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

end

of a

similar

pressure

diagram

will

run

to

zeto at the

downstream

face.

The

pressure

is

assumed

to

act

ovet

100

per-

cent of the

area.

(3)

Extreme

Loading

Condition: The extreme

loading

condition

specified

that

the

reservoir

water

surface

-would

be

raised

to

maximum

flood level:

drains

be

considered

ineffective

and

earthquake

effects

excluded.

The

uplift

pressure

was

assumed to

vary

linearly

from

full

pressure

at

the

upstream

face

to tail-water

pressure

or

zeio

-as

the

case

might

be

at

the

down-

stream

face,

the

pressure

acting

over

100

percent

of

the area,

If

the

up-lift

pressure

exceeded

the

vertical

normal

stresses at

the

upstream

face

(computed

without

uplift

-

but

including

.th9

effect

of the

c6nstruction

progamme)

then

under

such

conditions

a- horizontal

crack

should

be

assumed

to

exist.

This

crack

should

be

assumed

to

extend

from

the

upstream

face

into

the

interior

of

the

dam

to the

poiqt

where the

vertical

normal

stress

in

ine

cantilever

was equal

to

the

reservoir

pressure

at

that

elevation.

Ing.

uplift

for

ihis

condition

was

taken

as

full

reservoir

pressure

extending

from

the

upstream

face

io

the

end

of

the crack

and from

there

varying

linearly

to

tail-water

pressure or

.zerio,

is

the

case

might

be,

at the

down-

stream

face

of

the dam.

(xff)

All

transverse

and

longitudinal contraction

joints,

whether

to be

grouted

or left

ungrouted,

assumed

to be

keyed.,

(xiii)

If results

determined

from trial load twist

studies showed that the

transverse

contraction

joints

in

the

dam'

should

be

grouted

it

was

to be

assumed

that

the

recommendation

would

be

carried

out

and that the

joints

would

be

thoroughly

grouted

with

the reservoir

level

at

the

elevation

determined

from the analysis.

(xiv)

The

inclined stress

parallel

to

the face

of a

cantilever

was

equal

to

the vertical stress

divided

by

the square

of the

cosine of the

angle between the

face and the

vertical direc-

tion minus the

water

pressure

normal to the

face multiplied by

the squ:rre of the

tangent

of

the angle

between the

face and

the

vertical

direction.

(xv)

The

dam

was

considered to be

non-symmetrical

and

non-symmetrically loaded.

(xvi)

The idealized

profile

of

the

dam

on

the

beam

centre

lines

was

used in

the

analysis.

(xvii) Due to the broken

condition

of

the

rock

above

EI.498.3

m

(1,635

ft) MSL

at

the

right abut-

ment

(looking

upstream), it

was

assumed

that

no

load

would

be

transferred horizontally

to

the

right

abutment

above this elevation.

(xviii)

For

the

purpose

of these

analyses all

references

-

made to the

left

and

right

side

of the

dam

were

for

the

profile

of the canyon

looking

upstream.

(vfi)

Uplift

pressure

assumed

earthquake.

to be

unaffected

bY

(viii)

Stresses

assumed

to

be

unaffected

by

pressure.

they

would

be excavated,

treated,

and-

filled

with concrete

so

that

uniformly

sound

foun-

dation

conditions

would

exist

under

the

dam.

(x)

The concrete

in the

dam

would

be

homogeneous'

:

uniformly

elastic

in

all

directions,

3ld

strong

enough

to car5y

the

applied

loads

with

stresses

well below

the

elastic

limit.

(xf) The

dam

would

be

thoroughly

keyed

into'

the

foundation

and abutment

rock

throughout

its

contact

with the canyon

profile,

so that

the

horizontal

elements

might be

considered

as

fixed

with

relation

to the

abutments

and the

cantilevers

as

fixed

rvith respect

to

the

foundation.

The

relevant

summary

and conclusions

of

1952

uplift

study

are as

follows

:

(a) The results

of study 2A

have

shown

that :

(l)

For

normal

operating

conditions,

earthquake

'

forces

excluded,

the

section

of the

dam

has

shear

friction

factors

on

horizontal

and

abutment

planes

greater

than

4.

(2)

For

normal

operating

conditions,

earthquake

forces

excluded,

the

maximum

compressive

stresses

created

in the

dam

are

less

than 43.9

kg/cm'

(625 p.s.i.).

(3)

For

normal

operating

conditions,

earthquake

forces

excluded,

no

beam

stresses

are

deve-

loped

even

when

the

transverse

joints

are

grbuted, because

beam

action

is

developed

6nty

during

an earthquake.

The

tensile

p.rin-

cipil

stress

developed

is

2-7

kg/cm2

(39 p.s.i.).

(a) Fof

normal

operating

conditions,.earthquake

forces

excluded,

the

upstream

cantilever

stress

including

construction

programme bears

a

minimum

ratio

of

70.4

percent

to

the

corres-

ponding

hydrostatic

pressure. If full

uplift

20

pressure is

developed,

and the

cantilever

is

assumed to crack, then

the

resulting minimum

shear

friction

factor over

the

uncracked

length

of

a horizontalsection

is

greater

than 1.5.

Judged

on the basis of design

criteria adopted for

dams

designed

by

and constructed

under the su1rcr-

vision

and

control of United

States Bureau

of

Recla-

mation,

the results

of

study

2A

indicated

rhat

under

normal

operating

conditions

earthquake forces being

excluded, the

section

of

the

dam is

satisfactory

whether

the

transverse

joints

are

grouted

or

not.

(b)

A

comparison

of the

analysis

which includes

earthquake

forces,

study

2-transverse

joints

ungrouted

and

study

zB-transverse

joints

grouted,

showed

that :

(l)

For study

2

the shear

friction factors are

greater

than 4

irrespective

of the

assumptions

for uplift'pressures

and

coefficient

of friction.

(2)

For study 2B

the

minimum

shear friction

factor

on

abutment

planes

is

3.75 when

two-

thirds

area uplift

and

coefficient of friction

0.65

are

assumed;

and is

3.99

when

the

new

uplift

criterion

and

coefficient of internal

friction

0.80 are

assumed.

(3)

The maximum

compressive

stresses are

less

than 43.9

kg/cmz

(625

p.s.i.)

for both

studies.

(a)

The

minimum

ratio

of upstreanr

cantilever

stress, including

construction

programme,

to

the

hydrostatic pressure

is 3.5

percent

for

study

2,

and 36.7

percent

for

study

28.

Subjec-

ted

to

the

extreme

loading

condition,

drains

being inoperative

and

the

cantilever

assumed

to crack,

the

resulting

shear

friction factors

are

greater

than 1.5.

(5)

No

beam

tension

is

created

in

the

conditions

represented

by

study

2. The

maximum beam

tension tbr

study 2B

is

6.61

kg/cmz

(94 p.s.i.).

(6)

The

maximum

tensile

principal

stress is7.73

kg/cm2

(l

l0

p.s.i.)

for

study 2 and

11.46

kg/cmz

(163

p.s.i.)

for study

28.

On

the basis

of

this

comparison

of

results it was

considered

advantageous

to

leave the

transverse

joints

ungrouted.

However, there were

some

factors that

werc

not

brought

out by a study

of the

results,

and

these relate

primarily

to

the fact that

a

dam with un-

grouted

transverse

joints

is

not

a

monolithic

structure.

For

a

dam

of less

height

than Bhakra.Dam this might

not

have

been

an

important

consideration.

There was

no precedent

of

a

dam

of

the

size of Bhakra having

been

constructed

with

ungrouted

transverse

joints.

The

proposal

of

not

grouting

the transverse

joints

in

a

dam

of the

size

and

configuration

of

Bhakra

was

considered

unsuitable.

This objection

was

raised from two

consi-

derations

;

first,

that in

ungrouted

dam the

transfer

of

load

to

the abutment

is

effected

through

the keyways.

surface

at

El.

512.1

m

(1,680

ft)

MSL.

_

(c)_

It was

proposed

that

the

transverse

joints

should

be

grouted

with

the reservoir

water

surface

held

at

El.

512.1

m

(1,680

f0

MSL.

The

effecr was

to

reduce

the maximum

beam

stress

in

comparison

to the

condition

of reservoir

El.

466.3 m

(1,530-f0

IUSI-.

However,

from

practical

consideratiohs

the trans-

verse

joints

were

grouted

when

the average

reservoir

was

at El.

499.9

(1,640

ft)

MSL

but above

El.

403.8 m

(1,620

ft)

MSL.

Subsequently,

the

adequacy

of

structure was

tested

for

maximum

reservoir

El. 515.1

m

(1,690

ft) MSL.

In

view

of

the

maximum

reservoir

level being

effective

only

for

short

duration,

the increased

stresses were

considered

to be

within

safe limits

for the section

already

provided.'

In

addition

to

these studies, photo-elastic

studies

and biharmonic

analysis

of the

dam section

for

delinea-

tion

of upstream

strut

and

plug (provided

for upstream

claystone

band

and

not

considered

part

of

section for

trial load

studies)

were

also made.

Another

set

of

trial load

twist studies

for

actual

valley

profils

and

construction

schedule

were

made

for

study

of

prototype

behaviour.

2.5

Foundation

Treatment

of the

Dam

Treatment

of Ctay

Bands:

The

three

clay-banrJs,

i.e.,

the heel

clay

stone

band,

the

middle

clay stone band

and

the

downstream

clay

stone

band

traverse the foun-

dation area

as shown

in

[Figures

7

(a)

& 8].

These clay

bands

though capable

of carrying

great

loads in

a

confined and unweathered

stage

become

plastic

when

submerged

and disintegrate

under conditions of alter-

nate drying

and

wetting.

As such

suitable

steps

were

taken to treat

these bands

as described

hereafter.

2l

,;"^lIeellClay,Stone

:

The

heel-clay

stone

is

30

tb

45

m

(I00.to

'150_ft)

wide

and

dips

at an

angle

of

70"

down_

stream-.

with -

the

nearest_point

22.5

m

(zs

ft) upstream

of

thb

heel

of

the

dam.

Ii

recedes

away

fro'rnthe

dam

at

higher-elevation's.

It

was

considered

ihat

on

accounr

of

continued

submergence

under great

d-pths

of

water,,

this

band

pig-ht

become plistic

and

livJwat

under

the load

of

the

dam.

It

wai,

therefoie,-decidei

to

bxca'vate

the

clay

band

in

the

river

r""iion

to

a

suitable

depth

and

backfill with

concrete.

Further-

more'

a'concrete

sffut

of

adequate

thickness,

spannin!

Jh!.

clay-band,r,

lvas -prop

osed-for

transferring

tde

roadi

to

the upstieam'sandstone,.called

footwall.

-

Photoelastic

studies

were

carried

out

to determine

the stresses

expected

to

exist

in

the

vicinity

of

the

clay

'stonii/silf

stonel

under

various

conditioniof

load

and

with various

depths

of

,proposed

treatment.

These

tests indicated

that

stresses'iin

the

bed rock

adjacent

Jo

the

ploposed

treatment

in the

clay

stone/silt-stone

stratum

decreased

rather

rapidly

for

depthi

down

to

30

rn

(100

ft)

andvarygradualiy

thereafter.

Itwas

'apparent

that

the depth

of

plug

beyond

30

m

(100

ft)

did not

materially

bontribute

to

-reduction

in

i

the

stresses

at the

base

of rhe

plug.

A

22.5 m

(75

ft)

plug

red,ug-qd

'stresses

to

"within

p-ermissibf"

fiiits

uod

*ur,

therefgre,adopted.',

-,

:

!

rj

Photoelastic

experiments

further

indicated

that if

the

bottom

of

the

plug

was

sloped

parallel

to the

strut,

tensile

stresses

in

it were

eliminated.

This

fact

caused

4e

gpgtqeam

end

of

footwall

contact

to be

depressed

to

El.

292,6

m

(960

fr).

_

T*o

longitudinal

galleries

(which

were

connected

1q

thg-dam

!y 1oeans

of three

transverse

galleries)

were

provided

within

the

plug

following

the

upstream

and

downstream

clay

sandstone

junctiois

for

^grouting

the

contacts.

and

consolidating

disturbed

sandstone

beds

to.?

denth of

about

-15.2

m-(50

ft),

This

grouring

was

a laborious

task and

completed

in

1960.

Water

tisting

in

these

zones

in

1963-and 1964

showed

good

water

tightness.

For

side

slopes

above

the rivEr

bed

an

adequate

toncrete

ccver

was

provided

to,confine,:the

clay

stone

members.

i,

"

,_.

!t[id{e Qtoy

Stone:

'

The

midOle

clay stone

band

varies

in

width_

from

6 m

(20

ft) to

I m

(30

ft)

and is

comp.letely

confined

by

the

dam

except

where

it

passes

out

from

under

the

dam

in

the

left

abutment.

.It.;is

treated

by

excavating

the

same

and

backfilling

with

sp^ecially

-p_re_c^o_oled

cbncrete

with

placing

temperature

of

10o

to

l2.8oC

(50:

to

s5"r;.

The

treichin!

depth

was

based

on

formula

derermined

by the

Unitet

stites

Bureau

of

Reclamation

for

Shasta

Da*

:

.,

d=0.002

H'W

*,,I0

ft.

Where

,

d

is

the

normal

depth

of

trench

in

feet.

H

is

the

height

of

the dam

above

sound

rock

infeet.

r;

:---:-.

,

.

W

is

the

width

of"the

zong

in

feet.

22

The

sandstone

contact

special

feature

for

the

r

supplementary

longitudin

runs

;ust

upstream

of

th

provided

with

a

view

to

yhic-h

might

pile

up

agains

.Dand.

"

Downstream

-clay

pand:

This

band

iJbes

not

affect

the

stability

otthe

dam.in

any

*uv.--rr"*".*r,

the rert

Foygr

pl?nt

is

founded

on'it

uii.,

urrvioiir;

suirable

raft

foundation.

.,.

'S'hear

Zones

s

mostly

in

the

body

of

the

I

the

axis

from

station

3.7

m

17

ft).

On

right.

abutment

nerge

into

the

thrust zone

at

i

m

(1,550

ft). In width

the

rm

3,m

to

6

m

(10

to

20

ft).

this

zone

to

prevent

further

rock

in

proximity

or

under

The

treatment

consisted'of

:

(t)

Cold

concrete

c?p

to

formula

depth,

i.e.,

l!

to

2

tlmes

^the

width,

subject

i.?_i"i_um

of

l

m

(r0.ft)

lp

to

erevatioii

oi

jis.il^tizoo

rt)

(top

of

dam).

(ii)

consolidation

grouting

of

afljoining

rock

on

both

sides

of

ihe

"on".,

uoa

p".ooiri6n-of

ade-

quate

sub-surface

drains

whire

;ti,

thin

to

prevent

uplift

pressure

as

a

consequence

of

rapid

drawdown.

Toe

Shear

Z9n9:

This

zone

runs

along

the

toe

of

the,dam

on

the

reft

abutment

and

varies

l" *ioin

from

6 tg

]8

m(20

to_

60fr).

The

trearmentof

this

bed

TocF

feature

in

_the,

area

where

substantial

toe

thrust

i.:,.1-ry:.^1^ty

the

toade{

Oam

consisted

of

piugging

wltn

concrete

as

per

standard

formulae,

,uppGmenteO

by

a

fillet.!9

r99k

on

the

downstream

side

of

the zone

wnere

practrcable.

it

zone

consisting

of

gouge

arying

from

0.6

to 4.3

m

(2

butment

obliquely

from

El.

rwnstream

side'to E,l.

457.2

area,

this

thrus

t

zone

joins

t,li?,i1T;.,:'rll:r"rH:";i

alogt

Et..472.4

m

(r,550

ft).

c;

rh;

;;;;;;;.;m

side

or rhe

abutment

area

but

rvithin

the

section

of dam,

the thrust

zone

joins

into

a

claJ;

stone

band.

The

strike

of

the

thrust

zole

in

question

is

nearry

at

right

angles

to

the

gorge-

fne,,Aiir

along

ihe

rigti

QL-LI&-

CLttoo,.

4.tq!l)

Ch.9ean

4.9tta

tA.rhro

cA.tw

h!2.50.

aL.Em?

Ch.r3+3O

Q.llt-@

Ch.nt&_

ct

Eg_

Ch.tsolro*

Ch.rtfil

_

$$lil

$

sfl

$l$!l!1

fl{$$l

nfiEi

.t

qd

L)/

:4_-_

__l

I

h.AleA

ch.

tttp

-Jct4r*

J7!Q

$

$$

R $

flfifis$

I

PLr

MAIN GEO

IN

FOUNDATI(

r

23

.

BHAKRA

DAM

PLAN

SHOWING

MAIN

GEOLOGICAL

FEATURES

l]'f

FoUitDATtoN

a AEUTTENTg

OF

grag

I

t

a

$

I

t

s

I

+

|o

t

Y)

Et

t7O0

fl 6e0t

?xl

-1

I

F

\

i

250

, t-1_.|"--|_}-l

drilled

downtords

fftrtTTTfi-iT]

t.

,--Pro'

lz-Fffitz.4ptlofhola,.tobe

ffi

-.-J'

pres,

-

l-Lfffi

-

anlcd upwrds

ft'1] |1Tf l I I i]

{r

zont

ll

litrilt'++t'++ffi1 i+i1+fiifll

----

ptt*,

ul

qatting

9".d

d'd:

SO

Tii,g,;"-i

tz'lc'

from

th

5i

'-

f-l

iffift1j1+lf#{+i,h,s

smph

h",*,t?:,t

ry:

2OO 25A

bol

inlo cone,,ctC

)

--Olac!-*

-rr

1RAPtj

FoR

'G'uott

LENGTHS

(to

u

dri//ed

lrom Harn

Foudohort 6al9ry

od

'olleryotd

6t

D

ftnrcls)

upword

'6'hoEs

blwcen

iourtoh'on

gailcra and

ft

I

tl

rl

il

tl

!i

tl

I

1

I

finol

acortliu,

ltE

AtLOcl<

30

ghplum

--6toulng

qd

druooi,

lfiTl'

'"F'

Ho'lal

t

l'

mn

dioqP1

b'notcs

ti-,

Lttt-

n

DL

0cl4

25

,

Y.

itu

I

SECTION

A-A

o

t

N

o

a

o

I

s

/

--1---/

-

-- _L--+--

//

ll

Yet6,6!

'6'lo/es

ar,/,

b"

nci;ncd

'wrlh

lhc'

tvnYord

f'holabcltcan

illerl ond

lurnel

Y%,_____

lNOATION

6I LLENY

dja O5't

cln

AXts oF

0A

(s::'r^--filiiiiii

i\iixy,n#ii::,',)

rili

i

;

I''donoe

htrnct

i |

|

(iiiii

itr

rrat.ct

r,o

ni,r,

6A

\

'6'

Ho/os

6

5't

ctn

ll"

6'rl'

nrouli rrg ort

i!.1,1,

/e*top

lutncl

i ll

El.

ltfl|. 6

ltt

10.

t !

1j,4

itzrtthat

unlt

iiijiqiiiiii

o'e

El

plane

vilh

lhe,ailtcol

SCALE

O

/OO

FEET

BHAKRA

DAM

FOUNDATION

TREATMENT

CURTAIN

GROUT

ING

FIGURE

8

(bI

It

rl

It

tl

il

ll

I

\

I

t

I

ii

;l

!l

rl

It

ll

It

lr

I

abutment

face varies

from

moderate

up to

about

50

degrees

in

a downstream direction,

with a

slight com-

ponent

of

dip

into

the cliff.

The

defective

thrust zone is important as

there

was

the

chance of sertlement

of overlying

rock

and

section

of

dam

above, due

to

consolidation

and

squeezing

under

combined load

of dam and

reservoif water.

Treatment

necessary

to

prevent

undesired settlement

either

as

a

result

of load,

or in combination with

effects

of

piping

through

seepage

was

as

follows :

(a)

Percolation

of reservoir water

along

the

thrust

zone was

stopped by

a

tunnel 30.5 m

(100

ft)

driven

in

line of the

principal grout

curtain

into

the

abutment,

backfilled with

concrete and

contacts grouted.

(D)

Prevention

of squeezing

out of disturbed

material

was

achieved

by

two

plug

tunnels,

one

15.2 m

(50

ft)

deep

along

the

zone

under the

heel

of

the dam

and

the

second tunnel of

12.2

m

(40

ft) depth

along

the

zone,

at

the toe

of

the

dam.

The contacts of

these concrete

plug

tunnels

were

pressure

grouted.

Inter-

mediate

concrete

plug

tunnels

were

also

put

in

to confine the

material.

(c)

In

order

to

prevent

settlement

where

the

over-

Iying wedge

of rock

in the abutment was thin,

a dental f,ll

of

concrete to a depth

of 6.1

m

(20

f0

minimum

was

formed

along

the full

trace of

the

thrust

zone in the abutment

area

of

the

dam

and

to the axis

shear

zone

upstream to ensure

that

there

was a

thickness

of

23 to 30.5

m

(75

to

100

f0

of

good

rock

immediately

above

the zone capable

of

carrying

the

weight

of

the

loaded dam.

Near

Horizontal

Cross Shear

Zones

Many

near horizontal

cross

shear

zones,

varying

in

width

from

a

few centimeters

to

about

a metre,

intersect

the

abutments

with strike

nearly

at

right

angles

to

the

gorge.

These

cut the sandstone

strata

and

consist

of

-

crushed material

with clayey material

infiltered

in

a closely criss-crossed

jointing

pattern.

The

fautt

planes

are

comparatively

flat and

irregularly

bedded

and

occasionally

shift

the

boundaries

of the

normal

beds.

These zones

needed

special

treatment

on

account

of

their

low

bearing

strength,

the tendency

of

the dam to slide

on shear

planes

and

percolation

of

water through

the seams

from

the

reservoir.

The

zones

were

exiavated

and

backfiiled

with

concrete.

Concrete

plugs

of

adequate

depth

were

provided at

suitable

places

as

described

below :

(i)

Plug tunnels

in

the

plane

of

the

cross

shear

zones at

the heel

of the dam extending

15.2

m

(50

ft)

into the abutment.

(tt)

A

plug

tunnel

30.5

m

(100

ft) in

length

in the

plane

of

the

cross

shear,zone

along

the line

of

main

grout

curtains.

(iii)

A

12.2

m

-(40

ft)

long

plug

tunnel

along

the

plane

of

the cross

shear

zones

at the

toe df

the

dam or

on

the

termination

of the

cross

shear

zone

out-crop

where

they

terminated

at

an

upstream

location.

(iv)

Dental

caps

to

a

depth of

about 1.5

m

(5

f0

were provided

along

the

outcrop of

the.cross

shear

zones.

The

bountlary

sandstone

along

the tunnel

plugs

and

dental

treatment was

grouted

under

pressure.

2.6

Consolidation

(Blanket)

Grouting

Besides the

special

treatment

of

weak

zones

men-

15.2

m

(50

ft)

below El.

426.7

m

(1,400

fr).

Consolidation

grouting

of

foundation

of

Bhakra

Dam

by

pressure

grouting

consumed

500,000 bags

of

portland

c€ment

(50

kg

each)

through 457,205.5

m

(1,500,000

ft)

depth

of

diamond drilled

holes.

The

intake

of

grout

at elevations

higher than

426.7 m

(1,400

ft) was

more

than

that

at

lower

elevations. Some

holes

'consumed

hundreds

of

bags even though

adjacent

holes had

previously

been

grouted

to

refusal

with nominal intake.

The holes

were

generally

aligned

so

as to

cut

maximum number

of

bedding

planes.

The

criterion

of

completion

was

to achievE water loss

of

less than

1.49

litre per

minute

per

metre

(0.1

gallon

per

minute

per

ft)

length of the hole

at the specified

grout

pressures

in a

diagonally drilled

test hole. The maxi-

mum

pressure

applied

did

not

exceed 7.03 kg/cmz

(100

lb

per

sq

in.)

[See

Figure

8

(a)].

2.7

Intermediate Curtain Grouting

(F-Holes

Grouting)

The

depth

of

intermediate

grout

curtain

varies

from

23 m

(75

ft) at

the

abutments to 38 m

(125

ft) in

the

river

section

with

corresponding

pressures

varying

from

7.03

kgicm2

(100 p.s.i.)

to

17.6 kg/cmz

(250 p.s.i.). The

grouting

was

done

from

the

main

foundation

gallery

through

holes drilled

at 3 m

(10

ft)

centres

at

an angle

of

50o

with

the

veftical

towards

upstream.

The

work

was finished

upto

El. 487.7

m

(f,600

ft)

by

June

1962. Mean

grout

intake

in the

central

portion ranged

from 3

to

55 bags

of

50

kg

each

for

a

total

of

45.7

m

(150

ft) stage

depth

of

3

co'npa-

nion

holes

in

a

group.

The

maximum

intake

was

1,249

bags

ior

45.7

m

(150

ft)

stage depth

of

3

holes

taken

slmultaneously

in block 2

and

believed

to be

due to the

proximity

of

downstream

contact

of

sandstone

with

heel clay

stone.

Sornewhat

erratic

----4

"v

25

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

Подождите немного. Документ загружается.