class 5 types of dams and Merits Demerits .pdf

Hydraulic Structures

1. Reservoirs
StorageWorks-Reservoirs-Typesofreservoirs,selection
ofsiteforreservoir,zonesofstorageofareservoir,
reservoiryield,estimationofcapacityofreservoirusing
masscurve-ReservoirSedimentation–LifeofReservoir..
DamsGeneral-Typesofdams,factorsaffectingselection
oftypeofdam,factorsgoverningselectionofsitefora
dam.
10/26/2021 Dr GK Viswanadh Prof of Civil Engg. &
Director UGC HRDC JNTUH
1

2. Types of Dams
DAM-animperiousbarrierconstructedacrossariveroranatural
streamtocreateareservoirforimpoundingwatertofacilitatethe
diversionofwaterfromtheriverortoretaindebrisflowinginthe
riveralongwithwater.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 2

3. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 3

4. DAMS
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 4

5. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 5

6. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 6

7. About India’s dams
https://www.youtube.com/watch?v=vBaSD_F1IcI
https://www.youtube.com/watch?v=YnmQdWs1epY
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 7

8. Dams
•Damsmaybeclassifiedonthebasisoftheir
–Function/purpose
–hydraulicdesign,
–natureofstrength
–materialsofconstructionand
–structuraldesign.
•Theselectionofthetypeofadamtobeconstructedataparticularsite
andtheselectionsiteforaparticulartypeofdamarebasedonseveral
factors.
•Thevariousforcesactingonadam,inparticularonagravitydamareto
beconsideredindesigningthedam.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 8

9. Classification of Dams:
I. According to the function/Purpose-
i)Storage dam
ii)Diversion dam
iii) Detention dam
iv) Debris dam
v) Coffer dam
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 9

10. Storagedams–
•AStoragedamisconstructedtoimpoundwaterduringtheperiodsof
deficientsupply.
•Astoragedamismeanttosupplywaterforirrigation,domesticand
industrialwatersupply,orpowergeneration.
•Usuallythedamismeanttostorerequiredquantityofwatersufficientfor
anyear.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 10

11. •Diversion dams –to raise the water level in the river sufficient to flow
into the canal.
•Adiversiondamisadamofsmallerheightanditcausesthewaterlevel
intherivertoprovidesufficientheadtodivertwaterintoditches,canals
orotherconveyancesystems.
•Weirsandbarragescomeunderthistype.
•Duringfloodswaterpassesoverthesediversiondamswhileduring
periodsofnormalflow,theriverwaterispartlyorwhollydiverted.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 11

12. •Detentiondams–todetainthewaterduringthefloodsandallow
downstreamundercontrolledconditions.
•Adetentiondamismainlyintendedtotemporarilydetainpartofthe
floodwatersofriverandreleasethewatersostoredatcontrolled
ratessoastoprotecttheregiondownstreamofthedamagainstflood
damage.
•Adetentiondammayalsobeusedasastoragedamandvice-versaby
suitableoperationofthereservoir.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 12

13. •Debrisdamisadamconstructedto
retaindebrissuchassand,siltanddrift
woodflowingwithwaterintheriver.
•Cofferdamisatemporarydam
constructedtoexcludethewaterfrom
aspecificareafortheconstructionof
anactualdamacrosstheriver.Sucha
damisconstructedontheupstream
sideoftheproposedsiteforadamand
sometimesonthedownstreamside
also.Thecofferdamthsbehavesasasa
diversiondam.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 13

14. II. According to Hydraulic design
1.An overflow dam is one in which the surplus water to flow over the
crest. Example for Overflow dams is spillways in which water is
allowed to flow over the top of the dams.
2.Non-overflow dams in which will not allowed to overflow. A non
overflow dam is one in which the top of the dam is kept at a higher elevation than
the maximum water level expected and water is not allowed to overtop the dam.
Classification of Dams contd…
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 14

15. Classification of Dams contd…
III. According to Nature of the strength
1. Rigid dams –which are made of rigid materials which are not easily
erodable.
2. Non-rigid dams –which are made of earth or rock-fill.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 15

16. IV. Based on structural design
Gravity dams, Arch dams, buttress dams, Arched buttress, earth dams
•Gravitydamisamasonryorconcretedam,whichresistsvarious
forcesexertedonitbyitsownweight.InaGravitydam,thewater
pressureisresistedcompletelybytheweightofthedammaterial.
Theymaybestraightorcurved.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 16

17. •Archdamisacoveredmasonryorconcretedam,withconvex
upstreamface,andresiststheforcesexertedonitbyarchaction.
•Inarchdam,thewaterpressureisresistedandtransferredtothe
abutmentsbyarchactioni.ebythrustandbendingmoment.
•Theymaybeofconstantradiustype,variableradiustype,
constantangletype,doublecurvature(cupola)typeandarch
gravitytypeandmassivearctype.
•Anarchgravitydamresiststheforcescomingonitpartlyby
gravityactionandpartlybyarchaction.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 17

18. •AButtressdamconsistsofawaterretainingsloping
membranesupportedbyaseriesofbuttressesonthe
downstreamside.
•Theymaybesimpledeckslabtype,continuousdeckslab
typeorcantileverdeckslabtypebuttressdams.
•Insomecases,theupstreamslabisreplacedbymultiple
archessupportedonbuttressesandarecalledmultiple
archbuttressdams.
•Inothercases,theupstreamedgeofthebuttressesspan
thedistancebetweenthebuttressesandtheyarecalled
massiveheadorbulkheadbuttressdamsandmultiple
domebuttressdams.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC JNTUH10/26/2021 18

19. •Arched Buttress Dam –which are the combinations of arch and
buttress. Buttress is designed as gravity dam.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 19

20. •Anembankmentdam(Earthdam)isanonrigiddams,
whichresiststheforcesexerteduponitmainly
byitsshearstrength.
•Basedonthemethodofconstruction,theymaybei)Rolledfilledtype
ii)Hydraulicfilltypeandiii)Semi-hydraulicfilltype.
•Therolledfilledearthdamsmaybeofi)homogeneoustypeii)Zoned
typeandiii)diaphragmtype.
•Earth and Rock fill dam in which the stability is governed by the soil
properties and slope consideration
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 20

21. V. Based on the material used for construction
1.Masnory or Concrete dams
2.Earth dams
3.Compositedam–Apartofthedamisofmasonryaandapartof
thedamistoreducethecostofconstructionearth.
4.Rockfilldam–Boulderswillbebasedoneabovetheother,to
makethedamimperiousalayerofsoilisplacedabovethat.
5. Steel dam-lesser height, suitable for small works
6. Timber Dams-purely for temporary purposes. Timber planks
inserted and supported.
Classification of Dams contd…
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 21

22. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 22

23. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 23

24. Merits and demerits of various types of dams
1.Gravitydamsresisttheoverturningmomentofthewaterpressure(external
forces)bytheirweightalone.Thesearestraightinplanandapproximately
triangularinsection:usuallyhavingalengthtoheightratioexceeding7.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 24

25. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 25

26. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 26

27. Advantages of gravity dams:
1.They are strongand stable.
2.They are adaptable for overflow section.
3.They can be of any height, if suitable foundations are available
4.They require least maintenance cost.
5.Failure, if any, is not sudden.
6.Scouring sluicescan be provided in the dam.
7.They are cheaper in the long run.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 27

28. Disadvantages of gravity dams:
1.They require sound rock foundations
2. Initial cost is high
3. They require skilled labour for construction.
4. They do not allow subsequent raise in the height of dam.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 28

29. 2. Arch dams(Masonry or concrete)
•In arch dams, water pressures are resisted by the reaction of the
abutments at the ends of the arches.
•Thesearecurvedinplanandresistthepressureofwaterpartlybytheir
weight(withverticalelementsactingascantilevers)asingravitydams
andpartlybyarchactionwithhorizontalelementsactingasarches
spanningfromabutmenttoabutment.
•Usually,thelengthtoheightofarchdamsislessthan5.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 29

30. Merits of arch dams:
1.The rock foundations need not be as strong as in gravity dams.
2.Section of the dam is much less.
3.Problems of uplift pressure is minor.
4.The strength of materials used in the construction of arch dams is
more fully developed than in gravity dams.
Demerits of arch dams:
1.The arch dams require skilled labour and sophisticated formwork for
the construction.
2.The speed of construction is slow.
3. They require strong abutments to resist arch action
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 30

31. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 31

32. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 32

33. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 33

34. 3. Buttress dams
•Buttressdamsconsistofanumberofbuttressesorpiersdividingthe
spacetobedammedintoanumberofspans.
•Toholdupandretainwaterbetweenthesebuttresses,panelsare
constructedconsistingofR.C.C.slabsorbuttressesagainsttheheight
ofthedamareasfollows:
Height of Dam15 to 30m 30 to 45m >45m
Spacing of
Buttresses
5 to 6m 9 to 12m 12 to 15m
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 34

35. Advantages of buttress dams
1.Per unit length of dam, buttress dams require less concrete(30 to 40%)
than solid dams.
2. The cost is less since less quantity of materials are used.
3. Problem of temperature control in concrete is minimum.
4. Uplift pressures are less.
5. Inspection and maintenance is easy.
6. Excavation is needed only at buttress and deck slab.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 35

36. Advantages of buttress dams
7. Power House, switch yards can be provided between the buttresses.
8.Spacingofbuttressescanbevariedtoutilizezonesofgood
foundations.
9. They require relatively weaker foundations than gravity dams.
10.Stressdistributionismoreuniformthaningravitydamand
thereforeefficientuseofconcreteispossible.
11. Head dissipation is better and the speed of construction is more.
12. Access is possible to the back of buttresses.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 36

37. Disadvantages of buttress dams:
1.They require richer mix of concrete,morecomplicated formwork and
skilled labour.
2.They are susceptible to damage or destruction by sabotage or military
action more easily than in massive dams.
3.They are sensitive to moderate deterioration of concrete and much
care is needed in the construction.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 37

38. Disadvantages of buttress dams:
4. The pace of construction is slow.
5. Since reinforcement is used, smaller size aggregate is required and
therefore unit cost is high.
6. With more joints, they need greater attention.
7. They do not permit easy means of providing openings for sluices and
penstocks.
8. Overflow arrangements require complicated layout.
9. The number of water seals to be provided and maintained in more.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 38

39. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 39

40. 4. Steel Dams
•Thesedamsareconstructedofaframeworkofsteelandsteelskin
platesontheupstreamsidestoholdwater.Theyarefeasiblefor
heightsuptoabout15mandcanbeconstructedquicklyandcheaply.
Theyaredirectstruttedtypeorcantilevertype.
Advantages of steel dams:
1.The speed of construction is high.
2. They are cheaper than other rigid dams.
3. Leaky joints could be repaired by welding easily.
4. They have greater flexibility to resist unequal settlement without
excessive leakage.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 40

41. Disadvantages:
1.Life is shorter than concrete dams.
2.Constant maintenance is required.
3.They have to be anchored at foundations.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 41

42. 5. Timber dam
•Timberdamscanbeconstructeduptoabout10mheightwheretimber
ischeapandplentifulatdamsitewhileothermaterialsarescarce.
•Inthesedamleakageisgreatandrepairstoleakageisdifficult.
•Advantages:
1.Low initial cost.
2.They are suitable for any type of foundations
3.They are used for temporary dams.
4.The speed of construction is great. s
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 42

43. Disadvantages:
1.They require high maintenance cost.
2.They have short life.
3.They are suitable for small heights(less than 10m)
4.They involve more seepage losses.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 43

44. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 44

45. 6.Earth dam:
•Theearthdamsaremadeoflocallyavailablesoilsandgravel.
•Inrolledfilleddams,15to45cmlayersofsoilislaidandrolledwith
powerroller(sheepfootroller)withoptimummoisturecontentfor
propercompaction.
•Materialsreachthesiteintheformofaflowingmixtureofsoiland
water(orslurry)fromwhichsurpluswaterwilleventuallydrainout.
•Insemi-hydraulicfilldamsthematerialsareexcavatedandconveyedto
sitemechanicallyanddepositedinpositionhydraulically.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 45

46. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 46

47. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 47

48. Advantages of earth dams
1.Earth dams can be designed to be safe on any type of foundations.
2.They utilize a wide variety of materials.
3.They can be constructed quicklywith unskilled labour.
4.Where suitable materials are available locally, they are usually cheaper
for a given height compared to masonry or concrete dams.
5.Earth dams can be subsequently raised, if desired without any
complications. This is not so with rigid dams unless provision is made in
original design.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 48

49. Disadvantages of earth dams:
1.Earth dams are vulnerable to damage by floodsand fail suddenly
without warning.
2.They require a closer watch and heavier maintenance cost.
3.No overflow sectioncan be provided in this dam. Arrangement
for spillway must be made separately.
4.These are not suitable at locations of heavy downpour.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 49

50. 7. Rock fill dams
•Rockfilldamscanbeprovidedonlessrigidfoundationsthanmasonryor
concretedams.
•Theyaresuitableinremotelocalitieswheresuitablerockinplentyis
availablenearthedamsite.
•Thedesignofrockfilldamsisempirical.
•Rockyfoundationsaredesirableforthesedamssothatsettlementis
absentornegligible.
•Theyaresuitedformoderateheights.
•Sluicingisresortedbyforcingajetofwaterontheworktowashaway
smallrockchipsandrockpowdertoavoidanysettlement.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 50

51. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 51

52. Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 52

53. Theslopeofthedumpedrockis1.3:1to1.5:1tobothfaces.The
thicknessoftheslabprovidedontheu/ssideis1%ofthedepthbelow
theH.F.L.subjecttoaminimumof30cm.Thedownstreamfaceofthe
slabmaybeslopingorsteppled.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 53

54. 8. Composite dams
•Compositedamconsistsofearthfillinsteadofimpervious
membraneontheupstreamside,supportedbyrockfillonthed/s
sideforstabilityanddrainage.
•Filterlayerisprovidedbetweenthetwomaterialssothatthe
earthfillmaynotbewashedawaythroughthevoidsoftherockfill.
•Alternatively,theremaybeacoreofimperviousearthsupportedby
rockfillonbothsides.
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC
JNTUH
10/26/2021 54

55. Composite Dam
Dr GK Viswanadh Prof of Civil Engg. & Director UGC HRDC JNTUH10/26/2021 55