hydropower plant that is found in Ethiopia.

1. Koyesha Hydroelectric Power
Project

2. GIBE-OMO Cascade hydro Plant & project location

3. BACKGROUND
Project Name Koysha Hydroelectric Project.
Employer Ethiopian Electric Power (EEP).
Contractor Webuild (former Salini Impregilo SPA.)
Contract type
EPC (Engineering, Procurement and
Construction).
Contract Signing Date 28th March, 2016.
Installed Capacity 1,800 MW
Total Project Cost 2.5 Billion Euro.

4. Main features
 Roller compacted concrete dam (RCC
Dam).
 Independent an overflow gated spillway.
 Two diversion box culvert.
 Upstream and downstream cofferdam.
 2 waterways comprising intakes,
penstocks and manifolds.
 Powerhouse.
 Switchyard.
 400kv transmission line from gibe iii.
 Two middle level outlets (MLO).

5. RESERVOIR
 Maximum operating
level- el.680m a.s.l.
 Minimum operating
level- el.660m a.s.l.
 Surface area at
maximum operating
level 100km2
.
 Total storage 6.5Bm3
.
 Dead storage 483Mm3
Reservoir
Omo River flow
Legend
Existing Road
New Road
alignment

6. LAYOUT OF KEY STRUCTURES

7. CIVIL WORKS
Diversion Culvert &Cofferdams
 Excavation quantity 2.6 Mm3,
 Two Diversion Box Culverts 9m x
11.5m and 284 long,
 Concrete quantity 119,000m3.
 38m high U/S Cofferdam &14m high
D/S Cofferdam
Status:-operational since July 20, 2018.

8. RCC Dam
 The Dam Crest level is -
el.688.5m a.s.l.
 The Crest length is 1,012 m.
 The max. height above
foundation 201.5m.
 RCC volume 7.4Mm3.
Status:
Excavation works
 Substantially completed.
 Dam foundation treatment on
progress.
 RCC placement on progress( to
date 299,218m³ RCC placed)

9. Major advantage of RCC
 Rapid construction (It have fast construction time)
 Economically
 It use minimum cement
RCC Dam Cont ….

10. Activities during RCC Placement
The dam construction is done by repeating the process by considering if there is contraction
joint, and Waterstop on the construction drawing.
1. RCC cleaning
2. Spread Bedding
3. RCC damping
4. RCC Spreading
5. RCC compaction
6. GERCC activities
7. RCC Curing
RCC Dam Cont ….

11. RCC Dam Cont ….
Spread Bedding

12.  Is located on the left side of
the river.
 Dimensions (l x w x h)
211m x 51.5m x 44.3m.
 The erection bay floor is
located - el. 541m a.s.l.
 The turbines axis is at el.
518m a.s.l.
Power house

13. Power House Cont.…
Status:
Excavation works
 Foreseen quantity 2.0Mm3,
99% is completed.
 Rebar fixing & Concrete
casting on progress.
 To date 38,999 m³ concrete
casted.

14. Parts of Power House
Power House is composed of the following structural elements, which are separated
by contraction & expansion joints:
1. Intake
2. Penstock
3. Manifold
4. Erection bays and control building
5. Power house Units
Power House Cont…

15. Power House Cont…

16. Construction Process of PH
1. Survey Setting‐Out
2. Foundation Preparation
3. Rebar Preparation And Placing
4. Formwork Application
5. Concreting
Power House Cont.…

17. Geology
In this section the contact or consolidation grouting will be performed in the dam
foundation. The purpose is to consolidate the rock below the dam and to fill the void (if
any) between leveling concrete (RCC) and the rock itself.
The contact/consolidation grouting activities will be carried out during the RCC
dam construction period. The works will be performed when the RCC surface is available
(when the compaction is done). The minimum cover criteria for RCC thickness is above
3m for starting the drilling and grouting activities.

18. • Contact/consolidation grouting: purpose of consolidating the rock below the dam and
filling the void between leveling concrete and the rock.
• Curtain grouting: Purpose of curtain grouting is to prevent risk of erosion of foundation
material sand control permeability by establishing an effective seepage barrier along the
dam upstream face in order to limit seepage discharge under and around the dam.
• Bulb grouting: completed the curtain grouting increasing the effectiveness of the screen
near the dam upstream toe. Executed from the galleries inside the dam body, one in every
40 m of height and extended inside both right and left abutment of the dam to control the
seepage of front water from the reservoir and the rock of the abutment.
Consolidation grouting is a treatment for the rock and RCC itself. There are different
types of treatment:-
Geology Cont…..

19. Laboratory
Laboratory tests are done to check the workability of the raw and processed construction
materials before they deliver it to the construction site. Laboratory tests are carried out daily,
which gave me an opportunity to observe tests like-
1. VeBe Test (vibrating table)
2. Compressive Strength Tests
3. Materials Finer Than
4. Density Test for Cement

20. VeBe Test (vibrating table)
Laboratory Cont …..
Objective: to know the workability of concrete and slump value

21. Procedure:
• Fresh RCC mix is placed into slump cone, inside the cylinder
• Clean plastic disk then placed on the top of the concrete and the vibrating table is
turned on and simultaneously starts the stopwatch.
• Immediately when the conical shape of the concrete disappears and takes a cylindrical
shape, which is observable through the glass disk, switch off the stopwatch.
• The time taken measured for the concrete cone to shorten and change from the conical
to a cylindrical shape, until the transparent disk to be completely covered concrete, is
measured in seconds and is reported as the number of VeBe seconds.
Laboratory Cont …..
Procedure of VeBe Test

22. Compressive Strength Tests
Laboratory Cont …..
Objective: to check the cylindrical compressive strength of hardened concrete.
Procedure:
1. Place the fresh prepared concrete mix (CVC or RCC) in to cylindrical plastic mold
with three layers & compact each layers for 12 sec.
2. Dates chosen between 7, 28, 90 and 365 days, weather they attain the required
strength or not within the specified days before applying for structures.
3. Leave the sample for 4hrs in air & soak in water for the dedicated dates for
each sample.
4. Take the sample from soaking room & make the sample saturated surface dry.
5. Place the sample in to compressive strength machine and apply the load
progressively until the spacemen collapse and read the displacement for each
applied load per second.

23. Materials Finer Than
Laboratory Cont …..
Objective: determination of the amount of material finer than a 75-μm (No. 200)
sieve in aggregate by Washing. The procedure is using only water for the
washing operation.

24. Procedure of Materials Finer Than
• Dry the test sample in the oven to constant mass at a temperature of 110 °C.
• Determine the mass of the test sample.
• Place the test sample in the container and add sufficient water to cover it.
• Agitate the sample with sufficient vigor to result in complete separation of all particles
finer than the 75-μm (No. 200) sieve from the coarser particles, and to bring the fine
material into suspension.
• Immediately pour the wash water containing the suspended and dissolved solids over
the nested sieves, arranged with the coarser sieve on top. Take care to avoid, as much as
feasible, the decantation of coarser particles of the sample. Add a second charge of
water to the sample in the container, agitate, and decant as before. Repeat this operation
until the wash water is clear.
• Return all material retained on the nested sieves by flushing to the washed sample. Dry
the washed aggregate in the oven to constant mass at a temperature of 110 °C and
determine the mass to the nearest 0.1 % of the original mass of the sample.
Laboratory Cont …..

25. Density Test for Cement
Laboratory Cont …..
Objective determination of the density of hydraulic cement. Its particular usefulness is
in connection with the design and control of concrete mixtures.

26. Procedure:-
• Fill the flask with kerosene to a mark on the stem between the 0 and the 1 cm mark.
• Place the flask in a constant temperature bath and record the initial height of
the kerosene in the flask.
• Carefully introduce about 64 grams of cement, weighed to the nearest 0.1 grams.
• Remove the flask from the bath and place it on the rubber mat. Take off the
lead weight and manipulate the flask on the mat so as to remove all air bubbles from
the flask.
• Return the flask to the bath and check the temperature within the flask. If it is within
0.2°C of the original temperature inside the flask, take the final reading.
Laboratory Cont …..
Procedure of Density Test for Cement

27. Thank you!!!