In geology

1. Topic: Dams and Reservoirs

2. Contents:
 Introduction
 History of dams
 Types of dams
 Parts of dams
 Geotechnical considerations of dams
 Criteria consideration for dam site selections
 Geological investigation for dam site selection
 Dams failure
 Reservoirs
 Categories of reservoirs
 Geological investigation
 Conclusion
 Reference

3. Introduction
 DAMS may be defined as a solid barrier constructed as
a suitable location across a river valley with a view of
impounding water flowing through that river.
 Objectives
I. Generation of hydropower energy
II.Irrigation facilities
III.Domestic consumption and industrial uses
IV.Fighting droughts and controlling of floods
V.Navigation facilities

4. History of Dams
 The word dam can be traced back to Middle
English, and before that, from Middle Dutch,
as seen in the names of many old cities
 The earliest known dam is the Jawa Dam in
jordan, 100 kilometres (62 mi) northeast of the
capital Amman.
 Dams are constructed in the type of : arch –
gravity dams, arch dams, buttress dams and
multiple arch buttress dams,

5. Contd…
 French engineer Benoit Fourneyron developed
the first successful water turbine in 1832.
 The era of large dams was initiated
after Hoover Dam was completed on the
Colorado River near Las Vegas in 1936. By 1997,
there were an estimated 800,000 dams
worldwide, some 40,000 of them over 15 m
(49 ft) high.

6. Contd…
 Biggest dam-
Hoover
 Highest dam-
Bhakra dam
 Longest dam-
Hirakud dam

7. TYPES OF DAMS
 Classified on the basis of
a) Design of construction
b) Material of construction
c) Size of the construction
 International congress defines on large dams -
o has a height more than 15m from foundation
area

8. ACCORDING to the STATICAL DESIGN of DAM
BODY
 Gravity Dams
 Arch Dams
 Butress Dams
 Embankment Dams
 Composite Dams

9. Types of dam
Arch
Gravity
Buttress
Embankment
or Earth

10. Gravity Dams
 Gravity Dams use their triangular shape and the
sheer weight of their rock and concrete structure
to hold back the water in the reservoir.

11. Arch Dams
 Arch Dams utilize the strength of an arch to
displace the load of water behind it to the rock
walls that it is built into.

12. Buttress Dams
 Buttress Dams use multiple reinforced columns to
support a dam that has a relatively thin structure.
Because of this, these dams often use half as
much concrete as gravity dams.

13. Embankment Dams
 They are mostly composed of natural materials
such as, clay, sand, gravel etc...
 Impervious core is placed in the middle of the
embankment body
 Generally riprap is used to control erosion

14. Composite dams
 Composite dams are combinations of one or more
dam types. Most often a large section of a dam will
be either an embankment or gravity dam, with the
section responsible for power generation being a
buttress or arch.

15. Parts of dam:
 Heel :- upstream portion of the dam where it
contact the bearing surface
 Toe :- the down stream portion of the dam where it
contacts the bearing surface
 Crest :- the top of the dam
 Free board :- the distance between the level of water
in reservoir and top of the dam

16. Axis of the dam : imaginary line- along the crest up and
down stream
Gallery : opening with it dam it may be longitudinal,
transverse , inclined.
Tail water : water at the down stream base of the dam

17. GEOTECHNICAL CONSIDERATIONS:
 The exact location where the dams should be place
against the river along its longitudinal profile
 The type of the dam that will be most suitable for
that particular site
 The availability, cost and quality of the materials
required for the construction of the dam

18. Criteria consideration for dam site
selections:
 Basement rocks :- hard , sound , resistance to
static and dynamic forces
 Valley slope, abutment slope should be stabled
 Dam foundation :- safe from sliding
 Foundation rocks :- one geological units, to avoid
modulus elasticity variations
 Foundation and reservoir rocks should be tight for
water leak

19.  Rocks and dam structure should be resistance to
erosion and decomposition, drying, wetting, freezing
 Geologic and topography - favourable
 Seismic stability of the site
 Location of the construction material
 Submergence of natural resources in upstream side
 Importance of archeological interest

20.  Environmental hazards problems
 Benefit
 Human settlements

21. Details of geological investigation for
dam site selection:
1. Geology of the area :
preliminary geological survey
Main topographic features
Natural drainage patterns
General characters and structures of rock
formations such as their stratification,
folding and faulting and igneous intrusions
The trend and rate of weathering and erosion in
the area

23. Detail exploration :
 Outline design of dam
 Investigation of over burden on the bed rocks
 Location of potential leakage
 Ground water observation
 Geophysical- sub surface investigate
 Location of the dam axis
 Interpretation of surface and sub surface geology

24. Preconstruction stage of dam:
 Fixation of dam axis
 Dam height fixation
 Section of the dam axis
 Stress, strain, static force
 Elastic constant determination
 Earthquake problems

25. Construction stage of dam
 Drill holes at regular intervals
 Re-allocation of other structures i.e. railways,
highways, transportation of materials
 Ground water observation
 Sub surface maps for foundation excavation(soil, rock
types)
 Differential settlement and instability

26. Force acting on dam
1.Static force
a)Vertical:- weight of the concrete steel
bridges, water silt deposited over slope
b)Horizontal:- lateral pressure of water and
silt deposited in upstream side
c)Pore pressure acting on all direction
d)temperature

27. 2.Dynamic pressure:- by wave action, over flow of water
shocks, seismicity
Dam is safe when p/w is minimum if the ratio exceeds
critical value dam will slide down

28. Dam failure: earthquake

29. Dam failure: bombs

30. Important examples of dams failure:
 St.Francis- California, due to weak
abutment rock types, divergent rock types
 Austin- Texas, due to slide down of faults
 Quina- India, due to the horizontal static
pressure of seismic activity
 Chikka Hole- Chamarajanagar, due to poor
contruction

31.  Lake Gleno- Italy, slide down due to poor
abutment and heavy rain
 Hondo reservoir- New Mexico, due to
leakage of ground water
 Bouzey- France, due to poor gravity
contruction

32. Dam sites: geology
 Poor geological characterisation of dam
foundation responsible for 40% of dam failures
 Need proper site investigation

33. Reservoirs :
Reservoir defined as artificially created water
storage basins with storage capacity that may range
from few thousands cubic meters to thousands of
million cubic meters

34. Reservoir are classified into three
categories :
I. Storage of conservation- where the river water is
stored by creating barrier in its path
II. Flood control reservoir which have as their
main function accommodating large volume of
surplus water during peak flow times of a
river
III. Distribution reservoir- small storage reservoir
which hold water supply in a water supply
system for short spells of time

35. Storage capacity of reservoir:
it is expressed as
1. Useful storage- volume of water available between
minimum pool level and normal pool level
2. Dead storage – water store below the minimum pool
level
3. Surcharge storage- volume of water between the
maximum reservoir level and normal pool

36. Geological investigation:
a)Topographical :–
1. the area should be natural valley preferably ending
in narrow gorge
2. the valley can be glacial valley or V shape valley
b)Ground water condition: –
storage capacity of the re thoroughly established for
approximately accurate evaluation of reservoir
i) water table is much above the top of the reservoir
ii) water table is much below minimum, water level
iii) Top of Water level and water table are almost same

37. c) Permeability property:-
 primary nature, due to the inherent porous
texture of the rocks and
 secondary nature, it is caused due to
structural deformation of rocks
d)Structural constitution of the area is an important
identify those along the flanks which are liable to
failure by sliding , subsidence
Eg: Dam disaster of vaoint , italy

38. Trends and weight of weathering:
 Importance in determining the age of reservoir
 Decrease the effective storage capacity of the
reservoir
Major reservoir of India:
1) Govind Sagar (himachal pradesh),7191.00
million cubic meter (sc)
2) Gandhi sagar (MP), 6827 millon cubic
meter(sc)
3)Hirakud dam (orissa), 5822millon cubic
meters(sc)

39. Silting of reservoir:
 Uncontrolled sedimentation lead to the indirect
failure by gradually deduction by storage capacity
 removal methods - take time and energy and money
 Streams along with their tributaries are major
agents of silting of reservoir and much affected
by their velocities their catchments zones,
climate , topographic, vegetation etc.
 Control – treatment include better reservoir designs,
installation of check times , forestation, etc.

40. Reservoirs: leakage
Water
added
Leakage
from
reservoir
Water
subtracted
Rainfall
in river
basin
Infiltration
Evaporation
Transpiration
Net amount
of water
available
for storage
Runoff
1. Dam bypass
2. Water table
effects

41. Conclusions:
 Dams are used for various purposes and it gives
very useful to mankind
 It provides electricity, prevent flood control , river
channelization , control of silt and debris transport
 Moreover reservoir are useful to feed the channel
system for irrigation , power and others also.

42. Reference:
(1) Engineering and general geology by Parbin
singh , page 522-539
(2) A text book of geology by PK mukherjee
(3) Wikipedia.com

43. Thank You