Indian National Committee on Large Dams. Design and Construction Features of Selected Dams in India
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Sto.
t6
+45.9?
l7+OA88
t8+28.8O
I I +
50.72
GI
tt?
@
rq
+
o
Droinogc
holcs
o
uriliory kcy ?rench
roundotion
tygc
prczome?er
?ips
Cut
off
kays
Axis
of
dom
3m
below
rnoin
key tranch
Cut
off
keys
Foundotion
ly
pe
piezorn-
€ter
ttps
2.5:l
R-rA
to
3A
\
lls
aa
UG
.c
rout
hohG
U/S
Corc frcnch
ott
PLAI{-
RTVER
BEO
pORT|ON
Axis
of
dom
Ef.435.864
s-l
Plosfic
rcom
R-
lA
ro
3A
Ercovolion
line
SEC
TION
LEFT
AEUT}IENT
FIGURE
5:
Foundation
treatment
details,
q
$
to
+
o
-c
o
Growl
fitl
Er.3
74.
Morsive
conc
shofts
($"'^-..
ryc
(b)
Lsrr
Asurr\,rnr.lr
LEGEND
lo
Selected
cloyshole
lb
Selecfed
soridrock
2o
Selected
sond
ond
grovel
2b
Setected
sond,
grqfrt,
cobbles
and
boulders
Rip rop
25h
FIGURE
6:
Beas
Dam-Maximnm
section.
Axis
q;
66sn
t+-
'Top
9f
.dom
8t.435.96
m
.434.34m
r
Fgg.am
-fFl ?Qr./
l3.ZZm
.
Normolreservoir
-J
E1.426-72mt
jt
112.2m.91.
q
fiso.sz
189
Part
ll-nesign
4.
(i)
Design
of
Dam
-
The
type
of
foundation
alternate
layers
of sand ro
definite
limitations
on the
of
dam
that
could
be
safe
tests
showed great
differer
and
character
of various
Ia
that
concentration
of load
be
avoided.
Hence
the
feasibility
of
a
mass
concrete
gravity
section
was
ruled
out.
Further,
in
view
of
the
high
seismic
activity
oj
the- regio-n,
it was
necessary
th.at
the
lype
of
dam
tb
be
adopied
ihould
be
able
to
withstand
the
probable
earthquake
rt
oikr.
The
alternative
of
adopting
a
hollow
buttress
itructure
s-uppo-rted
on
a
mass
concrete
pedestal
was
also,
$e1ef9re,
not
considered
suitabre
in
-view
of
the
eiesirabiliry
for avoiding
high
cantilever
.struciures.
In view
of
the
above,
an
earth
core
graver
sheil
dam,
for
rvhich
construction
naterials
weie
availabre
within
convenient.
distances,
had
b.en
-riti.t.o,
as
it
wouici
permit
deformation
*itnoui--;up;;r.
and
c.ould
provide
flexibitity
against
unequal
setllement
in
the
foundation.
The
full
reservoir
revel
at
pong
Dam
is
El. 426.72
m.
The
dead
storage
level,
based
"oo
ii.
Lqoir"-""t
of
minimum
head
l9r.
th-e.
powe-q
*iti-rrur--b1;
k;t;
at
El.
384.05
m..
This
givbs
a
Iye
,torug.
capacity
oi
0.2:90
million
hecrare
tietres,
fni
ri"-."-g.
li'"
..uo
year..being
0.6059
nrilrion
hectare
metres,
the
surprus
supplies
available
in
good
years
would
de
sioreo
ana
carried
our
for
utirisation
in
succeedi"t;t
y.urr.
Further,
to
carer
for
the
design
flood
with
a
peak
dischar-ee
of
j
j,5j5
cumecg--(frequency
of I
in
10,000
-vears).
and
a vorume
of
o.5624
mittiottni.turr--erres,
the
flood
routing
studies
indicated
a tnuiir"-
reser-
voir
level
at El. 433.
r-z
m
when
tue
auoue-A;;il"
flood
is
impinged_on
the
furr
reservoii
re*f?
hi.-iz"s.lz
m.
Bes^ides,
a flree
board
of
2.7 4
m,
to
cater
for
wave
action,
was
considered
nec(
of
dam
at
El.
435.85
m.
Thr
for
the rvave
height
(based
c
of
96.56
km/houi
and
fetcj
conventional
formulae.
Thr
ajlopin-e
surface
for
maximum
computed
wave
height
of
2
m
would
be
keeping
in
view
thd
raie
porriuiliiioi
the
maximum
llood
and-worst
rvinds
o..'ulr]ng"ut
the
same
time
on full
reservoir.
A numb€r
of
srudies
for
the
choice
of
axis
of
dam
The
*ere
ca',ied
oui.'
-ii;1il;i
's-Jcction
oi
triJ-.ii.-
o-r
or,"iilj,i"Tl"'#
#:f'y,i:H,rj"lfl,"l*ri"X*
190
4.
(ii)
Section
of
Dam
4.
(iii)
River
Diversion
l.
First
Stage
Diversion
a.
(iv)
Structural
Design
of
Dam
1.
Staiitity
Analysii
The
section
was
analysed
!y
tne
conventionar
slip
circle
and
w.edge
methods
of- analysis.
The
various
loading
conditions
for
which
the
slopes
were
tested,
are
as
below
:
(a)
Upsrnelu
Srope
pore
pressures
accounted
for
and with
hori_
zontal
earthquake
acceleration
of 0.C6
g.
(2)
Steady
state
seepage
condition
with
reser-
voir
El.
426.72
m ahO
with
horizontal
earth-
quake
acceleration
of
O.l2
g.
(3)
Sudden
drawdown
condition
with
reservoir
depleted
from
normal
level
El.426JZ
m
to
dead
qtgragg
level
EI.
3g4
m assuming
sheH
material
to
be
free
draining
and
notlnclud_
ing
earthquake
forces.
(b)
Dowxsrneeu
Slopr
(l)
steady
state
condition
with
furr
reservoir
level
at
El.
426.72
m wirh
horizontal
earth_
quake
acceleration
of
0.12
g.
(2)
construction
condition
with
construcrion
pore
pressures
accounted
for and
horizontal
earthquake
acceleration
of
0.06
g.
The
following
minimum
factors
of safety
against
sliding
of
the
embankment
slopes
rvere
aOJptiO.
-
Non-seismic
condition
1.5
Seismic
condition
1.1
2.
Structural
Behaviour
Testittg
Apparatus
In
order
to observe
and
monitor
the behaviour
of
the
Pong
Dam
during
construction
as well
as
in
the
operation-sJage,
instruments
have
been
installed
within
and
outside
the dam
embankment.
observations
on
these
instruments
would
heln
,r"
making
comparison
with.design
assumptions
on
the
dam
and
li
o.teiril;g
the
design
practices
for
future
construction.
.
Mainly
two
types
of
instrument
installations
have
been
used
on
Beas
Dam.
one
is
the
piiio;;t*
instal-
lation
for measuring
pore
pressures
anld the
other
is
the
settlernent
installatibn
for
observing
displacement
of
the
dam
embankment
and
foundat"ion.
^
In
-
addition
llTre is
a
slope
indictor
installation
for
measuring
Iateral
movements
in
the
dam
alongwith
some
instrur
ments
for
recording
seismic
activity"
around
the dam.
The
'location
of
-various
instruirents
is
shown
in
Figure
7.
4.(v)
Elechical
System
The
electrical
system
has
been
divided
into four
Putt1,namely,.(f)
Power
and
Control
System,
(ii)
Light-
1ng
System,.(iii)
9ro_unding
System,
and
(iv)'Telephine
fystem.
The
brief
descrip-tio-n
of tir.
iyriem-
li
Ciu.o
below:
| . Power
and
control
system
step-down
sub-stations
Two
number,
11000/415
volts,
step-down
sub-
stations
have
been
located
as
near
to
the
^road
ceutres
(1)
Construction
condition
with
construction
t9l
1oo.9gOOm
LEGEND
Poropel
rclllcmml
poin
Rip rop
Ticr
Et.326"t4
m
25
24J
Top
of don
Et.435.96
n
Tier
Et.4O8.a3n
Tier
Et.39t.6Zm
Tier
8.365.?6m
Tier
Et.
aOO.gtm
Terrninol
wcll
or
E|.377.95
n
*Et.387.tOm
Tnrmlnol
well
SEC.
AT
Sto.
tA+Ag.gOm
Tirr
Et.4O8.43
m
Ticr
Et.39t.6?m
Ticr
8t.365.26m
fior
Et.349.9r
m
Ticr
Et.3Zg,tgm
Terminol
wdtl
cs-l4A
SEC.
AT
Sto.2Zt55.52
m
FIGURE
7.:
Soil
instrumentation.
192
as
possible
so
as
to
reduce
the
vortage
drop
and
to
economise
the in
length
and
size
or
irrJlJa;i
cabtes.
The
main
sub-station
has
been
rocated
in a build-
ing
O.f.app_roximate
size
I1.90
m x
9.14
m
and"umprises
one
ll
kv power
board,
one 415
voltJ
dirtribution
Doard
and
two
250
kVA
step-down
11000/415
volts
distribution
transformers.
^
,
T\..
arrangement
comprises
a sectionalised
L.T.
ous
whrch
ls
connected
through
a
bus
coupler.
Each
section
is
independently-
fJO
inrougfr-"'rtrp_down
transformer.
The-
system-
has
bein
r?-
o,,iln.o
that
normally
both
the
buses
sharr
remain.;;rt;;Eindepen-
d9n1ly,
but
in
case
of
fault
or
maintenuo.?
on
uny
one
of
the
transformers,
1r
kv
or
L.T.
i""o-io!
breakers,
the
supply
ro
its
bus
can
be
restorea
inioufn
1n,
bus
coupler,
thus
transferring
the
whole
load
ori
one
trans-
IOrmer.
.For
the_ purpose,
the
incoming
breakers
have
been
so
rnterlocked
with
the
bus
couprer
breaker
that in
the
€vent,
an
incoming
breaker
tripi
by
operation
of
con_
trol
switch
or
by
-under
vortige
cotiaitions..
the
bus
couplel
breaker
wiil
crose
autoilati.ad
piluiceo
the
latter's
contror
switch
ir
in-1rtr
-"t;
piriii"".
The
transfer
shall
be
blocked
when
tf,"
ln"6-lrrg
breut(e,
ttipt
by
its
protective
oue.ioad
uod
-
rt.it
circuit
devices.
The
I I
kV
supply
is
taken
from
the
I
I kV
power
board
located
in'
^
t[e
p;;;
;ower
plant
switchyard.
Two
No.
1l
kV
cables
travE
i..r, provided
for this
pu.rpose
and
have
been
routed
throuih
tni
-caHe
tun-
nel.upto
the
power
planf
;d
tnereiireitniougr,
the
cable
trench
fo the
iuU_statlon.
'
.
From
this
sub-station,
two
sets
of
L.T.
cables
com_
taken
and
routed
through
rminates
in
the
L.T.
distii-
shaft
houses
of
irrigation
ate
hoist
control
chahber,
r
lhese
structures.
The
:
L.T.
distribution
boards
board
located
in
the
pong
p!we1
plant
switchyard
and
is
transmitted
through"ttrd
r
t
tv-overtreaa
trans-
mission
line-
This
sub-itution
caters
to
the
loads
of
drainage
tunnels
in
the
right
aiutment
of the
dam.
2.
Illumination
The
illumination
levels
provided
at various
loca-
tions
have
been
based
on
-tf,.
various
standards
and
practices
as
adopted
on
oth.,
projects.
3. Telephone
System
5.
Design
of
Spillway
The
spillwav
has
g
bays
of
I4.47g
m
each,
the
totalwidth
between
the
aiutitents
being
r02.10g
m
and
clear
waterway
of
g6.g6g
;.
,_- Jh.t
.
phase
power
outlets
hale
been
provided
at
lmportant
Iocations
for
connecting
temporary
loads
such
as
welding
sets,
compressors,
etc.
.
Two.No.
spare
breakers
have
been
provided
in
the
sub-station
foi
any
futui;
i";;.
-
The
other
sub-station
comprises
a 40
kVA
pole
mounted
I1000/41,5
volts.
-s_tep_down
transfonner,
an
I
I
.
kV
H.
T.
swirch
and
415
volts
L.
T.
switch
fuse
units.
The
I
t
kV
supply
is
taken
from
I
I
kV power
193
t
10
o
v
ct
fil
)
3
F
o
€
o
z
€
o
,\
o
(v)
(n
J
3
F
x
o
o
3
o
L
(,
o
,i
c
o
*K"*lE
<----l
!
c
o
o
a
o-
€
\
L
c')
il)
cll
o
.€
L
D
a
6
L
lJ
(D
(f,
AJ
x
Ot
o.J
J-
a
p
()
fr
a\.,.P
r =Q
z
J
o
J
U
o
o
o
Cr
p
194
upstream of
dam
axis to about
403.86
m
at
its
entrance.
The
side walls
ate straight
for a length
of
33.528 m
upstrqam of dam
axis. Thereafter,
the
left
side
wall
has
been
given
a
curvature
of 46.482
m
radius and
terminates
in
the
core
of
the
left side
auxiliary
dam. The right side wall
has been
given
an
elliptical
curve shape conforming
to the equa-
xz
v2
tion
a,
+
zr
:
I
where,
c
:
46.482
m and
b
:
27.432 m. The
height
of
wall
is 24.384 m.
l. Design
Data
No.
of spillway
openings
Clear
opening between
piers
Size
of
gate
Full
reservoir
level
Max.
reservoir
level
Top level
of
gate (when
fully closed)
Bottom
level
of
gate
(when
fully
open)
No.
of
hoists
Capacity
of
hoist
Total
lift
Lifting
and Lowering
speed
(electric
drive)
(fii)
The
centre
line
of
spillway
has been finally
kept
at station
9
*
81.456 m
in
order
to
obtain
a balanced
excavated
section
and
also
to obtain
a
suitable
common bank
./
between
the
exit
channel of
the spillway and
tail-race
channel of
Pong
power
plant.
3.
Selection
of Type
of Spillwty
The
spillway
had
to
pass
a
maximum
discharge
of
12,374 cumecs.
For
such a large discharge, the
suitable
type
of
spillway which
could be
provided,
was
a
con-
crete
gravity
section
or
a
chute spillway.
In
view
of
the
high seismicity
of
the
area,
the
presence
of
a
sus-
pected
tear
fault
along
the
river course at the
dam site
and thrust
fault
situated
at
about 3
to
5
km down-
stream
of
the dam
site
at a depth of
900
to 1,800
m
below
the base
of
the
dam, a concrete
gravity
section
for the
spillway
was
not
adopted.
Also,
the
most
suitable
type
of
spillway
which
is
generally provided
energy.
4.
Design
Flood
Tle
design
flood
hydrograph
for determining
the
g?pacity
of
the
spillway
was
worked
out by
"Unit
Hydrogra_ph
Method".
For
this, all
available
daily
rain-
fall data
for
the
years
1935
to
1962
for
variotrs
rain-
gauge
stations
situated
in
the
catchment
and
river
discharge
data
at dam
site
for the
years
192I-62,
was
utilised. For
a
few
years,
hourly
gauge
readings
for
the
duration
of
the floods
were
also
available.
The
maxi-
mum peak
discharge
of
17,000
cumecs was
recorded on
26 September
1947.
The-value
of
maximum
discharge
was subsequently
recorded
as
about
19,800
cumecs
on
4
August
1977.
A maximu
u
flood
volume
of
0.21 million
ha
m
for five
days
was
recorded
from 2
October 1955
to 6 October
1955.
The
design
flood
hydrograph
has a
peak
discharge
of 33,555
cumecs
and
a surface runoff
volume of
5.
Flood
Routing
Studies
Flood routing
studies
were carried out
by the usual
step-by-step method
by
superimposing the
design
flood
of
33,555
cumecs
on
the
normal
reservoir
level
of
at
Diesel
engine
-6
:
14.478
m
:
14.478
m
X
12.344
m
:
426.720
m
:
433.72
m
:
428.244
m
:
432,50
m
:
6
with
one
addi-
tional
driving
unit
-
150
tonnes
:18m
:
0.5
m/minute
:
24.5
H.P. at
1500 r.p.m.
Lifting
and Lowering
speed
(diesel
drive)
:
0.15
m/minute
2. Location
The chute
spillway
has
been located
on the
left
abutment.
Before
final layout
of
the spillway was
adopted,.a
number
of
alternative
layouts
-of
spillway
along with
dam and its
appurtenant
works
were
studied. The
following
factors
favoured
the
location
of
the
spillway
on
the
left
abutment
:
(ii)
The
existing
road
and
rail
communications
were
up
to
the
left
bank
of
the
River
Beas.
S
major
crossing
of
the
river for
carrying
heavy-
construction
machinery
to the
righi
was obviated.
1,95
El.
426.720
m.
For
this.
outflr
;l':":flq",i;1t#i"'l#"HH[if,iiH?ri]'iti
il:".:,#:,"ff*ito;;o.o
,''e
accep,abi,i,v
6.
Control
Structure
and
Radiat
r*$nttx;qg'frl'tl:;'-'"r,u:*,
ffi
;Tf":*#*Tl'f
f.'rr";.,il',t"lx,:tffi
,'i
j##"lTli'ili-u.uir,
ll"b'i:iijfiifh"H..i':,',,:ln;,;i"ir"rl*"f,1:*",1*o*tJ;x,.i:
mdd..;*:*fr*;$#iqgffitrffi
ir
EI.
416.05
m
is
controlled
m
radial
gates.
In
closid
Ho";oiiJ'1,1,\^i:*{i
7.
Hydraulic
Design
(a)
AppnoAcu
CnenNrr
The
bed
of
!!g
cha-nnel
upstream
of
the
crest
has
been
kepr
4.57?
;
il16;?.
.
crest
level,
which
is
about
rl4th
of
the-;;il;;i".*ign
head
of,
r7.069
m
over
cresr'
This
has-
been
"oor]d.r.i*#.qJur,
to
avoid
shallow
approach
.onaiiioor.
to
the
approach
channel
;harge
worked
out-
to
be
196
(c)
CHuru
.pose.
The
anele
of
flare
of
the
ch,ute.
was
determined
by
the
widrh
riquired
ii-A;
_tijiine
basin.
As
the
chure
width
varies
il..
I't.
tdS
;'#
upsrream
end
ro
213.360
*rt::
i,'#'i1?T-
',19:-;h;vau.
or
Froude
number
At points
1l :luoe.
of
stopes,
curves
have
been
giv_en
to
streamlinr
the.reverse
slope
ui
tr,"
loiu.r'rio
of
,
radius
of
33.5ig
*,
tr,"f
lr,
ui*,
rou
of
water
for
maximu.
ouiirliu]
nu,
u,
The
probubl:
ytl"r
profile
in
.
the
chure
has
been
computed
by
rh_e.
usuai
;;;h".d
-;i
;;;;r#?ion
or
energy
of
theflowing
water.
--i*g
sets
of
.orputu-
tions
have
been
.ma-d?-f;i;;i.".s'of
n:0.018,
and
n_
0'009'
the
former
for
evaruurin!
dept!
of
flow
with
air
swell,
etc.,
and
ttr.
lattli'H."f.t.rmining
the
iighest
The
wall
heights,
as
adopted,
satisfied
the
USBR
criterion
of
freeboard
given^Uy
tnoioi-ulu
i^'
Free
board
:
2.00
+
0.025 v
3{T
y,therg,
y_is
the
velociti
in
ft/sec
and d
the
depth
of
flow
in
feet.
A minimum
free
board
of
2.2g6
m
has been pro_
vided.
(d)
Srrlrruc
BasrN
(e)
Exrr
CH.c.llNnr,
6.
Irrigation
Ouflets
-
Each
irrigation
outlet
comprises
the
foriowing
main
component
structures
:
(a)
Intake
structure
and
shaft
;
(b)
Tunnel;
(c)
Hoist-cum-elevator
shaft
and hoist
house
i
and
(d)
Stilling
basin
and
exit
channel.
The
outlet
tunners
were
rocated
to
the
reft
of
the
power
tunnels
on
a straight
alignment,
crossing
undei
the
spitlway
app.-roacn
Jnannii:;;?-L;;G;s
dowt-
stream
of
the
spilrway
exit.
Trus
arrangement
permit-
ted
the
shorter.
tunnel
under
the
dam
to
be
used
for
power
penstocks.
The
other
broad
considerations
that
were
kept
in
view
while
planning
tt.
*oi[,
are
as
under
:
(i)
separation
of
the
intake
and
sti[ing
basins
for
each
tunlel
was
considered
desirabTe
to
secure
construction
and
water
control
advantages.
Under
such.gllangements,
a"-uge-iaused
to
onedue
to
sliding-or
earihwort<"wouro
leavi
the
other
availa6le
for
,.t.uiing
.uppfi.,
oi
water.
(ii)
lutgq
underground
openings
for
gate
contror
chamb.er,
erc-.,
particularlt;;d;;
tfi.
Ju_
have
oeen
etlmrnated.
(ttt)
feparatestilling
basil_for
the
spilrway
and
out-
let
tunnels
werd
considered
deslirabre"
for
ins-
pection
of
tle
_spillway
apron
and
for
better
operation
of
the
spillway.
(iu)
For
maintaining
stability
of
the high
hill
over-
Iooking.tunnel
lntakes
3gd
upstrJam
portalq
-
excavation
at
the
toe
of
ttre
triit r,as
Ge"
mini_
mised.
l.
Type
of
Intake
Structure
The
following
arternative
types
of intake
structures
were
considered
before
the
adopii";-;?-.orop
inlet,
type
:
(a)
Intake
with
semi-circular
or
rectangurar
trash-
racks
projecting_-from
a
verrical
?;;;d
con-
crete
gravity
wall.
(6)
Intake
with
sloping
trashracks,
with
emergency
gates
in
upstr-eam
end
operated^
on
indtinefr
tracks
from
the
hill
side
from
uuou.
irre-
maxi-
mum
reservoir
elevation.
-
(c)
'Drop-inret'
intake
with
trashracks
forming
a
several
sided
cage
surmounting
tLi
vertical
inlet
shaft
__.,,
Al,.roative
(a)
envisaged
high
concrete
structures
wnose
provlsrons
was
considered
undesirable
in
the
*
Jt"
?d
197