CHAPTER-IV
DESIGN ASPECTS
4.1
Introduction
Presently under Ken-Betwa Link Project, Phase – II, following
five components are proposed:
1.
Lower Orr dam across Orr river (a tributary of Betwa) located in
Ashoknagar and Shivpuri district of MP
2.
Neemkheda barrage across Betwa river located in Raisen district
of MP
3.
Barari barrage across Betwa river located in Vidisha district of
MP
4.
Kesari barrage across Keotan (a tributary of Betwa) river located
in Vidisha district of MP
5.
Kotha barrage across Betwa river located in Vidisha district of
MP
An Index map of the Ken – Betwa Link Project, Phase-II is given
as Plate No. 4.1 in Volume - V (Part-2).
The main aim of proposing a number of barrages across of Betwa
river under the Project is to provide irrigation water to the villages which lie in
drought prone and backward areas in Raisen and Vidisha districts of Madhya
Pradesh. The villagers shall utilise pounded water of barrages by lift irrigation
in water deficit upper area to cultivate farm land throughout the year. It will
definitely bring economic prosperity to the backward areas of Shivpuri, Raisen
and Vidisha disticts of Madhya Pradesh.
The design aspects of the above five components are described in
the following paragraphs.
163
4.2
Lower Orr dam
Engineering Assessment
As already discussed, the Ken – Betwa link project envisages
diversion of water from Ken river to the Betwa river as mandated in the
Memorandum of understanding between the state Governments of Madhya
Pradesh and Uttar Pradesh. In order to rope in the vast experience of other
central orgnisations in relevant fields and also to complete the DPR preparation
of this important project within the scheduled time, the works related with the
design aspects of various components of the project were entrusted to and
carried out by different concerned Directorates of CWC, based on the inputs
from NWDA, GSI, NIH, CSMRS etc. Design philosophy for the components,
their preliminary design, along with underlying considerations, assumptions
and parameters and the basis for selecting the parameters form the subject of
the design aspects in this chapter. The salient details of the designs carried out
by respective Directorates of CWC in respect of various main components are
briefly discussed in this chapter.
4.2.1
General
The Lower Orr dam envisages construction of a composite dam
(Earthen and Concrete) across the Orr river near Didauni village on the border
of Shivpuri and Ashok Nagar districts in MP to store 372 MCM water for
irrigation to water deficit areas of Shivpuri district.
The 75% and 50% dependable annual yield of the sub-basin up to
the proposed dam site has been assessed as 363 MCM and 501 MCM
respectively. From the simulation studies it is seen that about 329.67 MCM
water can be utilized from the reservoir for irrigation (apart from 6 MCM for
drinking water supply and 44.9 MCM environmental releases) at 371.80 MCM
storage capacity.
In the proposed composite dam, the concrete dam portion is
487.00 m long with 247 m long spillway in the left bank and 240 m long Non
Overflow blocks. The earthen dam proposed is 1731 m long with a maximum
164
height of 45.0 m. A 91.260 km long main canal has been proposed on the left
bank of river. The project will provide annual irrigation to 67570 ha area
Shivpuri district of MP. Besides 6 MCM water will be provided for drinking
water supply to the enroute villages and towns in the vicinity of the canal.
About 1.65 lakh people will get drinking water at a consumption rate of 100
lpcd. The FRL of the Lower Orr project is kept as 380 m. The submergence
area at FRL is 2724 ha.
4.2.2
Geology, Seismicity and foundation – Brief
(i) Geology
The proposed Lower Orr dam site is about 8 km upstream of the
confluence of Orr river to that of the Betwa River. The area is flat with rolling
undulations displaying elevations between 340 m to 400 m. The Orr River
flows towards east with about 60 m wide channel close to the left abutment
hill. The entire dam alignment is located in the basement granite/granite
gneisses as the contact between the granite and the overlying sandstone
(Kaimur Group of the Vindhyan Supergroup) lies much above the TBL on both
the abutment. Outcrops of granite/granite gneisses have been found on the left
abutment and the Orr river bed between reduced distance (RD) 0.00 m and 240
m. From RD 240 m to 2130 m, the dam axis is covered with alluvial soil.
(ii) Seismicity
As already mentioned in the Chapter – I, the site specific seismic
study for the Lower Orr dam has been carried out by the Central Water and
Power Research Station (CWPRS), Pune. For the deterministic estimate of the
site-specific design ground motion for Lower Orr dam, the magnitude of the
controlling MCE is estimated as 6.0 at a closest distance of 24.7 km from the
site with 15.0 km as depth. The values of the peak ground acceleration for
horizontal and vertical components are found to be 0.113 g and 0.089 g for
MCE; and 0.051 g and 0.041 g for DBE conditions respectively. These values
have been approved by National Committee on Seismic Design Parameters
(NCSDP) of the Ministry of Water Resources.
165
According to the study, the proposed Lower Orr dam site in
Shivpuri / Ashoknagar districts of Madhya Pradesh lies in Seismic Zone-II as
per the seismic zoning map of India given in the IS 1893 (Part I)-2002,
‘Criteria for earth quake resistant design of structures’. Zone II indicates low
seismicity of the area. The data on 110 past earthquakes up to December 2011,
with magnitudes greater than or equal to 2.0, are available for the region. The
histogram for earthquake magnitude indicates that, in general, the relative
number of earthquakes is not represented in a consistent manner, perhaps due
to limited period and area covered by the catalogue. The histogram for distance
distribution also shows the significant events with magnitude greater than or
equal to 5.0. It is observed that no events have occurred within 60 km of the
site. There are 3 events observed at the same location at 62.9 km from the site
which have occurred on 31st December 1926, 10th April 1929 and 25th June
1930 and all the three have magnitude of 5.5. Out of the 2 events of magnitude
greater than or equal to 6, one 6 magnitude event occurred at the distance of
276 km and the other 6.5 magnitude event occurred at the distance of 204 km
from the site.
The study report of Specific Design Ground Motion for Lower Orr
Dam conducted through CWPRS, Pune is appended as Appendix 2.1.3 of
Volume – III.
(iii)
Foundation
A total number of 15 drill holes were drilled for assessing the
foundation geology. Based on the interpretation of subsurface data, it was
found that competent foundation grade granite/granite gneiss is available at
much higher elevation on the left flank where location of spillway has been
fixed on techno-economic considerations. In the remaining areas, where
earthen dam has been planned the bedrock is available at a considerable depth
below the over burden.
At the location of spillway (RD 0.0 m to 400.0 m), granite and
granite-gnesiss belonging to Bundelkhand granioid complex of Precambrian
166
geological age has been found in the river portion and in the left abutment of
dam site whereas massive sandstone of Kaimur group of Vindhyan Supergroup of Precambrian geological age have been found non-conformably over
granite on left bank much above TBL. Grade III/IV weathered granite is
exposed on D/S of dam axis. On left abutment between RD 0.0 m and 100 m,
slope is overlain with huge boulders of sandstone and granitic soil. The Non
Overflow blocks would be founded over fresh granite which is expected at 2-5
m depth below the ground level. The lithological characteristics of the
subsurface geology are given in Table 4.1.
Table-4.1
Lithological Characteristics of subsurface geology along the dam
alignment.
S.
Lithology
No.
Lithological characteristics
Thickness
1.
Overburden.
Dark, light grey to yellow brown, 4.5 to 20.0 m
sandy-silty-clayey and concretionary
soil, riverine sediments and rock
fragments of sandstone and granite.
2.
Granite/granite Pinkish brown, medium to coarse 30.0 m
gneiss
grained, inherently hard and compact,
fresh to moderately, massive and
foliated granite.
The Geotechnical investigation for foundation strata for earth dam
was carried out by CSMRS. In all, 6 pits were excavated in the foundation
(overburden) along the dam axis at RD 110 m, 750 m, 900 m, 1150 m, 1350 m
and 1650 m respectively. Undisturbed soil samples were collected for
conducting laboratory tests to determine soil parameters needed for earth dam
design. The soil samples in general indicate dominance of sand sizes except
167
one soil sample which indicate dominance of silt sizes. The Insitu densities
vary between 1.63 gm/cc to 1.80 gm/cc and moisture content varies from 5.9 to
12.7%. The test results indicate that the strata beneath the foundation are dense
and are unlikely to undergo excessive settlement during post construction/
operation stage. The specific gravity test values vary from 2.61 to 2.65. The
details are furnished at Table-2 of Appendix 2.1.5 of Volume – III ‘Report on
Foundation Soil Investigation of the proposed Lower Orr Dam’.
The properties of the soil obtained indicate that soil present in the
dam foundation would exhibit satisfactory performance and no special
treatment is warranted. The Index properties and Tri-axial test results adopted
in the design are given in Table-4.2.
Table-4.2
Results of Tri-axial Shear Tests adopted in the design
Lab. No.
RDm
In-situ
Dry
Density
(t/m3)
Moisture
Content
(%)
Specific
Gravity
Effective
Cohesion
Effective
Angle of
Shearing
Resistance
Classific
ation as
per BIS
2013/95
TP-1/10
1.63
6.0
-
0.15
28.7
CL
2013/100
TP-7/ 1650
1.80
5.9
2.63
0.26
29.3
SC
4.2.3
Sample No./
Alternative studies carried out for selection of site and type of
Structures
The proposed dam site had been earlier explored by the
Government of Madhya Pradesh, when this project was conceived for
supplying water to a proposed Atomic Power Plant. At the proposed dam site,
granitic gneisses are exposed at the river bed where spillway has been
proposed. In general, Bundelkhand granite gneiss, over-lain by Kaimur
sandstone form the rock type in the area. Granite gneisses form broad valley
and the sandstone cover the top of the low flat topped hills.
168
The axis originally selected by the Madhya Pradesh state appeared
to be technically satisfactory. However, for better abutting of the dam, both on
the left and right bank, the dam axis has been shifted 50 m upstream of the
earlier proposed axis. The axis, as proposed, now, is normal to the river flow.
This will result spillway placement normal to river flow resulting in better flow
conditions downstream of the spillway. The proposed dam axis has a kink, in
between, as there is an offset between the left and right abutment point of dam.
A curve tangential to both the ends of the axis has been provided.
A homogeneous / zoned earth fill dam consisting of CI type of soil
is proposed. The top width of dam provided is 7.0 m. The width of berms on
u/s and d/s varying from 3.5 m to 7.0 m.
4.2.4
Choice of final layout of all major components of the project
The dam site had been visited by the officials of CWC, GSI,
CSMRS and NWDA at different times and the location of dam axis and
spillway are finalised accordingly. Lower Orr dam has a maximum height of
45 m and is about 2.218 km long composite (earth + concrete) dam with top at
EL 384.00 m and having river bed EL +339.0 m. The right side of the dam is
wraped around non-overflow blocks of 100 m length. The Wraparound
proposed is a conventional one which will be designed before taking up
construction. The spillway is located on the left flank. The right flank is resting
on hill slope. The layout of the dam and appurtenant structures is shown as
Plate No. 4.1.1 in Volume - V (Part-2).
4.2.5
Design flood and sediment studies
a) Design Flood
The design flood for the Lower Orr dam has been estimated using
Unit Hydrograph approach using PMP values computed by IMD. Since
sufficient historical data is not available at the project site for UH computation,
synthetic unit hydrograph has been derived and is convoluted with a critical
design (critical sequencing of PMP) to produce corresponding PMF
hydrograph at the project site. The PMF at the project site is estimated to be
169
12067.67 cumec with time to peak at 32 hours and the time base of the
hydrograph is 91 hours. The coordinates of the Flood hydrograph at Lower Orr
dam site is given at Annexure 4.1 in Volume – II.
b)
Reservoir Sedimentation
The Lower Orr reservoir is classified as Type II reservoir (flood
plain foot hill type). The available sediment rate of Rajghat dam (located on the
Betwa river) which has been worked out at 367.03 m3/sq km/year has been
considered appropriate for design purpose. The catchment area of Orr river at
the project site is 1843 sq.km.
The total sediment deposition in the reservoir during 50 and 100
years are estimated as 33.90 MCM and 67.80 MCM respectively. The sediment
distribution is worked out for the two periods, viz. 50 years and 100 years, by
Empirical Area Reduction method. The new zero elevations after 50 years and
100 years have been found to be as 351.80 m and 353.53 m respectively.
The original and revised (after 50 and 100 years) Elevation–Area–
Capacity values are given at Annexure 4.2 in Volume – II.
The design flood and sedimentation computations which form the
hydrological analysis of the project are discussed in detail in Chapter – III.
4.2.6
Free Board
Free board for the dam has been provided as per the
recommendations of IS: 10635-1993 (Reaffirmed 1998) “Guidelines for free
board requirements in Embankment dams”. For freeboard computations, the
wind velocity at the dam site over land has been taken as 39 m/s. The
computed free board is 2.94 m. For fixing the dam top, settlement of an
embankment will be caused by consolidation in the foundation and in the fill.
A settlement allowance of 2% has been considered which is generally
provided. Further, in case of dams of more than 30 m height, an extra 1%
allowance is provided to account for the settlement due to earthquake.
Accordingly, the top of dam has been fixed as El. 384.0 m against FRL of
170
380.0 m. The maximum height of dam will be 45.0 m above river bed level of
+339.0 m.
The design computations of freeboard have been presented in
Drawing No. KBL- 8100-P-1601 given as Plate No. 4.1.2 in Volume - V
(Part-2).
4.2.7
River diversion arrangements
As per the guidelines laid down in the ‘Report of Ministry of
Irrigation, 1980 for arriving at the diversion design flood according to criteria
of risk and damage for different types of dams and barrages’ the diversion
floods for construction shall be as follows.
(i) Diversion capacity for concrete dams and barrages
The capacity of the diversion flood for concrete dams and
barrages may be less because flood higher than the designed one could be
passed safely over the partly constructed dam. The following criteria would
help in deciding the capacity. Maximum non-monsoon flow observed at the
dam site.
or
25 years return period flow, calculated on the basis of nonmonsoon yearly peaks.
The higher of the two should be taken as the design flood for
diversion.
(ii) For large dams
For large dams, it is desirable that 100 year return flood should be
adopted for diversion works. NIH, Roorkee has analysed the flood
characteristics for Lower Orr dam site and recommended 1 in 100 year
monsoon flood at the dam site for diversion which is computed as 4430.9
cumec.
171
However, no formal diversion arrangement has been provided.
The diversion arrangement during project construction will be evolved
depending upon the requirement. As sufficient width is available, the flow only
needs to be channelized through formal channels which can be decided at
construction stage. Also the sluices proposed can be used for diversion during
construction stage.
4.2.8
Construction materials
In all, 35 representative bulk soil samples were collected from 35
borrow pits (borrow area AB-1 to AB-6). All the soil samples were subjected
to Mechanical Analysis and Atterberg limits tests. The results of mechanical
analysis show that the soil samples predominantly contain silt sizes followed
by clay and gravel. The plasticity index values of the tested soil samples
indicate that the borrow areas material in general have low to medium
plasticity characteristics.
Out of 35 soil samples, 28 soil samples falls under CI (clay of
intermediate compressibility) group, 2 under CL-CI (clay of low to
intermediate compressibility) group and 5 under CL (clay of low intermediate)
group as per BIS soil classification system (IS 1498:1970). Standard Proctor
Tests give good compaction densities. Specific gravity varies from 2.64 to
2.70. The results of Triaxial shear indicates materials are likely to exhibit
reasonable shear strength characteristics. Also, soils are non-dispersive in
nature.
The Index properties and Tri-axial test results adopted in the
design are listed in Table-4.3.
172
Table-4.3
Index properties and Tri-axial test results of construction materials
Lab. No
Sample
No.
In-situ Moisture
Dry
Content
Density (%)
(t/m3)
Specific Effective Effective
Gravity Cohesion Angle of
Shearing
Resistance
Classifi
cation
as per
BIS.
S-II/2012/156 TP-1
1.74
18.5
2.69
0.16
23.2°
CI
S-II/2012/164 TP-1
1.80
15.5
2.66
0.17
25.9°
CI
S-II/2012/169 TP-3
1.71
18.5
2.70
0.11
28.4°
CI
S-II/2012/178 TP-6
1.81
14.5
2.67
0.16
23.3°
CI
S-II/2012/185 TP-6
1.74
17.0
2.66
0.06
31.1°
CI
S-II/2012/190 TP-5
1.85
18.0
2.66
0.08
27.0°
CL
The details are furnished at Appendix 2.1.7 and 2.1.8 of Volume –
III ‘Report on Soil Investigation of borrow area and Report on Construction
material survey for suitability of river bed samples for use as coarse and fine
aggregates’ respectively.
4.2.9
Details of the model studies for important structures
No model studies have been carried out at this stage. Model
studies need to be undertaken to ascertain the discharging capacity of spillway,
efficiency of energy dissipation arrangement and layout and profile of
approach and spill channel at pre-construction stage.
4.3
Lower Orr Dam
4.3.1
Earth Dam - Design criteria and stability analysis
The geometry of the homogeneous/ zoned earth dam has been
evolved taking into account the structural safety, Seismic aspects, seepage
173
control and material properties etc. Detailed investigation and laboratory
testing of the construction material was undertaken for determining the
material properties. However, additional supplementary tests would have to be
taken up before construction.
The dam section consists of homogeneous/zoned section with top
width of 7.0 m. The upstream face has slope varying from 2.5 (H):1 (V) to 3.5
(H):1 (V) while downstream face has slope varying from 2.5 (H):1 (V) to 3.5
(H):1 (V). The upstream face is protected by dumped riprap of 0.6 m thickness
laid over 0.2 m thick crushed stone/aggregate and 0.2 m thick sand filter. There
are three berms on upstream face at EL 373.0 m (4.0 m wide berm), EL 361.0
m (5.0 m wide berm) and at EL 349.0 m (7.0 m wide berm). The downstream
face also has three berms, at EL 373.0 m (3.5 m wide berm), EL 361.0 m (4.0
m wide berm) and at EL 349.0 m (5.0 m wide berm) respectively.
The material of the embankment dam is mainly CI type of soil. To
take care of slope stability under sudden drawdown condition 0.6 m thick sand
drains at 5.0 m interval have been provided in the upstream slope to relieve
pore pressure.
Rock toe having maximum height of 10 m has been provided in
the downstream portion from ground level to EL 349.0 m.
The Plan and L-section of the earth dam as given in Drawing No
KBL- 8100-P-1609 is given at Plate No. 4.1.3 in Volume - V (Part-2). The
typical section of Earth dam shown in Drawing No. KBL- 8100-P-1607 is
given at Plate No.4.1.4 in Volume - V (Part-2) and Cross-section at RD 950 m,
1100 m, and 1300m (Drawing No KBL- 8100-P-1610) and Cross-section at
RD 1500 m, 1750 m and 2050 m (Drawing No. KBL- 8100-P-1611) are given
as Plate No. 4.1.5 and 4.1.6 in Volume - V (Part-2). The wrap around details
furnished in Drawing No. KBL- 8100-P-1613 are given as Plate No. 4.1.7 in
Volume - V (Part-2).
174
4.3.1.1
Estimation of Design Shear Strength Parameters.
For estimation of shear strength properties of overburden material
in foundation 100% dependable values were adopted. The evaluation of shear
parameters of foundation overburden is shown in Drawing No. KBL- 8100-P1602 is given at Plate No. 4.1.8 in Volume - V (Part-2).
The shear strength parameters (c '& ø') for earth dam and
foundation material adopted in the stability analysis were obtained through Triaxial shear tests undertaken by CSMRS. For estimation of design shear
strength parameters of borrow area materials 75% dependable values of borrow
area test results were adopted. The details are presented in Drawing No. KBL8100-P-1603 given as Plate No. 4.1.9 in Volume - V (Part-2). The properties
adopted for design are summarized below in Table-4.4.
Table 4.4
The shear properties adopted in the design of earth dam
S.
Materials
No.
Saturated
Cohesion C’
Unit Weight
Angle of Shearing
Resistance Φ’
1
Embankment
Material
2.11 t/m3
0.87 t/m2
25.80
2
Foundation
2.28 t/m3
1.5 t/m2
28.50
3
Rock fill
2.11 t/m3
0
40.00
4.3.1.2
Seismic Design Considerations
For siesmic design earthquake coefficient, αh as 0.03g and αv as
0.02g has been adopted for Pseudo-static analysis of the section. This has been
approved by the National Committee on Seismic Design Parameters (NCSDP)
in 2012.
Adequate factor of safety has been provided against slip failure of
slopes during earthquake combined with steady seepage. A wide abutment
175
core-contact will ensure the safety against opening of joint during the
earthquake.
4.3.1.3
Stability Analysis
The stability analysis has been carried out in accordance with IS
7894-1975 using an in-house Software based on Swedish slip circle or
Fellinious method. “Effective stress method” of analysis has been used. The
minimum factors of safety obtained for various loading conditions and at
various levels is indicated in Table-4.5 to 4.8. The results are also shown in
Drawings No. KBL- 8100-P-1604 to 1606 given as Plate 4.1.10 to 4.1.12 in
Volume - V (Part-2).
Table 4.5
Minimum factors of safety obtained (U/S steady seepage)
S. Circle
Touching F.O.S.
No. Elevations.
With E.Q.
Required F.O.S.
Required
as
per Without as
per
B.I.S.
E.Q.
B.I.S.
1.
373.00 m. (Berm)
1.419
1.594
2.
361.00 m. (Berm)
1.468
1.730
3.
356.50 m. (MDDL)
1.468
1.743
4.
349.00 m. (Berm)
1.539
1.862
5.
339.00 m. (NSL)
1.581
6.
334.00 m. (Foundation)
1.729
2.125
7.
329.00 m. (Foundation)
1.748
2.144
8.
324.00 m. (Foundation)
1.819
2.255
9.
319.00 m. (Foundation)
1.838
2.287
1.0
176
1.936
1.5
Table 4.6
Minimum factors of safety obtained (U/S sudden draw down)
S.
No.
Circle
Elevations
Touching F.O.S.
With E.Q.
1.
373.00 m. (Berm)
1.506
2.
361.00 m. (Berm)
1.447
3.
356.50 m. (MDDL)
1.445
4.
349.00 m. (Berm)
1.358
5.
339.00 m. (NSL)
1.341
6.
334.00 m. (Foundation)
1.481
7.
329.00 m. (Foundation)
1.555
8.
324.00 m. (Foundation)
1.616
9.
319.00 m. (Foundation)
1.658
Required as per
B.I.S.
1.3
Table 4.7
Minimum factors of safety obtained (D/S steady seepage)
S.
Circle
No. Elevations.
Touching F.O.S
With E.Q
Required F.O.S
Required
as
per Without as
per
B.I.S.
E.Q
B.I.S.
1.
373.00 m. (Berm)
1.606
1.749
2.
361.00 m. (Berm)
1.498
1.710
3.
349.00 m. (Berm)
1.498
1.649
4.
346.80 m. (TWL)
1.491
1.645
5.
339.00 m. (NSL)
1.441
6.
334.00 m. (Foundation)
1.556
1.750
7.
329.00 m. (Foundation)
1.544
1.753
8.
324.00 m. (Foundation)
1.473
1.674
9.
319.00 m. (Foundation)
1.473
1.706
1.0
177
1.609
1.5
Table 4.8
Minimum factors of safety obtained (D/S sudden drawdown)
4.3.1.4
S. Circle Touching Elevations
No.
F.O.S
With E.Q
1.
373.00 m. (Berm)
1.749
2.
361.00 m. (Berm)
1.710
3.
349.00 m. (Berm)
1.649
4.
346.80 m. (TWL)
1.645
5.
339.00 m. (NSL)
1.597
6.
334.00 m. (Foundation)
1.711
7.
329.00 m. (Foundation)
1.633
8.
324.00 m. (Foundation)
1.560
9.
319.00 m. (Foundation)
1.574
Required
as
per
B.I.S.
1.3
Zoning of Dam Section
The dam section comprises of 5 kinds of material viz.
embankment material, sand drains, filter (Sand layer & crushed stone layer),
compacted rockfill in rock toe and dumped riprap. At the time of construction,
material excavated from the gravity dam foundation, if found suitable, could be
used for rip rap/ filter.
The embankment material should be compacted to an average
density of 100% of the standard proctor density subject to a minimum density
of 98% of proctor density.
The material to be used for different parts of the dam section
would have to be finalized after assuring their strength parameters and
gradation of the materials at the pre-construction stage.
178
4.3.1.5
Protection of Slopes of Dam Section
Upstream Slope Protection
The upstream slope protection has been ensured by providing
riprap. A 600 mm thick dumped riprap over 400 mm thick filter layer (200 mm
thick stone aggregate +200 mm thick sand) have been provided up to the top of
dam. The riprap consists of angular rock fragments with 80% fragments
heavier than 50 Kg. In the remaining 20% not more than 50% fragments shall
be smaller than 75 mm in the minimum dimension. However, this will be
finalized after detailed survey prior to construction stage
Downstream Slope Protection
The downstream slope protection is ensured by providing and
turfing and suitable surface drainage. Provision of turfing is a standard practice
to protect the downstream slope from rain cuts. Turfing has been proposed on
the entire downstream slope from top to toe.
Surface drainage
For surface drainage of the downstream slope of the earth dam, a
system of open paved drains (chutes) along the sloping surface terminating in
the longitudinal collecting drains at the junction of berm and slope have been
provided at 50 m c/c to collect and drain out the rain water. The section of
precast drain is rectangular in shape having depth of 15 cm. From longitudinal
collecting drain, the rain water is carried through 15-cm diameter pipes placed
at 25 m c/c into paved chutes on the d/s slope. The open paved drains (chutes)
terminate in the downstream toe drain.
The surface drainage arrangement is presented in Drawing No.
KBL- 8100-P-1612 given at Plate No. 4.1.13 in Volume - V (Part-2).
4.3.1.6
Internal drainage system
The Vertical filter (Chimney filter), Horizontal filter, Rock toe and
Toe drain have been provided as a part of internal drainage arrangement of the
embankment dam.
179
As far as possible locally available sand, gravel, rock etc have
been proposed for the internal drainage system. The vertical filter is provided
just on downstream side of the core to arrest the phreatic line. Its thickness is
kept as 3.0 m (1 m thick sand+1 m thick gravel+1 m thick sand). In
conjunction with vertical filter a 1.7 m thick horizontal filter has been provided
to collect seepage from vertical filter & foundation, and carries to the rock toe
& toe drain. The standard filter criterion between filter and adjoining soil
(casing or foundation) should be satisfied. In case where the head of water is 3
m or less it is not required to provide chimney filter or horizontal filter. For
protection from Tail Water Level (TWL), toe protection in the form of rock toe
has been provided. The height of rock toe is generally provided as 0.2 H, where
H is the height of embankment. However, height of rock toe has been kept as
10.0 m (max). Rock toe is not necessary where height of embankment is 3 m or
less. The toe drain is provided at the downstream toe of the earth dam to collect
seepage from horizontal filter, rock toe & through foundation and to discharge
it away from the dam by suitable surface or sub surface drains. The section of
toe drain has been designed to carry seepage. The bed of toe drain has been
given a suitable slope to lead the seepage to natural drains. Depth of toe drain
is usually provided as 1.5 m with bottom width of 1 m minimum and side
slopes of 1:1. The internal drainage arrangement has been worked out on the
basis of provisions given in IS: 9429-1980.
4.3.1.7
Filter
The filter should have an average relative density of 75% with a
minimum acceptable relative density of 70%. The filter material shall satisfy
the following criteria:
D15 of Filter material
<5
D15 of base material
D15 of filter material
<5
D85 of base material
180
Where D15 and D85 are 15% and 85% finer material by weight.
Further the grain size curve of the filter material will be parallel to that of the
base material. The maximum particle size of the filter material shall not be
more than 75 mm and it should not contain more that 5% of the material finer
than 0.074 mm (200 mm Sieve).
4.3.1.8
Cut-off trench (COT)
The design of cut-off trench has been done as per the guidelines of
IS: 8414 -1977, taking into account the result of detailed geological
investigations. COT has been keyed 1.0 m into continuous impervious stratum/
fresh rock and a minimum bottom width 6.0 m has been provided. The
centerline of COT has been kept H/3 from the axis of the dam where ‘H’ is the
depth of water from FRL to bottom of COT. A minimum side slope of 1:1 has
been provided in the case of over burden and 1/2:1 and 1/4:1 in the case of soft
rock and hard rock respectively. The back fill material for cut off trench have
the same properties as those specified for impervious core.
4.3.1.9
Foundation Treatment
The foundation treatment has been decided based on the
geological interpretation carried out from the data of drill holes and other
investigations. To control the under seepage, grout curtain in three rows
staggered at 3 m centre to centre up to a depth half of the hydraulic head
measured above the base of the cut-off trench up to FRL has been provided.
The minimum depth of curtain grouting has been kept as 8 m. In addition,
peripheral grouting would be carried out at FRL at the time of pre
construction/construction. Tests would be undertaken to ensure that the postgrouting permeability shall not be less than 5 lugeons.
The foundation treatment of the right and left abutment is based
on limited investigation carried out at DPR stage. Detailed investigation would
have to be carried out at pre construction stage for evolving treatments to
control seepage through the abutment.
181
The foundation treatment details presented in Drawing No KBL8100-P-1608 are given as Plate No. 4.1.14 in Volume - V (Part-2).
4.3.2
Concrete dam, Non-overflow section - design crieria, Stability
analysis,
4.3.2.1
Spillway section - design criteria Concrete dam
A concrete dam (OF section & NOF section) of maximum height
51.00 m and 487 m length is proposed across river Orr near village Didauni on
the border of Shivpuri and Ashok Nagar Districts in Madhya Pradesh.
Out of the total length of 487 m, 240 m length consists of NOF
Blocks in which 140.0 m long NOF section is on the left side and 100.0 m long
NOF section is on the right side of the spillway blocks. The OF section has a
length of 247.0 m (12 bays of 15.0 m length with a bay of 7.5 m each on both
ends and 13 piers of 4.0 m width) which has been proportioned to pass a peak
flood of 12067.67 cumecs (PMF).
4.3.2.2
Non over flow section - design criteria
The stability analysis for non overflow section has been done at
the deepest foundation level i.e. 333.00 m as per IS-6512-1984 for all the seven
load combinations i.e.
i) A (construction condition),
ii) B (Normal Operating Condition),
iii) C (Flood Discharge Condition),
iv) D (Combination A with earthquake),
v) E (Combination B with earthquake but no ice).
vi) F (Combination C but with extreme uplift drains inoperative) and
vii) G (combination E but with extreme uplift drains inoperative).
The stresses obtained in all above mentioned conditions are
compressive and the factor of safety against sliding is more than 1 as per IS:
6512-1984.
182
The following data have been adopted for the design of Non
Overflow (NOF) sections:
a) Maximum water Level (MWL)
= 380.408 m
b) Full Reservoir Level (FWL)
= 380.000 m
c) Maximum Tail Water Level (Max. TWL)
= 346.800 m
d) Minimum Tail water Level (Min. TWL)
= 333.000 m
e) Silt Level
= 353.530 m
f) Top width of dam
= 8.0 m
g) U/S slope (H: 1)
= 0.100
h) Horizontal seismic coefficient
=0.051g
i) Vertical seismic coefficient
=0.041g
j) D/S slope
= 0.85
k) Cohesion of Dam & rock interface
=50.0 t/m2
l) Angle of internal friction of dam & rock interface
=350
m) Width and height of foundation gallery
=2.5 m x 2.5 m
The proposed Lower Orr dam falls in zone II, that has low
seismicity as per IS: 1893-1984 “Criteria for earthquake resistant design of
structure”. The value of horizontal and vertical seismic coefficients, (as
approved by NCSDP) adopted are 0.051g & 0.041g respectively.
The cohesion and angle of internal friction of the concrete rock
interface has been taken as 50 t/m2 and 350 respectively.
The maximum non-over flow section, zoning of material (NOF)
section and water Stop details of NOF section as furnished in Drawing Nos.
KBL-8200-P-1701, KBL-8200-P-1702 and KBL-8200-P-1703 are given as
Plates Nos. 4.1.15, 4.1.16 and 4.1.17 in Volume - V (Part-2) respectively.
The stability analysis of the NOF section is furnished
at Annexure 4.3 in Volume – II.
183
4.3.2.3
Over flow section
The overflow section has been sized to pass peak flood of
12067.67 cumecs (PMF) keeping crest level at El. 370.00 m and maximum
water level at El. 380.408 m. An upstream slope of 1H: 3V has been provided
from El. 368.619 m to 344.619 m and from El. 344.619 m up to foundation
level a slope of 1H:2V has been provided. The crest shape, discharge
coefficients and d/s water surface and water nappe profiles have been worked
out as per relevant IS Codes.
The stability analysis for OVERFLOW section has also been done
at the deepest foundation level i.e. 333.0 m as per IS: 6512-1984 for all the
seven load combination as mentioned above.
The data used for design is as given below:
Radial gate Trunion (C.L) elevation level
= 372.96 m
Bridge weight
= 15 t/m
Top width
= 8.0 m
Width of block
= 19.0 m
Elevation of T.P. (D/s)
= 361.213 m
Top Bridge level
= 384.0 m
Cm
= 0.630
Top of crest
= 370.00 m
The stresses obtained in all seven loading conditions are
compressive and the factor of safety against sliding are more than 1 as per IS:
6512-1984.
The maximum over flow section, zoning of material (OF) section
and water Stop details of OF section as furnished in Drawing Nos. KBL-8200P-1704, KBL-8200-P-1705 and KBL-8200-P-1706 are given as Plates Nos.
4.1.18, 4.1.19 and 4.1.20 in Volume - V (Part-2) respectively.
The Stability analysis of the OF section is furnished
at Annexure 4.4 in Volume – II.
184
The Plan and upstream elevation of concrete dam furnished in
Drawing No. KBL-8200-P-1707 is given as Plate No. 4.1.21 in Volume - V
(Part-2).
4.3.2.4
Foundation treatment and seepage control
The following provisions have been made for foundation
treatment and seepage control:
(a) Consolidation grouting has been proposed throughout the base
of the dam foundation. Six metre deep holes at 3000 mm spacing, staggered
both ways to be drilled and grouted under low pressure. The consolidation
grouting is expected to increase the foundation properties.
(b) Curtain grouting has been proposed through foundation gallery
as a part of seepage control measure. Holes having a depth of (2/3H+8) m,
where H is the height of reservoir at hole location. The holes will be drilled and
grouted under pressure. The curtain grouting holes are proposed to be spaced at
2000 mm c/c.
(c) Drainage holes have been proposed to arrest seepage water and
reduce uplift pressure. These holes will be drilled to a depth of 75 % of the
depth of curtain grout holes at a spacing of 3000 mm c/c.
The foundation grouting and drainage details furnished in
Drawing No. KBL-8200-P-1708 is given at Plate No. 4.1.22 in Volume - V
(Part-2).
4.3.2.5
Energy Dissipation Arrangement (EDA)
Stilling basin has been provided for dissipation of the energy of
the outflow. The proposed stilling basin with top at EL 335.0 m is 50 m long.
Chute blocks and end sill (dentated) have been provided in accordance with
codal provisions. The performance of the proposed EDA has to be checked
through model studies during pre-construction stage.
The stilling basin details furnished in Drawing No. KBL-8200-P1709 is given at Plate No. 4.1.23. in Volume - V (Part-2).
185
4.3.3
Opening through dam
Three sluices in the spillway portion have been provided for

Meeting the water requirements of the downstream areas.

Emergency depletion of reservoir
Each sluice has a size of 5.0 m (H) x 3.0 m (W). These sluices are
proposed to be provided in spillway block numbers 16, 17 & 18. The invert
level of the sluices has been kept at EL 340.00 m. Radial gates have been
proposed for controlling the flow through these sluices. The description of
various gates is as follows:
4.3.4
Gates, types of gates and hoist bridge and stop logs Spillway
Radial Gates
12 no. spillway Radial Gates of size 15000 mm X 10000 mm will
be provided to control the flow of spillway. These gates shall be operated by
downstream twin cylinder Hydraulic Hoists.
The gate shall consist of curved skin plate stiffened by vertical
stiffeners. The vertical stiffeners shall be supported by three (3 Nos.)
Horizontal girders. The load from horizontal girders shall be transmitted to
trunnion by three radial arms on each side of gate. Corbel type of arrangement
is proposed where the load from trunnion shall be further transferred to
concrete. The trunnion support structure of the gate would be above the water
profile. Thrust block/Tie Beam shall be provided to transfer the lateral load of
radial arms. Suitable bracings shall be provided for Horizontal girder and arms.
The Radial gate shall be designed in accordance with the
provision of IS: 4623 (latest revision) in general. The gate shall be designed for
a total head of 10.37 m corresponding to FRL of EL 380.00 m. The radial gate
shall be operated with the help of Twin cylinder hydraulic hoist with minimum
hoist capacity of 140 T (approx.). The Hoist cylinders shall be pivoted on the
Hoist Support structure mounted on the pier. The power pack shall be installed
on the top of the pier. Each gate shall have individual Power Pack. Operating
186
speed shall be approx. 0.65 m/min. the design of Hydraulic Hoist components
shall conform to IS: 10210. However, provision shall be made to operate the
adjacent hoists in case of emergency.
The sill level of gate shall be 369.628 m and trunnion shall be
installed at 373.33 m. The radius of gate leaf shall be kept as 11.5 m. Bottom
seal of gate shall be provided as wedge type. The side seals shall be of Z type
and will move on curved seal seat.
The general assembly of Radial gate has been shown in Drawing
No. KBL-8200-P-1501 & KBL-8200-P-1502 are given at Plate No. 4.1.24 &
4.1.25 respectively in Volume - V (Part-2).
4.3.4.1
Spillway Stoplogs
One set of stoplogs for opening size of 1000 mm X 10482 mm
shall be provided to carry out the maintenance of spillway Radial Gate. Each
set of stoplogs shall consist of Nine units of 15000 mm X 1250 mm. Bottom
Unit shall be non interchangeable type. All other units shall be interchangeable.
The stoplogs shall be operated under balanced water head condition except top
most unit which shall be lifted under unbalanced water head condition for one
gate unit height water head.
Downstream skin plate and downstream sealing shall be provided.
Wedge type bottom seal and solid bulb type side seals shall be provided to
make the gate water tight. The stoplogs shall be operated by gantry crane
moving on the bridge. The stoplogs shall be connected to gantry crane through
Lifting Beam and Ramshorn Hook.
The general assembly of stoplog gate has been shown in Drawing
No. KBL-8200-P-1503 is given as Plate No.4.1.26 in Volume - V (Part-2).
4.3.4.2
Gantry Crane
The spillway stoplogs shall be operated by moving Gantry Crane.
The capacity of gantry crane shall be 30 T (approx.). The Gantry Crane shall
have hoist machinery mounted on trolley. The trolley shall be of moving type.
187
The crane structure along with trolley shall be capable of moving in
longitudinal direction with the help of LT travel mechanism. Suitable counter
weight shall be provided to make the crane stable for different stability
conditions. The crane shall be designed as per IS: 3177 and IS: 807.
The general assembly of Gantry Crane has been shown in
Drawing No. KBL-8200-P-1504 is given as Plate No. 4.1.27 in Volume - V
(Part-2).
The salient details of spillway gates, stoplogs and Gantry crane of
the Lower Orr dam are given at Annexure 4.5 in Volume – II.
4.4
Lower Orr Canal
4.4.1
Description of canal system including ridge/contour/lift canal
capacity and considerations for fixing alignment etc.
The Lower Orr main canal takes off from the left bank of the
proposed Lower Orr dam. The canal has been aligned as a contour canal. The
alignment of the canal has been proposed on the basis of survey data. It is
mentioned that the canal alignment is tentative and shall be optimized at the
time of construction stage planning.
4.4.1.1
Bed slope and side slopes
The canal is designed as contour canal with a bed slope of 1 in
9000 in reaches from RD 0 M to RD 61650 M, 1 in 7500 in reaches from RD
61650 M to RD 80850 M & 1 in 6000 in reaches from RD 80850 M to RD
91260 M. It has been tried to optimize the cutting and filling, through the
proposed alignment. The side slope in whole canal has kept 1:1.5. Contour plan
and longitudinal section of Lower Orr canal from RD 0.00 km to RD 91.26 km
is given in the Plate Nos. 4.1.28 (1/92) to 4.1.119 (92/92) in Volume – V
(Part -2 & 3).
4.4.1.2
Canal Section
Typical sections of the Lower Orr main canal have been shown in
Drawing No. KBL – 7730 – P – 1160 & KBL – 7730 – P - 1161 are given at
188
Plate No. 4.1.120 & 4.1.121 in Volume - V (Part-3) respectively. Drainage
arrangement of the lined canal is shown in Drawing No. KBL–7730–P–1164 is
given at Plate No. 4.1.122 in Volume - V (Part-3).
Free board
The free board has been taken as 0.75 m throughout in the canal.
4.4.2
Study of integrated network of canal system and its operation
to utilize the water potential of streams crossed by main canal
system by provision of storage/tail tank etc.
Detailed study of integrated network of canal system will be taken
up at pre construction stage.
4.4.3
Description of soil profile along the canal and canal alignment
based on pit/auger holes.
Study of soil profile along the canal through trial pits and auger
holes would be taken up at pre construction stage. It is assumed that expansive
soil conditions are not met within canal alignment. However if such conditions
are found to exist at any location along the canal alignment, suitable CNS layer
shall be provided below canal lining as per codal provisions.
4.4.4
Details of lining if provided
The canal is proposed to be lined with 75 mm thick unreinforced
concrete lining of M15 grade. There is a curvature provided with curvature
angle of 34 degree at the junction of side slope and canal bed. 400 micron
HDPE is also proposed to be provided below the lining.
4.4.5
Transmission losses assumed for lined/unlined channel with
justification for (cumec/million sq.m)
As provided in IS: 4745-1964 transmission losses at 0.6
cumec/million sq m of wetted perimeter are to be considered in the canal.
However, there is no committed transfer of water from the project except for
189
irrigation use under the Lower Orr project command. As such, transmission
losses which form part of the conveyance losses are accounted for in the
overall irrigation efficiency considered while working out monthly crop water
requirement for the proposed cropping pattern.
4.4.6
Cut- off statement showing the details of the discharge
required from tail to the head considering the irrigation
requirement and transmission losses in taking off canal
The location of branch canals off taking from the Lower Orr canal
will be finalised at pre construction stage. Based on Irrigation requirement in
the command area under the canal, the reachwise design discharge is
computed.
4.4.7
Design calculations for adequacy of canal sections adopted
Considering the discharge requirements at various reaches of the
canal, the sections adopted for the Lower Orr main canal are furnished
at Table-4.9.
Table 4.9
Sections adopted for Lower Orr canal
S.
No.
1
2
3
4
5
6
Reach (m)
From
0
32580
61560
74220
80850
90360
To
32580
61560
74220
80850
90360
91260
Bed width
(m)
5
5
5
5
4
3
Depth
(m)
3.06
2.92
2.58
2.14
2.12
1.70
Velocity
(m/sec)
0.917
0.894
0.911
0.823
0.893
0.764
Discharge
(cumec)
31.988
28.970
24.392
16.689
15.965
8.474
The reachwise designed parameters of the canal are furnished at
Annexure 4.6 in Volume – II.
190
4.4.8
Design discharge data (irrigation requirement etc.)
The monthwise irrigation and domestic water requirement for the
command area under the Lower Orr canal considered for the design of the
canal is furnished in the Table 4.10.
Table 4.10
Monthly irrigation and domestic water requirement in Lower Orr canal
Month
Water requirement under the Lower Orr canal (MCM)
Irrigation
Drinking water
Total
June
36.966
0.5
37.466
July
11.912
0.5
12.412
August
12.978
0.5
13.478
September
35.504
0.5
36.004
October
33.010
0.5
33.510
November
35.984
0.5
36.484
December
28.937
0.5
29.437
January
37.632
0.5
38.132
February
47.621
0.5
48.121
March
26.801
0.5
27.301
April
2.697
0.5
3.197
May
21.631
0.5
22.131
Total
329.67
6.0
335.673
It could be seen that the peak demand of 48.121 MCM occurs in
February. Considering 20 days of canal supply in a month and adding 10%
extra discharge for rush irrigation etc., the discharge required at the head of the
canal works out to about 31.80 cumec.
191
4.4.9
Canal structures (Cross drainage works/regulators etc.)
Cross communication i.e. bridges have been provided along the
alignment of the canal. Further since the canal are proposed as contour canal,
the canal shall have to cross a number of drains. Suitable CD works have been
proposed as indicated in the longitudinal section of the canal and their probable
head losses are also accounted for.
4.4.9.1
Bridges
Bridges shall be provided at suitable location along the canal
alignment. Since the Maximum bed width of canal is only 5 m, slab type bridge
by keeping the bed width of the canal and fluming the canal sides from sloping
to vertical, is proposed.
4.4.9.2
Aqueduct/Drainage syphon
Where the canals are passing above the big drains and suitable
freeboard between FSL and lower level of canal duct bottom slab is available,
Canal Aqueduct / Drainage syphon structure has been proposed. A typical
drawing of Marahi nalla drainage syphon at RD 12.930 km as shown in
Drawing No. KBL – 7730 – P – 1162 is given at Plate No. 4.1.123 in Volume V (Part-3) and typical drawing of canal aqueduct as shown in drawing No.
KBL – 7730 – P – 1163 is given at Plate No. 4.1.124 in Volume - V (Part-3).
Other type of cross drainage works viz. Drainage Syphon or Level
crossing are also required along the canal alignment. However this shall be
required to be reviewed at construction stage planning. The details of Main
CD structure along the lower Orr Main Canal is enclosed at Annexure 4.7 in
Volume – II. The typical design of Aqueduct & drainage siphon are annexed
at Annexure 4.8 in Volume – II. A list of CD works encountered across the
Lower Orr canal is annexed at Annexure 4.9 in Volume – II.
4.4.9.3
Falls
There are 11 nos. of falls (Unflumed Straight glacis non meter
Fall) between RD 73890 m to 80160 m. Depth of falls varies from 1.25 m to
192
3.05 m. The list of falls provided across the Lower Orr canal is furnished in
Table 4.11. A typical drawing of canal fall at RD 75810 m is shown in drawing
no. KBL-7730-P-1159 and given at Plate No. 4.1.125 in Volume – V
(Part – 3).
Table – 4.11
List of falls across Lower Orr canal
S.
RD (m) Fall depth Type of Fall
No.
(m)
1
73890
2.01
Unflumed Straight Glacis Non meter Fall
2
74520
3.04
Unflumed Straight Glacis Non meter Fall
3
74890
2.50
Unflumed Straight Glacis Non meter Fall
4
75810
3.05
Unflumed Straight Glacis Non meter Fall
5
76080
2.55
Unflumed Straight Glacis Non meter Fall
6
77280
2.52
Unflumed Straight Glacis Non meter Fall
7
78000
2.53
Unflumed Straight Glacis Non meter Fall
8
78840
2.62
Unflumed Straight Glacis Non meter Fall
9
79110
3.05
Unflumed Straight Glacis Non meter Fall
10
79920
3.08
Unflumed Straight Glacis Non meter Fall
11
80160
1.25
Unflumed Straight Glacis Non meter Fall
The design details of a sample fall (at RD 75810 m) are furnished
at Annexure- 4.10 in Volume – II.
4.4.9.4
Head regulators
A head regulator along with single lane slab bridge is provided at
the out lets of left bank Lower Orr main canal. The head regulators are
designed to pass design discharge at MDDL of dam. Some surplus capacity to
193
cater to the increase in demand of irrigation at a later stage has also been
provided.
4.5
Barrages
As discussed earlier, four barrages are proposed under Ken-Betwa
Link Project (Phase-II) viz. Neemkheda barrage on Betwa river, Barari barrage
on Betwa river, Kesari barrage on Keoton, a tributary of Betwa and Kotha
barrage on Betwa river. The design particulars of these four barrages are
discussed in the following paragraphs.
4.5.1
Neemkheda barrage
The Neemkheda barrage envisages construction of a 10.65 m high
barrage with 200 m long water way across the river Betwa with a pond level of
426.0 m. The proposed site is located near village Neemkheda which lies on
Bhopal-Raisen road, about 30 km from Bhopal, in district Raisen at 23 016’40”
N latitude and 770 40’ 49” E longitude (SOI Toposheet No. 55E/11) to
facilitate irrigation in the proposed 3066 ha of command area.
Following design flood Values have been considered for design:
S. No.
Return Period
Flood Value (cumec)
1
20 yr
3133.00
2
50 yr
3978.19
3
100 yr
4668.44
4
200 yr
5408.80 say 5410
5
500 yr
6472.60
Considering the importance of Barrage, 1 in 200 yr flood has been
used for the design of various components of Barrage i.e. Stilling basin
dimensions etc. except freeboard.
194
4.5.1.1
Sediment data
No sediment data is available at the barrage site. However Silt
Factor value is required to access the depth of scour. In the present case as the
barrage is founded on good quality rock, scour is not critical design issue.
However to be on conservative side, a value of 1 has been assumed for the
design calculations.
4.5.1.2
Assumed retrogression at maximum and minimum discharges
Following retrogression values have been assumed to consider
retrogressed level.
S. No.
Discharge (cumec)
Retrogression (m)
1
Low flood
1.5
2
5410 (1 in 200 yr- Designed flood)
0.5
The provided water way has been checked for to pass the designed
discharge, for the assumed crest level & assumed afflux. In this barrage the
crest level has been assumed 1.50 m higher than average floor level which is
416.20 m & assumed afflux is 0.60 m.
4.5.1.3
Scour depth
The scour holes may occur both U/s & D/s so that cut offs are
required in the U/s & D/s end of the floor to prevent failure by slipping of the
soil into the scour holes by simple earth pressure. The value of scour in U/s &
D/s has been taken R & 1.5 R respectively.
4.5.1.4
Exit gradient value
The exit gradient is very important aspect to be considered for a
safe design. It depends on the head of water at the point of consideration,
length of barrage section and depth of downstream cut off. In this case the exit
gradient has been taken as 1/6. The total floor length of barrage has been
195
checked against exit gradient i.e. provided length is greater than required, so
barrage is safe against exit gradient.
4.5.1.5
Barrage design details
4.5.1.5.1
Waterway and HFL
Eight number bays are provided each with 10 m clear waterway.
The crest level for all the bays is kept at EL 421.25 m to have better control
over sedimentation. The waterway provided is checked for 1 in 200 year design
flood (5410 cumec). For determination of u/s affluxed HFL, it is assumed that
all the gates are fully open and discharge coefficient (Cd) is based on
Mallikpur curves as per drowning ratio. D/s HFL corresponding to water level
against Maximum design flood is considered. It is assumed that designed
discharge will pass through barrage. The total length provided between left
abutment & right abutment is 200 m against the width between banks 203.2 m.
4.5.1.5.2
Piers
Total 9 nos. of piers are provided in barrage out of which 1 nos.
are double pier. The thickness of single pier is 2.0 m & thickness of double
piers are 4.0 m. The length of piers from U/s to D/s upto end of Floor i.e.
50.230 m up to the length of floor. The top thickness of abutment has been
fixed same as thickness of pier i.e. 1.6 m & side slope 0.7:1.
4.5.1.5.3
Crest width & level
Width of crest t=√H +√h where H is the height of barrage & h is
depth of water over crest. T has a minimum value of 3h/2w1 where w is the
density of concrete. The crest level of spillway of barrage is kept generally 1.0
to 1.5 m above the average u/s floor level. In this barrage the crest width is kept
5.0 m & crest level is kept 1.0 m above the u/s floor level.
4.5.1.5.4
R.C.C. Raft
A 3.0 m thick combined RCC Raft (M-30) has been provided
throughout the length of barrage. The thickness of raft will increase up to 4.5 m
below foundation of piers as well as in abutments. 50 mm thick construction
196
joints have been provided throughout the raft after every 3 bays where double
pier is provided.
The Hydraulic design of the barrage is given at Annexure 4.11 in
Volume – II. The General Layout Plan (KBL-7730-P-1151) and Detailed
layout Plan (KBL-7730-P-1152) are given at Plates No. 4.2.1 and 4.2.2 in
Volume - V (Part-3) respectively.
4.5.1.6
Type (concrete/masonry)/profile cut off, upstream and
downstream aprons, uplift pressure relief arrangements etc.
4.5.1.6.1
Cut off
The U/s cut off is provided at EL 405.0 m which is 9.70 m below
U/s floor & D/s cut off is provided at EL 397.0 m which is 15.0 m below the
cistern level.
4.5.1.6.2
Aprons and protection works
Since rock is available at shallow depth, scouring is not
anticipated and therefore flexible protection work provided on the basis of
scour depth is not warranted. However, flexible protection works in the form of
CC blocks and launching apron is proposed at downstream as well as at
upstream as shown in the Plate No.4.2.2 in Volume - V (Part-3) for required
nominal distance. The extent and other details of flexible protection work may
be finalized as per site conditions at the time of construction stage planning.
Minimum weight of stone to be used in protection work should be
such as to resist a flow velocity of 5 m/s or 50 kg whichever is more. If found
economical, wire crates may also be used in place of stones. The Block
protection in U/s is provided in 13 nos. of rows of C.C. block size 1.5x1.5x0.9
m in 19.50 m length over 0.6 m thick loose stone apron & launching apron 1.5
m thick up to 20 m. The Block protection in D/s is provided in 20 nos. of rows
of C.C. block size 1.5x1.5x0.9 m over 0.6 m thick inverted filter in 34.43 m
length & launching apron 1.5 m thick up to 29.4 m with 0.5 m thick two nos.
curtain wall.
197
4.5.1.6.3
Energy Dissipation Arrangement
To dissipate the energy of water coming out from the barrage
spillway, a stilling basin type arrangement has been proposed so that it may not
cause excessive scour immediately downstream of barrage. The level and
length of stilling basin is so provided that the hydraulic jump formed under
various possible flow conditions is contained within the stilling basin. As per
design the length of cistern has been provided as 47.0 m and cistern level kept
at EL 412.00 m.
In this regard the following criteria is proposed:
The cistern level & length has been find out for the different flow
condition such as (i) At HFL (without concentration retrogression) (ii) At HFL
with 20% concentration & 0.5 m retrogression (iii) At pond level (without
concentration retrogression) (iv) At pond level with 20% concentration & 0.5
m retrogression. The cistern level has been adopted as lowest & cistern length
will be maximum 5(D2-D1) in all above 4 flow condition.
The Longitudinal sectional details (KBL-7730-P-1153) and Cross
sectional details (KBL-7730-P-1154) of Neemkheda barrage are given as Plate
Nos. 4.2.3 and 4.2.4 in Volume - V (Part-3) respectively.
4.5.1.6.4
Seepage control
Since rock is available at shallow depth, the cutoffs may be taken
1 m into good quality rock. To relieve the seepage pressure built up underneath
the floor, 75 mm dia. drainage pipes 4.5 m deep and 3 m c/c (two rows per bay)
shall be provided in the sloping glacis. As the river bed is rocky, seepage may
not pose much problem, provided presence of impermeable rock is confirmed
by further exploration at the construction stage. However for preliminary
design, upstream and downstream RCC cutoffs are provided. Some curtain
grouting at upstream and drainage arrangement for the stilling basin may also
be required which may be finalized at the construction stage.
198
4.5.1.6.5
Special features of the barrage
In view of the hard strata available at shallow depth, the thickness
gravity type floors too much so throughout RCC raft with piers & abutment are
proposed. The double piers shall be provided after each 3 bays with 50 mm
thick construction joint separated by PVC seal conforming to IS: 12200.
To take care of high permeability of foundation material, it is
proposed to provide a drainage filter below the floor. Further 250 mm dia. half
round concrete pipes 3000 c/c in two rows in each bay shall be provided to
collect the seepage water from filter and the same shall be released from the
pipes provided through piers and cutoff.
Further 25 mm dia. rock anchors 4.5 m deep are also proposed to
take care of excess uplift. Their spacing is proposed tentatively as 3 m c/c
which is required to be revised at construction stage planning
Provision for grouting on upstream and downstream of barrage is
also made in the DPR. The details in this regard shall be finalized at the
construction stage planning.
At construction stage planning, it is recommended that bearing
capacity of the foundation may be verified by plate load test at most heavily
loaded location (below Abutment / central pier in zone where hydromechanical components are provided).
4.5.1.6.6
Materials used
Barrage bed is proposed as a RCC Raft having thickness
minimum 3.0 m and below piers / abutment raised up to 4.50 m with M30
concrete. Piers, Divide walls, Abutments and gantry cum Road Bridge are
proposed with M30 Grade concrete. Flared-out walls and CC blocks are
proposed with M15 grade plain unreinforced concrete. Skin reinforcement 16
mm dia. 200 c/c shall be provided at water surface with 75 mm clear cover.
150 mm lean concrete (M10 grade) shall be provided below Pier footings, raft
and other RCC work.
199
Fe 415 / 500 HYSD bars conforming to IS 1789 are proposed as
reinforcements.
4.5.1.7
Gates, types of gates and hoist bridge and stop logs
4.5.1.7.1
Spillway Fixed Wheel Vertical Lift Gates:
The Spillway of Neemkheda barrage shall be provided with 10
numbers fixed wheel vertical lift gates of size 18,000 mm X 4750 mm. Sill
level of the gate shall be EL 421.25 m. The gate shall be designed to Pond
Level of EL 426.00 and checked for HFL of EL 430.377 m (1 in 500 years).
The gate shall be provided with upstream skin plate and upstream
sealing to avoid silt on horizontal girders. Wedge type seal shall be provided
for bottom sealing and music note solid bulb seals shall be provided for side
sealing. The seal shall remain in contact with stainless steel seal seats to make
the gate water tight.
The gate structure shall consist of skin plate stiffened by vertical
stiffeners and horizontal girders. The horizontal girders shall be supported by
end vertical girders on each side. The water thrust will be transferred to
concrete structures from the end vertical girder through wheels and wheel
track. The wheels shall be mounted on self lubricating bush bearings. The
BHN of wheel track shall be 50 BHN higher than the wheel material. 20 mm
guide and two number guide shoes shall be provided on each side to guide the
gate in grooves.
The gates shall be operated by independent rope drum hoist of 100
T (approx.) capacity. The Rope Drum Hoist shall consist of hoist machinery
mounted on hoist support structure. Each hoist machinery will be equipped
with two rope-drums, gears, pinions, couplings, shafts, worm reducer, motor
and brakes. The hoist bridge shall be supported on trestles.
The maintenance of these gates are proposed to be carried out at
level EL 431.90 m. The gate shall be designed in accordance with the provision
200
of IS: 4622 (latest revision). The design of Rope Drum Hoist shall conform to
IS: 6938 (latest revision).
The general assembly of Fixed Wheel gate has been shown in
Drawing No. KBL-7730-P-1505 is given at Plate No. 4.2.5 in Volume - V
(Part-3).
4.5.1.7.2
Barrage Stoplogs
Stoplogs are proposed to carry out the maintenance of spillway
gates. One set of stoplogs of size 18000 mm X 1225 mm shall be provided.
The stoplogs shall be operated in balanced water head conditions. However,
the top most unit can be lifted under unbalanced water head for one unit height
water head. All units are interchangeable. The stoplogs shall be operated with
gantry crane. The stoplog units shall be stored in stoplog groove above HFL.
The stoplog units shall have bronze pad sliding on stainless steel track. 20 mm
guide shall also be provided to guide the stoplog units
The skin plate and sealing gate shall be kept d/s side.
The general assembly of Stoplog gate has been shown in Drawing
No. KBL-7730-P-1506 is given at Plate No. 4.2.6 in Volume - V (Part-3).
4.5.1.7.3
Gantry Crane
The Spillway Stoplogs shall be operated by moving Gantry Crane.
The tentative min. capacity of gantry crane shall be 30 T. The Gantry Crane
shall have hoist machinery mounted on trolley. The trolley shall be of moving
type. The crane structure along with trolley shall be capable of moving in
longitudinal direction with the help of LT travel mechanism. Suitable counter
weight shall be provided to make the crane stable for different stability
conditions. The crane shall be designed as per IS: 3177 and IS: 807.
The general assembly of Gantry Crane has been shown in
Drawing No. KBL-7730-P-1506 is given at Plate No. 4.2.6 in Volume - V
(Part-3).
201
The salient details of spillway gates, stoplogs and Gantry Crane of
the Neemkheda barrage are given at Annexure 4.12 in Volume – II.
4.5.1.8
Detail of spillway bridge, abutments etc.,
4.5.1.8.1
Road Bridge & Gantry Bridge
Pier & abutment top has been provided at EL 430.65 m in U/s and
430.05 m in D/s Which is 1.5 m above the U/s & D/s HFL level . A road cum
gantry bridge has been proposed with deck level at 432.15 m. This approach
bridge shall continue on either flank of the barrage. The bridge shall support
gantry crane provided for operation of stop logs and also the single lanes of
class ‘A vehicle loading with 55.4R loading. Trestles for operation of service
gates of barrage are provided at pier top level of 431.35 m.
4.5.1.8.2
Abutment
The top width of abutments is kept as 3.0 m and side slope is kept
as 0.7:1. The length of abutment in U/s & D/s up to end of Floor i.e. 82.60 m.
The return walls in the U/s & D/s is provided at the ends of both abutment on
both side with 0.7:1 slope. The purpose of return wall is for uniform flow & &
make connection between abutments & banks of river.
4.5.2
Barari barrage
Barari barrage has been proposed over River Betwa near village
Barrighat in Vidisha district of Madhya Pradesh at 23 040’30” N latitude and
77050’30” E longitude (SOI toposheet No. 55 E/14). Following data has been
adopted for the design of barrage:
1.
Maximum Observed Non Monsoon 25 year flood = 653 cumec
2.
Pond Level
= 407.72 m
3.
Average River Bed Level
= 400.00 m
4.
High Flood Level
= 412.90 m
5.
Standard Project Flood
=12283 cumec
6.
Silt Factor
= 1
202
The details of design of Barari barrage are given at Annexure 4.13
in Volume – II. The detailed layout plan of Barari barrage provided in Drawing
No. KBL-7230-D-2702 is given as Plate No. 4.3.1 in Volume - V (Part-3).
4.5.2.1
Sediment data
Sediment analysis has not been carried out at this stage. A silt factor of 1 is
adopted for the design of the barrage.
4.5.2.2
Assumed retrogression at maximum an minimum discharges
The d/s unretrogressed HFL is 412.90 m and an afflux of 0.07 m
is assumed initially.
4.5.2.3
Looseness factor
For the flood discharge estimated at the barrage site, the Laceys
water way is worked out as 535.3 m and the total water way provided is 440 m.
The looseness factor is worked out as 0.822.
4.5.2.4
Scour depth
With looseness factor less than one the scour depth is worked out
as 12.43 m where as with looseness factor more than one, the scour depth is
10.93 m. As such the scour depth is adopted as 12.43 m.
4.5.2.5
Intensity of discharge under design flood condition
The intensity of discharge under design flood condition is 30.51
cumec/m, against the total length of spillway bays of 250 m and the discharge
through spillway equal to 7628.2871 cumec. The discharge through under
sluice is 5182.54 cumec.
4.5.2.6
Co-efficient of discharge
The coefficient of discharge for the under sluices (drowned weir
formula) is 1.08 and drowning ratio is 0.99. The coefficient of discharge for
the spill way is 1.09.
203
4.5.2.7
Exit gradient value
The exit gradient shall be determined from accepted formulae and
curves. The factors of safety for exit gradient for different types of soils shall
be as follows:
a) Shingle
: 4 to 5,
b) Coarse sand : 5 to 6, and
C) Fine sand
: 6 to 7
The exit gradient value is worked out as 0.17465 or 1 in 5.7
4.5.2.8
Stress allowed
The residual stresses at various points from u/s sheet pile to d/s
sheet pile are 100% (at E1 – top of u/s sheet pile), 85.07% (at D1- bottom of
u/s sheet pile) , 80.81 (at C1 – top of u/s sheet pile – inside face), 29.82% (at
E2-top of d/s sheet pile – inside face), 20.69% (at D2-bottom of d/s sheet pile)
and 0% (at C2 – top of d/s sheet pile).
4.5.2.9
Type (concrete/Masonry)/profile cut off, upstream and
downstream aprons, uplift pressure relief arrangements etc.
Sheet pile cutoff is proposed for safe exit gradient. Various
components of the barrage e.g. raft, piers, flexible apron etc have been
designed by the relevant provisions of IS Codes. The L-section of Spillway and
Under sluice portion of the Barari barrage furnished in Drawing No. KBL7230-D-2703 is given as Plate No. 4.3.2 in Volume - V (Part-3).
4.5.2.10
Gates, types of gates and hoist bridge and stop logs
4.5.2.10.1
Spillway gates
The Spillway of Barari barrage shall be provided with 25 numbers
fixed wheel vertical lift gates of size 10000 mm X 3720 mm. Sill level of the
gate shall be EL 404.0 m. The gate shall be provided with upstream skin plate
and upstream sealings to avoid silt on horizontal girders. Wedge type seal shall
be provided for bottom sealing and music note solid bulb seals shall be
204
provided for side sealings. The seal shall remain in contact with stainless steel
seal seats to make the gate water tight. The gate structure shall consist of skin
plate stiffened by vertical stiffeners and horizontal girders. The horizontal
girders shall be supported by end vertical girders on each side. The water thrust
will be transferred to concrete structures from the end vertical girder through
wheels and wheel track. The wheels shall be mounted on self lubricating bush
bearings. The wheel shall be made up of corrosion resistant steel. The BHN of
wheel track shall be 50 BHN higher than the wheel material. 20 mm guide and
two number guide shoes shall be provided on each side to guide the gate in
grooves. The gates shall be operated by rope drum hoist of 25 t capacity. The
Rope Drum Hoist shall consist of hoist machinery mounted on hoist support
structure. Each hoist machinery will be equipped with two rope-drums, gears,
pinions, couplings, shafts, worm reducer, motor and brakes. The hoist bridge
shall be supported on trestles. Drawing showing Barari barrage spillway
vertical lift fixed wheel gate general installation (KBL-7230-P-1521) is given
as Plate No. 4.3.3 in Volume - V (Part-3).
4.5.2.10.2
Under Sluice Gates
The barrage shall be provided with 10 numbers under sluice gates
of size 10000 mm x 7720 mm. The sill level of gate shall be kept at EL 400.0
m. The gate shall be provided with upstream skin plate and upstream sealings
to avoid silt on horizontal girders. Wedge type seal shall be provided for
bottom sealing and music note solid bulb seals shall be provided for side
sealings. The seal shall remain in contact with stainless steel seal seats to make
the gate water tight. The skin plate of gate shall be stiffened by vertical
stiffeners and horizontal girders. Numbers of girders and their location shall be
optimized at design stage. The gate shall be operated by Rope Drum Hoist.
The hoist shall be capable of lifting the gate above groove for servicing of gate.
The hoist machinery shall be supported on hoist supporting structure. The gate
shall be regulating type and can be kept at desired level between sill and FRL.
Drawing showing under sluice gate (KBL-7230-P-1522) is appended as Plate
No. 4.3.4 in Volume - V (Part-3).
205
4.5.2.10.3
Stoplogs
Stoplogs are proposed to carry out the maintenance of spillway
gates and under sluice gates. Four sets of stoplogs of size 10000 mm X 1320
mm shall be provided. The stoplogs shall be operated in balanced water head
conditions. However, the top most unit can be lifted under unbalanced water
head for one unit height water head. The stoplogs shall be operated with
gantry crane. The stoplog units shall be stored in stoplog groove above MWL.
The stoplog units shall have bronze pad sliding on stainless steel track. 20 mm
guide shall also be provided to guide the stoplog units. The skin plate and
sealing gate shall be kept d/s side. Drawing showing spillway stoplog gate
(KBL-7230-P-1523) & under sluice stoplog gate (KBL-7230-P-1524) of Barari
barrage are appended as Plate No. 4.3.5 and 4.3.6 in Volume - V (Part-3)
respectively.
4.5.2.10.4
Gantry Crane
20 T gantry is planned to be provided to operate the stoplogs. The
gantry crane shall be centrally lifted. The crane shall move on gantry girders.
Walkway shall also be provided along the gantry girder. The gantry controls
shall be provided in operator cabin. The gantry shall be designed as per IS:
3177 and IS: 807.
4.5.2.11
Barari canal
The canal taking off from the barrage is from right bank only.
Initially the water will be lifted through a height of 21 m (static) over a length
of 4.0 km through a pipe line and there after it runs by gravity for 4.7 km. Due
to low discharge of diversion canal (5.72 cumec only) and lifting of water to
command, Head Regulator has not been proposed with barrage. If more
command or water is made available at a later stage due to change if any in
overall planning of the project, diversion arrangements may have to be
modified. The full supply depth of the canal in its head reach is 1.18 m and
FSL at head is 424.0 m. The bed slope adopted is 1 in 10000. Since the canal is
aligned as a ridge canal no CD/ CM works are proposed. The details of L
206
section of the canal and its cross section is illustrated in Drawings no. KBL7230-D-2705 to 2707 which are appended as Plate Nos. 4.3.7, 4.3.8 and 4.3.9
in Volume - V (Part-3) respectively.
4.5.3
Kesari barrage
Kesari Barrage has been proposed over River Keoton a tributary
of Betwa river at 24052’32” N latitude and 78001’34” E longitude (SOI
toposheet No. 55 I/1). Following data has been adopted for the design of
Barrage:
1.
Maximum Observed Non Monsoon 25 year flood = 109 cumec
2.
Pond Level
= 403.90 m
3.
Average River Bed Level
= 399.00 m
4.
High Flood Level
= 405.60 m
5.
Standard Project Flood
= 2772 cumec
6.
Silt Factor
= 1
The details of design of Kesari barrage are given at Annexure 4.14
in Volume – II. The detailed layout plan of Kesari barrage provided in Drawing
No. KBL-7230-D-2709 is given as Plate No. 4.4.1 in Volume - V (Part-3).
4.5.3.1
Sediment data
Since the catchment area of the Keoton at Kesari barrage site is
marginal no significant sediment flow is expected. A silt factor of 1 is adopted
for the design of the barrage.
4.5.3.2
Assumed retrogression
The d/s unretrogressed HFL is 405.60 m and an afflux of 0.4 m is
assumed initially.
207
4.5.3.3
Looseness factor
For the given flood discharge, the Laceys water way is worked out
as 254.3 m and the total water way provided is 181 m. The looseness factor is
worked out as 0.711.
4.5.3.4
Scour depth
With looseness factor less than one the scour depth is worked out
as 8.33 m where as with looseness factor more than one, the scour depth is 6.65
m. As such the scour depth is adopted as 8.33 m.
4.5.3.5
Intensity of discharge under design flood condition
The intensity of discharge under design flood condition is 14.74
cumec/m, against the total length of spillway bays of 100 m and the discharge
through spillway equal to 1474.17 cumec. The discharge through under sluice
is 1297.24 cumec.
4.5.3.6
Co-efficient of discharge
The coefficient of discharge for the under sluices (drowned weir
formula) is 1.36 and drowning ratio is 0.94. The coefficient of discharge for
the spill way is 1.47.
4.5.3.7
Exit gradient value
The exit gradient shall be determined from accepted formulae and
curves. The factors of safety for exit gradient for different types of soils shall
be as follows:
a) Shingle
: 4 to 5,
b) Coarse sand : 5 to 6, and
C) Fine sand
: 6 to 7.
The exit gradient value is worked out as 0.170148 or 1 in 5.9.
208
4.5.3.8
Stress allowed
The residual stresses at various points from u/s sheet pile to d/s
sheet pile are 100% (at E1 – top of u/s sheet pile ), 83.01% (at D1- bottom of
u/s sheet pile) , 81.23% (at C1 – top of u/s sheet pile – inside face), 36.46%
(at E2-top of d/s sheet pile – inside face), 25.05% (at D2-bottom of d/s sheet
pile) and 0% (at C2 – top of d/s sheet pile).
4.5.3.9
Type (concrete/Masonry)/profile cut off, upstream and
downstream aprons, uplift pressure relief arrangements etc.,
Sheet pile cutoff is proposed for safe exit gradient. Various
components of the barrage e.g. raft, piers, flexible apron etc. have been
designed by the relevant provisions of IS Codes. The L-section of Spillway and
Under sluice portion of the Kesari barrage furnished in Drawing No. KBL7230-D-2710 is given as Plate No. 4.4.2 in Volume - V (Part-3).
4.5.3.10
Gates, types of gates and hoist bridge and stop logs
4.5.3.10.1
Spillway gates
The Spillway of Kesari Barrage shall be provided with 10
numbers fixed wheel vertical lift gates of size 10,000 mm X 2400 mm. Sill
level of the gate shall be EL 401.50m. The gate shall be provided with
upstream skin plate and upstream sealings to avoid silt on horizontal girders.
Wedge type seal shall be provided for bottom sealing and music note solid bulb
seals shall be provided for side sealings. The seal shall remain in contact with
stainless steel seal seats to make the gate water tight. The gate structure shall
consist of skin plate stiffened by vertical stiffeners and horizontal girders. The
horizontal girders shall be supported by end vertical girders on each side. The
water thrust will be transferred to concrete structures from the end vertical
girder through wheels and wheel track. The wheels shall be mounted on self
lubricating bush bearings. The wheel shall be made up of corrosion resistant
steel. The BHN of wheel track shall be 50 BHN higher than the wheel
material. 20 mm guide and two number guide shoes shall be provided on each
side to guide the gate in grooves. The gates shall be operated by rope drum
209
hoist of 20 t capacity. The Rope Drum Hoist shall consist of hoist machinery
mounted on hoist support structure. Each hoist machinery will be equipped
with two rope-drums, gears, pinions, couplings, shafts, worm reducer, motor
and brakes. The hoist bridge shall be supported on trestles. Drawing showing
spillway vertical lift gates of Kesari barrage (KBL – 7230-P-1517) is appended
as Plate No. 4.4.3 in Volume - V (Part-3).
4.5.3.10.2
Under sluice gates
The Kesari barrage shall be provided with 5 numbers under sluice
gates of size 10000mm x 4900mm. The sill level of gate shall be kept at EL
399.00M. The gate shall be provided with upstream skin plate and upstream
sealings to avoid silt on horizontal girders. Wedge type seal shall be provided
for bottom sealing and music note solid bulb seals shall be provided for side
sealings. The seal shall remain in contact with stainless steel seal seats to make
the gate water tight. The skin plate of gate shall be stiffened by vertical
stiffeners and horizontal girders. Numbers of girders and their location shall be
optimized at design stage. The gate shall be operated by Rope Drum Hoist.
The hoist shall be capable of lifting the gate above groove for servicing of gate.
The hoist machinery shall be supported on hoist supporting structure. The gate
shall be regulating type and can be kept at desired level between sill and FRL.
Drawing showing under sluice gate of Kesari barrage (KBL-7230-P-1518) is
appended as Plate No. 4.4.4 in Volume - V (Part-3).
4.5.3.10.3
Stoplogs
Stoplogs are proposed to carry out the maintenance of spillway
gates and under sluice gates. Four sets of stoplogs of size 10000 mm X 1300
mm shall be provided. The stoplogs shall be operated in balanced water head
conditions. However, the top most unit can be lifted under unbalanced water
head for one unit height water head. The stoplogs shall be operated with
gantry crane. The stoplog units shall be stored in stoplog groove above MWL.
The stoplog units shall have bronze pad sliding on stainless steel track. 20mm
guide shall also be provided to guide the stoplog units. The skin plate and
210
sealing gate shall be kept d/s side. Drawing showing spillway stoplog gates
(KBL-7230-P-1519) & under sluice stoplog gates (KBL-7230-P-1520) of
Kesari barrage are appended as Plate Nos. 4.4.5 and 4.4.6 in Volume - V (Part3) respectively.
4.5.3.10.4
Gantry Crane
15 T gantry is planned to be provided to operate the stoplogs. The
gantry crane shall be centrally lifted. The crane shall move on gantry girders.
Walkway shall also be provided along the gantry girder. The gantry controls
shall be provided in operator cabin. The gantry shall be designed as per IS:
3177 and IS: 807.
4.5.3.11
Kesari canal
The canal taking off from the Kesari barrage is from right bank
only. Initially water will be lifted through a height of 8 m (static) over a length
of 2.9 km through a pipe line and there after it runs by gravity for 9.6 km Due
to low discharge of diversion canal (1.07 cumec only) and lifting of water to
command, Head Regulator has not been proposed with Barrage. If more
command or water is made available at a later stage due to change if any in
overall planning of the Project, diversion arrangements may have to be
modified. The full supply depth of the canal at its head is 1.16 m and FSL at
Head is 409.50 m. The bed slope adopted is 1 in 10000. Suitable CD/CM
works are proposed along the details of L-section of the canal and its cross
section is illustrated in Drawings no. KBL-7230-D-2720 to 2726 which are
appended as Plate Nos. 4.4.7 to 4.4.13 in Volume - V (Part-3) respectively.
4.5.4
Kotha barrage
The Kotha barrage envisages construction of a 13.50 m high and
with 576 m long barrage waterway across the river Betwa with a pond level of
396 m. The proposed site is located near village Kotha in tehsil Korwai,
district Vidisha at 24003’28” N latitude and 780 01’16” E longitude (SOI
Toposheet No. 54L/4) to facilitate irrigation in the proposed 17357 ha
command area.
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Following Design flood Values have been proposed for design:
S. No.
Return Period
Flood Value (cumec)
1
20 yr
9532.30
2
50 yr
12104.10
3
100 yr
14204.20
4
200 yr
16456.70
5
500 yr
19693.60
Considering the importance of barrage, 1 in 200 yr flood has been
used for the design of various components of barrage i.e. Stilling basin
dimensions etc. except freeboard.
4.5.4.1
Sediment data
No sediment data is available at the barrage site. However Silt
Factor value is required to access the depth of scour. In the present case as the
barrage is founded on good quality rock, Scour is not critical design issue.
However to be on conservative side, a value of 1 has been assumed for the
design calculations.
4.5.4.2
Assumed retrogression at maximum and minimum discharges
Following retrogression values have been assumed to consider
retrogressed level.
S. No.
Discharge (cumec)
Retrogression (m)
1
Low flood
1.5
2
16457 (1 in 200 yr- Designed flood)
0.5
The provided water way has been checked for to pass the designed
discharge, for the assumed crest level & assumed afflux. In this barrage the
crest level has been assumed 1.0 m higher than average floor level which is
384.59 m & assumed afflux is 1.50 m.
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4.5.4.3
Scour depth
The scour holes can be occur both U/s & D/s so that cut offs are
required in the U/s & D/s end of the floor to prevent failure by slipping of the
soil in to the scour holes by simple earth pressure. The value of scour in U/s &
D/s has been taken R & 1.5 R respectively.
4.5.4.4
Exit gradient value
The exit gradient is very important aspect to be considered for a
safe design. It depends on the head of water at the point of consideration,
length of barrage section and depth of downstream cut off. In this case the exit
gradient has been taken as 1/6. The total floor length of barrage has been
checked against exit gradient i.e. provided length is greater than required, so
barrage is safe against exit gradient.
4.5.4.5
Barrage design details
4.5.4.5.1
Waterway and HFL
32 number bays are provided each with 15 m clear waterway. The
crest level for all the bays is kept at EL 384.50 m to have better control over
sedimentation. The waterway provided is checked for 1 in 200 year design
flood (16457 cumec). For determination of u/s affluxed HFL, it is assumed
that all the gates are fully open and discharge coefficient (Cd) is based on
Mallikpur curves as per drowning ratio. For D/s HFL corresponding to water
level against Maximum design flood is considered. It is assumed that designed
discharge will pass through barrage. The total length provided between left
abutment & right abutment is 576 m against the width between banks of 579
m.
4.5.4.5.2
Piers
The total 32 nos. of piers are provided in barrage out of which 1
nos. are double pier. The thickness of single pier is 3.0 m & thickness of
double piers are 6.0 m. The length of piers from U/s to D/s up to end of Floor
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i.e. 50 m up to the length of floor. The top thickness of abutment has been
fixed same as thickness of pier i.e. 1.5 m & side slope 0.7:1.
4.5.4.5.3
Crest width & level
Width of crest t=√H +√h where H is the height of barrage & h is
depth of water over crest. T has a minimum value of 3h/2w1 where w is the
density of concrete. The crest level of spillway of barrage is kept generally 1.0
to 1.5 m above the average u/s floor level. In this barrage the crest width is kept
5.0 m & crest level is kept 1.0m above the u/s floor level.
4.5.4.5.4
R.C.C. Raft
3.0 m thick combined RCC Raft (M-30) has been provided
throughout the length of barrage. The thickness of raft will increase up to 4.5 m
below foundation of piers as well as in abutments. Construction joints of 50
mm thick have been provided throughout the raft after every 3 bays where
double pier is provided.
The Hydraulic design of the barrage is given at Annexure 4.15 in
Volume – II. The General Layout Plan (KBL-7730-P-1155) and Detailed
layout Plan (KBL-7730-P-1156) are given at Plate Nos. 4.5.1 and 4.5.2 in
Volume - V (Part-3) respectively.
4.5.4.6
Type (concrete/Masonry)/profile cut off, upstream and
downstream aprons, uplift pressure relief arrangements etc.
4.5.4.6.1
Cut off
The U/s cut off is provided at EL 376.0 m which is about 7.60 m
below U/s floor& D/s cut off is provided at EL 370.0 m which is 7.50 m below
the cistern level.
4.5.4.6.2
Aprons and protection works
Since rock is available at shallow depth, scouring is not
anticipated and therefore flexible protection work provided on the basis of
scour depth is not warranted. However, flexible protection works in the form of
CC blocks, and launching apron is proposed at downstream as well as at
214
upstream as shown in the relevant drawings for required nominal distance. The
extent and other details of flexible protection work may be finalized as per site
conditions at the time of construction stage planning
Minimum weight of stone to be used in protection work should be
such as to resist a flow velocity of 5 m/s or 50 kg whichever is more. If found
economical, wire crates may also be used in place of stones. The Block
protection in U/s is provided In 12 nos. of rows of C.C. block size 1.5x1.5x0.9
m over 0.6 m thick loose stone apron in 18.0 m length & launching apron 1.5m
thick up to 27.0 m. The Block protection in D/s is provided in 24 nos. of rows
of C.C. block size 1.5x1.5x0.9 m over 0.6 m thick inverted filter in 40.73 m
length & launching apron 1.5 m thick up to 35.50 m with 0.5 m thick 2 nos.
curtain wall.
4.5.4.6.3
Energy Dissipation Arrangement
To dissipate the energy of water coming out from the barrage
spillway, a stilling basin type arrangement has been proposed so that it may not
cause excessive scour immediately downstream of barrage. The level and
length of stilling basin is so provided that the hydraulic jump formed under
various possible flow conditions is contained within the stilling basin. As per
design the length of cistern has been provided as 58 m and cistern level kept at
EL 377.50 m.
In this regard the following criteria is proposed:
The cistern level & length has been find out for the different flow
condition such as (i) At HFL (without concentration retrogression) (ii) At HFL
with 20% concentration & 0.5 m retrogression (iii) At pond level (without
concentration retrogression) (iv) At pond level with 20% concentration & 0.5
m retrogression. The cistern level has been adopted as lowest & cistern length
will be maximum 5(D2-D1) in all above 4 flow condition.
The Longitudinal sectional details (KBL-7730-P-1157) and cross
sectional details (KBL-7730-P-1158) of Kotha barrage are given as Plate Nos.
4.5.3 and 4.5.4 in Volume - V (Part-3) respectively.
215
4.5.4.6.4
Seepage control
Since rock is available at shallow depth, the cutoffs may be taken
1 m into good quality rock. To relieve the seepage pressure built up underneath
the floor, 75 mm dia. drainage pipes 4.5 m deep and 3 m c/c (two rows per bay)
shall be provided in the sloping glacis. As the river bed is rocky, seepage may
not pose much problem, provided presence of impermeable rock is confirmed
by further exploration at the construction stage. However for preliminary
design, upstream and downstream RCC cutoffs are provided. Some curtain
grouting at upstream and drainage arrangement for the stilling basin may also
be required which may be finalized at the construction stage.
4.5.4.6.5
Special features of the barrage
In view of the hard strata available at shallow depth, the thickness
gravity type floor is too much so throughout RCC raft with piers& abutment
are proposed. The double piers shall be provided after each 3 bays with 50mm
thick construction joint separated by PVC seal conforming to IS: 12200.
To take care of high permeability of foundation material, it is
proposed to provide a drainage filter below the floor. Further 250 mm dia. half
round concrete pipes 3000 c/c in two rows in each bay shall be provided to
collect the seepage water from filter and the same shall be released from the
pipes provided through piers and cutoff.
Further 25 mm dia. rock anchors 4.5 m deep are also proposed to
take care of excess uplift. Their spacing is proposed tentatively as 3 m c/c
which is required to be revised at construction stage planning.
Provision for grouting on upstream and downstream of barrage is
also made in the DPR. The details in this regard shall be finalized at the
construction stage planning.
At construction stage planning, it is recommended that bearing
capacity of the foundation may be verified by plate load test at most heavily
216
loaded location (below Abutment / central pier in zone where hydromechanical components are provided).
4.5.4.6.6
Materials used
Barrage bed is proposed as a RCC Raft having thickness
minimum 3.0 m and below piers/ abutment raised up to 4.50 m with M-30
concrete. Piers, Divide walls, Abutments and gantry cum Road Bridge are
proposed with M-30 Grade concrete. Return walls and CC blocks are proposed
with M15 grade plain unreinforced concrete. Skin reinforcement 16 mm dia.
200 c/c shall be provided at water surface with 75 mm clear cover. 150 mm
lean concrete (M-10 grade) shall be provided below Pier footings, raft and
other RCC work.
Fe 415 / 500 HYSD bars conforming to IS: 1789 are proposed as
reinforcements.
4.5.4.7
Gates, types of gates and hoist bridge and stop logs
4.5.4.7.1
Spillway Fixed Wheel Vertical Lift Gates
The Spillway of Kotha barrage shall be provided with 32 numbers
fixed wheel vertical lift gates of size 15000 mm X 11500 mm. Sill level of the
gate shall be EL 384.50 m. The gate shall be provided with upstream skin
plate and upstream sealings to avoid silt on horizontal girders. Wedge type seal
shall be provided for bottom sealing and music note solid bulb seals shall be
provided for side sealings. The seal shall remain in contact with stainless steel
seal seats to make the gate water tight.
The gate structure shall consist of skin plate stiffened by vertical
stiffeners and horizontal girders. The horizontal girders shall be supported by
end vertical girders on each side. The water thrust will be transferred to
concrete structures from the end vertical girder through wheels and wheel
track. The wheels shall be mounted on self lubricating bush bearings. The
wheel shall be made up of corrosion resistant steel. The BHN of wheel track
217
shall be 50 BHN higher than the wheel material. 32 mm guide and two number
guide shoes shall be provided on each side to guide the gate in grooves.
The gates shall be operated by independent rope drum hoist of 220
T (approx.) capacity. The Rope Drum Hoist shall consist of hoist machinery
mounted on hoist support structure. Each hoist machinery will be equipped
with two rope-drums, gears, pinions, couplings, shafts, worm reducer, motor
and brakes. The hoist bridge shall be supported on trestles.
The maintenance of these gates are proposed to be carried out at
level EL 398.00 m. The gate shall be designed in accordance with the provision
of IS: 4622 (latest revision). The design of Rope Drum Hoist shall conform to
IS: 6938 (latest revision).
The general assembly of Fixed Wheel gate has been shown in
Drawing No. KBL-7730-P-1507 is given at Plate No. 4.5.5 in Volume - V
(Part-3).
4.5.4.7.2
Barrage Stoplogs
Stoplogs are proposed to carry out the maintenance of barrage
gates. Four sets of stoplogs of size 15000 mm X 1450 mm shall be provided.
The stoplogs shall be operated in balanced water head conditions. However,
the top most unit can be lifted under unbalanced water head for one unit height
water head. All units are interchangeable. The stoplogs shall be operated with
gantry crane. The stoplog units shall be stored in stoplog groove above HFL.
The stoplog units shall have bronze pad sliding on stainless steel track. 32 mm
guide shall also be provided to guide the stoplog units. The skin plate and
sealing of stoplog gate shall be kept d/s side.
The general assembly of Stoplog gate has been shown in Drawing
No. KBL-7730-P-1508 is given at Plate No. 4.5.6 in Volume - V (Part-3).
4.5.4.7.3
Gantry Crane
The spillway stoplogs shall be operated by moving Gantry Crane.
The tentative min. capacity of gantry crane shall be 30T. The Gantry Crane
218
shall have hoist machinery mounted on trolley. The trolley shall of moving
type. The crane structure along with trolley shall be capable of moving in
longitudinal direction with the help of LT travel mechanism. Suitable counter
weight shall be provided to make the crane stable for different stability
conditions. The crane shall be designed as per IS: 3177 and IS: 807.
The general assembly of Gantry Crane has been shown in
Drawing No. KBL-7730-P-1509 is given at Plate No. 4.5.7 in Volume - V
(Part-3).
The salient details of spillway gates, stoplogs and Gantry Crane of
the Kotha barrage are given at Annexure 4.16 in Volume – II.
4.5.4.8
Detail of spillway bridge, abutments etc.
4.5.4.8.1
Road Bridge & Gantry Bridge,
Pier & abutment top has been provided at EL 400.00 m in U/s and
398.505 m in D/s which is 1.5 m above the u/s & d/s HFL level. A road cum
gantry bridge has been proposed with deck level at 401.50 m. This approach
bridge shall continue on either flank of the barrage. The bridge shall support
gantry crane provided for operation of stop logs and also the single lanes of
class ‘A’ vehicle loading with 55.4 R loading. Trestles for operation of service
gates of barrage are provided at pier top level of 400.70 m.
4.5.4.8.2
Abutment
The top width of abutments is kept as 3.0 m and side slope is kept
as 0.7:1. The length of abutment in u/s & u/s up to end of Floor i.e. 96.27 m.
The return walls in the u/s & u/s is provided at the ends of abutment on both
side with 0.7:1 slope. The purpose of return wall is for uniform flow and to
make connection between abutments and banks of river.
4.6
Infrastructure Studies
Almost entire area of the project is well connected with road and
rail net works. No constraints on transportation of heavy equipment up to
project sites are envisaged. For transportation of heavy machinery to project
219
sites some of the road bridges and culverts may have to be strengthened at the
time of preconstruction stage.
4.7
Navigation and Tourism Development
There is no provision for development of navigation aspect in the
project. As far as the development of tourism is concerned the dam/barrage
sites has got full potential. Appropriate provision for development of tourist
huts, picnic spots etc., has been made in the estimates.
4.8
Operation and Maintenance
The proposed organizational set up at the construction stage of the
dam/barrages can be made available for operation and maintenance of the
projects at post construction stage. A suitable operation and maintenance
programme has to be developed for meeting the various objectives of the
project.
4.9
Other Studies
The studies which are not covered in the DPR stage will be
planned at the preconstruction stage. However, if any study is suggested by
Design organization of CWC, the same may be carried out at appropriate stage.
220