This presentation provides an overview of repairs being conducted on the Pandoh spillway in Himachal Pradesh. Some key points: - The spillway experiences significant damage every monsoon season from debris carried by flood waters. Approximately 30,000 square feet is damaged annually. - A temporary barrier wall is constructed to separate the spillway into sections so repair work can be conducted safely in phases while continuing to release water. - The damaged areas are assessed and prepared for repair work by cleaning surfaces and reinforcing any exposed rebar. - Repairs use epoxy mortar and concrete matching the original specifications. Deeper damage over 2 inches is repaired with concrete. - Over 30 years,

1. WELCOMEWELCOME
TOTO
PRESENTATIONPRESENTATION
ONON
PANDOH SPILLWAY REPAIRPANDOH SPILLWAY REPAIR
:-Er HIMANSHU:-Er HIMANSHU

2. General View of Pandoh Dam & SPILLWAY

3. General View of Pandoh SPILLWAY

5. • Pandoh Dam spillway is meant for the release of
water of R-Beas in excess to the requirement at
Pandoh after maintaining the required PRL
during the monsoon season and also for the
continuous release of 15 % water for the rest of
the period during the year. The release of 15 %
water downstream of Pandoh Dam has been
made mandatory by the Hon’ble High court
Shimla (HP) since -2005.

6. • Pandoh spillway is an orifice type chute
spillway and there are 5 No radial gates
having size 12mt x 13 mt each which are
designed for the maximum release of
3,51,000 cusec of discharge. The width of
the spillway at the crest is 74 mt and the
clear water way is 60 mtr. The overall area
of the spillway from the zero RD to the end
of flip bucket is 93,413 sq ft.

7. • The total spillway area can be divided into three
parts :-
• 5 No crest blocks,
• 42 No. chute blocks
• 7 No. flip bucket blocks.
• The spillway chute has a slope of 2.5: 1. The
energy dissipater type flip bucket has been
provided at the end of the spillway chute having
50 ft radius and the angle of the flip bucket is 350

8. • The thickness of the conc. floor of the spillway
chute is 3 ft which increases to 10 ft in the
middle of the flip bucket and 19 ft at the end of
flip bucket. The chute floor has been tied to the
underlying rock by means of 25mm dia
deformed anchors 15 ft deep into the rock and
spaced at 6 ft c/c.
• Reinforcement bars 20mm dia @ 30 Cm c/c
has been provided both in longitudinal & cross
direction on the spillway chute & flip bucket floor
area. A top cover of 6” has been provided to the
steel reinforcement .

9. Total 0.127x106
m3 of the conc. of various
strengths has been used for the construction of
Pandoh spillway:-
1. 1500 psi - for protective coat
over rock
2. 4000psi - water contact surface for
abrasion resistance
3. 3000psi - for all other sections of spillway

10. • Every year during the monsoon season the river
discharge carries a huge quantity of silt laden
water, boulders and tree logs which rolls over
the spillway surface and also the frequent
flushing operations which are carried out during
the monsoon season for the exclusion of
deposited silt in the Pandoh reservoir causes
heavy damage to the spillway chute and flip
bucket.

11. • It has been observed from the past experience
that every year after the monsoon season,
approximately 30,000 sq ft of the spillway area
gets damaged which includes the area of
spillway chute, flip bucket and the area of one
No. gate from sill plate to the end of stop logs,
taken up for major repair during the year
• The extent of the average damage on the
spillway chute and flip bucket is generally found
between 2” to 4 “.

12. Some times reinforcement bars provided in the
chute surface & flip bucket also gets exposed
due to hit of the heavy tree logs & continuous
rolling of boulders & other material over the
spillway surface during the flushing operations.
The steel plate provided at the end of the flip
bucket also gets eroded at many places due to
continuous passing of silt laden water & rolling
of boulders during the monsoon season.

13. • The maximum damage to the spillway area
occurred so for after the construction of the
project was observed in the year 1995 when the
historical flood to the tune of 1,61,000 Cs was
passed through the Pandoh spillway.
• The heavy rains of (2480 mm)97” was recorded
during the year in the catchment area upstream
of Pandoh Dam which was much more than the
Av. Annual rain fall of 54” in the catchment area.
• The damage to the spillway observed after the
flood season of 1995 was 58,310 sq ft .

14. • The year wise area damaged and repair of the
spillway carried out so for since the year 1985-
86 has been summarized as :-

15. Year wise area damaged & S/wayYear wise area damaged & S/way
Repair Carried OutRepair Carried Out
Year Area Damaged (Sq. Ft( Area Repaired (Sq. Ft(
1985-86 7120 7120
1986-87 22128 22128
1987-88 19353 19353
1988-89 45026 45026
1989-90 29450 29450
1990-91 12000 12000
1991-92 4360 4360
1992-93 29000 29000
1993-94 34840 29800
1994-95 48240 40900
1995-96 58310 43890

16. Year wise area damaged & S/way RepairYear wise area damaged & S/way Repair
Carried OutCarried Out
Year Area Damaged (Sq. Ft( Area Repaired (Sq. Ft(
1996-97 38550 35700
1997-98 33300 33300
1998-99 40000 40000
1999-2000 34800 34800
2000-01 30800 30800
2001-02 20000 20000
2002-03 20020 20020
2003-04 15898 15898
2004-05 27761 21000
2005-06 33410 33410
2006-07 45332 45332
2007-08 28000 28000

17. Year wise area damaged & S/way RepairYear wise area damaged & S/way Repair
Carried OutCarried Out
Year Area Damaged (Sq. Ft( Area Repaired (Sq. Ft(
2008-09 36000 36000
2009-10 7000 7000
2010-11 15800 15800
2011-12 6300 14700
2012-13 6000 6000
2013-14 21000 21000
2014-15 22218 22218
2015-16 12288 12288

18. • CONSTRUCTION OF TEMPORARY
BANDH AND SEPERATOR WALL

19. To start with the repair work first of all a
temporary bandh is constructed across the flip
bucket & the flip bucket is divided into two parts.
It thus facilitate the repair work to be carried out
in two phases:-
• in the first phase the water is released through
Gate No 5 and the area in front of gate No-1 to
gate No -4 up to the end of flip bucket is
repaired.
• In the second phase the water is released
through Gate No- 1 and the area in front of Gate
No-5 is repaired.

20. • To start with the work for the construction of
temporary bandh and separator wall first of all
the leakages from all the five no. radial gates is
diverted towards Gate No-5 after getting the
permission for the closure of 15 % discharges
D/stream of Pandoh Dam for at least 15 days
from HP Environment & Pollution Control Board
Shimla.
• The temporary bandh is constructed in the line
of pier of Gate No 4 & 5 in the flip bucket using
jute bags of 50 kg capacity filled with clay.

21. • A two ft wide Separator Wall consisting of hollow
block masonry is also constructed throughout
the length and height of the bandh
simultaneously with the raising of the bandh.
• Loose clay filled in plastic bags is placed and
compacted in the voids between the gaps of
hollow block masonry wall and temporary bandh.
• One side of the separator wall is plastered to
prevent the leakage of water from the masonry
wall towards the working area in front of Gate No
1 to 4.

22. • The height of the bandh and masonry is kept 2 ft
above the height of flip bucket so as to ensure
the continuous release of 15 % of water
downstream of Pandoh Dam without spilling into
the working area prepared for carrying out the
repair in front of Gate No 1 to 4.

23. COLLECTION OF MATERIAL FOR KATCHA BANDH IN FLIP BUCKET

24. CONSTRUCTION OF KATCHA BANDH IN FLIP BUCKET IN PROGRESS

25. CONSTRUCTION OF KATCHA BANDH IN FLIP BUCKET IN PROGRESS

26. CONSTRUCTION OF KATCHA BANDH IN FLIP BUCKET IN PROGRESS

27. VIEW OF THE COMPLETED KATCHA BANDH IN FLIP BUCKET

28. VIEW OF THE COMPLETED KATCHA BANDH IN FLIP BUCKET

29. LIFTING OF MATERIAL AFTER THE COMPLETION OF BANDH

30. LIFTING OF MATERIAL AFTER THE COMPLETION OF BANDH

31. RELEASE OF WATER D/S OF S/WAY AFTER THE COMPLETION OF BANDH

32. • ASSESSMENT OF DAMAGED AREA

33. • After the construction of the Separator Wall and
making the surface approachable the whole of
the area is surveyed to know the extent of
damage occurred and to make the planning's for
the repairs to be carried out.
• The photography & video-graphy of the
damaged area is also done and kept as record
for future .

34. DAMAGED AREA OF PANDOH SPILLWAY CHUTE

35. DAMAGED AREA OF PANDOH SPILLWAY CHUTE

36. DAMAGED AREA OF PANDOH SPILLWAY CHUTE

37. DAMAGED AREA OF PANDOH SPILLWAY CHUTE

38. DAMAGED AREA OF PANDOH SPILLWAY CHUTE & FLIP BUCKET(2007-08)

39. DAMAGED AREA IN THE FLIP BUCKET

40. EXPOSED REINFORCEMENT BARS IN THE FLIP BUCKET (2007-08)

41. EXPOSED REINFORCEMENT BARS IN THE FLIP BUCKET(2007-08)

42. MEASUREMENT OF DAMAGED AREA

43. MEASUREMENT OF DAMAGED AREA

44. SURFACE PREPERATIONS FOR REPAIR

45. • After assessing the damaged area the work for
the surface preparation is started. The whole of
the area is first washed by air water jet to
remove elegy . The area is then dried & further
cleaning is made by steel wire brushes to
remove the dust.
• The loose concrete if any is removed by nicking
& hammering. Dust particles present in the pot
holes are also removed with the help of steel
wire brushes & compressed air so as to have a
good bond between the old and new area.

46. WASHING OF SURFACE WITH AIR WATER JET IN FLIP BUCKET

47. CUTTING OF LOOSE MATERIAL BEFORE REPAIR

48. • The reinforcement bars which are found
exposed and damaged are repaired &
maintained as per the original design .The
additional bars are provided in place where ever
required and the welding is done through out the
length of the joint between old & new steel bars.
• Additional dowels with split end on one side are
also provided at the junction of longitudinal and
cross reinforcement bars. The dowels are
anchored in the holes with wedge at the end and
are grouted with cement grout. The longitudinal
& cross reinforcement bars are then welded with
these dowels.

49. • The steel plate provided at the end of the flip
bucket is also maintained as per its original
shape. Pieces of M.S. plate are welded where
ever it is required and the pitting in the plate is
filled up with steel welding.
• Concrete is grouted under the steel plate where
ever a gap is found .The whole of the steel plate
after repair is covered with a protective coat of
epoxy mortar.

50. DRILLING WORK FOR PROVIDING ANCHORS IN THE FLIP BUCKET

51. REPAIR OF STEEL PLATE AT THE END OF FLIP BUCKET IN PROGRESS

52. REPAIR OF PANDOH SPILLWAY

53. The damaged area is classified into two
categories:-
1. Normal Abrasion i.e. depth of damage up to ½’’.
2. Heavy Abrasion where the depth of damage is
more than 2” & above

54. • i) For the repair of the normal abrasion up to
1/2” depth the repair is carried out with epoxy
mortar using three grades of emery powder Gr.
40,60 & 100 in equal proportion as filler.
• The epoxy mortar is laid over the surface
painted with bonding coat of epoxy paint and
the surface is finished with steel gurmalah at the
end.

55. • For the repair of heavily damaged area rich
c.conc. 7000 PSI strength was being used since
1993-94 to the year 2006-07 . In the year 2007-
08 the heavy damages of conc. in the flip bucket
to the tune of 6” to 9” were observed. The
reinforcement bars were also found badly
exposed.
• Keeping in view M-50 concrete with steel fiber
and admixtures (FRC) was got designed from
NCCBM Ballabgarh, on the initiation of sh SK
Duggal Technical Expert BBMB & was being
used for repair. Extra dowels 20mm dia with split
end & wedge at the end @ 30 cm C/C spacing
were provided and grouted with cement slurry.

56. • After preparation of the surface the bonding coat
of epoxy paint was applied over the surface with
painting brush and the FRC concrete was laid
over it to the designed depth and was finished
with trowel at the end.
• As per practice in vogue the area inside the
Gate from sill plate to the end of stop logs is
repaired by using wet epoxy mortar with emery
powder of three grades in equal proportion as
filler. The mortar is laid over the bonding coat of
wet epoxy resins & is finished with trowel.

57. • FARMULATION OF EPOXY &
CONCRETE USED FOR THE REPAIR
OF PANDOH SPILLWAY

58. FORMULATION OF EPOXYFORMULATION OF EPOXY
RESINS USEDRESINS USED
• Formulations of Epoxy resins
• 1 For Dry condition
• A. FORMULATION OF DR.BECK’S EPOXY RESINS
• Sr.No Combination Ratio
• 1. Dobeckot-505 C 100 PBW
• 2. Hardener EH-411 50 PBW
• 3. Filler material 800-900 PBW
• 4. Pot life 75 min at 250
C
• B. FORMULATION OF CIBA GEIGY’EPOXY RESINS
• Sr.No Combination Ratio
• 1. Araldite GY-257 100 PBW
• 2. Hardener HY 840 45 PBW
• 3. Hardener HY-960 3 PBW
• 4. Filler material as used 800-900 PBW
• 5. Pot life 90 Min at 300
C

59. FORMULATION OF EPOXYFORMULATION OF EPOXY
RESINS USEDRESINS USED
• 2 For wet condition
• A. FORMULATION OF CIBA GEIGY’EPOXY RESINS
• Ist Formulation
• Sr.No Combination Ratio
• 1. Araldite GY-250 100 PBW
• 2. Hardener HY 2958 13.5 PBW
• 3. Hardener HY-825 12.5 PBW
• 4. Filler material as used 400-500 PBW
• 5. Pot life 30 Min at 300
C
• 2nd Formulation
• Sr.No Combination Ratio
• 1. Araldite GY-250 100 PBW
• 2. Hardener HY 2958 18 PBW
• 3. Filler material as used 400-500 PBW
• 4. Pot life 20 Min at 300
C

60. FORMULATION OF EPOXYFORMULATION OF EPOXY
RESINS USEDRESINS USED
• B. FORMULATION OF DR.BECK’S EPOXY RESINS
• Sr.No Combination Ratio
• 1. Dobeckot - 505 C 100 PBW
• 2. Beck Bond UW grout 42 B 34 PBW
• 3. Filler material 700-900 PBW
• 4. Pot life 80 Min at 250
C

61. Mix Design for 7000 PSI C.ConcMix Design for 7000 PSI C.Conc
• Qty. of material for 7000 PSI mix design:
• Ratio 1: 0.66 : 1.35
• Per bag Per Cum
• i) Cement = 50 Kg = 14.2 bag
• ii) Sand = 33.31 Kg. (0.765 Cft.) = 0.312 cum
• or .022 cum
• iii) Aggregate = 67.60 Kg. (1.683 cft.) = 0.667 cum
• iv) Water cement ratio = 0.31
• V) Slump = 4 “ + 1/2 “
• Box size used for sand = 12 “ X 12 “ X 9 “ = 0.750 cft.
• Box used = 1.021 Box/Bag.
• Box size used for agg. = 12 “ X12 “ X10.5 “ =0.875 cft.
• Box used = 1.923 Box/Bag

62. RECOMMENDATIONS BY NCCBM BALLABGARH FOR THE CONCRETERECOMMENDATIONS BY NCCBM BALLABGARH FOR THE CONCRETE
MIX DESIGNMIX DESIGN
For M 50 Grade : Workability: 50-75mm Slump.For M 50 Grade : Workability: 50-75mm Slump.
Mix Constituents Per Cu Mtr (Kg)
Cement (43 grade OPC) 454
Micro Silica 39
Water 138
Fine Aggregate 678
Coarse Aggregate
10-20 mm (55%)
< 10mm (45%)
636
520
Admixture @ 1.1% by wt. of cement+
Micro Silica
5.4
VMA @ 0.10% by wt. of cement + Micro
Silica
0.50
Steel Fibre 25.0
Water/ Cement + Micro silica Ratio 0.28

63. MIXING OF STEEL FIBERIN THE MIXER FOR PREPRATION OF FIBER CONCRETE

64. WET EPOXY PAINTING BEFORE LAYING M-50 FIBER CONC.

65. VIEW OF ANCHORS PROVIDED IN THE FLIP BUCKET & LAYING OF CONCRETE

66. LAYING OF CONCRETE IN THE FLIP BUCKET IN PROGRESS

67. LAYING OF CONCRETE IN THE FLIP BUCKET IN PROGRESS

68. FINISHING OF CONCRETE IN THE FLIP BUCKET IN PROGRESS

69. FINISHED VERTICAL SURFACE WITH EPOXY MORTAR IN GATE NO. 2

70. VIEW OF THE FINISHED SURFACE WITH EPOXY MORTAR IN GATE NO. 2

71. CURING OF CONCRETE IN PROGRESS

72. PREPRATION OF EPOXY PAINTFOR EPOXY MORTAR

74. PREPERATION OF EPOXY MORTAR

75. REPAIR WITH EPOXY MORTAR IN THE FLIP BUCKET IN PROGRESS

76. REPAIR WITH EPOXY MORTAR IN THE FLIP BUCKET IN PROGRESS

77. FINISHED VIEW OF THE REPAIRED AREA WITH C.CONC. ON S/WAY CHUTE

78. CONC. JOINTS PAINTED WITH EPOXY PAINT ON S/WAY CHUTE

79. FILLING OF FLIP BUCKET AFTER COMPETION OF WORK IN BAY NO 1 TO4

80. FINISHED CONCRETE & EPOXY MORTAR IN FRONT OF GATE NO. 5

81. FILLING OF FLIP BUCKET AFTER REPAIR IN FRONT GATE NO. 5

82. VIEW OF THE STEEL GRATING FOR VENT PIPE GROOVES IN THE FLIP BUCKET

83. PLACING OF STEEL GRATING IN POSITION THE VENT PIPE GROOVES