Raabe J. Hydro power - the design, use, and function of hydromechanical, hydraulic, and electrical еquipment
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roo
,
19 20
I
438
,
-
t
goy
Fig.
3.2.1.
Cross section of an earth and rock filled gravity dam, 4ssuan power plant,
Nile.
E,o!pt.
Africa (owncr Egyptian statc powcr board). Dcsign and ercction of dan~ by Hydro Projcct Jloscoiv,
USSR.
Power station equippcd with
12
sets of
180
MW
FTs built by LhlZ, Leningrad.
H
=
75
m.
Only grout curtain
5)
prevents seepage between rocky ground 17) and loam core
1).
2)
rockfilling
3)
control galleries in the loam core;
4)
upstream dam;
5)
grout curtain;
6)
gravel:
7)
compressed
gavel;
8)
coarse gravel;
9)
rubble stone layer;
10)
slurry deposit;
I
I)
bouldcr:
11)
cllry layer; 13)
compressed slurry and rubble bed layer between layers of sand and boulder;
I.))
sofi clay; 15) sealing
blanket of
uppcr dam;
16)
main sealing grout curtain; 17) rock;
18)
axis of upper dam;
19)
axis of
main dam;
20)
axis of downstream dam. From the Moscow Hydro Project.
3.2.4.
Arch
dams
This has an arch structure with a convex curve towards the basin originally only with
a
curvature in its horizontal section, but sometimes varying over the width and heipht.
Nowadays designs have also
a
curvature, usually varying with height, in the vertical cross
section, sometimes leading to an overhanging crest at the top of dam. The
\I
all thickness
rises towards the piers and the base, sometimes designed as a
hin~e for reduc;ng stresses
there
[3.53 to 3.561.
Here the hydraulic thrust is aimed to be transmitted only by wall pressure into the
supports and foundation. Sometimes the wall thickness is enlarged
abo\.e the value
needed for rnaintenance of pern~issible pressure. Thus the additional \veight contribtites
to greater stability (mixed gravity-arch dam). To eliminate tensile stresses, the
Bureati of
Reclamation (USA) has tentatively introduced the prestressing of an arch dam. This 11.-as
achieved by embedding flat jacks within the dam wall and inflating them for prestressing
[3.57].
In consequence of its thin wall, the arch dam is more susceptible to vibrations [3.58].
Creeping may influence the stresses [3.59].
The material used for an arch dam decreases with rising pressure admitted. For
a
design,
which requires the minimum of material the latter increases with crest length
1,
being
about the width of valley. Below a certain value of
I,
ranging actually about 600
m,
the
material required for an arch dam is
snlaller than that for a gravity dam [3.60].
The latter results from the different laws the wall thickness has to follow for an arch dam
or a gravity dam. Assuming for simplicity a cylindrical arch dam with a radius of
curvature in the plan proportional to the dam width
1
and an admissible pressure in the
wall
th:
wall thickness is
s,
-
I
p,/pad
in which
p,
is the water pressure. Assuming
p,
to be proportional to the crest height
11,
the wall thickness of an arch dam is
s,
-
I
hip,,.
Contrary to this, the equilibrium of a gravity dam requires a wall thickness proportional
to
the crest height
s,
-
It.
Hence the material required, proportional to hls, is for an arch
cialn.
ru,
-
1'
11'
,I,,,,
;illit
for
it
griIb11y
Clam,
IN,
-
I/,'.
I-lc~icc tllc l.;ltio of nl;~tcrial
11scd
for
;In
arc11
c!.~!:l
10
.I
;!I
;I\
it!
kl;~r~i
is
proportiori;~l
to
thc width
I.
Tliis leads
10
t!;e ;~bdve r.csult.
Thc const
l-\~c.~ic\~l
of
;I
\i~iip!c ;trcli
dam
is not :.lclvis:tl,lc.
when
tllc
\vi~lti~
of v:~llcy is Inore
than
5
to
0
riilich 1;tr~c.r tha11
its
dcprh.
111
any c;tsc thc gr-oirnd
Ix!s
to be rocky and the
soi!
of
thc
~i\lIc?
at
SILL'
I~IKI~(
offer
200d
si~pport
011
the si~~pt's. O~lierwise
it
has to be
strcr1gihcnccl
by
injcc~ion of concrete and by reinfol-ccment.
In
any case
the
zcononly
in
working
lime
of
an
arch
dan~ is lcss tlian that of
a
grnvity
dam
because of the complicated
shuttering.
The arch
d;im
of Vajonr. the secontl highest
in
the
world,
Ixving
st~rvived the disastrous
landslide
in
it5
rcservoir, has thc followit~g cllaracteristics:
I!,
=
262m,
b
=
23
m,
I,
=
I90
m.
The
Figs.
3.3.2
and
3
show cross sections of some arch dams.
.
gi
Fig.
3.7.2.
Schematic
elevation of remark-
able dmns. Gravity dams:
a)
Hoover
d.
b)
Grand Cuulec
J.
c)
Grand Dixence d.
Arch dams:
d)
?I:iuvoisin
d.
c) Vajont d.
f)
'lignes. d.
g)
Cap Dclons
d.
h) Tolla
d.
Fis.
3.2.3.
Cross sections
of
Zillcrgriindl arch darn,
Zillcr, Ausrrirl (ownzr I-auernkraftwerke
AG
Salz-
burg) a) cross section through bottom discharge
b) section
of
the
right sidc with plumb shaft 1) rnaxi-
mum
pcrnlissible water lcvcl 1850
m;
2)
minimum
permissible water level
1740
m;
3)
control passage;
4)
valve chamber;
5)
stilling basin;
6)
brim passage;
7)
bottom discharsc;
8)
plumb shaft rockdrilled,
diameter
0,;
nl, depth
60
m.
3.2.5.
3~lultipic
arch
dams
This
dam
can
be used.
if
the width of the
valley
is
more than
5
to
6
tirlles its depth and
if
the fouridrltion
of
a
concrete structure
can
be built
on
rock
[3.61].
consists iisually of a large number (up to
40)
of parabolic cylindrical shells norma!ly
of
concrete,
which make an angle of about
45"
with
the ground level and
tvhose
upper
obliquely cut ends
are
covered
by
a horizontal plate-like cantilever forming the crest.
The
lateral ends of each arch are supported by abutments.
one of the most notable n~ultiple arch dams is the Daniel Johnson dam in the valley of Manicoua9an
river, Canada, for the power station Manicouagan
5 (1768
MW,
7,36
TWh,
H
=
150
m,
8
FTs) built
betwecn
1960
and
70
in the Virgin forest of the province Quebec (Fig.
3.2.4).
Its characteristics:
H,,
=
214
m, central arch
1,
=
161
m,
12
side arches each
1,
=
76,5
m.
Fig.
3.2.4.
Plan of Manicouagan
5
multiple arch dam (Daniel Johnson dam), Manicouagan, Quebec,
Canada (owner Hydro
Quebcc, Montreal, Canada), crest height
214
m, tallest multiple arch dam.
(From Water Power
16 (1964),
no.
10
p.
410;
no.
11;
p.
463).
Constructional details see Table
3.2.2.
Jncreasing capacity of a power station at the heel of
a
dam is facilitated by the angular dam
[3.62].
A
survey of dams
is
prescntcd by
Mackintosh
[3.63].
Research activities are listed in
13-64).
?'able
3.2.2.
Dctails
of
dcsign. nia1eri:ll, rcscrvoi'r, po\vcr house,
and
labour
for
thc
example
of
Danicl Jolinson
multiple
arch
tiam
(Ci~nad;~)
*)
-
--
\\'eight of concrctc: 6 .
lo6
tons.
1'0
obtain complccc :;ccurity of the d:lni
on
its foundation,
it
wns
necessary to cxcavntc bclow thc ccnrral arch
a
gorgc
40
ni dccp and
20
m
\vide.
To
sccurc ;tnd control
thc safety of thc foundation and thc supporting soil,
inspection
g;lllcrics havc bccn drilled in thc
adjacent rock. Similar p;ovision has been niadc in the concrctc. Morcovcr, itny displacement of thc
dam is continuously
controlled
by land survcying.
Total volume of concrctc used: 2.25. 10' m3.
Compression
rcsistancc: 316 bar ovcr 91 days.
Composition of colicrcte
Ccment 230 kglm3, Wclding sand 360 kg/m3
Stoncs in the rangc 75- 150 mm diarnctcr 360 kg/n13
Stones in the rangc 37,5-75 nim diamctcr 535 kg/m3
Stones in the
ranse 18.8-37,5 mrn Jiametcr 232 kg/m3
Stones in the rangc 9,4- 18.8 mm 148 kg/m3
Watcr 113 kg/rn3, additives for absorption of air 3,6 kg/1n3
Reservoir of the Daniel Johnson dam:
Surface: 2100
km2, length 200 km, total volume 133 km3,
storage volumc 36 km3, catchment
area 29000 km2.
Spillway: Height
21,3 m, width 440 m, nurnbcr of gates
3.
Volume of concrete
38
500 m3, flood flow 2830 m3,s.
Powcr station: Installed power capacity 1768
MW,
annual work 7,36 TWh,
number of sets 8. Francis turbines, net hcad 150 m,
rated discharge 642
m3/s, power station load factor 0,635.
Voitages- terminal 13,s kV, transmission to switchyard 3 15 kV,
long distance transmission 735 kV, (the first power station in the world using this voltage at the time
of its inauguration in 1970).
Admission: 4 gates, dimension
11
m 6,1 m,
number of galleries 2, diameter of galleries
I I
m,
length I100 m, maximum dischargc 960 m3/s.
Production of
concrete during the
erection:
hlonthly 105000 m3, %eekly
25
500 n13, dailv 4900 m3 (maximum values rcached).
Pressure shaft: number 8, diamcier 4560 mni, length
of
liner 176 m.
Labour involved:
hlan hours durins construction of the dam 31 350000,
totdl number of workers 12900, nurnbcr of workcrs during peak of construction 3544 in 1964,
number of
men, women children libing at site at peak of construction 4700.
*)
From special issue
of
Hydro Quebec, itlontrcal,
Canada
3.2.6.
Response
of
present society
to
social and ecological
impacts
of dams
There
is
no
doubt that the primary effects
of
the vast majority
of
dams have been
beneficial. Equally, however, there is no doubt,
that many
of
these dams have contributed
to unanticipated
zdverse secondary effects, many
of
which
could
have
been
eliminated by
a
proper planning process
[3.42].
In addition, there seems to be
a
considerable difference
of
opinion
in judei~ig the
success
or failure
of
some
projects.
The environmental
damages arising from the construction
of
dams are many, and they
have far
reachins effects, their interactions are often
so
complex and
so
little understood
that ecologists and environmentalists cannot predict them with certainty. Our current
knowledge of the eco-system
of
manmade lakes leaves much to be desired. According to
Bislcas
[3.42],
e.S. low water levels caused by the construction
of
a
dam msy result in
serious
consequelices to the
local
fauna and flora.
~cologists
3rd
sociologists, who often seriously qucsrion
a
certain projcct. find
it
inipossiblz
to
influence and convince engineers. econoniists and politicians, hailing
this
projcct
as
a
tcchnnlogicsl
triumph,
bccausc of the lack of liartl facts or solrd scientific cvidencc.
3.2.7.
Environniental conscquences of
large
dams
-
On the physical system: Dams invariably change the river and eco-system regime and
thus the real question is not whether a dam
will affect the environment but how much
change is
acccptable to society as a wholc and what countermeasures should be taken to
keep the changes to a minimum and within an acceptable range.
For example,
thc
Assuan dam
in
Egypt
has
reduced
the
fish population of the Mediterranean
by
abruptly breaking the aquatic food
chain
in
the eastern Mediterranean.
Nile
sedimentb
and
organlc
micro organism are now trapped
in
the reservoir. Erosion has become a major problem. and
the
fertility
of
the
Nile
valley
has
been
lowered by lack of sediments. Salinity
in
middle and
in
upyer
Egypt is
increasing
rapidly
[3.42].
Since practically a11 the dams built for hydropower
in
recent years have also been used
for
othcr purposes, notably irrigation, they also have contributed to the deterioretior? of
soil fertility and the resulting loss of good agricultural land due to salinity and
alkalinir);
[3.42].
-
Earthquakes: Several recent studies indicate, that observed seismic activity can be
attributed directly to the creation of dams and storage reservoirs
[3.42].
See also under
3.2.2.
-
Disease propagation: One of the most serious effects in tropical climates is the spread-
ing of water-born diseases, and the consequent suffering of millions of
human beings arid
animals. The relationship between increasing use of irrigation and the spread of bilhario-
sis (carried by snails) has been conclusively demonstrated in several countries in the
world.
-
Resettlement problems: Some of the dams have also created problems by the displace-
ment of population. The Kariba dam on the Zambesi dispiaced about
57
000 Tonp
tribesmen. What the planners there, often from outside Africa, did riot realize was the
enormously
colnplex relationship between tribes and their land. In the above case
it
took
two years to clear sufficient land to meet their subsistence needs and the government of
Great Britain had to step in to avert famine. Approximately
100000 people had to be
relocated for the
Aswan high dam without adequate planning, and the World Food
Programme had to rush in famine relief for the
Nubians
[3.42].
3.3.
The
spillway,
gates
and
shut
off
devices
3.3.1.
The
spillway
in
conrlcction
with
other members of
the
plant
The spillway as the structural member for by-passing the turbines may be located
separately from the power house or even from the barrage. In low head run-of-river
power plants, the power house and the spillway gates serve
to2ether with the embank-
ment as a damming device and thereby
conslitute
a
unit together with the power house
(see Fig.
3.3.1).
This unit is very compact, when the sets and spillway are located in a
conimon block of concrete in the case of a p!ant with ejector by-pass outlet (see Fig.
3.3.2).
Q., in the
USSR
to facilitate the transport of floes during the long winter. Also submer-
"ble plants (see
Fig.
3.3.3.),
abutment power stations (see
Fig.
3.3.4)
and certain designs
l*-ig.
5.3.1.
*l'hc
ScIi\v;~hcck run-of-rivcr poxcr
p1:11t. 11ri111. Austri:~. Ib\vcr
IIOUSC.
ill
bi~y.
and
spill\v;~y :Icrcws lhc sll-c:~ln coursc
;IS
;I
struc-
tul-ill uliit
corn^
thc
damming
dcvicc.
Drau
-
Fig.
3.3.2.
Ejector by-pass
outlzt
as spill\\.ay
in
USSR
plaiit Iik~tsk, Angara.
H
=
26
m:
n
=
83.Srpm:
Y
=
8
-
90
b1W
(Drawing from
H!
dro Project hlosco\v).
Axis
cf
power
house
/
'u
Fig.
3.3.3. Longitudinal
and
cross section of
set
(left) and sluice
(right)
of
submersible
plant.
Rott-
Freilassing, Saalach,
West Germany.
H
=
8,5m;
P=4-1MW.
From
Mosortyi
[I
-531.
Is'
'8
154
,
-
kr'ttv~~21~z
4
'
'4
*
6
--
--J
L---J
-----_-
i
(e
I--',
------<-
-
-
J-
-
-
-
r-----
-1-
Fig.
3.3.4.
Abutment power plants.
a)
through c) show Lavamiinti, Drau, Austria.
H
=
9
m,
P
=
3
.
7.3
11W
a) clcvation arid longitudinal section c) plan
of
the power housc in thc abutment of
the spill\v:ry: b) plan. From
H.
Larger
and
H.
GI-cII.~~.
d)
Perspective view of abutment power plant
KuBdorf,
Inn.
N'cst Gcrniany [owner Innkraltwerkc Toging).
2
welded gantry cranes built by Noell.
(Drawing courtesy lnnkraftwerkc Toging)
e)
Sectional drawing of KT NuDdorf,
Inn,
West Germany
(o\vnt.r Innkraft\verkt TiSging).
H
=
10,l
m,
11
=
75
rpm,
P
=
2
.24,9
MW.
KT
built by
J.
M.Voith.
T'nis type may yield the inost uniform inflow of all the sets (Drawing courtcsy
Voith).
of
barrage power houses with
a
ski jump spillway above them have this compact form
(see Fig.
3.3.5).
Here
by a skillfill arrangement of draft tube outlet upstream of the hydraulic jump due
to spillage, the head can
be
increased compared with plants in which the spillway is
situated separately from the power house
[3.18].
This is valid during spillage.
Fig.
3.3.5. Elevation of
the Karakaya dam and
power house, Euphrat,
Turkey (owner State wa-
ter authority of Turkey).
Ski jump spillway. oper-
ated
by
tainter
gate
at
the crest of the dam.
1)
butterfly valve;
2)
ma-
chine hall; 3) trans-
former hall;
4)
penstock;
5)
draft tube;
6)
high
water
spillway. From
Howald
et
al.:
Karakaya,
a
hydro electric power
plant in
Turkey.
BBC
review 67
(1980)
no
2,
p.
100/107.
This
unit
of spillway and power house disappears in the case of a diversion power plant. Here
the
power house lies
at
a
distance from
the
spillway. Now the spillway may be reduced
in
size as spillage
occurs
with
a spillway head usually rather small compared
with
the plant head under which spillage
occurs in barrage or run-of-river plants.
Sometimes in such diversion plants a sophisticated
spil!way is omitted, as the flood flow
here is left to the original river reach which has been short-circuited and which is capable
of receiving this flow
(e.g.
a
dpcp
gorge). Hence, e-g., a riprap flume nlay fit.
3.3.2.
The
spillway
3.3.2.1.
The duties
of
the
spillway
1)
Maintenance of maximum permissible water level in the head water reservoir.
2)
Dewatering of this reservoir so as not to be detrimental to the foundations and
construction of the plant in the case of catastrophic high water with closed turbines.
The
discharge due to the latter is usually
a
multiple of rated discharge. As an example, the
lower Inn along the West German-Austrian border has, downstream of its confluence
point with
the
Salzach at Simbach-Braunau, a catastrophic high water of
6000
m3/s,
6
times the rated flow. But there may exist cases in which the latter is a nearly vanishing
portion of the flood flow whereby the power house is degraded more or less to a small
appcntlis
of
the spillway. Such
;i
situatio:l
exist?;.
c.g.
iil
tllc first
SI;~$C
of
tl~c i!c\cIop111~11t
of
;t
hugc
I
iver
in
a
developing coilntry
(KC
Pis.
3.3.6)
[3.05
it)
3.7
I].
,-__--
___.-.__...
_
F
4bl
I
3h/
I
-+
--
------A.
-"
-
-
L
----------
-
I---
-1
0
50 10Om
Scale
L-
O
100
dcys
O
100
days
Fig.
3.3.6.
Examplc ofthe difircnce in the mcthod
of
river developlncn[ :I)
In
;i
dc\uloping
country,
St.
Paul river, Liberia, Africa, and b) in
a
dcvclopcd country. hcrc Tricr. R1osc.I. WCS~ Germany.
1)
Flow duration curve:
2)
river-bed;
3)
power
housc.
3
a.
1)
1st
stiigc;
3
a.
2)
2nd stage;
3
b) final
stage;
I)
spillnay;
5)
side barrage;
6)
main barsiigc.
I),,
mean
flow
rate.
Q,,
,
rated
flow
at'tcr 1st stage
of development.
Q,,,.
rated flow,
xQ,
mean n~;irrimrim
flow
riitv. (Drauing
and
graph courtesy
Messrs Siemens, Erlangen)
3.3.2.2.
Survey
of
flood
discharging devices
The flood discharging device may be
of
a fixed structilrc (weir on the crest of thc dam,
pits,
syphol~s) or a movable structure
(gatc)
of the trn~lslational or rotnr) typc. Ciiites may
be actuated manually, through servomotors and
aiitonistic:illy,
by
nicnns of electric,
hydrauiic or pneumatic devices. Imperative
is
the reliabi!ity of
n
spiliway.
3.3.2.3.
Fixed
flood
discharging devices
I.
Weirs on the crest of the dam:
The
utilization of the crest of
thc
dam
as
a
flood
dischareins device is a common practice, especially for'co1:crcte
or
masonry gravity
dcms. Its advantrige exists in the availability of the whole
width
of tile
dam.
thus t'acili-
-
tating a spilled flow iamina, combining
a
large capacity with a sniall dcpth of lamina
[3.72].
11.
Weirs
within the structure
of
a
dam,
locaied laterall? (scc Fig.
2.3.7).
Such a design
!eaves the central part
of
dam free for other purposes. Tillis the power house can
be
constructed there. In other cases
a
spillway of the ski jur!~p type is laid above the power
house in the dam's centre
[3.73].
111.
Pit
type weirs, (drop shaft, morning glory): In this case (see Fig.
3.3.8)
the weirs are
arranged around the circular crest
of
a
pit. This structure may be far
away
from the dam
and
Inay
dewater into a tunnel. Such
a
design is
recommended
for exnmplz with
a
thin-\valled arch dam, releasins the construction of the dam from possible vibratory loads
under
spillaee. It
may
also be fitted to rin earth- or rock-lil!ed embankment to avoid
erosion.
It
is preferable also for very large flows
[3.74].
11'.
Syphons:
This
design (see
Fig.
3.3.9)
consists of one or more syphons in par;lllel united
at their upper end with the
head water
and
at
their lower end with the tail water.
When the head water reaches the inncr crest of the syphon. the wntcr cornmenccs flowing. Then the
air within the syphon, now
separated
by
means of a trip
baMe
is spilled downstream. Hcnce the