This document discusses geological studies of tail channel erosion at four dams - Panshet, Ghod, Chaskaman, and Bhama Asked - built within Deccan trap basalts in India. Proper geological investigations were not conducted prior to construction at some dams, resulting in erosion issues. Remedial works like guide walls and concrete aprons were later required. The document emphasizes the need for thorough geological studies and modeling before finalizing dam and spillway designs within basaltic rock formations.

1. PGE STUDIES FOR TAIL CHANNEL
EROSION (GHOD, CHASKAMAN,
BHAMA ASKED DAM) IN DECCAN
TRAP ROCKS
DR. N. J. SATHE
PUNE
CONTACT NO. 7588046971
EMAIL. ID: drnjsathe9011414158@gmail.com
1 Dr. N. J. Sathe, Pune.

2. Basalts (Igneous Volcanic Rocks)
Dr. N. J. Sathe, Pune.
AREA
About Five Lakh square Km
STATES
85% of Maharashtra and some parts of
Madhya Pradesh, Gujarat, Karnataka &
Andhra Pradesh
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3. Dr. N. J. Sathe, Pune.
DECCAN TRAPS OF INDIA
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4. Basalts (Igneous Volcanic Rocks)
Dr. N. J. Sathe, Pune.
TYPES
 COMPACT BASALT
 VESICULAR BASALT
 AMYGDALOIDAL BASALT
 VOLCANIC BRECCIA
 TUFF BRECCIA / TUFF (only in Mumbai)
 TACHYLYTIC BASALT i.e. GLASSY BASALT
 CHLOROPHAEITIC BASALT
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5. Structural Geological Features
Dr. N. J. Sathe, Pune.
1. DYKE
Intrusion cutting across basalt flows, jointed, sometimes
more weathered than Basalts because of closely spaced
joints
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6. Structural Geological Features
Dr. N. J. Sathe, Pune.
2. FRACTURE
Tectonic cracks cutting across basalt flows without
any movement
Deep decomposition – sheeting, clay
maximum width 26 m.
A
B
C
D
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7. Structural Geological Features
Dr. N. J. Sathe, Pune.
A
B
C
A
B
C
3. FAULT
Tectonic fissures due to tensile forces, bed gets divided
into two parts, One part gets shifted vertically relative
to the other.
(no Faults in Deccan Trap area)
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8. Structural Geological Features
Dr. N. J. Sathe, Pune.
4. JOINTING
• Divisional planes
• Provide passage for water & provide inflow of
water in foundations,
• Volume and discharge depend on pattern of
jointing
• Produces instability
• Material in joints weathers.
• What is important for us is width of joint, quality
of material in it and direction.
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9. Dr. N. J. Sathe, Pune.
Geological
Investigations
Surface
Investigations
Subsurface
Investigations
The basic objective of geological investigation is to
provide complete, detailed geological information of the
proposed area.
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10. Dr. N. J. Sathe, Pune.
•Surface Investigations:
It is the first step in this work to establish general geology, lithology,
structures etc. It mainly includes
 Mapping – Geological, Topographical, geomorphological,
structural, lithological, tectonic etc.
 To determine name and geological age of rocks.
 To find out structural and general relations of rock formations.
 To know physiographic and topographic conditions.
 To find general attitudes (strike and dip), Structures like folds,
faults, joints in the field.
 To carry lithological studies to find out type, mineral
composition, texture, structures etc.
 To find different engineering properties of rocks like crushing
strength, durability, porosity etc.
 To know general slope of the area.
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11. Dr. N. J. Sathe, Pune.
SUBSURFACIAL
INVESTIGATION
S
• INDIRECT
METHOD.
• DIRECT
METHOD
SUBSURFACIAL
INVESTIGATIONS
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12. Dr. N. J. Sathe, Pune.
1.Indirect method:
It includes various geophysical investigations carried
especially by electric resistivity and seismic reflection
methods.
This study helps –
a. To determine the thickness of bed rock, basement.
b. To locate fault zones, weak planes, folds, faults etc.
c. To determine groundwater occurrence, adverse for
engineering structures.
d. To know types of rocks and their attitudes.
e. To locate good quality building stones.
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13. Geophysical methods have different advantages like:
a)These investigations are carried quickly i.e. time saving techniques.
b)These investigations are carried cheaply i.e. more economical than
others.
c)These geophysical instruments are easy to handle i.e. they are
simple and portable.
Dr. N. J. Sathe, Pune.13

14. Dr. N. J. Sathe, Pune.
2. Direct methods:
Geological investigations are carried by drilling methods
directly to confirm previous investigations.
Core drilling is most important process by which rock
specimens from different depths can be brought to
surface intact in the form of solid cylinders. These are
arranged on the surface depth wise to know lithology,
structures etc. Core drilling is done by two ways –
Diamond drilling and Calyx drilling. Diamond drilling is
done to know the basement up to greater depth and calyx
drilling is restricted up to shallow depth.
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15. Engineering Geological Investigation Report
1) Introduction:
a) Purpose of investigation Latitude
b) Geography of the area Longitude
Topography
c) Previous Investigations
2) Physical geology:
a) Climatic conditions and factors
b) Physiography Types of Drainage
River, Mountains.
Dr. N. J. Sathe, Pune.15

16. Dr. N. J. Sathe, Pune.
3) Regional geology:
a) Rock formation – age, lithology, type.
4) Structural Geology:
a) Regional structure.
b) Different geological structure in the area.
c) Lineaments.
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17. Dr. N. J. Sathe, Pune.
5) Subsurface Investigations: Electrical Resistivity
a. Geophysical Investigation: Seismic Reflection
b. Drilling Data;
c. Geohydrological Investigations.
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18. Dr. N. J. Sathe, Pune.
6) Local geology:
a) Geological characteristics of rocks, soils.
Engineering properties of rocks, soils.
7) Hydrogeological conditions:
a) Information about water table, aquifers
and their types.
b)Information about groundwater quality
8) Detailed engineering geological investigations.
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19. Dr. N. J. Sathe, Pune.
Stained Joints19

20. Dr. N. J. Sathe, Pune.
Stained joints & Fresh mech. Fractures
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21. Dr. N. J. Sathe, Pune.21
Core log boxes should be preserved

22. Dr. N. J. Sathe, Pune.22
Preparation of core log maps

23. Four Case Studies for this Tail Channel
1 is Panshet Dam Spillway at Pune
2 is Ghod Dam Spillway at Chinchani, Shirur.
3 is Chaskaman Dam Spillway near Rajgurunagar.
4 is Bhama Asked Dam Spillway near Talegaon
Dabade.
23 Dr. N. J. Sathe, Pune.

24. Dr. N. J. Sathe, Pune.24
PANSHET DAM NEAR PUNE
• Area Comprises of Basaltic Rock
• No Proper Geological Investigations were
carried.
• Evidenced by erosion/scouring of the tail
channel bed rocks.
• Creating danger to the Bridge foundation
near Panshet.
• In the first discharge flow itself has shown
rigorous scouring of the hard rock.

25. Dr. N. J. Sathe, Pune.25
PANSHET DAM NEAR PUNE
• Rock existing in the study area are
Compact Basalt with Columnar Structures,
Amygdaloidal Basalt, Red Tachylytic Basalt
with Lava Matrix as an intrusion (Sill)
• These rocks were eroded in the flow
discharge and due to which treatment was
provided later.
• Near the stilling basin the columnar basalt
was treated by constructing a guide wall
and covering the appron in stilling basin.

26. Dr. N. J. Sathe, Pune.26
Panshet Spillway.
Energy Dissipaters at Toe of
Spillway Gates in stilling basin.
Guide Walls Provided just
below the Spillway to avoid
further scouring of rock.

27. Dr. N. J. Sathe, Pune.27
Bridge Foundation Condition in Tail
Channel of Panshet Side spillway

28. Dr. N. J. Sathe, Pune.28

29. GHOD DAM AT CHINCHANI
• Area Comprises of Basaltic Rock
• No Proper Geological Investigations
were carried.
• Evidenced by erosion/scouring of the
tail channel bed rocks.
• Creating danger to the dam
foundation.
• First flow itself has shown rigorous
scouring of the hard rock.
Dr. N. J. Sathe, Pune.29

30. Dr. N. J. Sathe, Pune.
GHOD DAM AT CHINCHANI
 Area Comprises of Basaltic Rock
which are having Columnar
Basaltic flows as the outcrop
followed by the formation of
Tachylytic Basaltic flows.
 As on today PWD department is yet
poring lots of amount for
maintaining the spillway channel.
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42. Dr. N. J. Sathe, Pune.
CHASKAMAN DAM AT RAJGURUNAGAR:
•Area Comprises of Basaltic Rock
•No Proper Geological Investigations were
carried.
•Evidenced by erosion/scouring of the tail
channel.
•Creating danger to the dam foundation.
•First two seasonal flows itself has shown
rigorous scouring of the hard rock.
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43. Dr. N. J. Sathe, Pune.
CHASKAMAN DAM AT RAJGURUNAGAR:
Area Comprises of Sheet Jointed Basalt.
Followed by deposition of tachylytic
basaltic rock overlained on sheet jointed
basalts.
Evidenced by erosion/scouring of the tail
channel.
No water is driven out from the spillway
location.
Water is driven through the canal and this
canal produces 4 MW power generation.
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44. Dr. N. J. Sathe, Pune.Chaskaman Dam44

45. Dr. N. J. Sathe, Pune.
Chaskaman Dam45

46. Dr. N. J. Sathe, Pune.
Chaskaman Dam46

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Chaskaman Dam47

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50. Dr. N. J. Sathe, Pune.
BHAMA ASKED DAM AT TALEGAON DABHADE:
•Area Comprises of Basaltic Rock
•Proper Geological Investigations were carried.
•Evidenced by erosion/scouring of the tail
channel in the central part.
•Occurrence of the Doleritic Dyke and inclined
deeping red matrix.
•Creating danger to the dam foundation.
•Initial stage of spillway when gates were not
provided the exposure of the dyke rock and the
red lava matrix created danger in the stilling
basin.
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51. Dr. N. J. Sathe, Pune.
CHASKAMAN DAM AT RAJGURUNAGAR:
Area Comprises of Columnar Jointed
Basalt.
The spillway gates constructed have a
longitudinal dyke.
Evidenced by erosion/scouring of the tail
channel exactly within the stilling basin
55 tone concrete blocks constructed in the
stilling basin were uplifted.
The uplift pressure generated from the
tachylytic flow created a danger. Yet
research is going on.
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54. Occurrence of
Dyke running
Longitudinal is
clearly
evidenced now.
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CONCLUSION OF STUDY:
Area Should be scanned properly
before deciding the spillway location.
Sub surface geological aspect has to be
notified during the planning aspect of
the dam.
Demo or proto type model study has to
be performed by the geologist before
giving the site for spillway location.
Various treatments should be down for
small erosive rocks.
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65. Dr. N. J. Sathe, Pune.
CONCLUSION OF STUDY:
Subsurfacial investigations data should
be available with the sites.
Problems related to design should be
discussed with the field surveyor.
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66. That’s All For You
Dr. N. J. Sathe, Pune.
Thank You!!!
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