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

ffi

i'ni;til;",ii,::T:1,:#,,,"?f,

"**f:.:il;iH#,gri$;Hy

j:..*ff#lJTl#T,i

(t)

An

inlet

vertical

shaft

connected

with

the

tunner

through

a

90o

bend

"nJ"

iiu";l;i;".

(tt

A

twelve

sided.trashrack

structure

with

arrange_

ments

for

closing

the

no*

tt

ioogt'li.

iunn.r.

(iii)

A^peripheral

grid

structure

to

prevent

formation

- ..pvlindricar

bulkheads

are

made

up

of

three

units

for

or

vortices'

lvru^errvr

facilitilffi;rportation-"*i

ioou"nien..

in

handring

Shoff

housr

&lox.

w.L.433.t2

INTAI(E

STRUCTURE

xis

of

dom

Et.43

5.86

F"t''nto*c

rhofr

PROFILE

ALONG

TUNNELTI

Flot

bulthrod

Bo?iom

unii

of

cylindricof

Dutthcod

Ecnch

E|.374.90

c.L.Tunnci

(

Dimensions

ond

fevels

in

rnetres

,t

Ghomrur

divers

ion

/S

Portal

SECTION

A.A

9V54

Brocko

8f.396.24

I

C.Llloist-cum

alcvotor

rhofl

6.8c

dio.

PIUg

losing

t+T-

ali

198

FIGURE

9.

3.

Flat

Bulkhead

Thc flat

bulkhead

is

a

welded

steel

structure

with

4. Top

Cover

Frame

.

+

top

cover

fragr-e

is

provided

at the

top

of

each

intake

structure

at

El.

396.2q m

to

act as

a

roof

to

purposes.

entry.at_upstream

and

discharge

tunnel.

The

bell-mouth

has

been

into

the

free

flow

formed

by

elliptica,l

Item

Design

Data

Design

Dia.

Height

Weight

C to

C of

head

metre

in tonnes

Guides

xz,Yz

curves

7n

-1g:s

a)

:

I

in

both

horizontal

and

Clear

opening

Max.

designed

head

Max.

reservoir

level

Clear width

of

opening

Clear

height

of

opening

C

to

C

of

side

seals

Sill

to

C

of

top

seal

:2.13

mx3.2m

:105.46

m

:433.12

m

:2134

mm

:3200

mm

:2363

rnrn

.

:3320

mm

6.

Hydraulic

Hoists

Fu.b

gate

is

operated

by

an

independent double

acting

hydraulic

hoist

of

6ZS

tonne

-capacity

placed

Cylindrical

Bulkhead

Bottom

Unit

58

m

9480

mm

960

mm

Intermediate

20

m

9480

mm

3340

mm

Unit

Top

Unit 18

m

9480

mm

3340

mm

Flat

Bulk-

58

m

7020

mm

1000

mm

head

Top

Cover

30

m 10414

mm

660 mm

frame

32 9654

mm

30

9654

mm

30

9654

mm

26

7160

mm

37

10254

mm

5. Outlet

Works

-

The

irrigation.tunnels

designated

as

Tt

&Tz

have

four

number

irrigation

outlits.

In

the'gut.

'reach,

conduits

of

size

2.t3

mx

3.20

m

have

ueei

fiovided.

Each

tunnel

has

two

conduits

which

have

t6i-*outt

rI

-----r*w

t99

fii:

Top

El.

3 96.24

T

I

Top

€

ll

r(t

j

av

Er.396.?4

Bose

8f

.374.9O

LOAO

SHEAR

MOMENT

DEFL

ECTION

FIGURE

l0

: Variation

of load,

shear,

moment

and

deflection

along

the

height

of intake

structure.

over

the bonnet

cover

in

the

bonnet

chamber. Tech-

nical

data

of each

hoist

is

as

under

:,

8oseEl.374:90

Capacity

of Hoist

Time

of

gate

opening

or

closing

(two

motors working)

Cylinder

diameter

Rod

diameter

Normal

strokes

Cylinder

length

M3T.

operating

pressure

while

rarsrng

Max.

operating

pressure

while

lowering

Capacity

of

pump

motors

(2

Nos.)

The gfles

and hoists

have

been

supplied

by M/s

Iungabhadra

Mysore

in

collaboration

with

-Nyrpic

France.

7.

Hoist-cum-Elevator

Shaft

and

Hoist

House

The

hoist-cum-elevator

shaft

in

the

outlet tunnels

comprise

the

gate

control

chamber,

the

shaft

and

hoist

house.

In view

of

the

soft

rock

formations,

it

was

considered

desirable

to

locate

the

gate

bontrols

as

much

upstream

as

possible

so

as

to

aloid

pressurised

tunnels

downstream

of dam.

The

hoist-cum-elevator

shaft

housg

was,

therefore,

located

upstream

of dam

axis,

keeping

in

view

the

layout

of

spitlway'approach

works

and

general

suitability

of

the

geology

of the

area

for

the location

of underground

works.

The shafts are

partly

in rock

and

partly

in

fill of

the dam.

repalr.

7.

Power

Waterways

and

power

lfouse

625

tonnes

20

minutes

800

mm

:

250 mm

:3300

mm

:3840

mm

I40

Bar

128

Bar

40

H.P"

each

In

each

tunnel

the

tunnel

with

covers

and

hoist

200

a

control

chamber

is

provided

above

floor

at

E1.343.51

m.

The

bonnet

house

cylinders

for

gates

alongwith

the

dam

axis.

Steel lined

penstock

headers

start

from

downstream

of

the emergency

gate

transition

and

extend

upto the

downstream

portal

of tunnel. Each

of

the

penstock

headers is bifurcated into

two

branches

5025

mm inner

diameter

by

providing

a

wye

(bifurcal

tion) catering

for a hydrostatic

head

of

125 m.

The

diameter

of

penstock

branches has

been further

reduced

from 5025

mm

to

4500

mm

with

the

provision

of

a reducing

bend.

A flexible

sleeve type

coupling

is

provided

on

each

penstock

branch

further

downstream

to

cater

for

any

angular movement with

respect to

the

power

plant

building.

L

Design

Criteria

for

Penstock

Headers

The

penstocks

have

been

designed

for full

internal

pressure

without

any

reliance

on the surrounding

rock.

The liner

has

been

checked

for external

pressure

also.

The maximum

external

pressure

that

is

generally

provided

for in the

design

of

embedded

penstocks

is

equal to the depth

of

rock

cover over

the steel

liner.

When the reservoir

is

full

at El.

426.72 m, the

gross

head

on the

centre line

of

the header

would

be

91.745 rn

(that

is El. 426.720

m-334.975

m).

However

because

of loss

of head

in

the

friction

and

keeping

some reliance

on drainage

arrangement

provided

around

the

penstock

liner,

it has

been assumed that

even in

the

worst

case, the

external

pressure

around

the

liner

will

not be

more

than

80

percent

of

gross

head,

i.e., 73.457

m.

The

liner

has

been found safe for

external

pressure,

which is

otherwise

adopted

from the

consideration

of

internal

pressure.

The

most

economical diameter of the

penstock

was

worked

out

from

the

empirical

formulae

and

making

detailed

analysis

of

several diameters, determining

the

total cost of

each.

The

comparison

has

been

made

for

penstocks

of

sizes

6.096

m,

6.706 m

and

7.3L5 m

diameters. Any

size

bigger

than

7.315

m

diameter

is

considered

inconvenient for

installation

within

9.144

m

diameter tunnel. After

detailed

studies,

7.315

m

diameter

penstock

for

Pong

Power Plant

was adopted

due to the following

considerations :

(t)

The

average

result of

the

various empirical

formulae

for economic

diameter

worked

out

to

be 7.315 m.

.

(fi)

The

loss

of

power

was

the

least

with 7.315

m

diameter

penstocks.

(r:if)

From

consideration of

speed

rise

=of

the

generating

units, it was

considered

desirable

to

adopt 7.315

m

diameter

header.

Diameter of

the branches

has been

prop5sed

as.

5.080

m in

order

to keep

the maximum

veiocily

in

the'

branches

equal to the maximum

velocity

in

the

main

header.

2.

Design

of

Wye (Bifurcation)

I{.

is.

very

difficult

to

correctly

compute

the

loac

clrstnbution

between

the

splitter

and

the

ring

girder

The

total

internal

pressure

will,

of

course,

b;

Jhareci

by

both.

(a)

STnUcTURAL

Desrcr.r

pressure.

,

The

splitter

is

designed

to

resist

direct

tension

and

flexured

stress

due

to unbalanced

hydrostatic pressure

gl

it.

Wrapper

plate

has

been

provided

to

c-ater

for

direct

stress

developed

due

to component

of tangential

force.

(b)

F,tsnrcATroN,

HnNpr,rNc

AND

Tesurqc on Wyn

For other

details

reference

may be

made

to

Part

III

-construction

part

of

the

write-up.

3. Power House

the

tunnel

exit

portal.

This

location

accommodates

penstock

wye

branch,

compound

bends, expansion

coupling,

etc.,

in

the

portion

between tunnel

portal

,.*J*Ffl*'

201

Th"-

.length

of unlt

bays

has

been

kept

as

22.75g

m

to

enable

the

electric

overhead

traveiling

G.O.f.l

crane

to handle

.the

generating

equipment

ind

the

butterfly

valve-

The

spacing

of

unit

bays

ui-

ts.2as

,n

FIGURE

1l

:

Pong

polyer

plant.

202

8.

construction

organization,

Lanil

Acquisition

and

Job

Facilities

:

Organizational

planning

'

A.

ORGANIZATIONAL

SET-UP

Beas

Construction

Board

Punjab

Government

constituted

the

Beas

Control

Board in 196l

to exercise

technical

and

financial

control

overall

matters pertaining

to

the execution

of

the

project.

Consequent

upon

the

re-organiz.ation

of

the

State

of

P-unjab

into

punjab

and

Haryana

in

1966,

its

execution was'

vested

with

the

Government

of India,

_on

behalf

of

the

three

beneficiary

partner

States

of Punjab,

Haryana

and

Rajasthan

who

reconstituted

the

control

board and

namid

it as

Beas

Construction

Board.

Purt

lll-Constructian

B.

PROJECT

ADMINISTRATION

Irrigation

Wing

The

main

functional

units

for

the construction

of

Beas Dam

under

the

overall

charge

of

General

Manager,

Beas Project,

were

as

under

:

Bens

DrsrcNs

OncaxlzATroN

CoNsrnucrroN

Onc,c.NrzATroN

The

construction

organization,

responsible for

actual execution

of

the

project,

was headed

by

a

Chief

Engineer.

The

organization

comprised

a number

of

243

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2A4

circles,

namely

Plant

Design,

Embankment

Place-

ment,

Mechanical,

Administration

and

Stores,

etc.,

each

under the control of a Superintending

Engineer.

A system of

'Functional

Control'

where

the

person

in

charge was

'responsible

for

each

particular

function

for

the

entire

project,

was in operation

so

as to ensure

the closest technicat supervision.

INspncrroN

AND

Conrnor" DrnncroRATE

In

order to

ensure correctness

of layout,

adherence

to

prescribed

specifications and strict

control

over the

quality

of construction

of

permanent

structures,

this

directorate functioned

under the

charge

of

a

Superin-

tending Engineer who was

directly under

the

adminis-

trative

control of

the

General Manaeer.

The

Directo-

rate also maintained well

equipped

Joil

and

concrete

testing

laboratories

at the dam site.

The

Directorate

was

also responsible for

observing

and

recording

the

data recorded

by

the

embedded instruments

in

the

dam.

The work

relating to the

land

acquisition

and

rehabilitation of oustees

was

also entrusted

to

this

Directorate.

Puncgnse OnceNlzATroN

The

purpose

of machinery, equipment,

plant

and

stores

was

handled

by

a centralised

Purchase Organiza-

tion under

the charge

of a

Superintending

Engineer

designated

as

the

Chief

Purchase

Officer.

This

organization

has

played

a

key role

since the

speedy

completion

of works

is dependent,

to

a

large

extent

upon the

timely delivery

of

plant,

machinery,

spare

parts,

etc.

Resrorr{r Geor,ocrsr

An

Engineering

Geologist

from

the

Geologic.al

Survey of tndia

wai

posted

to the

project

during

itt

entirs construction

period.

The

Resident

Geologist

carried

out detailed

surface

and

sub-surface

geological

mapping

of the foundation

and

assisted

-the

Pfolect

engineers

in

carrying

out the

programme

of

foundation

treatment.

Power Wing

This organization,

headed

initially

by

one

and

subsequently

two Chief

Engineers-one

for

Power

Stations

and

the other

for

Transmission

lines-is

res-

circles.

Accounts

and

Finance

Organization

Under

the sole charge

of

'Financial

Adviser

and

Chief

Accounts

Officer'

this organization

is

respon-

th.

sJstery

of

cen_tral

payment

and

accounting

(popularly

known

as

Model

Scheme),

Financial

Advisei

Regular

Personnel

The

regular

staff, required

for execution of

the

project,

was

originally

drawn

almost

exclusively from

the

Irrigation

Department

of

the

former

Punjab.

With

the

re-organisation

of

the

State,

the

regular establish-

ment working

on

the

project

was

allocated to

the

successor

States

of Punjab

and Haryana. All

the

employees, according

to the

Punjab Reorganization

Act, 1966, continued

to work on

the

project

on the

same terms and conditions

which

were applicable to

them

before

the re-organization.

As and when

the

work-load

increased,

additional

personnel

were

drawn

from the three

partner

States.

However, recruitment

to the

posts

of

junior

officers

aud subordinates

was

made

by

the

project

administration

during the

peak

period

of

construction, when the States

were

unable

to

meet

the demand.

Work-charged

Estublishment

The

workmen

employed on

the

execution

of works

were

work-charged

employees.

The recruitment and

payment

of salary,

etc., to

the workmen,

were

regula-

ted

by a centralized

'Time

Keeping System'.

Such

employees

were

paid

on

the

basis of the

'Schedule

of

Wages'sanctioned

by

the

Beas

Construction

Board

from

time to

time.

Additionally, they

were allowed

fringe

benefits,

like

dearness allowance,

ad hoc

relief,

special

project

allowance, rent-free

residentiatr

accommodation,

free medical

aid,

etc.

The

service

conditions, viz.,

leave,

punishment

and

appeal

procedures,

etc.,

of such

employees

were

aicording

to

the

'Certified

Standing

Orders',

made

applicabG

after

certifying by

the

Chief

Labour

Commissioner.

For other matters

such

as accidents,

compensation,

retrenchment;

gratuity, emqloyees

profident

fund, etc.,

statutory

provisions

of

labour

laws

of

the

country

were applicable.

205

Labour

Relations

and Welfare

Labour is

the true architect

of

any

project,

big

or

small.

The

administration

fully

recognised

the

fact, both

in letter

and spirit.

The

services

of a Labour

Welfare

Officer were

requisitioned

from

the

Labour

Department

of the

Punjab

Government

to

ensure

that

provisions

of the labour laws

were

duly enforced,

and

the

view

points

of

the

administration

were

properly

explained

to

the workmen.

The

difficulties

and

the

grievances,

ventilated

by

the

representatives

of

laboul,

wele

mutually

discussed,

carefully

looked into

and the

decisions

prom_otly

carried

into

effect.

On the

whole,

the

relations

between

the

labour

and

the

management

remained

quite

cordial

throughout

the

eonstruction

period.

C.

LAND

ACQUISITION

For

the

project,

30,729

hectares

of

land were

206

D.

CONSTRUCTION

SUPPORT

FACILITIES

;

I

Major dewatering operations

were for the

construc-

tion of various

bridges on

road from

Talwara

to dam

site,

percolation

wells,

seepage

water,

diversion

tunnels,

stilling

basins and

from recovery

sites'

of

pervious

shell

material.

Safety

The

construction

of Beas

Dam involved

hazards

of

every

conceivable

nature.

A

well organized

safety

organisation

was created

with the sole

object

of-prevent-

ing occurrence

of

avoidable accidents.

The

safety

pro-

gramme

was

outlined

in

three

major

aspects

:

(a)

Safety

as

an integral

part

of the

design

and

operation

methods

of

plant

and equipment.

(b)

Adequate

personal

safety

equipment.

(c)

Safety education and

programme.

(d) Safety from

fire.

Apart

from two

fire-fighting

stations,

fire-fighting

devices

like extinguishers

fully equipped

were

provided

in

all

shops and

work

areas.

9.

Construction

of Dam,

Power

Plant

and

Appurtenant

Works

1.

DIVERSION

AND CARE

OF

RIVER

Diversion Tunnels

For diversion

of river

during

construction

of

the

dam,

five

concrete

lined tunnels,

each

of

9.14

m

finished

diameter

were constructed.

The

tunnels

had

an

aggregate

length

of

4,774 m.

The number of

diversion

tunnels

was

fixed

stocks

(P1,

P2

and

P3)

for

the

power

plant.

P3) was

taken up

in

December

lg6filJanuary

1965-

Excavation

of tfie tunnels

was carried

out

by full

face

blasting

method. The

tunnels

were

fully

supported

with circular

steel

ribs

of size

ISMB

250

spaced

generalty

at

0.60

m centres.

For the

fabrication

of

Juch

ste6l

ribs, cold

bending

technique

of

steel

girders

was developed

at the

project for ttre

first

time

in

the

world

for

this

size

of

joists.

Thr.

lin-ing

-

of

tunnels

with

concrete

was

t'ully

mechanized

(Figure

13). The

concrete was

pumpeil

behind

the

steel forms with

the

aid

of

pump-cretes

and

pipelines.

Special

steel

gantry

forms

were

designed

and

fabricated for this

purpose.

The

diver-

sion

works

also involved

construction

of river

bed

entry for

each

tunnel, stilling

basins,

exit channels

and

permanent

intakes for ultimate

utilization

of

the

tunnels.

All these were

completed

by

the end

of 1969

when

the

flows

of River Beas were

diverted

through

the

tunnels.

Cofer Dams

In

order

to divert

the river.flows

for

the

construc-

tion

of the

dam

and its

appurtenant

structures, coffer

dams were

constructed

of

random fill

material, both

upstream

and

downstream

outlet and

penstock

tunnels

and dam.

For

construction

of

spillway

stilling basin

and

power

plant,

coffer

dams were constructed

on

downstream

side

to

block

river water

entry.

The

crest levels

of all

such coffer dams

were kept on the

basis

of observed

highest

flood

level

at

the

site

with

provisions

of sulicient

free board.

Diversion

Schedule

Diversion

schedule

of river was

linked

with

the

raising of

dam

in stages

to a

safe height

to

avoid

over-topping.

As

per programme

based

on

availablc

resources,

the

dam

was envisaged to

be

completed

in five

stages,

viz.,0

(zero)

or

pre-diversion

stage,

and

I,II,ULIV stages; each to

be

completed in

one working

season after diversion. However, during actual

execu-

tion,

adverse

geological

features

were

encountered

in the

foundations necessitating

extra

quantum

of

work and

a. little less

progress

than

anticipated.

The

construction

stages were recast and

the dam

was

completed in

six stages

(Figure

l4); against

five

planned

initially.

The

various

stages

in

diversion

schedule and the

progress

achieved

in

raising

fill

placement

of dam

are

given

on

the

After completion of

the

first

stage,

the

monsoon

flows of River Beas were

passed

through

five tunnels

and also

partly

completed dam

(Figure

15). In order

to

minimise

the

severity

of

the

flow

conditions

and

extent

of scour

of the

fill, the top

level of

fill

placement

for the first stage

was kept

at

the natural

river bed

elevation.

An

apron

consisting

of boulders

in wire crates was

provided

at the

downstream

end

of fill

placed

to

act as downstream

toe

protection-

After

monsoons, it

was

noticed

that but

for

some

pot-holes

on

the left side,

the

partly

completed

dam

section stood the

on-slaught

of

floods

well.

Closure

Sequence of

Diversion

Tunnels

The last

phase

of

river diversion

consisted

of

interruption of

the

river

through

the

tunnels

for their

conversion

into

irrigation outlets

and

penstocks. The

207

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

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