Elements of dam engineering

A hydraulic structure may be defined as any structure which is designed to handle water in any way
This includes the retention, conveyance, control, regulation and dissipation of the energy of water
Such water handling structures are required in many fields of civil engineering
The principal ones being water supply and conservation, hydroelectric power, irrigation and drainage, navigation, flood control, fish, wildlife service’s and certain aspects of highway engineering. Various equations, based on continuity, energy, and momentum principles, may be used
To calculate the most suitable length, width, shape, elevation and orientation of the structure.
The application of these basic principles to the practical problem of the design of hydraulic structures is called hydraulic design
Designed and constructed for managing and utilizing water resources to the best advantage of the human being and environment

1. CHAPTER 1
Elements of Dam Engineering
Compiledby:Chala.H(MSc)
JimmaUniversity
1

2. 1.1. Introduction
▪Ahydraulicstructuremaybedefinedasanystructure
whichisdesignedtohandlewaterinanyway
▪Thisincludestheretention,conveyance,control,
regulationanddissipationoftheenergyofwater
▪Suchwaterhandlingstructuresarerequiredinmany
fieldsofcivilengineering
▪Theprincipalonesbeingwatersupplyand
conservation,hydroelectricpower,irrigationand
drainage,navigation,floodcontrol,fish,wildlife
service’sandcertainaspectsofhighwayengineering
2

3. cont…
➢Variousequations,basedoncontinuity,energy,and
momentumprinciples,maybeused
➢Tocalculatethemostsuitablelength,width,shape,
elevationandorientationofthestructure.
➢Theapplicationofthesebasicprinciplestothe
practicalproblemofthedesignofhydraulicstructures
iscalledhydraulicdesign
➢Designedandconstructedformanagingandutilizing
waterresourcestothebestadvantageofthehuman
beingandenvironment
3

4. 1.2.Classificationofhydraulicstructures
Theprincipalhydraulicstructurescanbegroupedunder
thefollowingthreemaincategories:
✓Heading‐upandControlofwater
✓ConveyanceandNavigationworks
✓Storageworks

5. cont.….
Heading‐up and Control of water
➢Their main purpose is to raise the upstream water
level to feed the canals/tunnel
➢They also serve in controlling and regulating the rate of
flow and measurement of flow in the stream.
It comprise:
✓weirs
✓Barrages

6. …cont..
6

7. …cont…
7

8. Conveyance and Navigation works
➢Structures which are used for transportation and to
transport the fluid it self.
Conveyance and Navigation works includes:
➢Pipes
➢Open Channel
➢Pressure conduit
➢Canal system
➢Tunnels
➢Sewer pipes and etc.

9. …cont…
9

10. Storage Works
➢structureswhichstorewaterforfutureuse.
➢Thestoredwatercanbeusedwhenthenaturalflow
islessthantherequireddemand.Itcomprises:
✓LargedamsandTanks
10

11. reservoir
Dam axis
Spill way
Tail water

12. Classification of Hydraulic Structures by
function

13. 1.3. Dam and reservoir structures
Dam structures
➢Damsisabarrieracrossflowingwaterthatobstructs,
directsorretardstheflow,oftencreatingaReservoir.
➢Theblockageorstorageformed,canbeutilizedfor
variouswaterresourcesdevelopmentpurpose
➢Theprimarypurposeofadamistoprovidesafe
retentionandstorageofwater.

14. Cont.…
The specific main functions /advantages of dams
and reservoirs are:
➢Water storage for days, weeks, months, years, and over
years for power generation and sediment control.
➢Water supply (municipal, industrial or community
water supply, irrigation purposes)
➢Flood control
➢Regulation/balancing of river flow (such as navigation,
low flow augmentation)
➢Recreation
➢Multipurpose

15. Cont.…
Construction of the dam have also disadvantage
The disadvantages includes
➢Distraction of fauna and flora in the dam valley
➢Interference in the landscape through dams and
reservoirs
➢Change of ground water level
➢Strong influence on sediment balance
➢Change in water temperature and quality
➢Influence on fish
➢Displacement of people from reservoir site

16. Cont.….
Structure related to Dam includes
➢Spillway
➢Bottom outlet
➢Intake
➢Gate and valves
➢Service road
➢Reservoirs
➢Bridge
➢Energy dissipaters
➢Diversion structures

17. Figure Schematic diagram of the dam components
1. Reservoir
2. Dam
3. Service Intake
4. Bottom outlet
5. Spill structure
6. Diversion structure
7. Service road

18. Reservoir
➢Areservoirisalarge,artificiallakecreatedby
constructingadamacrossariver
➢Broadlyspeaking,anywaterpooloralakemaybe
termedasareservoir.
➢However,thetermreservoirinwaterresources
engineeringisusedinarestrictedsensefora
comparativelylargebodyofwaterstoredonthe
upstreamofadamconstructedforthispurpose
➢Thusadamandareservoirexisttogether.
➢Thedischargeinarivergenerallyvariesconsiderably
duringdifferentperiodsofayear
18

19. Cont.…
➢Ifareservoirservesonlyforonepurpose,itiscalleda
single-purposereservoir.
➢Ontheotherhand,ifitservesformorethanone
purpose,itistermedamultipurposereservoir.
Reservoir
Dam
Upstream
Downstream

20. 20

21. 21

22. 22

23. Cont.…
Dependinguponthepurposeservedbyagivenreservoir,
thereservoirmaybebroadlyclassified
➢Storageorconservationreservoir:Thosearereservoirs
whichretainexcesssuppliesduringperiodofpeakflow
andcanreleasegraduallyduringlowflowsorwhenthe
needarises.
➢Floodcontrolreservoirs:-storeaportionofflood
flowsinsuchawaytominimizethefloodpeaksatthe
areatobeprotecteddownstream.
➢Multipurposereservoirs:-arethosereservoirswhichare
plannedandconstructedtoservenotonlyonepurpose
butvariouspurposetogether.

24. Purposes of storage works
1. Irrigation
2. Hydro-electric power generation
3. Control of destructive floods
4. Low water regulation for navigation
5. Domestic and industrial water supply
6. Recreation
7. Preservation and breeding of useful aquatic life, etc.

25. Storage Components
The reservoir volume is subdivided in to the following parts, when seen in its
vertical section
Dead storage
Minimum pool level
Normal pool level
Live storage
Maximum pool level
Spillway
Outlet
Spillway crest
River bed
Surcharge storage

26. Cont.….
Deadstorage:Theportionofthestoragecapacityfrom
whichwaterisnotnormallywithdrawn,inaccordance
withoperatingagreements.Itisthestoragethatliesbelow
theinvertofthelowestoutletandthuscannotbeevacuated
bygravity.
Livestorage:Thevolumeofstorageinwhichwaterwillbe
takenfordemand,usingserviceoutlet.Itistheportionof
thestoragecapacityinwhichwaterwillnormallybestored
andwithdrawnforbeneficialuses.
Surcharge storage: This is required as a reserve between
full reservoir Levelandthe Maximum Water levelto contain
the peaks of floods

27. Cont.…
➢Bottomoutlet:Theoutletwhichismainlyusedto
dischargethewaterfromthereservoirforthe
environmentalflowandforflushingofsediments.
Sometimesitisalsoopenedtodischargewhenthereis
floodingontheupstream.
➢Serviceoutlet:Itisusedtodischargetherequired
amountofwaterfordownstreambeneficiariesastheir
need.

28. Basic terms
▪Yieldfromareservoir:isthevolumeofwaterwhichcan
bewithdrawnfromareservoirinaspecifiedperiodoftime.
▪Safeyield(Firmyield):isthemaximumquantityofwater
whichcanbesuppliedfromareservoirinaspecifiedperiod
oftimeduringacriticaldryyear.
▪Secondaryyield:isthequantityofwaterwhichis
availableduringtheperiodofhighflowintheriverswhen
theyieldismorethanthesafeyield.
▪Averageyield:isthearithmeticaverageofthefirmyield
andthesecondaryyieldoveralongperiodoftime.
▪Designyield:istheyieldadoptedinthedesignofa
reservoir.Thedesignyieldisusuallyfixedafterconsidering
theurgencyofthewaterneedsandtheamountofrisk
involved.

29. 1.4. Storage Capacity of the dam
➢Reservoirsimportantfunctionistostorewaterduring
floodsandtoreleaseitlater,i.e.,storagecapacityisits
mostimportantcharacteristics.
➢Theavailablestoragecapacityofareservoirdependsupon
thetopographyofthesiteandtheheightofdam.
➢Todeterminetheavailablestoragecapacityofareservoir
uptoacertainlevelofwater,engineeringsurveysare
usuallyconducted.
➢Thestoragecapacityandthewaterspreadareaatdifferent
elevationscanbedeterminedfromthecontourmap
➢Acontourplanoftheareaispreparedtoascaleof1cm=
100mor150mwithacontourintervalof1to3m,
dependinguponthesizeofthereservoir

30. Cont.…
Area-ElevationCurve
➢Fromthecontourplan,thewaterspreadareaofthe
reservoiratanyelevationisdeterminedbymeasuringthe
areaenclosedbythecorrespondingcontour.
➢Thestoragecapacityofthereservoiratanyelevationis
determinedfromthewaterspreadareaatvarious
elevations.
➢Generally,aplanimeterisusedformeasuringthearea.
Anelevation-areacurveisthendrawnbetweenthe
surfaceareaasabscissa(x-axis)andtheelevationas
ordinate(y-axis).
➢Generally,thevolumeiscalculatedinMm3.
30

31. …cont…
Elevation area curve

32. Cont.….
Reservoir Storage Capacity determination
Thefollowingformulaearecommonlyusedtodetermine
thestoragecapacity
▪Trapezoidalformula:Accordingtothetrapezoidal
formula,thestoragevolumebetweentwosuccessive
contoursofareasA
1andA
2isgivenby
where h is the contour interval.
Therefore the total storage
volume V is
where n is the total number of areas.

33. Coneformula:Accordingtotheconeformula,the
storagevolumebetweentwosuccessivecontoursof
areasA
1andA
2isgivenby
Cont.…

34. PrismoidalFormula:Accordingtotheprismoidal
formula,thestoragevolumebetweenthreesuccessive
contoursisgivenby
▪The prismoidal formula is applicable only when
there are odd numbers of areas (i.e. n should be an
odd number).
▪In the case of even number of areas, the volume up to the
second last area is determined by the prismoidal formula,
and that of the last segment is determined by the trapezoidal
formula.
Cont.…

35. Example: 1) A reservoir has the following areas enclosed by contours
at various elevation
Elevation(m) 200 220 240 260 280 300
Area (km
2
) 150 175 210 270 320 400
DeterminethevolumeofthereservoirUse
a.Conemethod
b.Trapezoidal
c.prismoidalformula

36. 1.5. Classification of dams
Dam:Isabarrieracrossflowingwater/riverthat
obstructs,directsorretardstheflowofwater,often
creatingaReservoir.
Therearevariouswaysofclassificationofdams.Someof
themare:
i.Classification based on function served
ii.Classification based on hydraulic design
iii.Classification based on material used
iv.Classification based on rigidity

37. i. Classification according to use
➢Storagedam:‐Itisacommontypeofdamconstructedtoimpound
surplusfloodwaterforuseindryperiod.Itmaybeconstructedofa
widevarietyofmaterialssuchasconcrete,stone,earthandrock‐fill.
➢Diversiondam:‐Itisadamofsmallerheightconstructedtoraise
waterleveloftheriverandnotforstorageorequalizationofflow.
➢Detentiondam:‐Itisconstructedtostorewaterduringfloodsand
releaseitgraduallyatasaferatewhenthefloodrecedes.
➢Debrisdams:‐isconstructedtoretaindebrissuchassand,graveland
floatingwoodsandthewaterthatpassesoverthedamisrelatively
clear.
➢Cofferdams:‐itisconstructedtodivertthewaterduringperiodof
construction.Itistemporarydamsconstructedforfacilitating
construction.Itisconstructedmainlyonupstreambutalsoon
downstreamdependingtheslopeoftheriveratthesite
37

38. ii. Classification according to hydraulic design
a.Overflowdam:Theyaredesignedtopassthesurplus
waterovertheircrest.Theymustbemadeofmaterials
whichwillnotbeerodedbysuchdischarges.E.g.concrete,
masonryetc…
b.Non‐overflowdam:Theyarethosewhicharenot
designedtobeovertopped.Thistypeofdesignextends
thechoiceofmaterialstoincludeearthfillandrockfill
dams.

39. iii. Classification according to construction
materials used
a)Masonrydams:‐madeofmasonry
b)Concretedams:‐madeofconcrete
c)Earthdams:‐madeofearthenmaterials
d)Rock‐filldams:‐madeofrock
e)Timberdams:‐madeoftimber
f)Steeldams:‐madeofsteel

40. 40

41. iv. Classification based on rigidity of
construction material
a. Rigid dams
➢Itisconstructedfromrigidmaterialssuchasmasonry,
concrete,steelortimber
➢Thesedamsdeflectanddeformverylittlewhen
subjectedtowaterpressureandotherforces.
b. Non‐rigid dams
➢It is constructed from non‐rigid materials such as earth
fill and/or rock‐fill.
➢There are relatively large settlements and deformations
in non‐rigid dam

42. 1.6. Characteristics of dams
Characteristics of concrete dams Gravity dam
➢It is constructed from concrete materials
➢Its stability is based on its own weight
➢The gravity dam section profile is essentially triangular to
ensure stability and to avoid over-stressing of the dam or its
foundation.
➢Concrete gravity dams could be straight or curved in plan
➢It is suited to wider valleys( relative to arch dam), provided
that excavation to rock is less than about 5m
➢It needs sound rock foundation
➢Requires imported cement

43. reservoir
Dam axis
Spillway
Tail water
43

44. Advantageous of Concrete Dams
➢Good for narrow valleys.
➢it also suitable for wide valleys.
➢Smaller construction fill volume (compared to
embankments)
➢Construction can takes place irrespective of weather
condition
➢Smaller free board (1-1.5m)
➢Can be constructed as overflow dam, i.e. can
accommodate spillway, hence cost for separate
spillway reduced.
➢Outlet pipe work, valves and other ancillary works can
be provided within the body of the dam

45. Disadvantageous of Concrete Dams
➢Sensitive to settlement, demanding sound rock
foundation
➢Sensitive to earth quake
➢Depending on the dam type, it’s construction is
demanding (technical personnel, machine
requirement, form work)
➢Bad interference in to natural landscape
➢Completed unit costs are much higher than
embankment fills, which seldom balanced by the
much lower volumes of concrete required in a dam
of certain height.

46. Characteristics of Arch dam
➢Arch dam is dam with upstream curvature which
constructed from concrete materials.
➢Stability is obtained by a combination of arch and
gravity action.
➢Utilizes the strength of an arch to resist loads placed
upon it by 'arch action‘.
➢The strength of the rock mass at the abutments and
immediately down valley of the dam must strong
enough.
➢It is suited to narrow gorges/ V-shape valley.
➢High abutment loading.
➢50-85% concrete saved relative to gravity dams.

47. Cont.…
➢Thefoundationsandabutmentsmustbecompetentnot
onlytosupportthedeadweightofthedamonthe
foundationbutalsotheforcesthataredirectedintothe
abutmentsbecauseofarchactioninresponsetothe
forcesactingonthedam.
➢Archdamcanbeclassifiedas
✓Single‐curvaturearchdams
✓Double–curvaturearchdams
✓Arch‐gravitydams

48. Types of diversion head Work
1.Diversionheadwork:
✓Diverttherequiredsupplyofwaterfromthesource
channeltotheofftakingchannel.
✓Thewaterlevelinthesourcechannelisraisedtothe
requiredlevelsoastodiverttherequiredsuppliesinto
theofftakingchannel.
✓Theheadworkmusthaveanarrangementforcontrolling
thesedimententryintothechannelofftakingfroma
river.(workforhead)
1.Storageheadwork:Besidesfulfillingallthe
requirementsofdiversionheadwork,storeexcesswater
whenavailableandreleaseitduringperiodswhen
demandexceedssupplies.(workforstorage)

49. 49

50. 50

51. Characteristics of buttress dam
➢Buttressdamsrequirebetweenonethirdsandhalfof
theconcreterequiredforagravitysection,hence
makingitmoreeconomicalfordamsover14m.
➢Concretesaved30-60%relativetogravitydams.
➢Threatofdeteriorationofconcretefromthe
impoundedwaterismorelikelythanfromathick
gravitysection.
➢Thereisalsoaneliminationofagooddealofuplift
pressure.
➢createhighercontactstress,needssoundrock.

52. Butters dam
52

53. 53

54. Gravity Dam
54
Load Resisting Mechanism of concrete dams

55. 1.Diversionheadwork:
✓Diverttherequiredsupplyofwaterfromthesource
channeltotheofftakingchannel.
✓Thewaterlevelinthesourcechannelisraisedtothe
requiredlevelsoastodiverttherequiredsuppliesinto
theofftakingchannel.
✓Theheadworkmusthaveanarrangementforcontrolling
thesedimententryintothechannelofftakingfroma
river.(workforhead)
1.Storageheadwork:Besidesfulfillingallthe
requirementsofdiversionheadwork,storeexcesswater
whenavailableandreleaseitduringperiodswhen
demandexceedssupplies.(workforstorage)
Gravity Dam
Arch Dam
55
Load Resisting Mechanism of Arch dams

56. 1.Diversionheadwork:
✓Diverttherequiredsupplyofwaterfromthesource
channeltotheofftakingchannel.
✓Thewaterlevelinthesourcechannelisraisedtothe
requiredlevelsoastodiverttherequiredsuppliesinto
theofftakingchannel.
✓Theheadworkmusthaveanarrangementforcontrolling
thesedimententryintothechannelofftakingfroma
river.(workforhead)
1.Storageheadwork:Besidesfulfillingallthe
requirementsofdiversionheadwork,storeexcesswater
whenavailableandreleaseitduringperiodswhen
demandexceedssupplies.(workforstorage)
Gravity Dam
Arch Dam
Buttress Dam
56
Load Resisting Mechanism of buttress dams

57. Characteristics Embankment dams
➢Any dam constructed of naturally excavated materials placed without
addition of binding material other than those inherent in the natural
material.
➢It is suited to either rock or compressible soil foundationand wide valley.
➢It can accept limited differential settlements.
➢Embankment dams are usually referred to be types such as Earth fill,
Rock fill, andHydraulic fill.
➢Earth fill dam: An embankment dam constructed primarily of compacted
earth in either homogeneous or zoned areas containing more than 50% of
earth.
➢Rock fill dam : The term rock fill dam usually represents dams that
contain more than 50% compacted or damped pervious rock
➢Hydraulic Fill dam: An embankment dam constructed of earth, sand,
gravel or rock generally from dredged material conveyed to the site of
placement by suspension in flowing water.

58. 58

59. 59

60. 60

62. Cont…
05-Nov-2019 Hydraulic structure I 62

64. Timber dam

65. 1.7. Phases of Engineering activity for site
investigation and construction of dam
What are the criteria to start huge project like dam?

66. Cont.…
Group work

67. Phases of Engineering activity for site
investigation and construction of dam
Damsmustbeplanned,designed,andconstructedtooperate
efficiently
a. Prior (preceding) to construction
Reconnaissance
➢Themainpurposeofsuchinvestigationsistoscreenoutthe
poorer(minor)alternatives.
➢Todecidethetypesandamountsofmoreexpensiveand
time-consumingdata(suchasstreamflowrecords,
topographicmapping,andsoon)whichneedtobe
collectedformakingfeasibilityinvestigationsofthe
remainingselectablealternatives.

68. Cont.…
Reconnaissance
✓Field tripsand reconnaissance of dam site, reservoir
area and downstream area.
✓Collection and evaluation of existing data
Like:-
▪Socio-economic
▪Political
▪Environmental and
▪Physical data of the catchment

69. Cont.….
Hydrologic data
➢Collection and analysis of stream flow (mean monthly
flow ) and precipitation record
➢Annual sediment load
➢Maximum observed flood level in the river
➢Report on damage caused by flooding
➢approximate maximum and minimum daily water
demand and Assessment of available yield
➢A flood occurring once in 100 years or less may cause
enormous damage. Therefore, stream gauging records
of 10, 20 or 30 years required based on size of dam

70. Cont.….
MeteorologicalData
➢Averagemonthlytemperature
➢Averagemonthlyrainfall
➢Maximumrecordedstormintensities
➢Annualrateofevaporation
➢Datacollectionlike,precipitation,evaporation,
infiltrationandpercolationconditionofthesite.
GeologicalData:
➢Geologicmapoflocationsite
➢Natureandtypeofrockoffoundationand
abutments(support)
➢GeologicconditionofdamandSpillwaysite

71. Cont.….
Earthquake information
➢Historical seismic information
Construction material type
➢Possible quarry sites for construction materials should
be identified with in a reasonable distance from the
construction site
Miscellaneous data
➢Erosion condition in the catchment area,
➢Transportation
➢Existing facilities and rates
➢Local labor

72. Cont.…
Preliminary and Feasibility studies
➢Detailed investigation of site conditions
➢The data collected is used for preliminary design and
economic analysis
➢Final selection of dam type, main dimensions, dam site and
layout, costs and etc.
Final investigation and Basic design
➢Completion of detailed site investigations
➢Detailed design, cost estimates, construction schedules,
➢Development of:
✓Basic report
✓Tender documents for the construction of civil works
(drawings, specifications, general and special contract
conditions)

73. Cont.…
b. During Construction
➢Detailed (design and construction execution)
➢Stepwise detail of dam design ahead of construction.
➢Site investigations oriented towards construction.
Construction activities
➢Preliminary installation of contractor at site
➢Construction of required infrastructure (road, camp, plant,
water and energy supply, etc.)
➢River diversion
➢Construction of dam and associated structures
Commissioning and operation manuals
➢Preparation of manuals for testing, monitoring and operation of
equipment.
➢Maintenance and service

74. Cont.…
c. After construction
Monitoring, surveillance, operation
➢Reading of instruments, evaluation of results
➢Planning of operation
➢Execution of operation activities

75. 1.7.1 Factors governing Selection of site for dam
As dams require huge amount of investment cost, care should
be taken while selecting the suitable site.
➢The following factors shall be considered when selecting
the site of a dam.
Topography
✓As much as possible, the dam should be located where the
river has narrow gorge which opens out upstream to create
a large reservoir .
Suitable foundation:
✓Suitable foundation is necessary for dam site
✓Theexistenceofjointpatternsinanabutment(their
orientation,inclinationandinfilling)affectthestabilityof
thedam.

76. Cont.…
✓Rockfoundation:‐Anytypeofdamcanbeconstructed
ongoodrockfoundation.
•Suchfoundationshavehighbearingcapacityand
resistanttoerosionandpercolationandareidealforall
typesofdams
✓Gravelandcoarsesandfoundation:‐suchfoundations
havelowbearingcapacityandearthandrockfilldams
aresuitable
•Astheremaybehighseepage,cut‐offmaybeprovided
✓Finesandandsiltfoundations:‐itissuitableonlyfor
earthandlowheightconcretedams.
•Asthereissettlement,piping,seepageerosionatthed/s
toeandliquefactionfailure,measuresshouldbedone.

77. Cont.…
✓Clayfoundation:‐itisnotsuitableforconstructionof
dam.Thesefoundationshaveverylowbearing
capacity.Thesettlementisquitelargeandhenceit
needsfoundationtreatmentbeforedamconstruction.
AvailabilityofTechnicalskills
•Atmanysitesneitherskilledcontractornorartisansare
available.
•Thiscanprecludetheadoptionofdamsthatrequire
intricateframeworkorveryhighqualityconcrete.The
embankmenttypedamsoramasonrygravitydammay
thenprovemostsuitable.

78. Cont.…
Costeffectiveness
•Siteconditionsnaturallyinfluencethecostofvarious
typesofdam.
•Expenditureforoperationandmaintenance(including
replacement)oftheproject.
•Thecapitalcostincludesthecostsofplanning,
investigations,designs,andconstructionbesidesthecostof
acquiringrightstotheuseofwater,litigations,and
rehabilitationoftheaffectedpeople.
•Thebenefitslikelytobereceivedfromawaterresource
projectarehavetobeknown.

79. Cont.…
•Foraveryhighdam,forinstance,thecostmaybehigh.
Forconcretedamscostsforexternalspillwaycanbesaved
incaseofspillwaylocatedatthedamcrest.However,
standardpricesofearthandrockfillmaterialsinthepast
havenotrisenasmuchasthoseofmassconcretedams.
Availabilityofmaterials
•Thecostoftransportofmaterialtothesitehastobe
considered,fordifferentdamoptions.

80. Cont.…
Environmentalandrelatedissues
•Environmentisbestdefinedasallexternalconditionswhich
affecttheexistenceofalllivingbeings.
•Differentlivingbeingsaffectoneanother,andtheenvironmental
requirementsofdifferentlivingbeingsareinterrelated
•Theenvironmental,economicandothersocio-politicalissues
associatedwithreservoirdevelopmentmustinallinstancesbe
acknowledgedattheoutsetandfullyaddressedthereafter.
•Thisisespeciallyimportantinthecaseofthelargerhigh-profile
projects.
•Especiallyoncrossboundaryriver

81. Cont.…
Hydrology
•Thepossibilityofinundationbyfloodsduringconstructionmay
favoraconcretedam.
•Wherehighflowoccurs,anembankmentdamwillrequire
specialanddetailedprotection;whereasconcretedamcouldbe
overtoppedwithlittledamage.

82. summarizes dam type characteristics in the
context of selection

83. summarizes dam type characteristics in the
context of selection

84. 1.7.2. Dam Site Assessment and Investigation
•Partiesdirectlyinvolvedinengineeringofdamactivities
are:
-Owner-publicorprivateorganization
oProvisionoffinancialresources
oEstablishmentofgeneralobjectives
-ConsultingEngineer
oPlanninganddesign
oConstructionsupervision
-Contractorforcivilworks
oConstructionofrequiredinfrastructure
oConstructionofcivilworks
•Assembly of equipment

85. Spillway site selection
➢Agoodsiteforspillwayshouldexistatornearthedam
site.
➢Availabilityofconstructionmaterials:damrequires
largeamountofconstructionmaterialsandhence,there
shouldbesufficientamountofconstructionmaterial
withhighqualityandquantityatnearbytoreduce
transportationcost.
➢Watertightnessofreservoir:thebedandsideofthe
reservoirshouldbewatertighttoreduceseepageloss
➢Submergencearea:theareasubmergedonthe
upstreamofthedamshouldbesmallandshouldnot
submergecostlylandandproperty

86. Cont.….
➢Accessibility:‐thesiteshouldbeeasilyaccessible
fortransportationofconstructionmaterial.Ifthere
wasnoroadtothesite,accessroadsshouldbe
constructedpriortheconstruction.
➢Sedimentrate:‐theincomingwatershouldbe
relativelyfreefromsedimentinordertoincreasethe
lifespanofthereservoir
➢Minimumoverallcost:‐itshouldberelatively
minimumcostincludingmaintenanceandoperation

87. 1.7.3. Foundation of dams and their treatment
➢Foundationtreatmentisatechniqueofimprovingthe
foundationpropertyfortheconstructionofhigh
concretestructures.
➢Forconvenience,foundationmaybeclassifiedasrock,
coarse‐grainedmaterialsandfine‐grainedmaterials
foundations
➢Thecommonlyadoptedfoundationtreatmentsare:
✓Surfacepreparationand
✓Foundationgrouting.

88. Cont.…
Surfacepreparation
✓Removingtheentireloosesoiltillsoundbedrockisexposed
withoutdamagingtheunderlyingrock.
✓Iffaults,seamsorshatteredrockzonesaredetectedinthe
exploratorygeologicalinvestigations,specialstepsandremedies
mustbetakentoensuretheirremoval.
FoundationGrouting
✓Pressuregroutingistheprocessofinjectingsuitable
cementations’slurriesorsimilarmaterialsintoinaccessibleplaces,
suchastheunderlyingformationoffoundationofdamsforthe
purposeofsealingseams,cracksandfissuresorfillingvoidsand
alsousedtoimprovethestrengthandelasticpropertiesofthe
materialintowhichitisinjected

89. Cont.….
Ingeneral,groutingforfoundationtreatmentmaybeclassifiedas
ConsolidationorAreaGroutingandCurtaingrouting
a.ConsolidationorAreaGrouting
➢Theobjectivesofconsolidationgroutingaretostrengthenthe
rock,tostopwaterpassagethroughthedisintegratedrockandto
increasebearingstrengthofthestrata.
➢Itisdoneinanarea,usuallytheentiredamfoundation,bydrilling
shallowholes(3to15mdeep)onagridpatternataspacingof5to
30m.
➢Thiscomparativelyshallowandlowpressuregroutingisdonefor
thegeneralconsolidationofthefoundationbeforeconcretingof
thedamsectionandisfollowedbyhighpressuregroutingafter
someconcretingofthedamhastakenplace.
➢Italsohelpsincheckingtheleakageofhigh‐pressuregrout
usedlaterinthecurtaingrouting

90. Cont.…
Curtain grouting
➢Curtain grouting (or high pressure grouting) is done to
form a deep curtain wall or an impervious barrier in the
foundation just down‐stream of the heelof the dam.
➢It is high pressure grouting is required and relatively
deeper holes are drilled near the heel of the dam.
➢It helps in reducing seepagethrough the foundation
and reducesthe uplift pressure.
➢Holes required for curtain grouting are quite deep.
The holes are usually vertical but some times it could
be inclined. Inclined holes are required to intercept the
inclined joints in the rock to develop an effective grout
curtain.

91. Thank you!
91