hiii, Im vithushan i hope this presentation help to know about dams function.

1. DAMS

2. WHAT IS DAM?
• A DAM IS A STRUCTURE BUILT ACROSS A STREAM, RIVER OR ESTUARY TO
RETAIN WATER. DAMS ARE MADE FROM A VARIETY OF MATERIALS SUCH AS
ROCK, STEEL AND WOOD

3. RESERVOIRS

4. WHAT IS SPILLWAY?
• A SPILLWAY IS A SECTION OF A DAM DESIGNED TO PASS WATER FROM THE
UPSTREAM SIDE OF A DAM TO THE DOWNSTREAM SIDE.

5. GENERAL PURPOSES OF DAMS
• STORE WATER FOR DRY PERIODS
• PREVENT FLOODING
• INCREASE RIVER DEPTH TO AID NAVIGATION
• STOCK WATERING AND IRRIGATION
• FISH FARMING
• GENERATE HYDRO POWER ELECTRICITY

6. STRUCTURE OF DAM

7. • HEEL: CONTACT WITH THE GROUND ON THE UPSTREAM SIDE
• TOE: CONTACT ON THE DOWNSTREAM SIDE
• GALLERIES: SMALL ROOMS LIKE STRUCTURE LEFT WITHIN THE DAM FOR
CHECKING OPERATIONS.
• 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.

8. CLASSIFICATION OF DAMS
CLASSIFICATION BASED ON FUNCTION
STORAGE DAM
 DETENTION DAM
 DIVERSION DAM
 COFFER DAM
 DEBRIS DAM

9.  CLASSIFICATION BASED ON STRUCTURAL BEHAVIOR
GRAVITY DAM
 ARCH DAM
 BUTTRESS DAM
 EMBANKMENT DAM

10. GRAVITY DAMS
• GRAVITY DAMS ARE DAMS WHICH RESIST THE HORIZONTAL THRUST OF THE
WATER ENTIRELY BY THEIR OWN WEIGHT.

11. ARCH DAM
• AN ARCH DAM IS A CURVED DAM WHICH IS DEPENDENT UPON ARCH ACTION
FOR ITS STRENGTH.

12. BUTTRESS DAMS
• BUTTRESS DAMS ARE DAMS IN WHICH THE FACE IS HELD UP BY A SERIES OF
SUPPORTS.

13. EMBANKMENT DAMS
• EMBANKMENT DAMS ARE MASSIVE DAMS MADE OF EARTH OR ROCK.

14. GENERAL DAM FAILURES
• SLOPE STABILITY FAILURES
• PIPING FAILURES
• OVERTOPPING FAILURES
• FOUNDATION FAILURES

15. Slope stability failure
IF THE DRIVING FORCE IS GREATER THAN THE RESISTING FORCE, THE SOIL
MASS WILL SLIDE ALONG THE SLIP SURFACE AND A SLOPE STABILITY
FAILURE WILL OCCUR.
THE POTENTIAL FOR FAILURE FOR A GIVEN SOIL MASS IS QUANTIFIED IN
TERMS OF THE FACTOR OF SAFETY, WHICH IS DEFINED AS THE RESISTING
FORCE DIVIDED BY THE DRIVING FORCE.
THERE ARE THREE TYPES OF SLOPE STABILITY FAILURES: STEADY-STATE,
SEISMIC, AND RAPID-DRAWDOWN

16. PIPING FAILURE
THE CAVITIES AND CRACKS CAN ACT AS PREFERENTIAL CONDUITS FOR
WATER TO FLOW FREELY THROUGH THE DAM AND ERODE THE DAM FROM
THE INSIDE OUT. THIS PHENOMENON, REFERRED TO AS “PIPING,”

17. OVERTOPPING FAILURE
• DAMS ARE DESIGNED WITH PRINCIPAL AND EMERGENCY SPILLWAYS TO
CONTROL THE MAXIMUM RESERVOIR ELEVATION AND PREVENT THE
RESERVOIR FROM FLOWING OVER THE TOP OF THE DAM, OR
“OVERTOPPING.”

18. FOUNDATION FAILURES
• IF THE FOUNDATION CONSISTS OF WEAK MATERIALS, SUCH AS SOFT CLAY, A
FOUNDATION STABILITY FAILURE CAN OCCUR, LEADING TO SIGNIFICANT
DEFORMATION OF THE EMBANKMENT
• PIPING WITHIN THE SEAM MAY ALSO BE A CONTRIBUTING FACTOR.
• LIQUEFACTION OF GRANULAR SOILS DURING AN EARTHQUAKE MAY REDUCE
THE STABILITY OF THE FOUNDATION

19. DAM FAILURE REAL TIME EXAMPLES
• TETON DAM, IDAHO
• JUNE 5, 1976:THE DAM FAILED BECAUSE THE BEDROCK WAS NOT STRONG
ENOUGH TO SUPPORT THE STRUCTURE. CURRENTLY THE DAM IS ONCE AGAIN
USED FOR HYDROELECTRIC POWER.

20. FOLSOM DAM, USA
• July 17, 1995 : a spillway gate of Folsom Dam failed, increasing flows into the
American River significantly. The spillway was repaired and the USBR carried out an
investigation of the water flow patterns around the spillway using numerical modelling.

21. PLANNING MEASURES
SURVEILLANCE OF SMALL DAMS, NOT ONLY LARGE ONES.
CAREFUL STUDY OF VARIOUS RISKS.(EARTHQUAKE , LANDSLIDE, FLOOD
ETC..).
CAREFUL STUDY OF THE ENVIRONMENT OF DAM AND THE RESERVOIR.
GEOTECHNICAL TESTING.
ANALYSIS OF RISKS.
EVACUATION PLANS FOR DOWNSTREAM VALLEY AREA.

22. TO DESIGN SAFETY DAM
LOCATE THE DAM AWAY FROM ACTIVE FAULTS.
OVERDESIGN TO ALLOW FOR DISPLACEMENTS.
USE WIDE SECTIONS THAT RESIST CRACKING.
USE SELF HEALING MATERIALS.
CONDUCT GEOLOGICAL AND GEOTECHNICAL SITE SURVEY.
DESIGN DAM TO RESIST ELASTIC AND PERMANENT DISPLACEMENTS.

23. ADVANTAGES OF DAMS

24. DISADVANTAGES OF DAMS
DAMS DETRACT FROM NATURAL SETTINGS, RUIN NATURE'S
WORK
DAMS HAVE INUNDATED THE SPAWNING GROUNDS OF FISH
DAMS HAVE INHIBITED THE SEASONAL MIGRATION OF FISH
RESERVOIRS CAN FOSTER DISEASES IF NOT PROPERLY
MAINTAINED
RESERVOIR WATER CAN EVAPORATE SIGNIFICANTLY
SOME RESEARCHERS BELIEVE THAT RESERVOIRS CAN CAUSE

25. REFERENCES
• LECTURER NOTES
• GOOGLE IMAGES
• GARG, S.K., (2012), “IRRIGATION ENGINEERING AND HYDRAULIC STRUCTURES.”
24TH EDITION, KHANNA PUBLISHERS.
• HTTP://WWW.SLIDESHARE.NET/SEARCH/SLIDESHOW?SEARCHFROM=HEADER&
Q=DAMSHTTP://WWW.SLIDESHARE.NET/MOHAMMEDSALAHAT1/CHAPTER-7-
DAMS-AND-RESERVOIRS?QID=C52763F0-E169-43F8-9743-
2B9824E2B4F9&V=DEFAULT&B=&FROM_SEARCH=1