Design of proposed_earth_dam_pdf

University of Sulaimania
Faculty of Engineering
Irregation Department
Graudated project (2014-2015)
Supervised By:
Dr. Kawa Zeidan
Prepared By:
Burhan Sabr Muhammad
Abdulmajeed M. Rahman
Shvan Fars Aziz
Kakamam Mahmud Homar

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Abstract
The presented paper describes a dam project which constructed in Alyawa village. After
considering all investigation types ( hydrological investigation , geological
investigation , engineering survey ) which done at the site , that selected to construct
the dam .the dam type is earth fill dam , it is selected according to the availability of the
material at the area around the site , after studying all aspects that affect the constructing
the dam , the cross section chosen consist of shell and core due to availability of the
materials , and this type of cross section is the most famous cross section that chose
for dams around the world. (Blanket or chimney and cut off and safety against seepage).

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Acknowledgment
We wish to express our gratitude to our supervisor, Dr. KAWA for his supervision,
guidance, constructive criticism and encouragement throughout the project work.
Finally, we also wish to express our sincere gratefulness to the staff of faculty of
engineering, irrigation department , Sulaimani University and all who taught us.

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The Object of the project:
The objectives of this study are:
 Selection of a suitable site for the earth dam, near Alyawa village.
 Determining the type of the earth dam based on the availability of the materials.
 Design of u/s and d/s slopes of the dam and checking their stabilities under the
most critical conditions using Geo-Studio software.
 Seepage analysis through the dam and its foundation using Geo-Studio software
and hand calculation.
 Selecting suitable diversion method according to hydrological and site
conditions.

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Content
Abstract …………………………………………………………………………………………………………………I
Acknowledgment……………………………………………………………………………………………………II
The Object of the project ………………………………………………………….…………………………III
Content …………………………………………………………………………………………………………………IV
List of figures ……………………………………………………………………………………………………….VII
List of Tables …………………………………………………………………………………………………………X
Chapter (One): (General introduction of dam) …………………………….………………..1
1.1. Introduction …………………………………………..…………………………………….……………….1
1.2. Terminologies of dams …………………………………………..………………….…………………2
1.3. Types of Dams …………………………………………..……………………………..………….……..3
1.3.1 Classification According to Purpose …………………………..………….………….3
1.3.2. Classification according to Hydraulic Design ………………..……….……………4
1.3.3. Classification according to materials used ……………………..……….…………..4
1.4. Why do we need dams …………………………………………..……………………..….………….9
1.5. The purposes of dams …………………………………………..…………………………….………10
1.5.1. Irrigation …………………………………………..………………………………………….……..10
1.5.2. Hydropower …………………………………………..…………………………………….………11
1.5.3. Water supply for domestic and industrial use ……………………………….………12
1.5.4. Inland navigation …………………………………………..………………………….…………13
1.5.5. Flood control …………………………………………..…………………………………………..14
1.6. The study area …………………………………………..………………………………………………..15
Chapter (Two): (Embankment dam) …………………………………………..………………..16
2.1. Embankment dam …………………………………………..………………………………………….. 16

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2.2. Basic Requirements of Embankment Dams ……………………………….…………………19
2.3. Selection site for the dam …………………………………………..……………….……………….20
2.4. Selection dam type …………………………………………..………………………..…………………22
2.5. Foundation for embankment …………………………………………..………..…………………..23
Chapter (Three): (Foundation of Alyawa dam) ……………….……….…………………....24
3.1. Foundation …………………………………………..…………………….……………………..24
3.2. Dam Construction Material ………………………………….…….…..………………….28
3.2.1 Clay …………………………………………..………………………………………………………..29
3.2.2. Granular material …………………………………………..…………..………………………30
3.3. In – situ enclosure …………………………………………..…………………………………….33
3.3.1. Standard penetration test ……………………………………………………………….33
3.3.2. Water pressure test …………………………………………………..………………….. 33
3.4. Laboratory enclosure …………………………………………………………………………….34
Chapter (Four): (GeoStudio Software) ……………………………………….……………………..35
4.1. Introduction…………………………..……..……….…….……………………35
4.2. Modeling Practice……………………..………………….….………………....35
4.3. Evaluation and Upgrading………………..………………..….………………..36
4.4. Groundwater seepage analysis ……………….…………...………..…………..36
4.4.1. Defining a Seepage/Air flow Model …………….………..……………….…36
4.4.2. Viewing the Analysis Results……………………..…….……………………37
4.5. Slope stability analysis…………………………...……….……………………..37
4.5.1. Defining a Stability Model ………………………..….……………………….37
4.5.2. Viewing the Analysis Results ……………………..…….……………………38
4.6. The Problems and Solutions ………………………..…….……………….……38
4.6.1. Dams and levees ……………………………………….…………………..….38
4.6.2. Reinforced walls and slopes…………………………..……………………….39
4.6.3. Excavations and open pit mines…………………...……………………..……40

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4.6.4. Roads, bridges & embankments …………………..…………………….……40
4.6.5. Environmental protection ………………………………………………...…..43
4.6.6. Construction ground freezing ………………………………………………..44
4.6.7. Climate change and arctic engineering……………………………………….45
4.6.8. Earthquake deformations……………………………………………………..46
Chapter (Five): (Design of Aliawa dam) …………………………………..………………………..47
5.1 Dam Design …………………………………………..…………………………….………………………….47
5.2. Selection preliminary section of earth dam ……………………………..……………………. 50
5.2.1. Crest width …………………………………………..…………………….……………………50
5.2.2. Side slopes …………………………………………..………………………………….………50
5.2.3. Free board …………………………………………..…………………………………………..51
5.2.4. Filter design …………………………………………..………………………………………..52
5.2.5. Type of filters …………………………………………..……………………………………..53
5.2.6. Rock toe …………………………………………..………………………………………………55
5.2.7. Central core …………………………………………..………………………………………..55
5.3 Earthfill Dam Stability …………………………………………..……………………..………………..57
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…………………………………………..……………………….………………….
.3.1. Seepage Analysis
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5.3.2. Side Slope and foundation Analysis …………………………………………..……………….60
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…………………..…………………
Stability analysis during earthquake consideration
.3.3.
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………………………………………………..………………..
3.4. Seismicity of Alyawa Dam Site
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5.4. Stability Analysis for Embankment Dam Section …………………………………………..62
References …………………………………………..………………………………………………………………..73
Conclusion …………………………………………..……………………………………………………………..70
Recomendation …………………………………………..………………………………………………………..72

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List of figure
Figure 1-1: Illustration of dam-parts in a typical cross section ............................ 2
Figure 1-2: Concrete Gravity Dams …………………………………………...… 5
Figure 1-3: Arch dam …………………………………………………………..… 6
Figure 1-4: Buttress dam ………………………………………………..…..…… 6
Figure 1-5: Types of dam …………………………………………………....…… 7
Figure 1-6: Embankment Dam …………………………………………..………… 7
Figure 1-7: Steel Dam ………………………………………………….……….… 8
Figure 1-8: Timber dam ……………………………………………………....…… 9
Figure 1-9: irrigated land covers ………………………………………………… 10
Figure 1-10: Hydropower ………………………………………………..….…… 11
Figure 1-11: Water supply for domestic and industrial use………….………… 12
Figure 1-12: Inland navigation …………………………………………..…….… 13
Figure 1-13: Flood control ………………….……………………………..…….… 14
Figure 1-14: Study Area ………………………………………………………..… 15
Figure 2-1: Earthfill dam section .………………………………………..………. 17
Figure 2-2: Rockfill dam section …….……………………………………….……18
Figure 3-1: Geological Cross Section ……………………………………….…… 25
Figure 3-2: Bore Hole location dam ……………………………………………... 27
Figure 3-3: Bore Hole NO.1 ……………………………………………………… 28
Figure 3-4: Quarries location map ……………………………………………… 31

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Figure 4-1: GeoStudio Tools .................................................................................... 35
Figure 4-2: barriers designed to retain surface water ………………………….. 39
Figure 4-3: Reinforced wall and slope …………………………………………... 40
Figure 4-4: Excavation …………………………………………………………… 41
Figure 4-5: Road and Bridge …………………………………………………….. 42
Figure 4-6: Environmental Protection ………………………………………….. 43
Figure 4-7: Ground freezing ………………………………………………….…. 44
Figure 4-8: Climate change …………………………………………….…….….. 45
Figure 4-9: Earthquake deformation ………………………………….…………46
Figure 5-1: Dam Axis Location ………… ……………………………..…………47
Figure 5-2: Plan View for Dam and Reservoir …………………………………. 48
Figure 5-3: Area-Capacity Curves ………………………………………………. 49
Figure 5-4: Rock toe drainage of Alyawa dam …………………………….…… 54
Figure 5-5: central core of Alyawa dam ………………………………………… 56
Figure 5-6: Slices and forces in a potential sliding mass ………………………. 57
Figure 5-7: Seepage vectors through the dam and its foundation
at station 0+040 …………………………………………………….. 59
Figure 5-8: Seepage through the dam and its foundation at station 0+050 …... 59
Figure 5-9: Seepage through the dam and its foundation at station 0+020 …… 60
Figure 5-10: Seismic Hazard Map for Middle East (GSHAP). ……………...… 63
Figure 5-11: Downstream Stability without earthquake ………………………. 65
Figure 5-12: Downstream Stability with earthquake ………………………..… 65

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without earthquake ……………………………………………..…. 66
Figure 5-14: upstream Stability during sudden drawdown with earthquake ….66
Figure 5-15 Typical Maximum Dam Section …………………………….…….. 67
figure 5-16 dam cross section st. 0+020 …………………………………….….... 68
figure 5-17 dam cross section st. 0+030 …………………………………….….... 68
figure 5-18 dam cross section st. 0+050 …………………………………………. 69
figure 5-19 dam cross section st. 0+060 ……………………………………….… 69
Figure 5-13: upstream Stability during sudden drawdown

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List of tables
Table 3-1: Borehole Record Summary…………………………………..……..….24
Table 3-2: Site Permeability Test Results………………………………………....26
Table 3-3: Description of Site Materials…………………………………………...29
Table 3-4: Drilling program……………………………………….…………….....32
Table 3-5: Field testing executed………………………………………….………..32
Table 3-6: Laboratory testing program…………………………………....…...…32
Table 3-7: chemical test result for clay construction material at borrow
area…………………………………………………………………………..………33
Table 3-8: shear strength, consolidation & permeability test results
for clay construction material at borrow areas…………………….………..…....34
Table 3-9: Grain size distribution, compaction, permeability and chemical test
results for granular material at borrow areas……………………………............34
Table 5-1: Preliminary side slope………………………………………….........…51
Table 5-2: Engineering Parameters used in Stability Analysis……………….....57
Table 5-3: Steady seepage…………………………………………………………..60
Table 5-4: Minimum Factor of Safety for Different Loading Conditions…..…..64

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Chapter (One)
General introduction of dam
1.1. Introduction:-
The construction of dams ranks with the earliest and most fundamental of civil
engineering activities. All great civilizations have been identified with the construction
of storage reservoirs appropriate to their needs, in the earliest instances to satisfy
irrigation demands arising through the development and expansion of organized
agriculture. Operating within constraints imposed by local circumstance, notably
climate and terrain, the economic power of successive civilizations was related to
proficiency in water engineering. Prosperity, health and material progress became
increasingly linked to the ability to store and direct water.
A dam is a structure built across a stream, river or estuary to retain water. There is no
unique way to retain water, which is why we see many different shapes for dams. Some
dams are tall and thin, while others are short and thick. Dams are made from a variety
of materials such as rock, steel and wood. We will concentrate on dams made
from concrete, a complex material, because it is important for the construction of large
dams.

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1.2. Terminologies of dams:
• Heel: contact with the ground on the upstream side
• Toe: contact on the downstream side
• Abutment: Sides of the valley on which the structure of the dam rest
• Galleries: small rooms like structure left within the dam for checking
operations.
• Diversion tunnel: Tunnels are constructed for diverting water before the
construction of dam. This helps in keeping the river bed dry.
• Spillways: It is the arrangement near the top to release the excess water of the
reservoir to downstream side
• Sluice way: An opening in the dam near the ground level, which is used to clear
the silt accumulation in the reservoir side.
Figure 1-1 Illustration of dam-parts in a typical cross section

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1.3. Types of Dams:
Dams can be classified according to different criteria as follow:
1.3.1 Classification According to Purpose
 Storage dams: they are constructed to impound water in periods of surplus
supply for use in periods of deficient supply. These periods may be seasonal,
annual, or longer. Storage dams may be further classified according to the
purpose of the storage, such as water supply, recreation, fish and wildlife,
hydroelectric power generation, irrigation, etc.
 Diversion dams: they are ordinarily constructed to provide hydraulic head or
lift for diverting water into ditches, canals, or other conveyance systems to
the place of use and are often designed to be overtopped. Such dams are used
for irrigation developments, for diversion from a natural flowing stream to
an off-channel location storage reservoir, for municipal and industrial uses,
or for any combination of the preceding.
 Detention dams: they are constructed to retard flood runoff and minimize
the effect of sudden floods. Detention dams fall into two main types. In the
more common type, the water is temporarily stored and released through an
outlet structure at a rate that will not exceed the carrying capacity of the
channel downstream. In other types, the water is held as long as possible and,
during the growing season, is released through a gated outlet and travels
though a dike system that irrigates the vegetation within the dike system.
 Multipurpose dams: they are Often dams are constructed to serve more than
one purpose. When multiple purposes are involved, a reservoir allocation is
usually made to each of the separate uses. A common multipurpose project
might combine storage, flood control, and recreational uses.

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1.3.2. Classification according to Hydraulic Design
 Overflow Dams: Overflow dams are designed to carry discharge over their
crests. They must be made of materials that will not be eroded by such
discharges. Concrete, masonry, steel, and wood have been used to construct
overflow dams. Overflow structures only a few feet high may require less
protection.
 No overflow Dams : No overflow dams are those that are not designed to be
overtopped. This type of design extends the choice of materials to include
earth fill and rock fill dams. Often a concrete dam combined with an overflow
spillway and earth fill or rock fill wing dams are used to form a composite
structure.
1.3.3 Classification according to materials used:
1. Concrete dams: the following figure shows different types of concrete
dams which are gravity, arch, and buttress dams.
CONCRETE DAMS:
 Concrete Gravity Dams
 Concrete Arch Dams
 Concrete Buttress Dams
Concrete Gravity Dams rely on the weight of the concrete of which they are
built to resist the forces (gravity, water pressure, earthquake) to which they
are subjected.

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Figure 1-2: Concrete Gravity Dams
Arch dam
An arch dam is a solid dam made of concrete that is curved upstream in plan.
The arch dam is designed so that the force of the water against it, known
as hydrostatic pressure, presses against the arch, compressing and
strengthening the structure as it pushes into its foundation or abutments. An
arch dam is most suitable for narrow gorges or canyons with steep walls of
stable rock to support the structure and stresses. Since they are thinner than
any other dam type, they require much less construction material, making
them economical and practical in remote areas.

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Figure 1-3: Arch dam
Buttress dam: - a buttress dam or hollow dam is a dam with a solid, water-tight
upstream side that is supported at intervals on the downstream side by a series
of buttresses or supports. The dam wall may be straight or curved. Most buttress dams
are made of reinforced concrete and are heavy, pushing the dam into the ground. Water
pushes against the dam, but the buttresses are inflexible and prevent the dam from
falling over.
Figure 1-4: Buttress dam

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Figure 1-5: Types of dam
Embankment Dams:
An earth dam is made of earth (or soil) built up by compacting successive layers
of earth, using the most impervious materials to form a core and placing more
permeable substances on the upstream and downstream sides.
Figure 1-6: Embankment Dams

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Steel Dams:
A steel dam consists of a steel framework, with a steel skin plate on its upstream
face. Steel dams are generally of two types: (i) Direct-strutted, and (ii)
Cantilever type. In direct strutted steel dams, the water pressure is transmitted
directly to the foundation through inclined struts. In a cantilever type steel dam,
there is a bent supporting the upper part of the deck, which is formed into a
cantilever truss. Examples of Steel type: Redridge Steel Dam (USA) and
Ashfork-Bainbridge Steel Dam (USA).
Figure 1-7: Steel Dams:

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Timber Dams:
Main load-carrying structural elements of timber dam are made of wood,
primarily coniferous varieties such as pine and fir. Timber dams are made for
small heads (2-4 m or, rarely, 4-8 m) and usually have sluices; according to the
design of the apron they are divided into pile, crib, pile-crib, and buttressed
dams.
Figure 1-8: Timber dam
1.4. Why do we need dams:
In ancient times, dams were built for the single purpose of water supply or irrigation.
As civilizations developed, there was a greater need for water supply, irrigation, flood
control, navigation, water quality, sediment control and energy. Therefore, dams are
constructed for a specific purpose such as water supply, flood control, irrigation,
navigation, sedimentation control, and hydropower. A dam is the cornerstone in the
development and management of water resources development of a river basin. The
multipurpose dam is a very important project for developing countries, because the
population receives domestic and economic benefits from a single investment.

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1.5. The purposes of dams:-
Most of the dams are single-purpose dams, but there is now a growing number of
multipurpose dams. Using the most recent publication of the World Register of Dams,
irrigation is by far the most common purpose of dams. Among the single purpose dams,
48 % are for irrigation, 17% for hydropower (production of electricity), 13% for water
supply, 10% for flood control, 5% for recreation and less than 1% for navigation and
fish farming.
1.5.1. Irrigation:
Presently, irrigated land covers about 277 million hectares i.e. about 18% of world's
arable land but is responsible for around 40% of crop output and employs nearly 30%
of population spread over rural areas. With the large population growth expected for
the next decades, irrigation must be expanded to increase the food capacity production.
It is estimated that 80% of additional food production by the year 2025 will need to
come from irrigated land. Even with the widespread measures to conserve water by
improvements in irrigation technology, the construction of more reservoir projects will
be required.
Figure 1-9: irrigated land covers

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1.5.2. Hydropower:
Hydroelectric power plants generally range in size from several hundred kilowatts to
several hundred megawatts, but a few enormous plants have capacities near 10,000
megawatts in order to supply electricity to millions of people. World hydroelectric
power plants have a combined capacity of 675,000 megawatts that produces over 2.3
trillion kilowatt-hours of electricity each year; supplying 24 percent of the world's
electricity.
Figure 1-10: Hydropower

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1.5.3. Water supply for domestic and industrial use:
It has been stressed how essential water is for our civilization. It is important to
remember that of the total rainfall falling on the earth, most falls on the sea and a large
portion of that which falls on earth ends up as runoff. Only 2% of the total is infiltrated
to replenish the groundwater. Properly planned, designed and constructed and
maintained dams to store water contribute significantly toward fulfilling our water
supply requirements. To accommodate the variations in the hydrologic cycle, dams and
reservoirs are needed to store water and then provide more consistent supplies during
shortages.
Figure 1-11: Water supply for domestic and industrial use

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1.5.4. Inland navigation:
Natural river conditions, such as changes in the flow rate and river level, ice and
changing river channels due to erosion and sedimentation, create major problems and
obstacles for inland navigation. The advantages of inland navigation, however, when
compared with highway and rail are the large load carrying capacity of each barge, the
ability to handle cargo with large-dimensions and fuel savings. Enhanced inland
navigation is a result of comprehensive basin planning and development utilizing
dams.
Figure 1-12: Inland navigation

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1.5.5. Flood control:
Dams and reservoirs can be effectively used to regulate river levels and flooding
downstream of the dam by temporarily storing the flood volume and releasing it later.
The most effective method of flood control is accomplished by an integrated water
management plan for regulating the storage and discharges of each of the main dams
located in a river basin. Each dam is operated by a specific water control plan for routing
floods through the basin without damage. This means lowering of the reservoir level to
create more storage before the rainy season. This strategy eliminates flooding. The
number of dams and their water control management plans are established by
comprehensive planning for economic development and with public involvement.
Flood control is a significant purpose for many of the existing dams and continues as a
main purpose for some of the major dams of the world currently under construction.
Figure 1-13:Flood control

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1.6. The study area:-
This project is concerned about designing a proposed earth dam in allyawa village near
the Qaradax town at Sulaymaniyah governorate. The important of this project is to
provide water for the villages locate downstream of the dam which used for irrigation
and domestic uses of the people who lives in the villages, inspite of that the people
who live in the village are not too much but we can say this project is not usefull just
for Aliyawa people rather it is usefull for all villages locate at downstream of the dam,
because the capacity of the dam is too much for one village and several villages can
use it.
Figure 1-14: Study Area

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Chapter (Two)
(Embankment dam)
2.1. Embankment dam:
Embankment dam: A dam structure constructed of fill material, usually earth or rock,
placed with sloping sides and usually with a length greater than its height. Types of
embankment dams include:
 Earth fill or Earth Dam: An embankment dam in which more than 50 percent
of the total volume is formed of compacted fine-grained material obtained
from a borrow area (i.e., excavation pit);
 Fill Dam: Any dam constructed of excavated natural materials or of industrial
waste materials;
 Homogeneous Earth fill Dam: An embankment dam constructed of similar
earth material throughout, except for the possible inclusion of internal drains
or drainage blankets; distinguished from a Zoned earth fill Dam;
 Hydraulic Fill Dam: An embankment dam constructed of materials, often
dredged, that are conveyed and placed by suspension in flowing water;
 Rock fill Dam: An embankment dam in which more than 50 percent of the
total volume is comprised of compacted or dumped pervious natural or crushed
rock;
 Rolled Fill Dam: An embankment dam of earth or rock in which the material
is placed in layers and compacted by using rollers or rolling equipment; and
 Zoned Embankment Dam: An embankment dam which is composed of zones
of selected materials having different degrees of porosity, permeability, and
density.

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 Diaphragm earth fill dam: This is a modification over the homogenous
embankment type in which the bulk of the embankment is constructed of
pervious material and a thin diaphragm of impermeable material is provided
to check the seepage the diaphragm may be of impervious soils cement
concrete.
Figure 2-1: Earthfill dam section

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Figure 2-2:Rockfill dam section

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2.2. Basic Requirements of Embankment Dams:
The following criteria must be met to ensure satisfactory earth and rock fill structures:
1. The embankment, foundation, abutments, and reservoir rims must be stable and
must not develop unacceptable deformation under all loading conditions
brought about by construction of the embankment, reservoir operation, and
earthquake.
2. The reservoir rim must be stable under the most severe operating conditions to
eliminate the possibility of an unstable thin rim or the possibility that large
existing landslides, when inundated by the reservoir or during rapid drawdown,
would be triggered and cause a large volume of slide material to fill the reservoir
and create a large wave that would overtop the dam.
3. Seepage through the embankment, foundation, abutments, and reservoir rim
must be controlled to prevent excessive uplift pressures, internal erosion and
piping, instability, sloughing, removal of material by suctioning, or erosion of
material by loss into cracks, joints, and cavities. In addition, the purpose of the
project may impose a limitation on the volume of seepage.
4. Filters must be required for any high or moderate hazard embankment dam, not
just something to consider.
5. Freeboard must be sufficient to prevent overtopping by waves.
6. Camber should be sufficient for allowance for settlement of the foundation and
embankment. It is not included as part of the freeboard except in rare cases
7. Spillway and outlet capacity must be sufficient to prevent overtopping of the
embankment and encroachment on freeboard.

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2.3. Selection site for the dam
The selection of a suitable site for the construction of a dam depends on various, factors
which are briefly described below:
1. There should be water tight rim for the reservoir formed by the surrounding hills
up to the proposed elevation of the dam.
2. The value of the property and land submerged in the reservoir created by the
propose dam should be as low as possible. Suitable foundations should be
available at the dam site. It's however possible to Improve the foundation
conditions by adopting appropriate foundation treatments. Special site
requirement for the spillway.
3. For economy it's necessary that the length of the dam should be as small possible
and for a given height it should store large volume of water. It therefore follows,
that the river valley at the dam should be as narrow as possible and should open
out upstream to create a reservoir with as far as possible large storage capacity
often the dam is located on the downstream of the confluence of two rivers, So
that advantages of both the valleys to provide larger capacity is available.
4. As far as possible the dam should be located on high ground as compared to the
river basin. This will reduce the cost and facilitate drainage of the dam section.
5. A suitable site for the spillway should be available in the vicinity of the dam if
the spillway is to be located separately from the dam.
6. From the standpoint of economy the economy the bulk of the materials required
for the Construction of dam should available at or near the dam site.
7. Immediately on the upstream of the dam site
8. Dam site should be such that the reservoir would not silt up soon.
9. For this if any of tributaries of the river is transporting relatively large quantity
of sediment, and then the dam site may be selected on the upstream of the
confluence of this tributary with the river.
10. It is preferable to select a dam site which is already connected or can be
conveniently connected to a nearby rail head by road or rail, so that the dam site

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is easily accessible. This would facilitate transportation of men, machinery and
various other essential items to the dam site.
11. In the near vicinity of the dam site sample space with healthy environment must
be available for establishing colonies for lab our and other staff members
associated with the construction of dam.
12. The dam site should be such that it involves minimum overall cost of
construction as well as minimum cost of subsequent maintenance.

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2.4. Selection dam type:
The following main factor are examined in stage of selecting dam type
1. Topography and geological condition of the proposed dam site.
2. Availability of suitable material for the dam.
3. The feasibility of spillway construction.
4. The need to be able to cope with conditions of extreme flood and earthquake.
2.5. Foundation for embankment:-
Foundation competence of the dam site must be assessed in terms of stability, load-
carrying capacity, compressibility (soils) or deformability (rocks), and effective mass
permeability. The investigative techniques to be adopted will depend upon the
geomorphology and geology of the specific site.
 Dams on competent stiff clays and weathered rocks: Serious under seepage is
unlikely to be a problem in extensive and uniform deposits of competent clay.
It is important, however, to identify and consider the influence of inter bedded
thin and more permeable horizons which may be present, e.g. silt lenses, fine
laminations, etc. Considerable care is required in the examination of recovered
samples to detect all such features. The determination of appropriate shear
strength parameters for evaluating foundation stability is of major importance.
For a foundation on rock positive identification of the weathered rock profile
may prove difficult. In situ determination of shear strength parameters may also
be necessary, using plate loading tests in trial pits or adits, or dilatometer or
pressure meter testing conducted within boreholes. The latter techniques are
particularly suitable in softer rocks containing very fine and closely spaced
fissures.

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 Dams on soft cohesive foundations: The presence of superficial soft and
compressible clay deposits normally ensures that seepage is not a major
consideration. The nature of such formations also ensures that investigations
are, in principle, relatively straightforward. The soft consistency of the clays
may necessitate the use of special sampling techniques. In such situations
continuous sampling or in situ cone penetrometer testing techniques offer
advantages. Stability and settlement considerations will require the
determination of drained shear strength and consolidation parameters for the
clay.
 Dams on pervious foundations: Seepage-associated problems are normally
dominant where a dam is to be founded on a relatively pervious foundation. In
a high proportion of such instances the soil conditions are very complex, with
permeable and much less permeable horizons present and closely interbedded.
 Dams on rock foundations: The nature of the investigation is dependent upon
whether an embankment or a concrete dam is proposed. Where the decision is
still open, the investigation must cover either option; both require a full
understanding of the site geology.

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Chapter 3
Foundation of Alyawa dam
3.1. Foundation
Three boreholes are drilled at dam axis as shown in figure 3.2 & 3.3, and Table 3.1
presents summary for borehole results, it shows that the water table is higher than the
invert of cutoff trench which means that there is a need for dewatering during
construction of the dam.
Table 3-1: Borehole Record Summary
Test
Borehole No.
BH No. 1 BH No. 2 BH No. 3
SPT
(Blows/30cm)
9
6 for 1m
10 for 2m
15-21 for 3m
-
TCR (%)
27-100 for depth
(2-10)
95-97 for depth
(10-12)
40 for depth (3-5)
45-95 for depth (5-
8)
10-69 for depth
(1-4)
20-100 for depth
(4-10)
RQD (%)
10-97 for depth (2-
10)
80-97 for depth
(10-12)
87 for depth (6-8)
0-15 for depth
(1-4)
0-89 for depth
(4-10)
Watertable
(masl)
833.9 840.4 842.6

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Cut slope were found based on the geotechnical cross section shown on Figure 3.1
where boreholes BH1, BH2 are shown. Overburden layer shall be removed therefore a
cut depths between 3 to 4 m are used.
Figure 3-1: Geological Cross Section.

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According to low permeability and sound foundation at dam site, there is no need for
curtain grouting or consolidation grouting; Table 3.2 below summarizes the results for
permeability test. And all logs information is listed in Annex 1.
Table 3-2: Site Permeability Test Results.
Location B.H. No. Test No.
Test Depth
(m)
Lugeon
Lit/m/min
K cm/sec
Dam Axis
Site
1
1 4.50 – 7.50 2.4 2.779 ×10-5
2 9.00 – 12.00 1.2 1.389×10-5
2 1 5.00 – 8.00 0.6 6.948×10-6
Spillway 3
1 1.50 – 4.50 0.7 8.106×10-6
2 4.50 – 7.50 1.4 1.621×10-5
3 7.00 – 10.00 0.7 8.106×10-6

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Figure 3-2: Bore Hole location dam

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Figure3-3: Bore Hole NO.1
3.2. Dam Construction Material
Construction material is available near the dam site. Samples were taken and required
tests were carried out. The embankment construction materials are available in the
vicinity of the dam. The quality and availability of the materials were proved by
extensive site and laboratory geotechnical investigation works as presented in the
geotechnical report. Table 3 shows the location, distance to dam axis, surface area and
approximate volume of materials

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Table 3-3: Description of Site Materials
Material
Type
Quarry
No.
Area Distance
pond km
Surface Area
m2
Approximate volume
m3
Clayey Materials QC1 0.1 3,600 10,800
Clayey Materials QC2 0.2 5,000 20,000
Granular Materials QG1 5.5 5,000 20,000
Granular Materials QG2 5.0 5,000 20,000
According to the required quantities for impervious clay core and shells, which is about
9,059m3
for clay core and 31,207m3
for shells, the available materials is enough to
cover the dam construction.
3.2.1 Clay
Clay is a fine-grained natural rock or soil material that combines one or more clay
minerals with traces of metal oxides and organic matter. Clays are plastic due to their
water content and become hard, brittle and non–plastic upon drying or firing .Geologic
clay deposits are mostly composed of phyllosilicate minerals containing variable
amounts of water trapped in the mineral structure. Depending on the content of the soil,
clay can appear in various colors, from white to dull gray or brown to a deep orange-
red.
Clays are distinguished from other fine-grained soils by differences in size and
mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend
to have larger particle sizes than clays. There is, however, some overlap in particle size
and other physical properties, and many naturally occurring deposits include both silts
and clay. The distinction between silt and clay varies by discipline Geologists and soil
scientists usually consider the separation to occur at a particle size of 2 µm (clays being
finer than silts),sedimentologists often use 4-5 μm , and colloid chemists use 1
μm Geotechnical engineers distinguish between silts and clays based on the plasticity

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properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay
particles as being smaller than 2 μm and silt particles as being larger.
3.2.2. Granular material
A granular material is a conglomeration of discrete solid, macroscopic particles
characterized by a loss of energy whenever the particles interact (the most common
example would be friction when grains collide). The constituents that compose granular
material must be large enough such that they are not subject to thermal motion
fluctuations. Thus, the lower size limit for grains in granular material is about 1 µm.
On the upper size limit, the physics of granular materials may be applied to ice floes
where the individual grains are icebergs and to asteroid belts of the solar system with
individual grains being asteroids.
Some examples of granular materials are snow, nuts, coal, sand, rice, coffee, corn
flakes, fertilizer and ball bearings. Powders are a special class of granular material due
to their small particle size, which makes them more cohesive and more
easily suspended in agas. Granular materials are commercially important in
applications as diverse as pharmaceutical industry, agriculture, and energy production.
Research into granular materials is thus directly applicable and goes back at least
to Charles-Augustin de Coulomb, whose law of friction was originally stated for
granular materials.
The soldier/physicist Brigadier Ralph Alger Bagnold was an early pioneer of the
physics of granular matter and whose book The Physics of Blown Sand and Desert
Dunes remains an important reference to this day.
According to material scientist Patrick Richard, "Granular materials are ubiquitous
in nature and are the second-most manipulated material in industry (the first one
is water)".
In some sense, granular materials do not constitute a single phase of matter but have
characteristics reminiscent of solids, liquids, orgases depending on the average energy
per grain. However in each of these states granular materials also exhibit properties
which are unique.

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Granular materials also exhibit a wide range of pattern forming behaviors when excited
(e.g. vibrated or allowed to flow). As such granular materials under excitation can be
thought of as an example of a complex system.
Figure 3-4: Quarries location map

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Table 3-4: Drilling program
Drilling program
Number of
boreholes
Each depth (m) Total depth Location
2 1.B.H of 12 m &
1B.H of 8 m
20 Dam axis site
1 10 10 Spillway
total 30
Table 3-5: Field testing executed
Table 3-6: Laboratory testing program

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3.3. In – situ enclosure
3.3.1.Standard penetration test
3.3.2.Water pressure test
Table 3-7: chemical test result for clay construction material at borrow areas.

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3.4. Laboratory enclosure
Table 3-8: shear strength, consolidation & permeability test results for clay
construction material at borrow areas.
Table 3-9: Grain size distribution, compaction, permeability and chemical test
results for granular material at borrow areas.

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Chapter (Four)
GeoStudio Software
4.1. Introduction:
While primarily intended for analyzing the stability of natural and man-made earth
slopes, you can also use GeoStudio Basic for the analysis of confined and unconfined
steady-state seepage problems, for the analysis of linear-elastic settlement and stress
distribution problems, for the tracking of contaminants within ground water flow, for
the analysis of freeze-thaw problems, and for 1D vadose zone and soil cover analyses.
Figure 4-1:GeoStudio Tools
4.2. Modeling Practice
A common tendency when using powerful modeling software is to build numerical
models that are geometrically too complex. The geometric complexity is usually not
required to obtain meaningful results. In fact, we at GEO-SLOPE strongly advocate
that a numerical model should be a simplified abstraction of the actual field conditions.
Adopting this modeling principle makes GeoStudio Basic a very powerful analytical
tool for use in practice in spite of its geometric limitations.

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4.3. Evaluation and Upgrading
GeoStudio Basic allows you to evaluate a very high-end geotechnical software package
with a minimal investment. Starting with GeoStudio Basic is an excellent strategy.
Once you are comfortable with using the software and you find that your projects
dictate analyzing more complexity, you can upgrade to the full-featured version.
Everything that you have learned and done with the Basic Edition will be directly usable
in the full-featured edition. Nothing will be lost by first acquiring the Basic Edition and
subsequently acquiring the full-featured edition.
4.4. Groundwater seepage analysis
SEEP/W is a finite element CAD software product for analyzing groundwater seepage
and excess pore-water pressure dissipation problems within porous materials such as
soil and rock. Its comprehensive formulation allows you to consider analyses ranging
from simple, saturated steady-state problems to sophisticated, saturated/unsaturated
time-dependent problems. SEEP/W can be applied to the analysis and design of
geotechnical, civil, hydrogeological, and mining engineering projects.
SEEP/W can model both saturated and unsaturated flow, a feature that greatly broadens
the range of problems that can be analyzed. In addition to traditional steady-state
saturated flow analysis, the saturated/unsaturated formulation of SEEP/W makes it
possible to analyze seepage as a function of time and to consider such processes as the
infiltration of precipitation. The transient feature allows you to analyze such problems
as the migration of a wetting front and the dissipation of excess pore-water pressure.
4.4.1. Defining a Seepage/Air flow Model
Beginning an analysis is as simple as defining the geometry by drawing regions and
lines that identify soil layers, or by importing a DXF™ file. Then graphically apply
boundary conditions and specify material properties. Material properties can be
estimated from easily measured parameters like grain-size, saturated conductivity,
saturated water content, and the air-entry value.

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4.4.2. Viewing the Analysis Results
Once you have solved your seepage analysis, SEEP/W offers many tools for viewing
results. Generate contours or x-y plots of any computed parameter, such as head,
pressure, gradient, velocity, and conductivity. Velocity vectors show flow direction and
rate. Transient conditions can be shown as a changing water table over time.
Interactively query computed values by clicking on any node, Gauss region, or flux
section. Then prepare the results for your report by adding labels, axes, and pictures, or
export the results into other applications such as Microsoft® Excel® for further
analysis.
4.5. Slope stability analysis
SLOPE/W is the leading slope stability CAD software product for computing the factor
of safety of earth and rock slopes. SLOPE/W can effectively analyze both simple and
complex problems for a variety of slip surface shapes, pore-water pressure conditions,
soil properties, analysis methods and loading conditions.
Using limit equilibrium, SLOPE/W can model heterogeneous soil types, complex
stratigraphic and slip surface geometry, and variable pore-water pressure conditions
using a large selection of soil models. Slope stability analyses can be performed using
deterministic or probabilistic input parameters. Stresses computed by a finite element
stress analysis may be used in addition to the limit equilibrium computations, for the
most complete slope stability analysis available.
With this comprehensive range of features, SLOPE/W can be used to analyze almost
any slope stability problem you will encounter in your geotechnical, civil, and mining
engineering projects.
4.5.1. Defining a Stability Model
Beginning an analysis is as simple as defining the geometry by drawing regions and
lines that identify soil layers, or by importing a DXF™ file. Then choose an analysis
method, specify soil properties and pore-water pressures, define reinforcement loads,
and create trial slip surfaces.

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4.5.2. Viewing the Analysis Results
Once you have solved your stability analysis, SLOPE/W offers many tools for viewing
the results. Display the minimum slip surface and factor of safety, or view each one
individually. View detailed information about any slip surface, including the total
sliding mass, a free body diagram and a force polygon showing the forces acting on
each slice. Contour the factors of safety, or show plots of computed parameters. Then
prepare the results for your report by adding labels, axes, and pictures, or export the
results into other applications such as Microsoft® Excel® for further analysis.
4.6. The Problems and Solutions
4.6.1. Dams and levees
Dams and Levees are engineered barriers designed to retain surface water. These
structures are often required to limit water losses and pore-pressures through the barrier.
This is often difficult to achieve because ideal natural materials are not always available
at the site. As a result, advanced designs of dams and levees may include internal drains
or barriers to trap or collect seepage water or to dissipate the hydraulic head that drives
flow through the dam. Operation of the dam under changing water levels can further
complicate the required design. Finally, it is imperative that the dam or levee be stable
under construction, operation, and draw down conditions.
The Solution
GeoStudio is a suite of software products that can be used to evaluate the performance
of dams and levees with varying levels of complexity. The seepage, settlement,
filling/draining, and stability performance of the structure can be simulated during the
entire construction sequence. Either long term (steady state) or detailed transient
analyses can be done to consider time-dependent responses. Pore-water pressures and
stresses can be included in an advanced stability analysis. The response of the structure
to earthquake loading or ground freezing/thawing can also be investigated.

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Figure 4-2: barriers designed to retain surface water
4.6.2. Reinforced walls and slopes
Many classes of geotechnical engineering projects require additional mechanical
support to ensure stability during and after construction. This mechanical support may
range from geosynthetics to tie-back anchors or retaining walls. Excavations are often
preceded by installation of sheet pile walls and then these are anchored or braced as
construction proceeds. Stresses in the structural components need to be estimated so
that they can be designed to accommodate the anticipated loading. Man-made or natural
slopes are often reinforced to increase stability and minimize risk.
The Solution
GeoStudio has many different options for dealing with structural reinforcements. In a
more rigorous analysis, the structural component properties can be included in a stress-
deformation analysis such that the forces and moments in the structure can be computed
along with the interaction between the structure and ground. In a less rigorous approach,
a stability analysis can be carried out with all or part of an assumed structural load
component applied to the sliding mass. Structural components can be applied and

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removed automatically at different stages of construction to simulate actual field
conditions. There is a friction based interface model in SIGMA/W to allow for soil-
structure interaction with or without slippage. Whether you are concerned about wall
loading, deformations, or stability, GeoStudio has a method of investigating your
concerns.
Figure 4-3: Reinforced wall and slope
4.6.3. Excavations and open pit mines
Excavations cover a broad range of geotechnical engineering from building
construction to open pit mining and can be the basis for a wide range of analyses,
depending on the questions being asked. Common to all issues in this category are the
release of locked in stresses when the soil or rock is unloaded. In addition, the presence
of water in the ground or free water on the surface can greatly change the excavation
behaviour from a seepage and stability perspective.

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The Solution
The integration in GeoStudio provides a wide range of approaches for dealing with
excavations. Insitu stresses and pore-water pressure conditions can be established such
that upon removal of the ground, rebound displacements can be computed. Steady state
or transient pore-water flow systems can be simulated and incorporated into dewatering
and stability evaluations. Detailed stress paths can be monitored during these transient
changes in pore-water pressure. In an advanced analysis, a slope failure in a pit can be
accounted for as a result of a sudden collapse of unstable ground. In addition, a dynamic
earthquake analysis can be carried out to assess the potential for generation of excess
pore-water pressures in the ground or plastic deformation due to stress-redistribution.
Figure 4-4: Excavation
4.6.4. Roads, bridges & embankments
There are a wide range of geotechnical engineering problems that fall under the broader
category of civil engineering works. These can often involve the construction of
roadways, rail beds, bridge abutments, and mechanically stabilized earth (MSE) walls.
The challenges associated with designing these structures are varied. Construction
sequences in the field often depend on transient changes in pore-water pressures due to
consolidation. Embankment construction often requires the interaction of typical soil

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materials as well as concrete and structural steel or geofabrics. Timing of the placement
of these components is often critical to construction and post-construction stability.
The Solution
GeoStudio is capable of analyzing many different construction projects. Staged
construction can be modeled in the same sequence as actual field construction and if
the process is time dependent, such as waiting for dissipation of excess pore-water
pressures, then it is possible to set actual time durations to the modeled stages so that
the results over time can be graphed and analyzed. Data from one construction stage to
the next is automatically carried forward and it is possible to branch the analysis to
consider different scenarios that both depend on the same previous stage analysis
results. In addition, the integration capabilities in GeoStudio allow for a wide range of
supporting analyses to be added to the project at any time, such as slope stability,
ground freezing, climate interaction, or earthquake stability.
Figure 4-5: Road and Bridge

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4.6.5. Environmental protection
Production and disposal of mining and municipal waste poses many challenges from a
geotechnical design and analysis perspective. Proper initial design can lead to much
more efficient management of waste during and after project closure. Issues of concern
from an analysis perspective include: stability of waste deposits such as landfills, waste
rock and tailings impoundments; seepage of water, gas and contaminants through these
facilities; design of cover or cap systems to prevent water infiltration or the release of
gases and water; settlement and consolidation of waste; long term performance; and
heterogeneity of waste and the associated characterization of material properties.
The Solution
GeoStudio can address these issues and concerns in a variety of ways from pre-
construction, through construction stages, and into long term performance analysis. The
strength of the integration capability in the software allows for differing levels of
complexity. Both steady state and transient process can be considered as can the
coupling of heat, gas and water fluxes to climate conditions. Through use of Add-In
models, the user can consider random variation in material properties or hysteretic
effects. In addition, seepage models can be linked with contaminant transport models
or with slope stability models as required for a comprehensive solution.
Figure 4-6: Environmental Protection

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4.6.6. Construction ground freezing
Artificial ground freezing can be an effective way to deal with various construction
ground control challenges such as the mitigation of seepage infiltration into tunnels and
shaft excavations; or ground strengthening for excavation. First used over 100 years
ago, it is common practice in several areas of geotechnical engineering. In many cases,
the presence of moving water adds more heat than can be removed by the chilled pipe
network. When this happens, closure of the barrier wall will not happen.
The Solution
GeoStudio can consider ground freezing and thawing with phase change due to
conduction or both conduction and convection of heat in moving water and or moving
air. There are a variety of boundary condition options that allow for steady state or
transient analyses. A “convective surface” boundary condition is specially implemented
to allow for artificial ground freezing where a flowing fluid in a close piping system
removes heat from the ground. The same boundary condition could be applied in
reverse to simulate forced heating of the ground in special circumstances. Using Add-
In constitutive models in SIGMA/W and SLOPE/W will allow for the results from a
thermal analysis to be used to assess deformations or stability due to changing ground
strengths that are temperature dependent.
Figure 4-7: Ground freezing

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4.6.7. Climate change and arctic engineering
Degradation of permafrost due to construction or climate change is a major concern in
arctic engineering. Melting permafrost results in ground strength loss, release of trapped
pore-water, and subsequent deformation and stability concerns.
The Solution
GeoStudio can consider ground freezing and thawing with phase change due to
conduction or both conduction and convection of heat in moving water and or moving
air. There are a variety of boundary condition options that allow for steady state or
transient analyses. Actual climate data can be used to couple the ground surface with
the climate using a rigorous method. Optionally, an Add-In has been written to apply
the Hwang (1972) climate algorithm within TEMP/W. A “thermo syphon” boundary
condition is specially implemented to allow for coupling of ground response to air
temperature and wind-speed. Using Add-In constitutive models in SIGMA/W and
SLOPE/W will allow for the results from a thermal analysis to be used to assess
deformations or stability due to changing ground strengths that are temperature
dependent.
Figure 4-8: Climate change.

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4.6.8. Earthquake deformations
Many regions of the globe are subjected to earthquakes and as such any geotechnical
structure must be functional under extreme shaking events. Earthquakes can result in
the generation of excess pore-water pressure which reduces effective strength and can
lead to failure. Dynamic shaking can cause collapse of certain types of soils and
dynamic inertial forces can in some cases result in permanent deformation. Loss of
strength due to pore-pressure changes and collapse can also result in permanent plastic
deformations.
The Solution
GeoStudio’s QUAKE/W can be integrated with the entire suite of models to allow for
dynamic analysis of earth structures. Depending on the analysis options, it may be
desired to perform a transient Newmark type analysis to determine deformations due to
inertial forces. If there is generation of excess pore-water pressure then dissipation of
that pressure can be considered within a seepage or stress-deformation model. Regions
in which there has been a loss of strength and collapse can be identified and permanent
plastic deformations can be estimated. Structural supports such as tie-back anchors and
sheet pile walls can be included in the dynamic analysis.
Figure 4-9: Earthquake deformation.

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Chapter (5)
Design of Aliawa dam
Dam design is started once the survey is finished, and according to the site visits,
the Client requirements, and sites conditions the location of the dam is selected.
The geological and geotechnical investigations are used to design the dam in a
proper section and profile.
The water storage capacity of a dam and reservoir is selected from area-capacity curves
and hydrological study. Figure 1 presents plan view for dam, spillway, and reservoir.
A check dam is provided at upstream of reservoir area to block the sediments from
entering the reservoir in order to increase the life time of dam.
Figre 5-1: Dam Axis Location.
4.1 Dam Design

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Figure 5-2: Plan View for Dam and Reservoir (after sulaimania directorate of
irrigation)
.

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Figure 5-3: Area-Capacity Curves.
The area-capacity curves are shown in Figure 5.3 which are derived in order to check
the reservoir’s capacity and to establish a storage-depth relationship for the routing
calculations. The proposed spillway crest level is at 853 meters above sea level (masl),
which will result in a reservoir capacity of 200,000m3
.

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5.2. Selection preliminary section of earth dam:
A preliminary section is selected and then subjected to the stability analysis to check
its safety. In the preliminary section, the following parameters are decided:
5.2.1. Crest width:
The crest width of an earth dam is determined only by the requirement of roadway at
the top of the dam. In general the crest width varies 6 to 12 m, with the wider dimensions
being adopted for the higher and more important dams. However, a crest width less
than 6 m may also be provided but it should not be less than 3 m because this is the
minimum needed for an access road to permit maintenance work. For Alyawa earth
dam 5 m will be adopted as a preliminary crest width.
The width should be sufficient to keep the seepage line within the dam when the
reservoir is full.
 For very low dams with height H<10m, top width: B = H/5 + 3
 For dams with height 10m<H<30m: B = 0.55 H + H/5
 For dams higher than 30 m: B = 1.65 (H + 1.5)1/3
 Top width should not be less than 3 m for any height of the dam.
5.2.2. Side slopes:
No specific rules can be given for determining the side slopes of an earth dam. The
general procedure is that on the basis of experience with similar dams side slopes are
considered and the same are modified if necessary after the stability is carried out.
The side slopes of earth dams usually vary in the range between 2 horizontal to 1
vertical and 4 horizontal to 1 vertical. However, where the foundation is weak side.

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Table 5-1: Preliminary side slope.
For Alyawa earth dam according to the available materials near the dam site
And refer to the table above the U/S side slope is (2.5:1) (H:V) and D/S side slope (
2.25:1) (H:V)
5.2.3. Free board:
Freeboard is the difference in the elevation of the crest of the dam and the maximum
water level in the reservoir which will result when the maximum flood will occur.
Sufficient freeboard must be provided so that there is no possibility whatsoever of the
dam being overtopped.
The necessary freeboard is calculated by assuming that the maximum flood will occur
when the reservoir is full and that the highest possible waves will develop at the same
time. The minimum freeboard shall be 1.5 times the wave height (for run up on
riprapped slopes), plus a safety factor.
The height of wave may be compacted by Molitor’s formula. The safety factor which
generally varies between 0.6 to 3 m is selected by considering the size of the reservoir,
the height of the dam, the reliability of the data from which the flood computations are
made, and the usual practice.
Freeboard is taken 1.5 times the wave height:

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FB = 1.5 hw
For F<32 km hw = 0.0322√FV + 0.763 – 0.271F0.25
For F>32 km hw = 0.0322√FV
Where:
V = wind velocity in km/hr.
F = fetch in km
hw = wave height in meters
F= 100 m
V= 80 km/h
Hw= 0.0322*√0.1 ∗ 80 + 0.763 – 0.271 *(0.1)0.25
Hw = 0.701 m
FB= 1.5 hw + additional safety provision
FB = 1.5 * 0.701 + 0.65 = 1.7m
5.2.4. Filter design
Filters in embankment dams are composed of specifically-designed entities (zones) of
coarser-grained soils placed at specifically-targeted locations within or adjacent to the
dam structure. Filters are designed and constructed to achieve specific goals such as
preventing internal soil movement and controlling drainage, and are typically installed
during new dam construction. Filters have also been added to existing dams to meet
specific requirements.
If filters are not designed and constructed correctly, embankment dams will have an
increased probability of failure, which endangers the public. The particular design
requirements and site conditions of each embankment dam are unique, and as such, no
single publication can cover all of the requirements and conditions that can be
encountered during design and construction. Therefore, it is critically important that
embankment dam filters be designed by engineers experienced with all aspects of the
design and construction of embankment dams.

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5.2.5. Type of filters
 Drainage filters (class I):
Filters whose purpose is to intercept and carry away the main seepage within a dam and
its foundation. These filters may have to remove large amounts of seepage for dams on
pervious foundations or dams of poor construction. The filters consist of uniformly
graded materials, typically in two stages. The filter must meet the requirements for both
particle movement and drainage. Toe drains typically fall into this class.
 Protective filters (class II):
Filters whose purpose is to protect base material from eroding into other embankment
zones and to provide some drainage function in order to control pore pressure in the
dam. These filters are typically uniformly graded and in several stages, but they can
also be broadly graded in the interest of reducing the number of zones to make the
transition to the base material. This class includes chimneys, blankets, and transition
zones on the downstream side of a dam.
 Choke (inverted) filters (class III):
Filters whose purpose is to support overlying fill (the base material) from moving into
pervious or open work foundations. These filters are typically broadly graded and have
a requirement only to stop particle movement. There is no permeability requirement.
Choke filter material is also used in emergency situations in an effort to plug whirlpools
and sinkholes.
 Seismic crack stoppers (class IV) –:
Filters whose purpose is to protect against cracks that may occur in the embankment
core, especially caused by seismic loading and/or large deformations. The dimensions
of this class of filter are controlled by expected displacement (horizontal or vertical).
While there is no permeability requirement for this type of filter, it should be relatively
free of fines so the zone itself does not sustain a crack. A second stage (gravel) filter
may be required if concern exists that the first stage finer zone might sustain or allow
propagation of a crack. Second stage filters may also be required for transition to a

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coarser shell material. This class of filter is typically used for chimneys and transition
zones.
The type of filter which is more suitable with Alyawa dam is drainage filter, and the
material used in filter is sand and gravel respectively
The minimum thickness of filter should not be less than 1.5m and for Alyawa dam a
1.5m thickness is provided for preventing moving of small particles which may lead to
creating piping through the dam body.
The filter help small particles to remain at their location and preventing leaving them
to the outside of the dam body with the seeped water.
5.2.6. Rock toe
In Alyawa dam rock toe is another way which is used to prevent piping through the
dam body and prevent leaving material from the dam body to the outside of the dam
which may lead to erode the D/S face of the dam caused by water that pass through the
drainage .
Figure 5-4: Rock toe drainage of Alyawa dam

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5.2.7. Central core
A zone of low permeability material in an embankment dam. Sometimes referred to as
"central core," "inclined core," "puddle clay core," and "rolled clay core."
Core in zoned earth dam are provided for reduce the seepage water through the earth
dam and act as an impervious layer which define with their low permeability of the
material that used for the construction of the central core usually clay material is
provided for central core in zoned earth fill dam however: there are other materials that
used as a central core at different types of the dam such as: asphalt, concrete,…….etc.
In Alyawa dam such as the most constructed earth fill dam in Kurdistan region clay
material is used for constructing central core.
Using clay as a core material is because of their availability of clay near the dam site
and its more economical to use clay as central core than using the other materials.
The type of core choice for Alyawa dam is minimum core A which is suitable for dams
on impervious foundation or shallow pervious foundations with positive cutoff trench.
Cutoff trench is used as a foundation that extent the core to impervious layer of the
foundation.be side of that in the case of large deep impervious layer under the
foundation the cutoff trench will not be economical to be provided until the impervious
layer.

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The size and dimensions of central core of the dam is shown below:
Figure 5-5: central core of Alyawa dam

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5.3 Earthfill Dam Stability
Stability is always a key issue in the analysis, assessment
or design of most earth structures. After all, the prime objective is to ensure that the
structure does not collapse and/or deform to the point that it causes unmanageable
property damage or in the
Worst case, the loss of human lives. It is by far the most common type of numerical
analysis in geotechnical engineering and has become routinely used in practice.
Historically, stability analyses have been completed using limiting equilibrium (LE)
formulations such as the well-known Bishop, Spencer and Morgenstern-Price methods.
The potential sliding mass is commonly discretized into slices as shown in Figure. The
forces on each slice, treated as a free body, are resolved to satisfy horizontal and vertical
force equilibrium together with the overall moment equilibrium of the entire potential
sliding mass. The factor of safety is defined as the value by which the soil strength must
be reduced to achieve
the limiting equilibrium condition.
Figure 5-6: Slices and forces in a potential sliding mass
Table 5-2: Engineering Parameters used in Stability Analysis
Layer PL LL PI c
[kPa]
Ø
[degrees]
γ
[kn/m3
]
[%]
Clay Core 33 4.30 28.70 200 4 19
Filter
Not Applicable
5 32 19
Shell 5 33 21
Rocktoe 3 45 22

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5.3.1. Seepage Analysis
One of the main causes of the earth dam failure is the seepage. This seepage can cause
weakening in the earth dam structure, followed by a sudden failure due to piping or
sloughing. For this purpose a finite element method through a computer program,
named Geo-Studio, was used to determine the free surface seepage line, the quantity of
seepage through the dam, the pore water pressure distribution, the total head
measurements and the effect of anisotropy of the core materials of Alyawa zoned earth
dam.
Seepage in earth dams cannot be avoided but ordinarily does not harm if it is
under control. Uncontrolled seepage may, however, cause erosion within the
embankment or in the foundation, which may lead to piping.The study of seepage
through earth dams is one of the important analysis in dam design to calculate the
quantity of losses from the reservoir, estimating the pore water pressure distribution,
locating the position of the free surface which is used in the analysis of the dam stability
against the shear failure. Finally, studying the hydraulic gradient gives a general idea
about the potential piping.When a dam is not safe against seepage there is a need to use
control device for seepage. The control devices for seepage are cut-off, dense core, and
grout curtain. The use of one of them, any combination of two of them, or all of them
with specified dimensions can be determined through an optimization study. In this
research, the safety of Alyawa dam against seepage will be studied first.
The seepage of water under a dam and through earth dam is governed by
0
y
x 





























………(1)
For homogenous and anisotropic soil, Eq. (1) becomes
0
y
x 2
2
2
2












………..(2)
Where Kx and Ky are the coefficients of permeability and  represents the piezometric
head.

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In this research seepage analysis in Alyawa earth fill dam has been done by seep/W
software. In order to evaluate the type and size of mesh size on the total flow rate and
total head through the dam cross section. Result showed that average flow rate of
leakage under the different mesh size for Alyawa dam equal 3.391*10-7
m3
/sec for the
entire length of the dam. Slope/W software is used under different conditions to
evaluate slope stability.
Figure 5-7: Seepage vectors through the dam and its foundation at station 0+040
Figure 5-8: Seepage through the dam and its foundation at station 0+050

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Figure 5-9: Seepage through the dam and its foundation at station 0+020
Table 5-3: Steady seepage
Dam section Steady seepage (m3
/s)
Station 0+020 3.391 *10-7
Station 0+040 1.417 *10-6
Station 0+050 5.52 *10-17

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5.3.2. Side Slope and foundation Analysis
Slope stability analysis is carried out to check the adequacy of the proposed
slope inclination in order to meet the required factor of safety for all loading
conditions. This analysis should be fully based on the soil parameters obtained
from the geotechnical investigation.
Alyawa dam is a modified homogeneous earth fill type dam covered with a layer
of Rip-Rap at the upstream face and a gravel protection layer at the downstream
face.
Cross‐sectional design for dam will be support by adequate slope stability
analysis. The analysis model should adequately represent the geometry and
zoning, shear strength parameters, material unit weights, and seepage
conditions, external loading, and other relevant factors of the critical cross
section or sections.
Dams should be designed to provide the following minimum factors of safety from
the stability analysis:
 The d/s slope during steady-seepage conditions.
 The u/s slope during sudden draw down conditions.
 Analysis of u/s and d/s with earthquake consideration.
 Stability analysis during sudden draw down conditions.
Stability analysis during rapid drawdown is an important consideration in the design of
embankment dams. During rapid drawdown, the stabilizing effect of the water on the
upstream face is lost, but the pore-water pressures within the embankment may remain
high. As a result, the stability of the upstream face of the dam can be much reduced.
The dissipation of pore-water pressure in the embankment is largely influenced by the
permeability and the storage characteristic of the embankment materials. Highly
permeable materials drain quickly during rapid drawdown, but low permeability
materials take a long time to drain.

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5.3.3. Stability analysis during earthquake consideration
There are numbers of natural calamities which cause damages and destruction of
properties and injuries and death of lives. Amongst them, earthquake is considered to
be the strongest forces in terms of severity of damages occurred to human civilization.
Therefore it is very much important
to understand the responses of structure against earthquake shaking. In countries like
Iraq or many other countries in the world, where major part of the economy largely
dependent on agriculture and consists of a numbers of rivers and canals, dams are often
built to control flood and for irrigation purpose. These dams are often made by natural
earth which is a softer material and thus it behaves like a flexible structure unlike
concrete dam which behaves like nearly rigid structure. Earthen dams are especially
important in terms of disaster prevention since they provide irrigation water and their
damage can cause secondary destruction of nearby habitation.
5.3.4. Seismicity of Alyawa Dam Site
According to ICOLD (International Commission on Large Dams, 1989), the operating
basis earthquake (OBE) should have a 50% probability of none-exceeding in a 100
years lifetime of structures. For Alyawa dam, the OBE is estimated to be approximately
equal to 0.1 g, this represents a return period of 145-year. This value was estimated
from the Global Seismic Hazard Assessment Program (GSHAP) as shown in Figure.
The values shown in Figure represent a return period of 475-year, the location of the
dam is at E: 539900.18, N: 3913230.98 and the PGA is about 0.15g.

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Figure 5-10: Seismic Hazard Map for Middle East (GSHAP).
5.4. Stability Analysis for Embankment Dam Section
Slope stability analysis is carried out using a software package GeoStudio 2007 using
SLOPE/W Analysis part, and using type of Morgenstren-Price. It is based on limit
equilibrium methods and gives a factor of safety as a measure of slope stability.
Detailed Stability Analysis is carried out for both static and dynamic effect to verify the
section characteristics including slopes. For dynamic effect, the acceleration used is equal
to 0.1g horizontal and 0.075g vertical. Static stability results are presented in Annex 2.
The criteria in Table 5 are considered, that are established for the minimum factor of safety
for various cases of loading in the stabilityanalysis. It is clear that all slopes are stable under
both static and dynamic effect at different loads cases. Therefore, the dam designed herein
is stable and the results are shown in Table 5.4.

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Table 5-4: Minimum Factor of Safety for Different Loading Conditions.
Situations
Minimum
factor of
safety
Calculated factor of safety
(obtained from geo studio)
d/s during steady seepage
without earthquake
1.5 1.802
d/s during steady seepage with
earthquake
1.0 1.286
u/s stability during sudden
drawdown without earthquake
1.5 1.822
u/s stability during sudden
drawdown with earthquake
1.0 1.248

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Figure 5-11: Downstream Stability without earthquake
Figure 5-12: Downstream Stability without earthquake

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Figure 5-13: upstream Stability during sudden drawdown without earthquake
Figure 5-14: upstream Stability during sudden drawdown with earthquake

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Figure 5-15 Typical Maximum Dam Section.

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Cross section of the dam at various Station:
Civil 3D program is used for drawing these sections of the dam
figure 5-16 dam cross section st. 0+020

69
69

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Conclusion:
Embankment dams are the most popular type of dams built in the world due to the
availability of its construction materials and equipment. In this study Alyawa earth dam
is designed by selecting a preliminary cross section of shell and core due to availability
of the suitable materials for that purpose. Stability analysis on the selected cross section
has been carried to make sure its stability in different critical conditions by using the
slope/W of Geo-Studio 2007. In addition, the seepage analysis is also executed for
different sections to compute the seepage through the dam body and its foundation.
Following are the main conclusions of this study:
1. Alyawa site is a favorable location for building a zoned earth dam due to the
availability of suitable material and good foundation condition. inspite of that its
foundation needs cut-off trench and grouting to minmize the seepage flow through
the foundation.
2. The dam height at maximum cross section is (18 m). but all of hight of dam are not
full of water because it have a free board of (1.7 m ) to prevent overflow above the
crest of the dam, and by evaluating that hight of dam is enough for that location.
3. The stability analysis revealed that the u/s and d/s slope are safe if they are
(2.5 H:1 V) And (2.25 H: 1 V) Respectively. and it is at the safe situation because
it is checked by geostudio program, and the following table show the factor of
safety for all situation that might happen for the dam in the future.
Situations
Minimum
factor of
safety
Calculated factor of
safety (obtained from
geo studio)
d/s during steady
seepage without earthquake
1.5 1.802
d/s during steady seepage
with earthquake
1.0 1.286
u/s stability during
sudden drawdown without
earthquake
1.5 1.822
u/s stability during
sudden drawdown with
earthquake
1.0 1.248

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4. the sepage analysis is also done for all the stations of the dam body by geostudio program,
seepage quantity for all the sations are shown in the folloing table and the seepage
quantity through the dam body and its foundation is (3.1428 * 10-5 cubics )
and by experiment of our supervisor it is allowable and not too much for the dam.
Dam section Steady seepage (m3
/s)
Station 0+020 3.391 *10-7
Station 0+040 1.417 *10-6
Station 0+050 5.52 *10-17

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Rcomendation:
We have some recommendations for who wants to study about this project and this
aspect:
1. It is better to design of the dam using rockfill material to show the different
between earth dam and rockfill dam.
2. Checking the stabillity and seepage analysis using other softwares and hand
calculation to check the results of this project.
3. For future projedct it is better to desgin the dam and its appurtenant structures
such as ( spillway and bottom outlet).
4. Estimating the life of the reservoir according to the sediment inflow from the
river.

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References:-
1. Irrigation, Water Resources and Water Power Engineering –
Dr.P.N.MODI -2000.
2. Design of Small dams, USBR, 1987 (newest edition –www.usbr.org)
3. Irrigation, Water Power and Water Resources Engineering –
Dr.K.ARORA-2001.
4. Barry, L. (2002). Farm dams Planning, Construction, and Maintenance.
Australia:nLandlinks Press.
5. Bureau of reclamation. (1987). Design of small dams. Wshington DC:
Water Resources, Technical Publication.
6. Bureau of Reclamation. (2002). 100 Years of Embankment Dam Design
and Construction. Denver, Colorado.
7. Christian, C. (1997). Earth and rock fill dams principles of design and
construction. Rotterdam: A.A. Balkema.
8. General Design and Construction Considerations for Earth and Rock-Fill
Dams , US Army corps of engineers .
9. irrigation engineering and hydraulic structure – SANTOSH KUMAR
GARG.(august 2005)
10. Hydraulic structure by P.Novak , fourth edition (2007)

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