A h

1. Design of Diversion Dam in Tarbela Dam Pakistan
Designed by: Muhammad Shoaib
Student # : 2015730558
Graduate School of Water Resources

2. Introduction
Contents
1.Site Selection
2.Site Study
3.Dam Type selection
4.Embankment
5.Geology and foundation conditions
6.Reservoir investigations
7.Test fills
8.Study of causes of dam failure
9.Flood Hydrograph
10.Basic Hydrologic and Meteorological
11.Flood Hydrology Reports
12.Engineering Design
13.Penstock
14.Construction

3. Introduction
The projectis located at a narrow spotin the Indus River valley
at Tarbela in Haripur.
The main dam wall, built of earth and rock fill, stretches 2,743
meters (8,999 ft.) from the island to river right, standing 148
meters (486 ft.) high.
The spillways, located on the auxiliary dams, in turn consistof
two parts.
The main spillway has a discharge capacity of 18,406 cubic
meters per second (650,000cu ft. /s) and the auxiliary spillway,
24,070 cubic meters per second (850,000cu ft. /s).
Now a new diversiondam projectis going to starton
Tarbela dam.
(Tarbela Dam Pakistan)

4. 1.Site Selection

5. Site Selection continues…..
(Site Selectiontop view)
Reasons for selecting this site
(Site SelectionFront view)
 If from the selected point the river flows forward, it will flow
through the valley of steep mountains and will flow again in the
Indus River.
 Advantages :
 There is no need to make tunnel to divert the flow during
construction
 Disadvantage/Environmental Issues:
 A bridge will need to be constructed to replace the road to let the
river flow in Indus River.
(Site SelectionBack view)

6. 2.Site Study
First we will conduct detailed geologicaland subsurface explorations, which characterize thefoundation,
abutments, potentialborrow areasand typeof Dam selection.
2.1 Geology of the Tarbela area:
 The phyllite unit forms the base of the Kingriali Formation nearly
everywhere in the Tarbella area. This unit was called the "basal
conglomerate member" by Ali (1962, p. 34). It is a gray- and
brown-weathering phyllitic sequence of shale and siltstone.
 Pebbles and cobbles in the conglomerate consist mainly of
Tanawal quartzite but also include phyllite, shale, and vein quartz.
 The dolomite unit of the Tarbela area consists of dark-weathering
interlayered brown and gray microcrystalline dolomite.
 In the Sherwan syncline, distinct layers of undolomitized gray
limestone are present within the dolomite.

7. 3.Dam Type selection
 Site conditions lead to selectionof an earth-fill dam
rather than a concrete dam (or roller-compacted
concrete dam) because it includes a wide stream valley,
lack of firm rock abutments, considerable depths of soil
overlying bedrock, poorquality bedrockfrom a structural
point of view, availability of sufficientquantities of
suitable soils.
 The geologyof the dam also supports the construction
of earthfill dam as Shale, Limestone,Siltstone and
dolomite are all softminerals which when compacted
alongside the soil can produce a strong embankment.
 Furthermore,the earthfill dams are the mostcommon
type of dam, principally because their construction
involves the use of materials from required excavations
and the use of locally available natural materials
requiring a minimum of processing.
 Moreover, the foundation and topographical
requirements forearthfill dams are less stringent than
those forother types
(Earthfill Embankment Dam)

8. 3.1 Technical requirements
 The dam, foundation, and abutments must be stable under
all static and dynamic loading conditions.
 Seepage through the foundation, abutments, and
embankment must be controlled and collected to ensure
safe operation
 The freeboard must be sufficient to prevent overtopping by
waves and include an allowance for settlement of the
foundation and embankment.
 The spillway and outlet capacity must be sufficient to
prevent over-topping of the embankment by the reservoir.
3.2 Administrative requirements
 Environmental responsibility.
 Operation and maintenance manual.
 Monitoring and surveillance plan.
 Adequate instrumentation to monitor performance.
 Documentation of all the design, construction, and operational
records.
 Emergency Action Plan: Identification, notification, and response
sub plan.
 Schedule for periodic inspections..
(Dam Foundation)

9. 4.Embankment
 Many differenttrial sections for the zoning of an
embankment should be prepared to study
utilization of fill materials; the influence of
variations in types, quantities, or sequences of
availability of various fill materials; and the relative
merits of various sections and the influence of
foundation condition.
4.1 Other Considerations
 Other designconsiderations include the
influence of climate, which governs the length of
the constructionseasonand affects decisions on
the type of fill material to be used.

10. 5.Geology and foundation conditions
 The foundation is the valley floorand terraces on which the
embankmentand appurtenant structures rest Gravel
foundations,if well compacted,are suitable for earthfill
dams.
 Because gravel foundations are frequently subjected to
water percolationat high rates, specialprecautions will be
taken to provide adequate seepage controlor effective
water cutoffsor seals.The liquefactionpotential of gravel
foundations will be investigated.
5.1 Comprehensive field investigations and/or laboratory testing will be required
where conditions such as those listed below are found in the foundation:
 Deposits that may liquefy under earthquake shock or other
stresses.
 Weakor sensitive clays.
 Dispersive soils.
 Varved clays.
 Organic soils.
(Weak or sensitive clay)

11. 5.2 Subsurface investigation for foundations should develop the following data
 Subsurface profilesshowing rock and soil materials and geological formations,including presence of
faults, buried channels, and weak layers or zones. The RQD is useful in the assessmentof the
engineering qualities of bedrock.
5.2.1 Fault
 To the researchers knowledge, there has as yet been no
historic case of an operating dam being displaced by a
fault during an earthquake, although there have been some
"near misses."
 This good record of worldwide performance is particularly
remarkable in view of the fact that many if not most dams
are located in river canyons whose courses are controlled
by preferential erosion along underlying faults and joints.
 Not surprisingly, almost all foundations for large dams
display some faults, however minor, and the geologic and
seismologic challenge is to determine whether such faults
are likely to rupture during the life of the structure (i.e., are
they "active"?) and, if so, with what displacements, with
what geometries, with what magnitudes, and with what
likelihoods
(Real time example of fault)

12. 6. Reservoir investigations
 The sides and bottom of a reservoirshould be
investigated to determine if the reservoirwill
hold water and if the side slopes will remain
stable during reservoirfilling, subsequent
drawdowns, and when subjected to
earthquake shocks
7.Test fills
 In the designof earth and rock-fill dams, the constructionof test embankments can oftenbe of
considerable value and in some cases is absolutely necessary.
 Factors involved in the designof earth and rockfill dams include the mosteffective type of compaction
equipment,lift thickness, number of passes,and placementwater contents; the maximum particle size
allowable; the amount of degradationor segregationduring handling and compaction;and physical
properties suchas compacted density, permeability, grain-size distribution, and shear strength of
proposed embankmentmaterials.

13. 8.Study of causes of dam failure
 An understanding of the causes of failure is a critical elementin the designand constructionprocess fornew
dams and forthe evaluation of existing dams.
 The primary cause of failure of embankment dams in the is overtopping as a result of inadequate spillway
capacity.
 The next most frequent cause is seepage and piping. Seepage throughthe foundation and abutments is a
greater problem than through the dam.
 Therefore,instrumentation in the abutments and foundation as well as observationand surveillance is the
bestmethod of detection.
 Other causes are slides (in the foundation and/or the embankmentand abutments) and leakage from the
outlet works conduit
8.1 Other factors that increase the likelihood of internal erosion and backward erosion
piping incidents developing at a given site include:
 Conduits constructed across abruptlychanging
foundation
 Circular conduits constructed without concrete
bedding
 Conduits with an excessivenumber of joints
 Excavations made to replace unsuitable
foundation
 Conduits with compressible foundations
 Conduits located in closure sections in
embankment dams

14. 9.Flood Hydrograph
 Design-floodhydrographs orparts thereof (peak or volume) are required for sizing the hydraulic features of
a variety of water controland conveyance structures.
 In the case of dams and their appurtenant features,flood hydrographs are required forthe sizing of
spillways and attendant surcharge storage spaces
9.1 PMF Hydrograph
 The PMF (probable maximum flood)
hydrograph represents the maximum runoff
condition resulting from the most severe
combinationof hydrologic and
meteorologicalconditions considered
reasonably possible forthe drainage basin
under study.
 The PMF is used by designand
constructionorganizations as a basis for
designin those cases where the failure of
the dam from overtopping would cause
loss of life or widespread propertydamage
downstream.

15. 10. Basic Hydrologic and Meteorological
 Data-compilation and analysis of hydrologic and meteorologicaldata accumulated during and after severe
flood events is necessaryforevery flood hydrologystudy
10.1 Hydrologic Data
10.1.1 Recorded Stream flow Data
 These data are collected primarily by the (Pakistan Geological Survey) at continuous recording stream flow
gauging stations. Generally, these publications presentthe stream flow in terms of the average daily flow for
each day for the period the stream gauge has been in operation
10.1.2 Peak Discharge Data
 Because the cost of installing, operating,maintaining, compiling,and publishing the data is high, there
are relatively few continuous-recording stream gauges, considering the number of rivers and streams
in the Pakistan
10.2 Meteorological Data
 Systematic acquisition of precipitationdata is accomplished primarily through the efforts of the NWS (National
Weather Service). The NWS maintains a network of “first order” weather stations. Each station in this network
collects continuous precipitation, temperature, wind, and relative humidity data.

16. 11.Flood Hydrology Reports
 Envelope curves
 Reservoir routing criteria
 Antecedent flood
 Frequency analysis
 Probable maximum flood
 Snowmelt
 Loss rates
 Unit hydrograph
 Storm study
 Basin description
 General
 Summary of study results
 Authority

17. 12.Engineering Design
12.1Dam Capacity
 Dam capacity = [ReservoirLength x ReservoirWidth(at the
dam) x Depth of the Water(maximum)] / 3
 In our case ReservoirLength = 900 meter
 ReservoirLength = 257 meterfeet
 Dam height = 15.20 meter
 Total Dam capacity = 900*257*15.20
 = 3,515,760 cubicmeter.
12.2 Force & Center of Pressure
 Average pressure = γ * h/2 = 9.81 * 15.20/2 = 74.556
 Length along which pressure acts =
L = h/sin θ = 15.20/sin 60 = 49.86 m
 Force = pA = 257 * 74.556 * 49.86= 955362.07 KN
 Center of pressure = h/3 from bottom
= 15.20/3 = 5.06 m

18. 12.3 Catchment runoff
 Catchment runoff = 100 *A*R*Y liters
 Where:
 A is the catchment area in hectares (ha)
 R is the average annual rainfall in millimeters (mm)
 Y is the runoff as a percentage of annual rainfall
 A= 23.13 Ha R=750 mm (average per year) Y= 7.5 %
 Therefore runoff = 23.13*23.13*750*7.5
= 3,009,357 Liters.
Note: Indus basin has never experienced a rainfall of more than
800 mm/year.
12.4Volume of Embankment
 V = D/6[A1+4M+A2]
 Where M is the area of the cross-sectionmidway
betweenA1 and A2.
 Height = 15.20 Meter.
 Bottom Length is 2/H.
 Bottom Length = 10.13 Meter
 D = 2.5 meter
 Dam Width = 257 Meter
 Bottom Length = 10.13-2.5=7.63A1 = 17.007*257=
4370.79 metersquare
 A2=A1 M= 2.5*257=642.5 metersquare
 V = 4370.79/6[4370.79+4(642.5)+4370.9]
 Volume of Embankment = 8,240,250 CubicMeter

19. 12.5 Power of Dam
Power The electric power in kilowatts (one kilowatt equals 1,000 watts).
Height of Dam The distance the water falls measured in feet.
River Flow The amount of water flowing in the river measured in cubic feet per second.
Efficiency How well the turbine and generator convert the power of falling water into electric power. While for
newer, well operated plants this might be as high as 90% (0.90).
11.8 Converts units of feet and seconds into kilowatts.
Power = (Height of Dam) x (River Flow) x (Efficiency) / 11.8
Power = (49.992 feet)x (70962 cubic feetpersecond)x (0.80) / 11.8 = 258,002 kilowatts
To get an idea what 258,002 kilowatts means,let's
see how much electric energy we can make in a year.
Since electric energy is normally measured in kilowatt-
hours, we multiply the powerfrom our dam by the
number of hours in a year.
Electric Energy = (258,002 kilowatts) x
(24 hours per day) x (365 days per year) =
2,260,097,520 kilowatthours.
The average annual residential energy use in the
Pakistan is about 1,500 kilowatt-hours foreach person.
So we can figure out how many people our dam could
serve by dividing the annual energy productionby 1,500.
People Served= 2,260,097,520 kilowatts-hours / 1,500
kilowatt-hours per person)= 1,506,731.68people.

20. 13.Penstock
 Metal pipes will be used in the construction of conduits.
 Steel is a strong alloy of iron and carbon that contains lower
carbon content than cast iron (lower than 2 percent).
 The amount of carbon determines the steel’s hardenability.
Advantages of using Steel pipes
 Welded joints provide water tightness
 High compressiveand tensile strength
 Flexible and deformable understress
 High modulus of elasticity to resistbuckling loads
 Various types of joints possible
 Flanges provide a rigid connectionto gates and valve
 Has the ability to be easily used as a redundant system
Disadvantages of Steel pipes
 High material costs
 Requires a concrete encasementfor
significant and high hazard embankment
 Requires speciallinings at reservoirs
 The properselectionof linings and
coatings and any associated
maintenance are required to prevent
corrosion.

21. 14.Construction
14.1 Construction of road to access the site
14.2 Leveling and excavation of the damsite
 The site need to be leveled and the required ditching
should be done to make the site ready for the
embankmentconstructionand ultimately dam
construction

22. 14.3 Clearing
 The area to be covered by the embankment* should be pegged outprior to commencementof any works.
 The embankment and the area to be excavated should be cleared and grubbed.
 Topsoilshould be heaped in areas outside of the area to be covered by the embankmentand all trees,
scrub and roots removed.
 Topsoilshould be placed in layers not exceeding 200 mm and planted with grass if it is to be left fora
considerable time (more than 6 months).
14.4 Foundation construction
14.4.1 Grouting
 Grout holes for the cut-off curtain are drilled to a depth where the grout curtain will effectivelysealoff the
seepage of water beneath the proposed data

23. 14.5 Installing penstocks
 Then the next step is the installing of Penstock.
14.6 Embankment compaction
 All fill material for the embankmentshould be placed
in layers (or lifts) no greater than 150mm thick.
 The largest size particle should not be greaterthan
1/3rd the height of the lift, that is, 50mm.
 Each layer should be thoroughly compacted before
the next layer is place
 The compactioneffortachieved should be on
average 98% Standard Maximum Dry Density
 The minimum compactioneffortshould be 95%
Standard MDD
 The material forming the embankmentshould be
placed with sufficientmoisture to ensure proper
compaction
 Before eachadditional 150mm lift is added to the
embankment, the preceding liftshould be scarified to
ensure that the two lifts are properlyjoined
 A wheeled scraperor truck should be used for
placing the clay on the dam site
(Installing the Penstock)
(Compaction of Embankment)

24. 14.7 Settlement of the embankment
 Settlementof soil banks is commonand an allowance must be made for settlementof the dam embankment.
 The embankment may settle to a level where it is overtoppedby water and failure will result.
 Or overtime settlementmay result in the height of the embankmentbecoming lowerthan the spillway.
14.8 Vegetation
 Topsoilshould be spread over the exposedsurfaces
of the embankmentto a depth of at least 150mm and
sown with pasture grass to establish a good coveras
soonas possible.
 Never allow any vegetation larger than pasture grass
to becomeestablished onor near the embankment.
 Tree roots, especiallyeucalyptus tree roots can
cause the core to crack resulting in the failure of the
dam.
 As a rule of thumb, trees and shrubs should be kept
to a minimum distance of 1½ times the height of the
tree away from the embankment of the dam.
 This especiallyapplies to eucalypts.
(Vegetation on Embankment)

25. 14.9 Spillway
The purpose of the spillway is to pass flood flows without overtopping the dam wall. Particular attention must be
paid to providing adequate width and depth(or freeboard)of the spillway as per the specifications givenin the
dam permit.
The following guidelines apply to spillways:
 The absolute minimum width of a spillway is three meters.
 Minimum spillway dimensions are given on the permit.