1. SELECTION CRITERIA FOR DAM CONSTRUCTION METHODS
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SELECTION CRITERIA FOR DAM CONSTRUCTION METHODS
Mohamed Darwish, PhD, PEng
Michael Thomas, BSc
Karim Wadeih, BSc
Nour Eldeeb, BSc
Mohamed Assy, BSc
Amr Eweida, BSc
Shady Wadie, BSc
Michael William, BSc
Amr Ali, BSc
Presented by:
Mohamed Darwish, PhD, PEng

2. Introduction Types of Dams Arch Dams Gravity Dams Arch-Gravity Dams
Buttress Dams
Embankment Dams
Barrages
Introduction
osp.mans.edu.eg

3. Dam Construction Methods
Conventional (In-the-dry cofferdam construction)
Filled Cellular Sheet Pile Cell Construction
Roller Compacted Concrete Method
Float-In Construction

4. Conventional Method (In-the-dry cofferdam construction)
A sheet pile cofferdam used to construct a lock in-the-dry in Nashville, Kentucky, USA (Tucker, 2012).

5. Conventional Method (In-the-dry cofferdam construction)
Construction method steps: 1
Divert the water stream into a temporary alternative route. 2
Construct the upstream cofferdam 3
Construct the downstream cofferdam 4
Dewater site and remove the loose rock and rubble from the site area 5
Construct the plinth to act as a foundation or connection between the dam and the valley walls and floor. 6
Finally the dam body itself is constructed in-the-dry like any typical structure

6. Advantages & Disadvantages
Time-consuming and effort-consuming specially for larger dams.
Disturbs ecology during construction (In-the-dry).
Concrete dam construction should include temperature reduction mechanisms for large concrete volums.
Advantages
Easy construction
Safe due to working in-the-dry
Cofferdams could be dismantled after construction (if made of sheet piles) hence minimizing the sheet pile material cost.
Equipment & materials needed are readily available
Known for most of contractors.

7. Cellular Sheet Piles Wet method Two types: Circular and diaphragm
Applications:
Deep maritime locks
Harbor front structures
Cofferdams
Dry docks

8. Methodology 1
Pre-dredge to remove soil or soft sediments and level area. 2
Main cells are pitched using a template (reusable) 3
Drive the sheet piles in the main cells 4
Fill the main cells 5
Pitch the connecting arcs between two completed main cells, using a template 6
Drive the connecting arcs 7
Fill between the main cells

9. Advantages & Disadvantages
Some skilled labor needed to perform welding between cells and arcs
If rushed, sheets can be driven out of locks or out of plumb
It is very difficult to dismantle hence the cellular cofferdams will remain as part of the dam body
Advantages
Cells can be filled immediately after being built regardless of relative height of fill in adjacent cells (independent)
Easy construction
Filled cells can be used as working platforms for installing new cells. (ex. cranes)
Equipment & materials needed are readily available
Cell could be constructed in the water, no need for dewatering
Cost could be minimized if site circumstances are good

10. Roller Compacted Concrete (RCC) dams Construction
Defined as concrete compacted by roller compaction. Thus the concrete must support the weight of full-sized compactor in its unhardened state. (ACI 207.5R-89)
Developed and first applied in 1974 in the U.S.
Offers improvements in cost, time and risk
Applied only with ‘In-the-dry’ method of dam construction

11. RCC- Construction Method Flowchart
Spreading:
Transportation:
Compacting:
Concurrent Activities
P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure, Properties, and Materials

12. Advantages & Disadvantages
Disturbs ecology during construction (In-the-dry).
Requires availability of large quantities of aggregate
The layer method allows for little room for error when compared to the conventional method.
Limited to areas with non-alkaline soils.
Needs efficient compaction.
Advantages
Relative ease of construction since it is in the dry.
Cost: 25 to 50% less than conventional concrete
Formwork cost: lower because of layer placement.
No pipe cooling required low heat of hyrdration.
Rapid Construction: 1-2 years less than regular mass concrete dams

13. Float-in Construction
Uses prefabricated steel or precast concrete
Steel or concrete segments are placed alongside each other
Dam is constructed without the need for dewatering

14. Methodology Construct precast concrete/assemble segments
Dredging of the site for foundations
Launching facilities
Flood casting basin to move segments by means of floating
Attach segments to foundations
Grout and infill with tremie concrete

15. Advantages and Disadvantages
Extensive planning and site preparation
Needs special equipment to transport and place the segments.
Difficult to construct, needs highly skilled labors and experienced contractors
Limited to locations with soils of large bearing capacities
Sensitive to weather conditions and water currents.
Advantages
Can offer cost and schedule savings for larger dams
Reduction in environmental impact as it doesn’t need rerouting the river
Flexible Design

16. Filled Cellular Sheet Pile Roller Compacted Concrete
Selection Criteria
Construction Method
Conventional
Filled Cellular Sheet Pile
Roller Compacted Concrete
Float-In
Cost
Cost-saving for small and medium dams
Cost-saving for medium and large dams
Cost-saving for large dams
Risk
Low-Medium risk
Higher risk
Highest risk
Materials
Concrete, steel, sand, gravel or soil
Precast Concrete or Steel and Tremie Concrete
Equipment
Simple
Requires special equipment
Labor
Semi-skilled
Skilled
Highly skilled
Construction Speed
Slowest
Medium
Fastest
Recommended Dam Size
Small – Medium
Medium – Large
Large
Soil Type
Applicable for most of soils
Not recommended for alkaline soils
Limited to soils with high bearing capacities

17. Case Study 1

18. Case Study 1 Cont’d Method statement phases:
5 years ( ) Preparation period and first stage construction.
6 years ( ) Construction of the main (right) part of the dam
7 years ( ) Construction of the left part, ship lifter and completion of all turbines.
Phase 1
Phase 2
Phase 3

19. Case Study 1 Cont’d Construction sequence flowchart Divert river flow
Reinforcement 1 8
Construct coffer dams
Pouring Concrete 2 9
Pump water out of enclosed area 3
Repair the soil with grouting 4
Test soil 5
Divide the dam into section 6
Formwork 7

20. Case Study 1: Method Evaluation
Using the float-in technique was impossible due to:
Low soil bearing capacity that couldn’t support the dam sections installed.
High water currents creating high risks while installing the segments.
Using RCC was risky due to uncertainty in soil chemical activity.
Using in-the-wet cellular cofferdams would have been risky in high water currents
Hence, the conventional method was the only alternative left.

21. Floating the dam segments (Bittner-Shen Inc., 2013).
Case Study 2
Braddock Dam
Location: Pittsburgh, PA, USA
Owner: U.S. Army Corps of Engineers
Budget: $107 Million
Duration: 5 years
Size: 32 m x 182 m
Weight: tons
Method used: Float-in
Floating the dam segments (Bittner-Shen Inc., 2013).

22. Case Study 2: Applied Method
The two dam segments were casted in a casting basin off-shore.
Simultaneously, foundations were installed in the site.
The segments were launched and dragged.
The segments were placed in their exact locations.
The bottom segments compartments were in-filled with concrete and while the segments were grouted to the foundations.

23. Case Study 2: Method Evaluation
Existence of sandstone layer at a depth attainable by short piles eased the use of this method as if that layer was deeper maybe using an in-the-dry method would have been better.
The presence of an old dam (went out of service after constructing this newer one) near the location helped in controlling the water currents.
Additionally, the consultant and contractor had the know-how which is the most important element when applying this method.

24. Conclusion
When examining the methods applied in the two cases discussed in this paper against the developed selection criteria, the selection criteria proved that it covered the different aspects governing the selection of the most suitable methods for different dam construction cases.
It is highly recommended when using the selection criteria matrix to take all the factors governing the method selection into account as neglecting some of them could cause real problems.

25. Acknowledgements
Department of Construction and Architectural Engineering in the American University in Cairo.
The British Dam Society
Bittner and Shen Inc.

26. References
ACI 207.5R-11. (2011). Report on Roller-Compacted. Farmingto Hills, MI: American Concrete Institute. Ben C. Gerwick Inc. (2013). Braddock Dam Lock #2. Retrieved November 19, 2014, from Ben C. Gerwick, Inc.: Bittner-Shen Inc. (2013). LOCKS AND DAMS. Retrieved November 17, 2014, from Bittner-Shen Inc.: British Dam Society. (2010). British Dam Society, About Dams, The Three Gorges Dam. Retrieved November 13, 2014, from British Dam Society: British Dam Society. (2012). Types of Dams. Retrieved November 10, 2013, from British Dam Society: British Dam Society. (2013). About Dams. Retrieved November 10, 2013, from British Dam Society: Butler, J. (2011, March 4). Dam Construction Alternatives. Retrieved November 23, 2013, from WORCESTER POLYTECHNIC INSTITUTE: Cimino, M. (2013, May 7). "Group : Three Gorges Dam." : Construction Techniques and Materials Analysis. Retrieved November 15, 2013, from blogspot.com: Gerwick, B. C. (1996). Cofferdams. In R. T. Ratay, Handbook of Temporary Structures in Construction (pp ). New York: McGraw-Hill. Limburg, K. (2006). ESF. Retrieved November 10, 2013, from ESF: Peurifoy, R. L., Schexneydar, C. J., & Shapira, A. (2006). Construction Planning Equipment and Methods. New York: McGraw-Hill. Schiffler, M. (2014, July 17). Bui Dam. Retrieved November 19, 2014, from Wikipedia: Spanish National Commission on Large Dams. (2012). TECHNICAL GUIDELINES FOR DAM SAFETY 2. Madrid: Spanish National Commission on Large Dams. Tucker, F. (2012, August 23). Kentucky Lock Addition Project . Retrieved November 15, 2014, from Flickr: US Army Corps of Engineers. (2013, June). Monongahela River Locks and Dams 2, 3, and 4 Project Fact Sheet. Retrieved November 19, 2014, from USACE: Wordpress. (2012, May 20). Sheetpile retaining wall design . Retrieved November 19, 2014, from wordpress.com: Zhou, P. (2014). Three Gorges Dam. Retrieved November 15, 2014, from About.com:

27. Thank you