Dams

costly.

Reasons

for

not choosing

an earthfill

dam

were

nea,riy

the

same.

Sand

for

transitions

was

not

available

except

at

a

lead

of 56.3

km

(35

miles).

With

no

suit-

able

material for

the shells

or

shoulders,

a

homogeneous

Seetion

III-The

Proieet

and'

the l)am

section

called for very flat

side

slopes

and the

quan-

tities

increased.

Other

reasons

of

working

period,

care

and

diversion

of

river

and

locating

a

flank

spillway were

common deterrents

from

adopting

a

earthfill

structure.

3.2

Choice between Masonry versus

Concrete

Having chosen to

have a rigid

masonry

dam,

the

choice

lay between

hand

placed

masonry

(stones

set

in

This

enabled

large labour forces

to

be employed-to

meet

the

monthly

piogress

aimed

at.

Space

restriction

mitigated

against

a

speedy construction

throu-gh

?

labo-ur

intenlive

proceis

ai involved

in

hand

placed

rubble

masonry

in cement

mortar.

Nevertheless,

three

alternatives

of

a

wholly

mecha-

nised

concrete

dam,

a wholly

hand

placed rubble

masonry

darn

and a

part

masonry

part concrete

were

put

to

tender.

3.3

Prepakt

and Colcrete

At

that

time

(1954-55)

prepakt

concrete

(USA)

and

colcrete

of

(UK-Patent) were

not

much

known,

nor

*"*

there

prbcedent of

dams

having

been

built

wholly

in

prepakt or

colcrete

masonrY.

Actually

prepakt

process

was

adopted

in

Bhakra

Dam

in

tire

upitream

middle

third

clay

seam

(trench

tt.ui*."t1,

unb

it

proved to

be

a

failure-

The

i"tr"t. thi;i'g

had

to b6

redone'in

cement

coxcrete

placed

by

adopting

mining

methods.

'

Iia''*4

r25

R.L.217l

R.LJ90g=

K.R.L.

2125

K R.

L3194

K.R.L206l

K.RL.

t900

R

aKRL.l842

i:

F

iK&L

r84e

-f

230.r8-j

to.33

l\on

overflow sectron

to.33

{

Overflow

secfion

I

st

stoge

2ndstoge

--:-

Note:

2ndstoge

width

uplo

gres66

Koyno

Dom

Section

Dec

1952ond

1956

Reports

Storoge

Ist

stoge-

36,000 M.cfr

t[nd

stoge

-98,OOO

M.cf

t

tevel

FIGURE

3.1

: Cross-section

of N.O.F:Qnd

O.F.

block for

t175.36

M

cu

m

(9g,0fi)

M

cu

ft)

and for

stage

I as in 1954

superimposed.

between

the

cement

concrete

and

hand

placed

masonry.

The

advantages

are obvious.

It is

as

watel-

tlght

as-

good

cement

concrete.

No

crushing

at

all

is

required.

Colgrout

used

in

mass worft

speedily

done,

varies

from

35 cu

m

to

'40

cu m

r26

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

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