Chapter – 6Design Aspects

6.0 Engineering Assessment

As already discussed in the foregoing chapters, the main objective ofPar-Tapi-Narmada link project is divertion of the surplus waters of Westflowing Par, Auranga, Ambica and Purna river basins to provide irrigationfacilities in tribal areas enroute the link canal lying on Right side, to caterthe command areas of five projects namely Khuntali, Ugta, Sidhumber,Khata Amba and Zankhari, proposed by Government of Gujarat along withenroute command area lying on left side by gravity, Command areas intribal areas of Chhota Udepur and Panchmahal districts from Narmada MainCanal of Sardar Sarovar Project on substitution basis, supply of drinkingwater to tribal dominant districts of Dang and Valsad of Gujarat State andNasik district of Maharashtra State along with drinking water supply tomost of the villages and filling of Panchayat tanks in the vicinity of the linkcanal and reservoirs. The link canal will take-over the part command areaof the existing Miyagam Branch Canal of Narmada Canal System. TheNarmada waters so saved in Sardar Sarovar Project would be utilized inSaurashtra region of Gujarat by substitution through Narmada Canal Systemto meet irrigation, domestic and other requirements.

With a view to complete the Detailed Project Report of this projectwithin scheduled time and also to utilize the vast experience of other Central/ State Government Organisation in the relevant fields, the works related todesign aspects of various components of the project have been got donethrough various Design Directorates of Central Water Commission (CWC).The details of the designs are briefly discussed in this chapter.

6.1 General

Par-Tapi-Narmada Link Project envisages construction of followingcomponents:

i) A 808.32 m long composite embankment (concrete face rock fill)cum concrete dam across river Par near village Jheri with FRL 246.00

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m and corresponding gross storage capacity 206.03 MCM. Thelength of concrete face rock fill portion of the dam is 663.32 m andthe length of concrete non-overflow section and spill way is 145.00m. The dam axis is located at Latitude 20°22'25" N and Longitude73°25'51" E.

ii) A 1431.85 m long composite embankment (concrete face rock fill)cum concrete dam across river Nar (a tributary of Par river) nearvillage Paikhed with FRL 248.00 m and corresponding gross storagecapacity of 229.53 MCM. The length of concrete face rock fillportion of the dam is 1310.85 m and the length of concrete non-overflow section and spill way is 121.00 m. The dam axis is locatedat Latitude 20°27'42" N and Longitude 73°23'37" E;

iii) A power house of 9 MW installed capacity at the toe of Paikhed damwith 3 units each of 3 MW.

iv) A 2781.00 m long composite embankment (concrete face rock fill)cum concrete dam across river Tan (a tributary of Auranga river) nearvillage Chasmandva with FRL 214.00 m and corresponding grossstorage capacity of 83.63 MCM. The length of concrete face rock fillportion of the dam is 2703.00 m and the length of concrete nonoverflow section and spill way is 78.00 m. The dam axis is located atLatitude 20°37'02" N and Longitude 73°22'36" E.

v) A power house of 2 MW installed capacity at the toe of Chasmandvadam with 2 units each of 1 MW.

vi) A 1887.00 m long composite embankment (concrete face rock fill)cum concrete dam across river Ambica near village Chikkar with FRL210.00 m and corresponding gross storage capacity of 141.99 MCM.The length of concrete face rock fill portion of the dam is 1736.00 mand the length of concrete non overflow section and spill way is151.00 m. The dam axis is located at Latitude 20°42'00" N andLongitude 73°30'50" E.

vii) A power house of 2 MW installed capacity at the toe of Chikkar damwith 2 units each of 1 MW.

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viii) A 1170.00 m long composite embankment (concrete face rock fill)cum concrete dam across river Khapri (a tributary of Ambica river)near village Dabdar with FRL 169.00 m and corresponding grossstorage capacity 222.38 MCM. The length of concrete face rock fillportion of the dam is 1035.00 m and the length of concrete nonoverflow section and spill way is 135.00 m. The dam axis is located atLatitude 20°48'58" N and Longitude 73°32'05" E.

ix) A power house of 3.2 MW installed capacity at the toe of Dabdar damwith 2 units each of 1.60 MW.

x) A 1330.00 m long composite embankment (concrete face rock fill)cum concrete dam across river Purna near village Kelwan with FRL164.00 m and corresponding gross storage capacity of 282.16 MCM.The length of concrete face rock fill portion of the dam is 1141.00 mand the length of concrete non overflow section and spill way is189.00 m. The main dam is located at Latitude 20°55'30" N andLongitude 73°32'00" E.

xi) A power house of 2.5 MW installed capacity at the toe of Kelwandam with 2 units each of 1.25 MW.

xii) A power house of 2 MW installed capacity at the fall of feeder pipeline connecting Kelwan dam with main link canal with 2 units each of1 MW.

xiii) A tunnel of about 12.70 km long with 3.00 m diameter (D shape) andbed slope of 1:875 connecting Jheri reservoir with Paikhed reservoir.

xiv) A 147.50 m long barrage in the downstream of Paikhed dam withcrest level of 136.00 m

xv) A 128.00 m long barrage in the downstream of Chasmandva dam withcrest level of 123.00 m.

xvi) A 369.043 km long link canal off-taking from Paikhed barrage at FSL142.800 m.

xvii) A 100 m long tunnel No.1 at RD 14.650 to 14.750 km; A 350 m longtunnel No.2 at RD 24.000 to 24.350 km; A 200 m long tunnel No.3 at

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RD 32.350 to 32.550 km; A 50 m long tunnel No.4 at RD 37.750 to37.800 km; and A 450 m long tunnel No.5 at RD 51.500 to 51.950km;

xviii) A 2.859 km feeder Pipe line connecting main canal with Chasmandvabarrage.

xix) A 14.342 km feeder Pipe line inters connecting Chikkar and Dabdarreservoirs.

xx) A 12.258 km feeder Pipe line connecting main canal with Dabdardam.

xxi) A 7.616 km feeder Pipe line connecting main canal with Kelwan dam.

xxii) Cross Drainage / Cross Masonry works including Regulators, Escapes, Road/ Railway bridges (469 No).

Index Map of Par-Tapi-Narmada Link Project is at Plate - 1.1 in Volume –VIII (A).

6.1.1 Geology, Seismicity and Foundation6.1.1.1 Geology

Geological Investigations of the Jheri, Chasmandava, Chikkar,Dabdar and Kelwan dam sites were carried out through Geological Surveyof India (GSI), Jaipur during preparation of Feasibility Report of the project.During preparation of DPR geological investigations could not be carriedout at these dam sites, except at Paikhed and Chasmandva dams, due toresistance from local people. Therefore, the geological investigations carriedout at DPR stage for Paikhed and Chasmandva dams and for other dams atFR stage have been used for design of dams. The Length and RDs of damaxis indicated in GSI report are as per the dam alignment adopted at FRstage.

The project area is occupied by Deccan Lava flows intruded bydolerite dykes and sill. Very commonly due to differentiation the middleportion of a flow exhibits a dolerite texture. They are of Cretaceous-Eocene

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age. The flows comprise vesicular and amygdaloidal basalts with vesiclesfilled by zeolite, calcite and green-earth. (Geological mapping in parts ofNasik district, Maharashtra; Unpublished Progress Report GSI F.S. 1974-75,Iyyer,R.K.). In general the basalts are without olivine, consisting of basicglass. Where coarsely crystalline they show appreciable quantity of olivine.Porphyry are formed by Phenocrysts of feldspar (Manual of Geology ofIndia and Burma, Vol. III, Pacoe, E.H. 1973). The flows commonly containash beds. These ash beds resemble the flows in their macroscopicappearance. Another feature of the Traps is the alteration of its basal portioninto green earth. Frequently it is found not only in between the flows butalso in vesicles. Another common occurring rock type is the red-bole,characterized by its conspicuous colour. The red-bole is clay formed bydecomposition of the crust of lower flow, something a kin to present daylaterisation of the traps. The area has been subjected to faulting andshearing. Several instances of block faulting with small throws are common.These are related to the Sone-Narmada-Rift system and the Sabarmati –west coast faulting.

Geophysical surveys were carried out by the officers of GeophysicsDivision-III, Geological Survey of India, Western Region, Jaipur forNWDA for delineating the bedrock and demarcating the subsurface featuresat dam sites. Geophysical surveys were carried out during the year 1993and1994 employing electrical resistivity, seismic refraction and magnetic(VF) techniques at Jheri in Nasik district of Maharashtra; Chasmandva inValsad district of Gujarat; Chikkar, Dabdar and Kelwan in Dang Districtsof Gujarat along dam and Energy Dissipation (E.D) line at each of thesefive proposed dam sites. A total of 179 vertical electrical resistivitysoundings (VES); 44 explosive source refraction seismic shots (S.P.); 186hammer sources seismic shots (H.S.); and 947 magnetic observations wererecorded at these five sites to achieve the objective.

The geo-technical investigations carried out by the GSI areprincipally confined to the masonry sections. These included large scale(1:1000) mapping of the dam site area, logging of exploratory bore holesand trial pits, geophysical traverses along the dam axis and across theenergy dissipating arrangements/stilling basin area, and photo-geologicalinterpretation of the area encompassing the dam site. While the photo-

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geological interpretation has been done for all the seven dam sites, the restof the work including field checks of the photo-interpretation has been donefor only 5 dam sites, viz. Jheri, Chasmandva, Chikkar, Dabdar and Kelwan.The work carried out at each of the 5 dam sites at Feasibility Report stage ofthe Link Project is given in Table- 6.1 below.

Table – 6.1Details of Geological Investigations at Various Dam

S.

No.

Work done Jheri Chasmandva

Chikkar Dabdar KelwanTotal

1 Photo-geologicalInterpretation –Scale:1:25000/30000(km2)

22 32 25 25 25 261 (includingPaikhed:60km2andMohankavchali:72km2)

2 Geophysical Traverses (in line kms/ shots/ soundings taken)

a) Seismic:

i) Refraction 0.346

4

3.488

16

2.065

8

0.895

8

1.60

8

7.334

44

ii) Hammer 0.66

22

2.79

62

1.61

46

1.766

44

1.33

12

8.156

186

b) Resistivity 2.18

22

7.82

51

11.18

42

6.58

28

6.36

36

34.12

179

c) Magnetic 1.359

84

5.953

321

4.17

225

2.379

149

2.96

168

16.821

947

3 Eng. Geology

a) Large scalemapping on1:1000 (km2)

0.56 1.98 2.1 1.3 1.788 7.628

b) Bore Holelogging (nos and

4 - 1 4 - 9

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S.

No.

Work done Jheri Chasmandva

Chikkar Dabdar KelwanTotal

aggregate lengthin ‘m’)

125.53 54.86 137.14 317.53

c) Trial pitlogging (nos andaggregate depthin ‘m’)

- 11

12.90

8

11.47

7

20.8

10

12.53

36

57.70

The details on Preliminary Geotechnical Investigations andPreliminary Geophysical surveys carried out at the dam sites are appendedas Appendix: 4.2, 4.4 and 4.8 in Volume-III: Appendices – Surveys andInvestigations.

The DPR stage Geotechnical Investigations could not be initiated atmost of the dam sites due to the hindrances created by the local people ofthe project area. However, the sub- surface exploration was carried out bycore logging of 19 nos. of bore holes drilled at the Chasmandva dam siteand 12 nos. of bore holes drilled at Paikhed dam site, to know the suitabilityof the foundation rocks, to decide the tentative foundation depth and toknow the permeability of the foundation rocks. The bore hole core loggingof 413.75 m and 622.95 m has been carried out in Chasmandva and Paikheddam sites respectively with an aggregate length of 1036.70 m. The detailsare furnished in Appendix: 4.5 of Volume-III: Appendices – Survey andInvestigations.

6.1.1.2 Seismicity

A site specific Seismic study of the project area has beencarried out by CWPRS (Report No. 4848, June 2011- revised as per NCSDPguidelines in June 2012) for determining the seismic design parameters fordams of the link project. The study is appended as Appendix: 4.3 inVolume-III: Appendices – Survey and Investigations. The seismiccoefficients adopted by CWC for design of Jheri, Paikhed, Chasmandva,Chikkar, Dabdar and Kelwan dams are given in Table – 6.2 below:

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Table – 6.2Seismic Coefficients Adopted for Dams

Dam Height of Dam (m)

Natural Period(s)

Horizontal Seismic Coefficient (αh), g

Vertical Seismic Coefficient (αv), g

Concrete Earthen Concrete Earthen Concrete Earthen Concrete Earthen

Jheri 36.5 76.0 0.089 0.882 0.090 0.017 0.085 0.012

Paikhed 90.0 5.4 0.221 0.666 0.086 0.024 0.078 0.017

Chasmandva 35.4 51.0 0.086 0.592 0.088 0.028 0.083 0.020

Chikkar 29.9 60.0 0.073 0.696 0.082 0.023 0.076 0.016

Dabdar 62.4 51.4 0.151 0.596 0.097 0.028 0.091 0.019

Kelwan 62.4 50.1 0.151 0.581 0.097 0.029 0.091 0.020

6.1.1.3 Foundation Treatment

Embankment

The abutments downstream of the plinth and upstream of the damaxis shall be stripped of all surface deposits and loose material to expose thehigh points of in situ rock. Any surface material remaining between rockpoints will not adversely affect embankment settlement after rockfillplacement. For a distance of 0.5H with minimum 10.0m downstream of theplinth, all overhangs and vertical faces shall be removed.

Plinth of the CFRD

The plinth of the CFRD is a significant part of dam construction. Theplinth or toe slab connects the foundation with the face slab. The plinthdesign, dimensions, stability, construction and foundation treatment aremost important. In case of all CFRDs, the dimensions of the plinth, selectedbased on precedent, vary with the reservoir head and with foundationconditions.

A continuous reinforced concrete plinth, cast on a competentfoundation at an acceptable depth along the upstream toe of the dam, formsthe ideal watertight connection between the concrete face slab and the rockfoundation. In case of CFRDs of Par-Tapi-Narmada Link Project, as per the

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geological conditions, plinth will be placed on competent rock in all thereaches. The plinth is proposed to be anchored into rock with steel bars andit will serve as the grout cap for foundation consolidation and curtaingrouting.

As the adequate information about the foundation in respect of all thesix dams in Par-Tapi-Narmada Link Project is not available, the specificdetails of foundation treatment can only be given only at the constructionstage after the availability of detailed realistic information pertaining to thefoundations of all the six dams, based upon the detailed geological andgeotechnical investigations. However, in the Drawings related to“foundation treatment” in respect of all dams, the tentative foundationtreatment in the form of curtain grouting, consolidation grouting and rockanchors of 32mm diameters below the plinth has been shown. The rockanchors assure good contact with the foundation. 32 mm diameter and 5meter deep (into rock) rock anchors at 1.5 m c/c have been proposed for allthe dams.

In the present DPR, the provisions of curtain grouting andconsolidation grouting have been made. Curtain grouting has been providedfor the 1/2 to 2/3rd of the reservoir head at that particular location subject toa minimum of 10.0m. For a CFRD, the consolidation grouting is of specialimportance because of the relatively short seepage path through the rockdirectly under the plinth. Consolidation grouting shall be carried out up to adepth of 0.15H (where H is Water head) subject to a minimum of 8.0m. Themaximum spacing of consolidation grout holes shall be about 3m.

The requirement and final details about curtain/consolidation groutingshall be firmed up at construction stage after detailed foundationinvestigations and in consultation with resident geologists.

Concrete Non-overflow and Overflow Portion

Grouting shall be done under close guidance of Geologist and procedureadopted at site should conform to IS 6066(latest edition). Any shear, fault

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plane or other geological features encountered in the foundation shall besuitably treated in consultation with the Geologist.

Curtain Grouting under spillway at u/s may be carried out as per IS 6066in consultation with the Geologist. The spacing, depth and inclination ofgrout holes may be modified depending upon the State of foundation rockafter excavation and based on the results of grout acceptance tests done inconsultation with the Geologist.

Consolidation grouting shall be done in 100 % of the base width inthe foundation area of overflow and Non-Overflow portion. Minimumdiameter of consolidation grouting holes shall be 38 mm.

The foundation treatment details are presented in Drawing Nos.PTNL-5900-P-1042, PTNL-5900-P-3045, PTNL-5900-P-1028, PTNL-5900-P-3004, PTNL-5900-P-1035, PTNL-5900-P-3025, PTNL-5900-P-1049andPTNL-5900-P-3065 (Plates –6.1, 6.18, 6.25, 6.41, 6.49, 6.64, 6.71,6.88) in Volume-VIII (A) and PTNL-5900-P-1056, PTNL-5900-P-3085,PTNL-5900-P-1063and PTNL-5900-P-3105 (Plates –6.95, 6.112, 6.119 and6.136) in Volume-VIII (B).

6.1.1 Alternative Studies Carried Out for Selection of Site and Type Of Structure

The dam sites have been selected by examining alternative locationsand site visits. The dam sites proposed are the narrowest portions with firmbanks and where the bed rock levels are available at reasonable depths.

6.1.3 Choice of Final Layout of all Major Components of the Projectand Reason

The Geological/ Geotechnical investigations were carried out at theFeasibility Report Stage by Geological Survey of India. The input of thegeological data for the design is based on the GSI report. These includeslarge scale(1:1000) mapping of the dam site area, logging of exploratorybore holes and trial pits, geophysical traverses along the dam axis and acrossthe energy dissipation arrangements/stilling basin area, and photo-geological interpretation of the area encompassing the dam sites. While thePhoto-geological interpretation has been done for all the 6 dam sites, the restof the work including field checks of the photo-interpretation has been doneonly for 5 dam sites viz. Jheri in Nashik district, Maharashtra; Chasmandva

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in Valsad district, Gujarat; Chikkar, Dabdar and Kelwan in the Dangsdistrict, Gujarat; and for the other dam site, viz Paikhed, this could not becarried out due to ‘local hindrances’. During DPR stage, the dam axis of allthe dam sites at spillway portion has been shifted in consideration to theabove Geological parameters.

To divert the water into Par-Tapi-Narmada Link Canal from Paikhedand Chasmandva reservoirs, two barrages, namely Paikhed Barrage andChasmandva Barrage are proposed at about 4.6 km and 8.5 km indownstream of the respective reservoirs. Originally at Feasibility ReportStage of the Link Project weirs were proposed for diversion of water to thelink canal but for better control and regulation Barrages have beenconsidered at DPR stage planning. The barrage location has been finalizedon the basis of FSL of canal off taking from the barrage, topography etc.The axis of barrage has been located where the river reach is straight and thebanks are well defined. The area on either flank of barrage (bank side) shallbe developed to suitable elevation so that water is safely contained in thebarrage pondage.

The locations of surface power houses have been selected by studyingthe limited contour details available as no site visits could be made toascertain the suitability of the strata due to public hindrance. Hence thePower House locations shall be confirmed after site inspections and inconsultation with geologist at pre-construction stage.

The reservoirs formed by Jheri and Paikhed dams are proposed to belinked by a link tunnel of 3.0m diameter (D-shaped) and 12.700 km, inlength. The alignment of the link tunnel and one construction adit has beenfinalized by CWC on the basis of contour maps and data supplied byNWDA. The layout of the intake structure has been planned based on thegeological and topographical data and the alignment of Jheri to PaikhedLink Tunnel. For discharge of water at the end of the tunnel from Jheri toPaikhed Reservoir, an out fall structure has been provided keeping in viewthe topography and geology at the outfall location in Paikhed Reservoir.

The alignment of the proposed Par –Tapi-Narmada link canal andfeeder pipe lines are finalized on the basis of field topographical surveysdone at Feasibility Report stage and DPR stage. The canals are aligned

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mostly as contour canals. The main link canal has to cross the ridgesbetween various basins and sub-basins wherein deep cuts are involved andalso to cross many rivers and streams requiring construction of crossdrainage works. Five tunnels of varying length have been proposed to avoidcircuitous route, CD works and deep cutting.

6.1.4 Design Flood and Sediment Studies6.1.4.1 Design Flood Studies

The design flood and diversion flood studies of Jheri, Paikhed,Chasmandva, Chikkar, Dabdar and Kelwan dams have been carried out byHydrological Studies Organisation (HSO), CWC, New Delhi using hydrometeorological approach. The PMF and 50 /100 year return period diversionfloods as finalized for these projects are given in Table – 6.3 below.

Table – 6.3PMF and 50 /100 Year Return Period Diversion Floods

S.No. Dam PMF

(cumec)

Diversion Flood (cumec)

50 Year ReturnPeriod

100 Year ReturnPeriod

1 Jheri 6539 2703 2989

2 Paikhed 5307 2017 2211

3 Chasmandva 2578 1024 1065

4 Chikkar 5649 2167 2374

5 Dabdar 6683 2539 2796

6 Kelwan 7979 3102 3428

The details of design flood and diversion flood studies of damsare furnished at Appendix-5.3 in Volume –IV.

6.1.4.2 Sediment Studies

As a part of Hydrological Studies of Par-Tapi-Narmada Link Project,the Sedimentation Studies of the reservoirs proposed under the Link Project

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have been carried out by Hydrological Studies Organisation, CWC, NewDelhi. The details of sedimentation studies are furnished in Appendix - 5.2of Volume – IV: Appendices – Hydrology and Water assessment.

In the above studies, the sedimentation rate was adopted based ondirect discharge and sediment data on catchment area, where the proposedproject is located near the GandD sites. Sediment rate of 9 ha.m/100 sqkm/year has been adopted in the studies. Using the Sedimentation rate thedeposited sediment volume in the reservoirs and new zero elevation for thedams has been determined. The New Zero Elevation for different dams asassessed after 50 and 100 years sedimentation are summarized in the Table6.4 below:

Table – 6.4New Zero Elevations

S.

No.

dam After 50 years After 100 years

SedimentVolume(MCM)

New ZeroElevation

(m)

SedimentVolume(MCM)

New ZeroElevation

(m)1 Jheri 18.01 185.00 35.94 198.50

2 Paikhed 13.57 164.34 27.11 171.88

3 Chasmandva 3.88 171.75 7.76 176.00

4 Chikkar 13.04 162.10 26.03 169.30

5 Dabdar 19.55 119.90 39.03 126.90

6 Kelwan 29.90 122.20 59.69 128.20

6.1.4.3 Flood Routing Studies

The flood routing analysis is performed and spillway capacity hasalso been checked for one gate inoperative condition as per the provisionscontained in para. 3.6.1 of IS: 11223 - ‘Guidelines for fixing spillwayCapacity’. The flood routing studies for the 6 reservoirs have been carriedout by Modified Pulse method to determine Maximum Water Level(MWL).The reservoir level at the beginning of flood routing has beenassumed at FRL. This will ensure maximum storage in the reservoir. Theresults of Flood Routing for all the 6 dams are given in Table – 6.5:

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Table – 6.5Results of Flood Routing at Proposed Dams

Sl.No Dam CrestLevel(m)

FRL(m)

MWL(m)

MaximumRoutedOutflow(Cumecs)

PMF (Cumecs)

1 Jheri 234 246 247 6586.04 65392 Paikhed 236 248 249 5225.9 53073 Chasmandva 202 214 215 3043.73 25784 Chikkar 198 210 212 5225.51 56495 Dabdar 157 169 170 6581.75 66836 Kelwan 152 164 166 6581.58 7979The salient features of dam spillways are given in Table – 6.6:

Table – 6.6Salient Features of Dam Spillways

Sl.No Details Jheri Paikhed Chasmandva Chikkar Dabdar Kelwan

1PMF(inCumecs) 6539 5307 2578 5649 6683 7979

2Top Of Dam(in m) 253 255 222 217 177 174

3 MWL (in m) 247 249 215 212 170 1664 FRL (in m) 246 248 214 210 169 164

5Crest Level(inm) 234 236 202 198 157 152

6 MDDL ( in m) 220 225 190 180 140 140

7Silt Elevation(in m) 234 236 202 198 157 130

8FoundationLevel (in m) 215 210 184 170 132 123

9Height ofSpillway(in m) 38 45 35 47 45 51

10 Size of Gate(WX H)

15 mx12m

15 mx12m

12 mx12 m 15 mx12 m15mx12m

15mx12 m

11 No. Of Bays 5 4 3 4 5 5

12Pier Thickness( in m)

4 4 4 4 4 4

13 U/S Slope 0.1:1 0.1:1 0.1:1 0.1:1 0.1:1 0.1:1

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Sl.No Details Jheri Paikhed Chasmandva Chikkar Dabdar Kelwan14 D/S Slope 0.9:1 0.8:1 0.9:1 0.9:1 0.9:1 0.9:1

15Horz. SeismicCo-efficient

0.09 0.09 0.09 0.09 0.09 0.09

16VerticalSeismicCo-efficient

0.06 0.06 0.06 0.06 0.06 0.06

17Type of EDA Ski

JumpBucket

SkiJumpBucket

Ski JumpBucket

Ski JumpBucket

SkiJumpBucket

SkiJumpBucket

18Radius ofBucket (inm)

30 30 30 30 30 20

19Invert level ofBucket(in m)

176 160 178 155 114 115

20 TWL (in m) 178 185 190 164 123 127

21Lip Level ( inm)

180 165 182 170 125 130

22Lip Angle(in Degrees)

30 35 35 30 30 30

6.1.5 Free Board for Fixing Top Elevation of Various Dams

Ample Free Board above the FRL has been kept for dams to mitigateagainst the effects of a major earthquake and wind conditions. Forcomputations of free board, in respect of all six dams envisaged in Par-Tapi-Narmada Link Project, guidelines given in IS 10635:1993 have beenfollowed. Due to non-availability of realistic wind velocity, based oninformation contained in IS 875 (Part 3), the Basic wind speed at the all thedam sites has been taken as 44m/sec (at land surface) while computing theFreeboard in respect of all six dams. Apart from the freeboard, a tentativesettlement allowance of 1% of the height of the dam above the approximatedeepest acceptable foundation level (based upon the data given in GSI’sreports) of the dam has also been taken into account while fixing the toplevels (the levels, arrived so have been rounded off to the nearest wholenumeric value to achieve the top level of a particular dam) of all the dams ofthe Link project. Features of the CFRDs may require revision based uponrealistic site conditions and related data at the construction stage of theproject.

6.1.5.1 Jheri Dam

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The FRL and MWL are at EL 246.00m and EL 247.00m respectively.Top level of Jheri dam has been fixed at EL 253.00 m and top of parapetwall has been fixed at EL 254.20 m.

6.1.5.2 Paikhed Dam

The FRL and MWL are at EL 248.00 m and EL 249.00 mrespectively. The top level of the Paikhed dam has been fixed at EL 255.00m and top of parapet wall has been fixed at EL 256.20 m.

6.1.5.3 Chasmandva Dam

The FRL and MWL are at EL 214.00m and EL 215.00m respectively.The top level of the Chasmandva dam has been fixed at EL 222.00 m andtop of parapet wall has been fixed at EL 223.20 m.

6.1.5.4 Chikkar Dam

The FRL and MWL are at EL 210.00m and EL 212.00m respectively.The top level of the Chikkar dam has been fixed at EL 217.00 m and top ofparapet wall has been fixed at EL 218.20 m.

6.1.5.5 Dabdar Dam

The FRL and MWL are at EL 169.00m and EL 170.00m respectively.The top level of the Dabdar dam has been fixed at EL 177.00 m and top ofparapet wall has been fixed at EL 178.20 m.

6.1.5.6 Kelwan Dam

The FRL and MWL are at EL 164.00m and EL 166.00 m respectively.The top level of the Kelwan dam has been fixed at EL 174.00 m and top ofparapet wall has been fixed at EL 175.20 m.

The wind velocity at the dam sites, the Free Board computed at FRLand MWL conditions and top of dam levels fixed for Jheri, Paikhed,

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Chasmandva, Chikkar, Dabdar and Kelwan dams are summarized in theTable – 6.7:

Table – 6.7Wind Velocity, Free Board at FRL and MWL and Top of Dam Levels

S.No. Dam WindVelocity(Land)(m/sec)

Free board (m) Top ofDam Level

(m)FRLCondition

MWLCondition

1 Jheri 44 7.00 6.00 253.00

2 Paikhed 44 7.00 6.00 255.00

3 Chasmandva 44 8.00 7.00 222.00

4 Chikkar 44 7.00 5.00 217.00

5 Dabdar 44 8.00 7.00 177.00

6 Kelwan 44 10.00 8.00 174.00

6.1.5.7 Paikhed Barrage

Paikhed barrage has been designed for 1:100 design flood i.e. 2223cumecs and free board has been checked for discharge corresponding to 1 in500 years (3606 cumecs). Due to proximity of dam on upstream, free boardhas been checked for PMF (5307 cumecs) as well. The top of pier andabutments were kept at 152.00 m.

6.1.5.8 Chasmandva Barrage

Chasmandva barrage has been designed for 1:100 design flood of1571 cumecs and free board has been checked for discharge correspondingto 1 in 500 yrs (2072 cumecs). Due to proximity of dam on the upstream,free board has been checked for PMF (2578 cumecs) as well. The top of pierand abutments were kept at 133.00 m.

6.1.6 River Diversion Arrangements

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No formal diversion arrangement has been provided. The diversionarrangement during project construction will be evolved depending upon therequirement. As sufficient width is available, the flow only needs to bechannelized through formed channels which can be decided at constructionstage.

6.1.7 Construction Materials6.1.7.1 Rock/River Boulder Samples (Coarse Aggregate)

The following physical and chemical tests were conducted in CSMRSlaboratory, New Delhi on the 12 rocks and river boulder samples whereinsix of rock and six of river boulder materials samples (Coarse Aggregate)designated CSM lab. No. as CA-10 to CA-21 as per IS: 2386-1963(Reaffirmed 1997) for their suitability for use as coarse aggregate inconcrete as per IS: 383-1970 (Reaffirmed 1997):

i) Specific Gravity ii) Water Absorption (%) iii) Soundness Loss (%) 5 cycles in Na2SO4 Solution iv) Aggregate Impact Value (%) v) Aggregate Abrasion Loss (%) vi) Aggregate Crushing Value (%) vii) Alkali Aggregate Reactivity Tests viii) Petrographic Analysis

The results of physical and chemical tests and detailed Petrographicexamination report of GSI, Faridabad on Petrographic examination of abovesamples are furnished in Appendix-4.9 of Volume-III: Survey andInvestigations.

Based on physical and chemical tests and ASR tests reportsconducted, it is found that the rock and river boulder quarries samples( Coarse Aggregates ) 10 Nos. of coarse aggregates samples bearing Lab.designated No. CA-10 to CA-13 and CA-15 to CA-17 and CA-19 to CA-21are conforming to the codal requirements for use as coarse aggregate inconcrete for both wearing as well as non-wearing surfaces as per IS: 383-

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1970. The two nos. river boulder samples bearing Lab. designated No. CA-14 and CA-18 are suitable only for non-wearing surfaces.

6.1.7.2 Fine Aggregate Samples

Twelve fine aggregate samples, six of natural sand and six crushedstone sand prepared from the crushing of rock samples, designated lab. no.FA-11 to FA-22 were subjected to the following physical and chemical testsas per IS: 2386-1963 to assess their suitability for use as fine aggregate inconcrete:

i) Fineness Modulus ii) Specific Gravity iii) Silt and Clay Content iv) Organic Impurities v) Soundness Loss (%) 5 cycles in Na2SO4 Solution vi) Alkali Aggregate Reactivity Tests vii) Petrographic Analysis

The results of physical and chemical tests conducted in CSMRSlaboratory, New Delhi on natural sand samples and crushed sand samplesand the report on detailed Petrographic examination of the samplesconducted by GSI, Faridabad are furnished in Appendix-4.9 of Volume-III:Survey and Investigations.

Based on physical tests report it is found that the natural sand samplebearing Lab. designated No. FA- 11, 13,15,17,19 and 21, the finenessmodulus is in the range of 3.11 to 4.19 which shows that sand is coarser innature and three samples FA-15, 17and 21 also do not conform to anygrading zones I to IV of BIS: 383-1970. However, natural sand which iscoarser in nature may be used in construction works after blending with finesand to make the FM 2.5 to 3.0. The crushed sand Lab. designated no. FA-12, 14,16,18,20 and 22, the fineness modulus varying between 2.73 to 3.77and conform to the grading zone –I and II as per IS: 383--1970. However,crushed sand having FM 3.77 which is coarse may also be used inconstruction works after more crushing the sand to make FM between 2.5 to3.0 so that it conforms the grading zone II/III of IS: 383-1970 and the dustfiner than 150 micron should not be more than 15%.

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6.1.8 Details of Model Studies for Important Structures

No model studies are carried out at this stage. However, the samemay be taken up at pre-construction stage of the project for ensuringsatisfactory hydraulic performance of these structures.

6.2 Dam6.2.1 Concrete Face Rock Fill Dam – Design Criteria and

Stability Analysis6.2.1.1 General Layout

The Jheri dam is a composite dam comprising of Concrete FacedRockfill Dam (CFRD) and Concrete Gravity Dam. The maximum height ofthe CFRD portion of Jheri dam above river bed is 75.88 m and its totallength is 808.32 m. Out of this, the length of CFRD is 663.32 m and the restis NOF and OF blocks. The interface Key wall provided on upstream sidehas a top width of 3 m and side slope 1.5(H): 1 (V) on the upstream side and0.65:1 towards dam side. On the downstream side the thickness of wall is 10m with slope of 1.5:1 and 0.25:1 towards dam side. The spillway blockshave a length of 91 m and the length of NOF blocks is 54 m.

The Paikhed dam is a composite dam comprising of Concrete facedRockfill Dam (CFRD) and Concrete Gravity Dam. The maximum height ofthe CFRD portion of Paikhed dam above river bed is 94.40 m and its totallength is 1431.85 m. Out of this, the length of CFRD is 1310.85 m and therest is NOF and OF blocks. The interface Key wall provided on upstreamside has a top width of 3 m and side slope 1.5:1 on the upstream side and0.65:1 towards dam side. On the downstream side the thickness of wall is 15m with slope of 1.5:1 and 0.25:1 towards dam side. The spillway blockshave a length of 72 m and the length of NOF blocks is 49 m.

The Chasmandva dam is a composite dam comprising of Concretefaced Rockfill Dam (CFRD) and Concrete Gravity Dam. The maximumheight of the CFRD portion of Chasmandva dam above river bed is 53.70 mand its total length is 2781 m. Out of this, the length of CFRD is 2703 mand the rest is NOF and OF blocks. The interface Key wall provided onupstream side has a top width of 3 m and side slope 1.5:1 on the upstream

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side and 0.65:1 towards dam side. On the downstream side the thickness ofwall is 15 m with slope of 1.5:1 and 0.25:1 towards dam side. The spillwayblocks have a length of 44 m and the length of NOF blocks is 34 m.

The Chikkar dam is a composite dam comprising of Concrete facedRockfill Dam (CFRD) and Concrete Gravity Dam. The maximum height ofthe CFRD portion of Chikkar dam above river bed is 62.27 m and its totallength is 1887 m. Out of this, the length of CFRD is 1736 m and the rest isNOF and OF blocks. The interface Key wall provided on upstream side hasa top width of 3 m and side slope 1.5:1 on the upstream side and 0.65:1towards dam side. On the downstream side the thickness of wall is 15 mwith slope of 1.5:1 and 0.25:1 towards dam side. The spillway blocks have alength of 72 m and the length of NOF blocks is 79 m.

The Dabdar dam is a composite dam comprising of Concrete facedRockfill Dam (CFRD) and Concrete Gravity Dam. The maximum height ofthe CFRD portion of Dabdar dam above river bed is 63.65 m and its totallength is 1170 m. Out of this, the length of CFRD is 1035 m and the rest isNOF and OF blocks. The interface Key wall provided on upstream side hasa top width of 3 m and side slope 1.5:1 on the upstream side and 0.65:1towards dam side. On the downstream side the thickness of wall is 15 mwith slope of 1.5:1 and 0.25:1 towards dam side. The spillway blocks have alength of 91 m and the length of NOF blocks is 44 m.

The Kelwan dam is a composite dam comprising of Concrete facedRockfill Dam (CFRD) and Concrete Gravity Dam. The maximum height ofthe CFRD portion of Kelwan dam above river bed is 57.95 m and its totallength is 1330 m. Out of this, the length of CFRD is 1141 m and the rest isNOF and OF blocks. The interface Key wall provided on upstream side hasa top width of 3 m and side slope 1.5:1 on the upstream side and 0.65:1towards dam side. On the downstream side the thickness of wall is 15 mwith slope of 1.5:1 and 0.25:1 towards dam side. The spillway blocks have alength of 91 m and the length of NOF blocks is 98 m.

The layout plans of the dams and appurtenant structures are shown inDrawing Nos.PTNL-5900-P-1036, 3041, 1022, 3001, 1029, 3021, 1043 and3061(Plates –6.2, 6.8, 6.26, 6.32, 6.50, 6.56, 6.72 and 6.78) of Volume –

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VIII (A) and Drawing Nos.PTNL-5900-P-1050, 3081, 1057, 3101(Plates –6.96, 6.102, 6.120 and 6.126) of Volume – VIII (B).

6.2.1.2 Background on Selection of CFRD

The Feasibility Report (FR) of the project was prepared by NationalWater Development Agency (NWDA) in October, 2005. At the FR stage, 7Nos. of Earth dams, namely, Jheri, Mohankavchali, Paikhed, Chasmandva,Chikkar, Dabdar and Kelwan dams were proposed along with the spillways.

At DPR stage, 6 Nos. of Concrete Face Rockfill Dams: Jheri,Paikhed, Chasmandva, Chikkar, Dabdar and Kelwan dams have beenenvisaged in the project. Mohankavchali dam where no field investigationscould be carried out due to public hindrance has not been considered in thepresent planning. During the design stage of all the six dams, a team ofCWC officers along with NWDA officers visited the Par-Tapi-NarmadaLink Project site during 20th -22nd November, 2012. During the visit, mostof the dam sites could not be approached by team up to the dam axis andcould only be seen from distance. However, all the storage sites witnessedwere found to be having exposed rock, which appeared to be sound from thevisual inspection. However, no sand or clay deposits could be seen. CWCteam noted that serious rethinking on the type of dam that is appropriate atall locations than what is proposed in Feasibility report.

Later, in a meeting amongst CWC and NWDA officers, chaired by theChairman, CWC, during May, 2014, it was decided that at the DPR stage,type of all six dams will be of Concrete Face Rockfill Dam (CFRD).

6.2.1.3 Attractive Features of a CFRD

As per ICOLD Bulletin No. 141, during the 1965-2000-developmentperiod, many CFRDs were adopted to replace a previously selected arch,gravity or earth-core-rockfill dam type. Reasons for the change to the CFRDincluded the late discovery of adverse foundation conditions for a concretedam, cost, or lack of appropriate core material for an earth-core-rockfilldam. Today, the CFRD is an established major dam type to be included ininitial project feasibility studies.

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As per the ICOLD Bulletin No. 141 on “Concrete Face RockfillDams-Concepts for Design and Construction” the attractive features ofCFRD in respect of design, construction and schedule are as under:

1. All of the zoned rockfill is downstream of the water barrier. Theoverall sliding factor of safety often exceeds 7. The dam can alsoreinforce abutments.

2. A parapet wall at the crest provides a wider surface for constructionof the face slab and reduces the volume of rockfill.3. Uplift under the plinth is not an issue. The pressure on the foundation

exceeds the uplift pressure over three-quarters of the base width.4. Water load is transmitted into the foundation upstream from the dam

axis, an inherently safe feature.5. Since all of the rockfill is dry, earthquake shaking cannot cause

internal pore water pressure.6. The conditions of high shear strength, no pore pressure, and small

settlement under seismic loading make the zoned rockfill inherentlyresistant to seismic loading.

7. The only credible mechanism of failure of a CFRD founded on rockis erosion by sustained overtopping flow. Hydrology, spillway, andfreeboard design is the response to this risk. Piping of the foundationis a potential mode of failure as a result of the increasing use ofCFRDs on weathered rock and alluvial foundations.

8. Post construction movements are small, and cease after several years.9. Surveillance by monitoring surface movement and measuring leakage

is required, as for any dam, but little or no instrumentation is neededfor safety monitoring.

10. Ramps are permitted within the body of the dam in any direction.This minimizes haul roads to the dam and facilitates traffic andplacement on the dam.

11. The plinth construction and grouting are outside the dam and do notinterfere with embankment placement or the construction schedule.

12. Rockfill placement is relatively unrestricted and not affected byrainfall. Scheduling is reliable.

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As per ICOLD Bulletin No. 141, the maximum heights underconstruction or planned exceed 200m. CFRD’s have performed well duringlarge earthquakes. In spite of poorly compacted rockfill in the older CFRD,remarkably little damage has occurred. The concrete face will be supportedby processed crushed rock, high strength and high modulus materials.Because the water barrier is located at the upstream face of the dam, theembankment materials will not be saturated and, therefore, no deformationswill take place during or subsequent to an earthquake as a result of increasedpore water pressure within the CFRD. Rockfill zoning in a CFRD is alsosuch that permeability increases progressively from upstream todownstream.

6.2.1.4 Design of Typical Section of CFRDs

All the CFRDs, envisaged in Par-Tapi-Narmada Link Project, havebeen assumed to be rested on competent rock. The top width of all the sixdams have been fixed at 10.00 m.

As per ICOLD Bulletin No.70, for good quality rockfill, bothupstream as well as downstream slopes of 1.3H: 1V to 1.4H: 1V have beengenerally used. Slopes may have to be flatter for weaker rock or lowstrength foundation and no steeper than 1.5H: 1V for gravel, steeper slopescausing raveling. Experience has demonstrated that there are no stabilityproblems with the CFRD. Old dams in California, with heights between 20and 50m, were constructed with 0.5H: 1V and 0.75H: 1V slopes. Thestability of these dams has been explained by the high friction angle at lowconfining pressures. Since the critical sliding planes are close to the surface,the strength is higher there.

The slopes of the upstream face as well as downstream face of all thesix CFRDs envisaged in Par-Tapi-Narmada Link Project, have been kept as1.5H:1V which are quite safe from stability point of view. On thedownstream side of the dam 4 meter wide berms have been proposed tofacilitate the construction and maintenance. Therefore, the averagedownstream slope gets further flatter. The upstream or downstream slopes ofthe CFRDs may require revision based upon realistic foundation features.

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The CFRD dam section consists of the following components:

Plinth: Reinforced concrete slab cast on sound, low permeability rock tojoin the face slab to the foundation.

Face Slab: Reinforced concrete, preferably between 25 cm and 60 cm thick,with vertical, some horizontal and perimetric joints to accommodatedeformation which occurs during construction and when the water load isapplied.

Embankment Zones: The zoning of the CFRD and the numericaldesignation of the zones, are standard. A brief description is presentedbelow: • Zone 1A, 1B: These are concrete face protection (upstream) zones, inincreasing order of maximum particle size.• Zone 2A, 2B: These are concrete face supporting (downstream) zones, inincreasing order of maximum particle size. • Zone 3A, 3B: These are Rockfill zones, in increasing order of maximumparticle size.

Brief Description of Various Zones in CFRD is Furnished Below:

Zone 1A: The zone serves as a source of material that, if required, canmigrate through cracks in the face slab. This zone is placed to a higherelevation on very high dams so that it can act as a joint or crack healer overthe perimeter joint and the lower part of the face slab. Fine-grained cohesionless silt and fine sand with isolated gravel and cobble sized rock particles upto 150 mm. The zone is maintained cohesion less so that brittle crackingdoes not occur. The zone is placed in 200 to 300 mm layers and lightlycompacted.

Zone 1B: This zone provides support for zone 1A and in some cases alsoresists uplift of the face slab prior to reservoir filling. Random mix of silts,clays, sands, gravels, and cobbles to provide protection to Zone 1A. Thiszone shall be placed in 400 mm layers and compacted.

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Zone 2A:Sand and gravel filter are located within two to three meters of theperimetric joint to limit leakage in the event of water stop failure and to selfheal with under water placement of silt or silty fine sand. In the event ofdisruption of the water- stops at the perimeter joint, the filter zone 2A willprevent the movement of silt size particles through the zone and, thus,serves as secondary defense against leakage. This zone consists of materialequal or nearly equal in quality to concrete aggregate. The material ismanufactured and processed to specific gradation limits. Zone 2A shall beplaced in 200 mm layers, well-compacted with vibratory compactors, andprotected from damage and erosion during construction. The zone 2A filtermaterial, placed immediately adjacent to the perimeter joint, needs to bewell compacted to strict specifications to minimize settlement.

Zone 2B: Zone 2B provides support to the face slab and consists of sandand gravel-sized particles, placed in 300 mm horizontal layers and normallycompacted with 4 passes of a 10-ton smooth-drum vibratory roller. Thehorizontal width of the zone varies from 2 to 4 m depending on the height ofthe dam. This zone consists of material equal or nearly equal in quality toconcrete aggregate. The material is a crushed product and manufactured tospecific gradation limits. The aim of the ICOLD Bulletin 70 specification isto limit maximum size, to provide a grading which will not segregate duringplacement, and to include sufficient fines to give an acceptable lowpermeability. A target permeability of 1 X 10-4 cm/sec is recommended. Thisgradation exhibits low permeability and some cohesion.

Zone 3A: Zone 3A is to provide compatibility and limit void size adjacentto Zone 2B.This zone is a transition between Zone 2B and rockfill Zone 3Band consists of rockfill with maximum size of 300 mm or less placed in 300mm layers and normally compacted with at least 6 passes of a 10-ton orheavier smooth-drum vibratory roller. The horizontal width of the zonevaries from 2 to 4 m depending on the height of the dam. For all CFRDs inP-T-N Project, horizontal width of this zone has been proposed as 4 m.

Zone 3B: This zone resists the water loading and limits face deflection.This zone commonly consists of rockfill with maximum size of 800 mmplaced in 800 mm layers and normally compacted with 6 passes of a 10-tonsmooth-drum vibratory roller. Water (10%-25% of rock volume) is added

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during fill placement. Increasing compaction coverage, using thinner layers,and application of water are means of achieving satisfactory density whenusing weak rock. Thinner layers are often used for sand and gravel fills.

Zone 3C: Zone 3C receives little water loading, and settlement isessentially during construction. This zone commonly consists of rockfillwith maximum size of 1000 mm placed in 1000 mm layers and normallycompacted with 6 passes of a 10-ton smooth-drum vibratory roller. As forZone 3B, layer thickness and compaction effort are adjusted based on thecharacteristics of the material. The thicker layer in Zone C accepts largerrock, is more economical to place, and its lower density (about 5% less thanZone 3B density) saves rock volume. Large rock placed at the downstreamtoe to resist scour and tail water action.

Zone 3D: The CFRD relies on a non-saturated downstream shell forstability. When hard and relatively uniform well graded free drainingrockfill are used, this requirement is met without difficulty andunexpectedly high leakage through the upstream face will not endangerstability. High capacity internal drainage is a key safety feature of theCFRD. Rockfill and coarse gravel-cobble fills will naturally segregateduring placement with finer less permeable material at the top of the layerand the coarser more pervious material towards the base of the layer. Thischaracteristic provides for a substantially higher horizontal permeabilitythan vertical permeability. Drainage is assured within the entire body of thedam. This rockfill zone provides positive drainage within the embankment.An under drain of the coarsest rock (zone 3D) is placed within the valleysection to enhance the overall draining ability of the dam. In all the CFRDsfor Zone 3D, use of oversize boulders of size more than 1000mm has beenproposed.

The details of the different zones and their gradation are given inCWC Drawings No. PTNL-5900-P-1037, 1023, 1030 and 1044 (Plates–6.3,6.27, 6.51 and 6.73) of Volume – VIII (A) and PTNL-5900-P-1051 and1058 (Plates-6.97 and 6.121) of Volume – VIII (B).

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6.2.1.5 Dam Slope Stability

As already mentioned above under para 6.2.1.4, the slopes of theupstream face as well as downstream face of all the six CFRDs envisaged inPar-Tapi-Narmada Link Project, have been kept as 1.5H:1V which are quitesafe from stability point of view. On the downstream side of the dam 4meter wide berms have been proposed to facilitate the construction andmaintenance. Therefore, the average downstream slope gets further flatter.

6.2.1.6 Plinth

The plinth or toe slab connects the foundation with the face slab. Thedimensions of the plinth have been selected based on precedent andgenerally vary with reservoir head and with foundation conditions. Thewidth of the plinth has been proposed to be changed in several steps and isnot tapered, mainly for construction convenience. For moderately to slightlyweathered rock, the width of plinth has been increased, such that amaximum hydraulic gradient of 10 is achieved. The minimum width hasbeen usually set at 3 m. The minimum design thickness T of the plinth isusually on the order of 0.3 to 0.4 m with thickness varying with reservoirhead, H.

In case of Par-Tapi-Narmada Link Project, the plinth thickness hasbeen determined in accordance with the expression T ( in m) = 0.3 + 0.003H (where H= head of water above plinth in metres).

For construction convenience, a constant thickness is often specified.A constant thickness of plinth of 600mm for Jheri, Paikhed and ChikkarCFRDs and a constant thickness of plinth of 500mm for Chasmandva,Dabdar and Kelwan CFRDs has been kept. However, the plinth length (i.e.length of plinth along the direction of flow) will vary with the head of waterabove plinth at any section. The criteria adopted for the determination oflength of plinth for various foundation conditions in terms of Head of waterabove plinth is given in the Table – 6.8.

Table- 6.8Head of Water Vis-à-vis Length of Plinth

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Current practice is to provide one layer of reinforcement in the plinthequal to 0.3% both ways. The reinforcement is located at 150 mm cleardistance from the top surface. Therefore, reinforcement of 0.30% (bothways) for plinth have been proposed for all the six dams. Concrete cover istypically set at a minimum of 150 mm.

6.2.1.7 Face Slab

The primary water barrier of the CFRD consists of concrete face slabspoured on underlying support zones of the rockfill body of the dam. Theface slab is fully supported by the underlying rockfill, and is mostly incompression under reservoir loadings, except towards the dam abutmentswhere tensile strains develop. Because of this, the design of face slabs inrecent years has concentrated more on water tightness and durability than ondesign of slabs, and increasing attention has been paid to identification andcontrol of crack development in face slabs. Deformation of the face slab willconform to the deformation of the underlying rockfill body of the dam. Thisfact highlights the importance of proper selection, placement andcompaction of the rockfill materials supporting the face slabs to limitexcessive deformations and cracking in the face slabs. Face slab generallymoves towards the centre of the dam and away from the dam abutments,highlighting the fact that most parts of the slabs are generally incompression except at the abutments. Successful performance of the CFRDface slabs, in terms of providing a reasonably waterproof barrier to thereservoir, is highly dependent on factors other than the design of the faceslab itself. In this respect, the determination of face slab dimensions, andreinforcing is based on previous experience rather than rigorous analysis.

6.2.1.7.1 Face Slab Thickness

For all the six CFRDs in Par-Tapi-Link Project, the thickness ofconcrete face slab has been proposed according to formula T (in m) = 0.3 +

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Type of Rock Length of PlinthNon-Erodible H/18Slightly Erodible H/12Erodible H/6

0.0035H (where H= head of water above the concerned elevation of Faceslab). The thickness of Face slab at the top level of the dam, is fixed as300mm. The thickness of face slab will vary linearly at various elevations,as per simple expression given above, and will be maximum at the bottom(i.e. at the junction with plinth).

In CFRD dam, RCC Face slab thickness of 30 cm at top to 50 cm atbottom have been provided. Refer Drawings Nos. PTNL-5900-P-1037,1023, 1030 and 1044 (Plates –6.3, 6.27, 6.51 and 6.73) in Volume –VIII(A).

6.2.1.7.2 Panel Width

Panel width for face slab typically ranges from 12 to 18m, with panelwidth of 15m being common. Factors affecting the width of face slab panelsare mainly related to the width of the slip forms and capabilities of concreteplacing equipment. Narrower panel widths are use where vertical joints aredesired due to changes in plinth geometry, rock topography, or adjacent tothe dam abutments, where larger panel movements may occur. Panel widthsgreater than about 18m are uncommon. Wider panel widths can increase theoccurrence of shrinkage cracks. In case of all the CFRDs in Par-Tapi-Narmada Link Project, the width of the concrete panels has been kept as15.0 metres.

6.2.1.7.3 Joints

The perimetric joint, vertical joints, and horizontal construction jointsare used to separate adjacent face slab panels on CFRDs. The perimetricjoint separates the plinth from the face slab. Vertical joints separate adjacentpanels along the axis of the dam. Horizontal joints separate different poursof the same slab, or separate starter slabs from the main face slab. Thelocation and design of each of these joints differs according to their purposeand importance in the performance of the face slab as the water barrier ofthe CFRD. The locations and use of vertical construction joints and verticalcontraction joints depends upon whether adjacent slabs are expected tomove away from each other under reservoir operation. The locations ofhorizontal joints are primarily controlled by the length of slab pours and bythe geometry of starter slabs.

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6.2.1.7.3 (a) Perimetric Joint and Water Stops

The perimetric joint connects the concrete face slab and the plinth ofthe CFRD to complete the upstream water barrier of the dam. Due to itslocation and movement that occur at this joint, the perimetric joint is hasbeen given special consideration. The main function of the perimetric jointis to maintain a watertight seal against full reservoir load while allowing foranticipated movements between the plinth and face slabs. The face slab canmove relative to the plinth in three different directions: normal to theperimetric joint (opening), normal to the face slab (settlement), and parallelto the perimetric joint (shear). Movement in any of these directionsseparates the face slab from the plinth. All longitudinal and transverse jointsin the plinth, the perimetric joint between face slab and plinth and jointbetween plinth and cut off wall were provided with the following provisionsto prevent potential leakage:

a) A bitumen graded sand mixture with a protection of hypalon bandat the top of joint anchored to concrete through steel angles.

b) A 300 mm wide PVC water stop in the centre of the joint c) A copper water stop (0.8 m thick) at the base of joint.d) A pad made of bitumen graded sand mixture at the base of joint.

The face slab rests on the rockfill body of the dam, and will move anddeform as the rockfill it rests on settles beneath it. Leakage is a keyparameter that relates to the overall performance of the CFRD. Largeleakage rates are an indication that damage has occurred to the perimetricjoint and/ or face slab has cracked to some extent. Seepage through thefoundation may also be a contributing factor to large leakage rates. Thefundamental design concept of the CFRD is that the several embankmentzones of the dam including the face support material, filters, transitions,under-drainage and the body of the dam must remain stable even ifextremely large leakage rates were to occur. It is well known the rockfill isable to accept and pass large flows. So even if large leakage rates occur, itmay not be an indication that the safety of the dam is jeopardized but itsuggests that remedial treatment to prevent the leakage is required.

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The details of perimetric joint provided are shown in Drawing Nos.PTNL-5900-P-1039, 1025, 1032 and 1046 (Plates –6.5, 6.29, 6.53, and6.75) in Volume –VIII (A) and Drawing Nos. PTNL-5900-P-1053 and 1060(Plates –6.99 and 6.123) in Volume –VIII (B).

6.2.1.7.3 (b) Tensile Vertical Joint (Near Abutments) and CompressiveVertical Joint

Tensile vertical joints are designed to allow movement betweenadjacent face slabs while maintaining a watertight barrier to the reservoir.They are located near the dam abutments or where two adjacent slabs havethe potential to separate from each other under self-weight or reservoirloading.

To allow for the anticipated movement at the expansion joint, slabreinforcement is terminated at the joint. To maintain water tightness, asingle or double water-stop and joint sealing materials are typically used.

Vertical compression joints are located between adjacent face slabsthat are not anticipated to separate away from each other. These joints arelocated towards the middle of the dam away from the abutments whereadjacent slabs will tend to move towards each other. Reinforcement may ormay not be continuous through vertical compression joints, depending onthe geometry and configuration of the dam alignment. Reinforcement is nottypically continued through the vertical compression joints of modernCFRDs constructed across U or V-shaped river valleys. In this situation thecompressive force acting between adjacent face slabs away from theabutments keeps them in contact and acting as a single unit. For CFRDsconstructed across long, flat or undulating river valleys, the force betweenadjacent face slabs may be compressive, neutral or possibly slightly tensiledepending on the profile of the plinth along the valley floor. In these casesreinforcement is carried through vertical joints to keep adjacent slabs fromseparating due to changes in the plinth profile. Typically only a bottomwater-stop is used to block seepage through the joint.

6.2.1.7.3 (c) Horizontal Construction Joint

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Horizontal construction joints are used when only a portion of a faceslab panel cannot be poured, either by design or due to an unscheduledinterruption. Reasons for horizontal construction joints include stagedconstruction of the rockfill dam body, use of starter slabs, interruptions inslab construction due to weather or equipment malfunction, long panellengths on high CFRDs. Horizontal construction joints typically do notincorporate any water-stops, and reinforcement is continuous through thejoints. It is important to thoroughly clean and repair any honeycombing orother damage to the joint before construction of the panel is continued.

6.2.1.7.4 Concrete Properties

Concrete mix design for CFRD face slabs should focus onminimizing shrinkage cracking in the face slab and increasing the durabilityof the concrete. Best practices followed for the production of durable andimpermeable concrete for other water retaining structures should befollowed for concrete face slabs and plinth of CFRDs as well. Qualitycontrol during concrete production, placement, consolidation, and curing isthe most important factor in this respect.

6.2.1.7.4 (a) Concrete Mix Design Properties

For the plinth, face slab and parapet wall of the all the six CFRDs inPar-Tapi-Narmada Link project, M25 grade of concrete conforming to IS456: 2000 has been proposed. The Grade of concrete for interface wall hasbeen proposed as M15 conforming to IS 456: 2000. However, M-20 Gradeconcrete has been proposed for 1m thick concrete over face of interface wallwhich will be in contact with water.

6.2.1.7.4 (b) Concrete Aggregates

Selection of aggregates for CFRD face slabs should considermaximum particle sizes for proper concrete cover and placement and thepotential for cement-aggregate reactivity. For all the CFRDs in the projectthe maximum aggregate size has been fixed as 38mm.

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6.2.1.7.5 Reinforcement

Reinforcement of 0.35% (both ways) for face slab has been proposedfor all the six dams. Concrete cover is typically set at a minimum of 150mm.

6.2.1.8 Parapet Wall

Unlike earth core rockfill dams, concrete face rockfill dams havetraditionally been provided with a concrete parapet wall at the upstreamedge of the crest. The parapet wall in CFRD also participates in thefunctioning of the Dam and may be kept a part of free board requirement ofthe dam. The height of parapet wall has been kept as 1.20m above the top ofdam, in case of all the six dams under the link project.

The main purpose of the parapet wall is to reduce the total volume ofrockfill. Commonly a single parapet wall is constructed. The face slabconstruction requires the use of winches at the crest to support the slip-forming and other equipment necessary for efficient construction.Additionally, access is required for personnel, for movement of equipment,and for delivery of concrete, steel and other material. To accommodate theseactivities, sufficient working space is required for an efficient concretingoperation. Thus, use of a parapet wall provides a sufficiently wide workingsurface at the elevation of the base of the parapet wall for face slabconstruction. In addition, the parapet wall serves as a wave splash barrieralso.

6.2.1.8.1 Joint between Parapet Wall and Face Slab

The joint between the parapet wall and the face slab must provide anadequate barrier against leakage from the reservoir water. Commonly, thebase of the parapet wall is located somewhat above the normal maximumoperating reservoir level (ie. FRL) so that the joint is not normallysubmerged. During flood, the wall contains the reservoir surcharge. Theelevation of the top of the wall has been selected such that overtopping doesnot occur during the probable maximum flood. In case of all the CFRDs

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envisaged in the link project, the base of parapet wall has been kept aboveMaximum Water level (MWL).

Minimum joint treatment consists of a water stop in the middle or atthe base of the joint and a mortar pad at the base of the joint to providesupport. Mastic filler is often used above the water stop. If the vertical faceslab joint contains both a middle water stop and a water stop at the base, it iscommon practice to place middle and base water stops within the parapet-wall/face-slab joint.

The details of Parapet wall provided are shown in Drawing Nos.PTNL-5900-P-1039, 1025, 1032 and 1046 (Plates –6.5, 6.29, 6.53, and6.75) in Volume –VIII (A) and Drawing Nos. PTNL-5900-P-1053 and 1060(Plates –6.99 and 6.123) in Volume –VIII (B).

6.2.1.9 Interface Wall

At the junction between the all the CFRDs and the spillways in the P-T-N project, interface wall has been proposed to prevent seepage. TheN.O.F. block adjacent to the CFRD has been utilized as Interface wall. Onboth, upstream and downstream sides, the slope of the interface wall hasbeen kept same as that of CFRD i.e. 1.5H : 1V. On the downstream side thethickness of wall is 15m for all the dams except Jheri CFRD where thisthickness has been kept as 10.0m. On the upstream side, the thickness ofinterface wall, in all the six dams, has been kept as 3.0m. The slope of 3.0mthick upstream side interface wall shall be 0.65:1 towards the dam side.The slope of 15.0m thick interface wall on the downstream side shall be0.25:1 towards the dam side.

The interface wall details are given in Drawing Nos.PTNL-5900-P-1040, 1041, 1026, 1027, 1033, 1034, 1047 and 1048 (Plates-6.6, 6.7, 6.30,6.31, 6.54, 6.55, 6.76 and 6.77) in Volume –VIII (A) and DrawingNos.PTNL-5900-P-1054, 1055, 1061 and 1062 (Plates – 6.100, 6.101, 6.124and 6.125) in Volume-VIII (B).

6.2.1.10 Filter (Zone 2A) - Filter Requirements

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As per ICOLD Bulletin 141, the filter-drain system provides an all-important second line of defense. If the water stops at the perimeter joint aredisrupted such that reservoir leakage through the joint occurs, the 2A filtermust retain silt and fine sand particles. High head loss will occur throughthe clogged filter interface and/or through the silts and sands trapped withinthe joint upstream of the filter. In addition, the filter must be considerablymore permeable than the clogged interface or the material trapped in thejoint.

The following criteria summarize these fundamental functions(ICOLD, 1994):

1. Retention Function: The classic Terzaghi criterion D15/d85< 4addresses this requirement. In this expression the following symbolsare used:

D15 = particle size in filter (protecting, or coarser material) for which 15% by weight of particles are smaller; andd85 = particle size in base (protected, or finer material) for which 85% by weight of particles are smaller.

2.Permeability Function: The classic Terzaghi criterion D15/d15> 4addresses this requirement. It is noted that strict adherence to thiscriterion with respect to Zones 2A and 2B is not required.

To achieve the above functions, the Zone 2A filter, it should notsegregate or change in gradation (degrade or breakdown) during processing,handling, placing, spreading or compaction. It should not have cohesion orability to cement as a result of chemical, physical or biological action. Itshould be internally stable, that is, the coarser fraction of the filter withrespect to its own finer fraction must meet the retention (piping) criteria.

The zone wise gradation provided in the six CFRDs of Par-Tapi-Narmada Link Project along with compaction parameters and SalientFeatures of various CFRDs are given in Table– 6.9 and 6.10.

Table – 6.9Zone wise Gradation in CFRDs and Compaction Parameters

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Zon

e Description Source Gradation Compaction ParametersDmax

(mm)<5mm(%)

<0.1mm(%)

Lay

er T

hic

kn

ess

(cm

)

No.

of

pas

ses

Den

sity

(t/

m3 ) Roller Wt

(t)

1A Silty fine sand

-- -- -- 20 -- -- By Construction equipment

1B Random fill -- -- -- 40 4 -- 10 2A Processed

fine filter Processed from Quarry

40 35-60 5-10 20 -- -- By Manual vibrator

2B Processed filter

100 35-45 4-7 30 4 2.20 to 2.30

10

3A Transition (Processed Rockfill)

Excavatedfrom Quarry

300 20-30 <5 30 6 -- 10

3B Major Rock fill (Main fill)

800 4 -15 <5 80 6 2.20 to 2.40

10

3C Rock fill or Gravel

1000 < 20 <5 100 6 2.20 to 2.30

10

3D Oversize Boulder

>1000

-- -- -- -- --

Table– 6.10Salient Features of various CFRDs

Name of Dam

FRL MWL Dam Top Level

Maximum Height of Dam above River Bed

Length of Dam (Excluding N.O.F. and O.F. Length)

Top Width of Dam

Slopes of u/s and d/s Face of Dam

Jheri EL 246.00

EL 247.50

EL 253.00

75.88m 663m 10.0m U/S: 1.5H : 1V

D/S: 1.5H : 1V

Paikhed EL248.00

EL 249.00

EL 255.00

94.4m 1310m 10.0m U/S: 1.5H : 1VD/S: 1.5H : 1V

Chasmandva

EL 214.00

EL 215.18

EL 222.00

53.70 2703m 10.0m U/S: 1.5H : 1V

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D/S: 1.5H : 1V

Chikkar EL 210.00

EL 210.50

EL 217.00

62.27m 1736m 10.0m U/S: 1.5H : 1V

D/S: 1.5H : 1V

Dabdar EL 169.00

EL 170.50

EL 177.00

63.65m 1045m 10.0m U/S: 1.5H : 1V

D/S: 1.5H : 1V

Kelwan EL 164.00

EL 165.00

EL 174.00m

57.95m 1141m 10.0m U/S: 1.5H : 1V

D/S: 1.5H : 1V

6.2.2 Concrete Dam6.2.2.1 Layout of Concrete Dam

The Jheri dam has been proposed across Par River as compositeembankment (CFRD) cum concrete dam. The total length of Jheri dam is808.32 m of which 145 m is concrete dam and remaining 663.32 m isCFRD. The Jheri concrete dam is 38 m high and the length of non overflow portion is 54 m and over flow portion is 91 m. The over flow portionconsists of 5 bays of 15 m length and 4 piers of 4 m width, to pass a peakflood of 6539 cumecs (PMF). Layout Plan, Spillway Plan and Spillwayelevation of Jheri concrete dam are at Drawing Nos. PTNL-5900-P-3041,PTNL-5900-P-3043 and 3044 (Plate –6.8, 6.19and 6.20) in Volume –VIII(A).

The Paikhed dam has been proposed across Nar River as compositeembankment (CFRD) cum concrete dam. The total length of Paikhed dam is1431.85 m of which 121 m is concrete dam and remaining 1310.85 m isCFRD. The Paikhed concrete dam is 45 m high and length of non over flowportion is 49 m and over flow portion is 72 m. The over flow portionconsists of 4 bays of 15 m length and 3 piers of 4 m width, to pass a peakflood of 5307cumecs (PMF). Layout Plan, Spillway Plan and Spillwayelevation of Paikhed concrete dam are at Drawing Nos. PTNL-5900-P-3001,3003 and 3005 (Plate –6.32, 6.42and 6.43) in Volume – VIII (A).

The Chasmandva dam has been proposed across Tan River ascomposite embankment (CFRD) cum concrete dam. The total length ofChasmandva dam is 2781 m of which 78 m is concrete dam and remaining2703 m is CFRD. The Chasmandva concrete dam is 35 m high and length

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of non over flow portion is 34 m and over flow portion is 44 m. The overflow portion consists of 3bays of 12 m length and 2 piers of 4 m width, topass a peak flood of 2578cumecs (PMF). Layout Plan, Spillway Plan andSpillway elevation of Chasmandva concrete dam are at Drawing Nos.PTNL-5900-P-3021, 3024 and 3023 (Plate –6.56, 6.65and 6.66) in Volume– VIII (A).

The Chikkar dam has been proposed across Ambica River ascomposite embankment (CFRD) cum concrete dam. The total length ofChikkar dam is 1887 m of which 151 m is concrete dam and remaining1736 m is CFRD. The Chikkar concrete dam is 47 m high and length of nonover flow portion is 79 m and over flow portion is 72 m. The over flowportion consists of 4 bays of15 m length and 3 piers of 4 m width, to pass apeak flood of 5649 cumecs (PMF). Layout Plan, Spillway Plan andSpillway elevation of Chikkar concrete dam are at Drawing Nos. PTNL-5900-P-3061, 3063 and 3064 (Plate –6.78, 6.89 and 6.90) in Volume – VIII(A).

The Dabdar dam has been proposed across Khapri River as compositeembankment (CFRD) cum concrete dam. The total length of Dabdar dam is1170 m of which 135 m is concrete dam and remaining 1035 m is CFRD.The Dabdar concrete dam is 45 m high and length of non over flow portionis 44 m and over flow portion is 91 m. The over flow portion consists of 5bays of 15 m length and 4 piers of 4 m width, to pass a peak flood of6683cumecs (PMF). Layout Plan, Spillway Plan and Spillway elevation ofDabdar concrete dam are at Drawing Nos. PTNL-5900-P-3081, 3084 and3083 (Plate –6.102, 6.113and 6.114) in Volume – VIII (B).

The Kelwan dam has been proposed across Purna River as compositeembankment (CFRD) cum concrete dam. The total length of Kelwan dam is1330 m of which 189 m is concrete dam and remaining 1141 m is CFRD.The Kelwan concrete dam is 51 m high and length of non over flow portionis 98 m and over flow portion is 91 m. The over flow portion consists of 5bays of 15 m length and 4 piers of 4 m width, to pass a peak flood of 7979cumecs (PMF). Layout Plan, Spillway Plan and Spillway elevation ofKelwan concrete dam are at Drawing Nos. PTNL-5900-P-3101, 3104 and3103 (Plate –6.126, 6.137 and 6.138) in Volume – VIII (B).

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6.2.2.2 Free Board

The free board requirement of the concrete dam is less as compared toa CFRD. As such, the free board as worked out in the case of CFRD hasbeen provided for the concrete dam.

6.2.2.3 Zoning

Concrete having different strength has been proposed for differentareas of the concrete gravity section based on the stress pattern. In eachzone, the concrete satisfies the strength requirement defined by the State ofstress. In the peripheral zones, the concrete is also subjected to the influenceof external factors-variation in the temperature of air, seepage of water,alternate drying and wetting, erosion of overflow surfaces due to abrasionand cavitations. As such the concrete, depending upon its exposure to theexternal influences, should satisfy other requirements too. Based on theabove considerations, the following zoning of the dam section in terms ofconcrete strength has been proposed (Table – 6.11 for non over flow sectionand Table – 6.12 for over flow section):

Table – 6.11Classification of Concrete in Non Over Flow Section

S.No.

Location Classificationof Concrete

Max. size of Aggregate(mm)

CompressiveStrength of150 mmCubes inN/mm2 (28days)

1 Concrete in Non overflow section (Except 1500 mm exterior thickness on u/s face)

C1 150 15.00

2 Concrete in foundation forfilling up crevices etc.

C2 40 12.50

3 Concrete in U/S face C3 75 16.50

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(1500 mm thick).4 Fillets concrete. C4 40 25.005 Concrete in parapet C5 20 20.006 Concrete around

foundation gallery, sump well, pump chamber, stair / lift well and other openings.

C6 40 20.00

Table – 6.12Classification of Concrete in Over Flow Section

S.No.

Location Classificationof Concrete

Max. sizeof

Aggregate(mm)

Compressive Strengthof 150 mm Cubes in N/mm2 (28 days)

1 (i) Concrete in spillway section (except 1500 mm exterior thickness on U/S face and D/S glacis).

C1 75 15.00

(ii) Left and right training wall gravity section (except 1000 mm thickness on water side).

2 Concrete in foundation for filling up crevices etc.

C2 40 20.00

3 (i) Concrete in exterior 1500mm thickness on U/S face of spillway

C3 75 20.00

(ii) Concrete in exterior 1000 mm thickness of the training wall (gravity section) on water side

4 Fillets concrete. C4 40 25.005 (i) Concrete in spillway

bridge, deck slab, beams and parapet etc.

C5 20 20.00

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(ii) Concrete around foundation gallery, sump well, pump chamber, stair case/lift well and other openings.

6. (i) Concrete in spillway crest, pier, glacis, training wall (RCC section) and anchorage length of pier.(ii) Concrete in stilling basin, apron (Excluding top 1000 mm).

C6 75 20.00

7 Concrete in exterior 1000 mm thickness of stilling basin and apron.

C7 75 25.00

8 Concrete in stilling basin chute block, basin block andend sill.

C8 20 30.00

The zoning of material for NOF and OF sections of Jheri dam areshown in Drawing Nos. PTNL-5900-P-3051, 3054 and 3048 (Plate –6.11,6.12, 6.16) in Volume – VIII (A). The zoning of material for NOF and OFsections of Paikhed dam are shown in Drawing Nos. PTNL-5900-P-3010,3013 and 3008 (Plate –6.36, 6.35 and 6.39) in Volume – VIII (A). Thezoning of material for NOF and OF sections of Chasmandva dam are shownin Drawing Nos. PTNL-5900-P-3031 and 3028 (Plate –6.59 and 6.62) inVolume – VIII (A). The zoning of material for NOF and OF sections ofChikkar dam are shown in Drawing Nos. PTNL-5900-P-3071, 3074 and3068 (Plate –6.82, 6.81 and 6.86) in Volume – VIII (A). The zoning ofmaterial for NOF and OF sections of Dabdar dam are shown in DrawingNos. PTNL-5900-P-3091, 3094 and 3088 (Plate –6.106, 6.105and 6.110) inVolume – VIII (B). The zoning of material for NOF and OF sections ofKelwan dam are shown in Drawing Nos. PTNL-5900-P-3111, 3114 and3108 (Plate –6.129, 6.130 and 6.134) in Volume – VIII (B).

6.2.2.4 Design of Concrete Dam6.2.2.4.1 Design Criteria for Non- Overflow Section

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The design has been carried out to fulfil the following requirements ofstability.

I. The dam shall be safe against sliding on any plane or combination ofplanes within the dam, at the foundation or within the foundation.

II. The dam shall be safe against overturning at any plane below the base.

III. The safe unit stresses in the concrete or masonry of the dam or in the foundation material shall not be exceeded.

Further, all the forces considered in the analysis have been taken asper IS 6512-1984. The unit weight of concrete has been taken as 2.4 T/cumand water as 1.0 T/cum. The project area falls under zone –III of the seismiczone of India. The foundation has been assumed to be granite and massconcrete (for dams).6.2.2.4.2 Stability Analysis of Non-Overflow Section

Jheri Dam:

A total of 2 nos. Concrete Non-overflow blocks, one on each side ofthe spillway have been proposed. The top width of the left and right NOFblock has been kept as 10.0m. The foundation level for the left and rightNOF block has been kept at EL.210.0m. With its top level at EL 253 m, themaximum height of the NOF section is 43 m.

The Non-overflow section has been designed with the following data:

a) Maximum water Level (MWL) = El.247.0mb) Full Reservoir Level (FRL) = El.246.00mc) Foundation Level = El.210.00me) Top width of dam = 10.0mf) U/S slope =0.1 H: 1Vg) D/S slope = 0.8 H: 1Vh) Horizontal seismic coefficient =0.1i) Vertical seismic coefficient =0.067j) Cohesion =100 T/sq.mk) Angle of internal friction =35 degrees

333

The stability analysis for Non-Overflow section has been carried outat the deepest foundation level i.e. at 210.00m, and the results are furnishedin Table - 6.13:

Table – 6.13Results of Stability Analysis for Non-Overflow Section

Sr.No.

LoadCombination

Vertical Stress (in t/m2) Factor ofSafetyAgainstSliding

PermissibleTensileStress (int/m2)

Upstream Downstream1 A 99.38 7.12 -- ---2 B 55.34 28.01 2.80 No Tension3 C 50.16 30.43 2.60 0.01 fc (20)4 D 113.95 -2.30 18.205 E 37.49 41.93 2.90 0.02 fc (40)6 F 35.54 29.30 5.90 0.02 fc (40)7 G 22.59 40.77 4.70 0.04 fc (80)

Paikhed Dam:

A total of 2 nos. concrete non-overflow blocks, one on each side of thespillway have been proposed. The top width of the left and right NOFblocks has been kept as 10.0m. The foundation level for the left and rightNOF block has been kept at EL 175.0m and EL 210 m. With its top level atEL 255 m, the maximum height of the NOF section is 80 m.

The non-overflow section has been designed with the following data:

a) Maximum water Level (MWL) = 249.0mb) Full Reservoir Level (FRL) = 248.00mc) Foundation Level = 175.00me) Top width of dam =10.0mf) U/S slope =0.1 H: 1Vg) D/S slope = 0.8 H: 1Vh) Horizontal seismic coefficient =0.1i) Vertical seismic coefficient =0.067j) Cohesion =509.858 T/sq.m

334

k) Angle of internal friction =55 degrees

The stability analysis for Non-Overflow section has been carried outat the deepest foundation level i.e. at 175.00m, and the results are furnishedin Table – 6.14:

Table – 6.14Results of Stability Analysis for Non-Overflow Section

Sr.No.

LoadCombination

Vertical Stress (in t/m2)

Factor ofSafetyagainstSliding

PermissibleTensile Stress(in t/m2)

Upstream Downstream1 A 169.24 17.74 -- ---2 B 41.63 87.06 5.1 No Tension3 C 38.12 87.41 5.2 0.01 fc (20)4 D 192.96 1.76 51.05 E 7.78 114.64 5.7 0.02 fc (40)6 F 18.55 86.00 12.9 0.02 fc (40)7 G -13.47 113.11 9.9 0.04 fc (80)

Chasmandva Dam:

A total of 2 nos. concrete non-overflow blocks, one on each side of thespillway have been proposed. The top width of the left and right NOF blockhas been kept as 10.00 m. The foundation level for the left and right NOFblocks has been kept at EL 184.0 m .With its top level at EL 222.0 m, themaximum height of the NOF section is 38 m.

The non-overflow section has been designed with the following data:

a) Maximum water Level (MWL) = 215.0mb) Full Reservoir Level (FRL) = 214.00mc) Foundation Level = 184.00me) Top width of dam =10.0mf) U/S slope =0.1 H: 1Vg) D/S slope = 0.8 H: 1Vh) Horizontal seismic coefficient =0.1i) Vertical seismic coefficient =0.067

335

j) Cohesion =509.858 T/sq.mk) Angle of internal friction =55 degrees

The stability analysis for Non-Overflow section has been carried outat the deepest foundation level i.e. at 184.00 m, and the results are furnishedin Table – 6.15:

Table – 6.15Results of Stability Analysis for Non-Overflow Section

Sr.No.

LoadCombination

Vertical Stress (in t/m2)

FactorofSafetyAgainstSliding

PermissibleTensileStress(in t/m2)

Upstream Downstream

1 A 80.08 2.46 -- ---2 B 35.98 33.27 11.50 No Tension3 C 29.93 33.18 11.10 0.01 fc (20)4 D 93.11 -6.28 95.905 E 19.19 46.99 13.30 0.02 fc (40)6 F 19.13 31.19 30.70 0.02 fc (40)7 G 6.88 44.72 24.90 0.04 fc (80)

Chikkar Dam:

A total of 5 nos. concrete non-overflow blocks, 1 on left side and 4 onright side of the spillway have been proposed. The top width of the left andright NOF block has been kept as 7.0m. The foundation level for the left andright NOF blocks has been kept at EL.170.0m and El.179.0 m. With its toplevel at EL 217 m, the maximum height of the NOF section is 47 m.

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The non-overflow section has been designed with the following data:

a) Maximum water Level (MWL) = 212.0mb) Full Reservoir Level (FRL) = 210.00mc) Foundation Level = 170.00me) Top width of dam = 7.0mf) U/S slope =0.1 H: 1Vg) D/S slope = 0.8 H: 1Vh) Horizontal seismic coefficient =0.1i) Vertical seismic coefficient =0.067j) Cohesion =100 T/sq.mk) Angle of internal friction =35 degrees

The stability analysis for Non-Overflow section has been carried outat the deepest foundation level i.e. at 170.00 m, and the results are furnishedin Table – 6.16:

Table – 6.16Results of Stability Analysis for Non-Overflow Section

Sr.No.

LoadCombination

Vertical Stress (in t/m2)

FactorofSafetyAgainstSliding

PermissibleTensileStress (in t/m2)

Upstream Downstream

1 A 104.84 8.68 -- ---2 B 54.95 37.06 2.40 No Tension3 C 46.55 38.61 2.20 0.01 fc (20)4 D 119.03 -0.36 18.605 E 37.05 51.00 2.6 0.02 fc (40)6 F 32.31 36.19 5.10 0.02 fc (40)7 G 21.47 48.34 4.20 0.04 fc (80)

Dabdar Dam:

A total of 3 nos. concrete Non-overflow blocks, 1 on left side and 2 onright side of the spillway have been proposed. The top width of the left andright NOF block has been kept as 7.0m. The foundation level for the left and

337

right NOF block has been kept at EL.132.0 m and El.145.0 m. With its toplevel at EL. 177 m, the maximum height of the NOF section is 45 m.

The Non-overflow section has been designed with the following data:

a) Maximum water Level (MWL) = EL.170.0 mb) Full Reservoir Level (FRL) = EL. 169.0 mc) Foundation Level = El. 132.0 me) Top width of dam = 7.0mf) U/S slope =0.1 H: 1Vg) D/S slope = 0.8 H: 1Vh) Horizontal seismic coefficient =0.1i) Vertical seismic coefficient =0.067j) Cohesion =100 T/sq.mk) Angle of internal friction =35 degrees

The stability analysis for Non-Overflow section has been carried outat the deepest foundation level i.e. at El. 132.00 m, and the results arefurnished in Table – 6.17.

Table -6.17Results of Stability Analysis for Non-Overflow Section

Sr.No.

LoadCombination

Vertical Stress (in t/m2)

Factor ofSafetyAgainstSliding

PermissibleTensile Stress(in t/m2)

Upstream Downstream

1 A 71.72 3.22 -- ---2 B 45.41 14.56 4.70 No Tension3 C 40.71 13.32 4.60 0.01 fc (20)4 D 82.42 -3.58 22.405 E 33.03 24.15 4.6 0.02 fc (40)6 F 35.71 11.81 11.50 0.02 fc (40)7 G 26.69 22.24 8.0 0.04 fc (80)

Kelwan Dam:

A total of 6 nos. Concrete non-overflow blocks, 5 on left sideand 1 on right side of the spillway have been proposed. The top width

338

of the left and right NOF block has been kept as 7.0 m. Thefoundation level for the left and right NOF block has been kept atEL.123.0m. With its top level at EL 174 m, the maximum height ofthe NOF section is 51 m.

The non-overflow section has been designed with the following data:

a) Maximum water Level (MWL) = El. 166.0 m

b) Full Reservoir Level (FRL) = El.164.0 m

c) Foundation Level = El.123.0 m

e) Top width of dam = 7.0m

f) U/S slope =0.1 H: 1V

g) D/S slope = 0.8 H: 1V

h) Horizontal seismic coefficient =0.1

i) Vertical seismic coefficient =0.067

j) Cohesion =100 T/sq.m

k) Angle of internal friction =35 degrees

The stability analysis for Non-Overflow section has been carried

out at the deepest foundation level i.e. at El.123.0 m, and the results are

furnished in Table - 6.18:

Table – 6.18Results Stability Analysis for Non-Overflow Section

Sr.No.

LoadCombination

Vertical Stress (in t/m2)

Factor ofSafetyAgainstSliding

PermissibleTensileStress (in t/m2)

Upstream Downstream1 A 108.72 7.39 -- ---2 B 60.16 27.83 2.70 No Tension3 C 51.93 29.56 2.70 0.01 fc (20)4 D 123.80 -2.25 18.405 E 41.64 42.30 2.80 0.02 fc (40)6 F 39.35 28.68 6.10 0.02 fc (40)7 G 26.80 41.26 4.60 0.04 fc (80)

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From above it is seen that:

I. The stresses developed at the base of the non-over flow section are withinthe permissible limits specified in IS code 6512 – 1984

II. The stresses obtained are compressive in all combinations

III.The factor of safety against sliding for the conditions of reservoirs emptyand full (FRL and MWL) and various load combinations as per IS code6512- 1984 are found to be greater than 1.00 as recommended in IScode.

As such the stability of Non-overflow section is in order.

The details of NOF sections of Jheri, Paikhed, Chasmandva, Chikkar,Dabdar and Kelwan concrete dams are at Drawing Nos. PTNL-5900-P-3049, 3052, 3011, 3009, 3030, 3033, 3069 and 3072 (Plates – 6.9, 6.10,6.33, 6.34, 6.57, 6.58, 6.80 and 6.79) in Volume –VIII (A) and DrawingNos. PTNL-5900-P-3092, 3089, 3109 and 3112 (Plates – 6.103, 6.104,6.127 and6.128) in Volume –VIII(B).

6.2.2.4.3 Design of Overflow Section (Spillway)

The hydraulic design of the spillway conforms to IS: 6934 – 1998(first revision) -“Hydraulic Design of High Ogee Overflow Spillway –Recommendations”.

Components of Dam Spillway:

a) Spillway control structure/overflow sectionb) Non-overflow section c) Chute Channeld) Ski-jump bucket for dissipation of energy

Spillway Profile:

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The ogee profile consists of two quadrants, the upstream quadrant andthe downstream quadrant. Once the design head Hd of the spillway is fixed,the crest geometry may easily be evaluated. The recommended shape isbased on detailed observations of the lower nappe profile of fully ventilatedthin-plate weir. Such a profile would generally result in atmosphericpressure along the entire spillway surface at design head Hd. For head lowerthan Hd the pressure would be higher than atmospheric and for higher heads,sub-atmospheric pressure would result.

(A) Upstream Profile:

The upstream quadrant of the crest conforms to the equation of ellipseas below:

The magnitude of A1 and B1 are determined with reference to as perfigure provided in IS: 6934 and the Co-ordinates for all the 6 dams are givenin Table – 6.19:

Table – 6.19Upstream Profile Co-ordinates

Jheri dam Paikhed dam

Chasmandva dam Chikkar dam

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12

1

21

21

21

B

Y

A

X

Dabdar dam Kelwan dam

(B) Downstream profile:

The downstream quadrant of the crest conforms to the equation asbelow:

The magnitude of K2 is determined with reference to the parameterP/Hd as per figure provided in IS: 6934. The co-ordinates are given in Table– 6.20.

Table- 6.20

Jheri dam Paikhed dam

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285.0

285.1

2 YHKX d

Chasmandva dam Chikkar dam

Dabdar dam Kelwan dam

6.2.2.4.4 Stability Analysis ofOverflow Section

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D/s ProfileX1 in metre Y1 in metre

0 0.0001 0.0622 0.2234 0.8036 1.7018 2.89610 4.37512 6.13114 8.154

14.49 8.690

The stability analysis for Overflow section has been carried out at thedeepest foundation level at which sound rock is available, for loadcombinations as Stated under: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).

Uplift pressure are assumed to act over the entire base width and varyfrom maximum at heel on upstream side to one third of its value at thedrainage gallery and to zero at toe on downstream side where no tail wateris assumed.

Jheri Dam

The overflow blocks of spillway consist of 5 spillway bays of 15 mwidth and 4 piers of 4.0 m thickness. Thus the total length of the spillwaycomes to 91 m. A spillway bridge with a roadway width of 7.0 m has beenprovided. The spillway has its crest at EL.234.00m and comprises ofstandard ogee profile with upstream slope of 0.1H:1V and downstreamslope of 0.9H:1V. It has 5 Nos. of 15 m x12 m radial gates. The foundationlevel has been kept at EL.215.00 m. With top level at EL.253.00 m, themaximum height of the overflow section is 19 m.

Following data have been used for stability analysis of overflow section:

1. Radial gate trunnion elevation level = El. 238.00 m2. Bridge weight = 10 t/m run (Aprox.)3. Bridge width = 7.0 m4. Width of block =19 m5. Elevation of T.P. = El. 224.96 m 6. Bridge Road level =El. 253.0 m7. Cm = 0.7308. Spillway Crest =El. 234.00 m

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9. Foundation level = El.215.0 m

Results of Stability analysis of spillway are furnished in Table- 6.21 below:

Table – 6.21Results of Stability Analysis of Spillway

Sr. No. LoadCombination

UpstreamStress(T/sq.m)

DownstreamStress(T/sq.m)

Factor ofSafety inSliding

PermissibleTensile Stress(T/sq.m)

1 A 84.074 6.715 -- ----

2 B 12.805 54.745 1.900 No Tension

3 C 13.478 47.640 1.974 0.01 fc (20)4 D 99.237 -5.739 25.4395 E -10.219 75.059 2.142 0.02 fc (40)6 F 0.090 46.207 4.674 0.02 fc (40)7 G -24.122 73.572 3.559 0.04 fc (80)

Paikhed Dam

The overflow blocks of spillway consist of 4 spillway bays of 15 mwidth and 3 piers of 4.0 m thickness. Thus the total length of the spillwaycomes to 72 m. A spillway bridge with a roadway width of 10.0m has beenprovided. The spillway has its crest at EL.236.00m and comprises ofstandard ogee profile with upstream slope of 0.1H: 1V and downstreamslope of 0.8H: 1V. It has 4 Nos. of 15 m x12 m radial gates. The foundationlevel has been kept at EL.210.00 m. With crest level at EL.236.0 m, themaximum height of the overflow section is 26 m.

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Following data have been used for stability analysis of overflow section:

1. Radial gate trunnion elevation level = El. 237.54 m2. Bridge weight = 10 t/m run (Approx.)3. Bridge width = 10.0 m4. Width of block =19 m5. Elevation of T.P. = El. 224.74 m 6. Bridge road level = El. 255.0 m7. Cm = 0.7308. Spillway crest = El. 236.00 m9. Foundation level = El.210 m

Results of Stability analysis of spillway are furnished in Table- 6.22 below:Table – 6.22

Results of Stability Analysis of Spillway

Sr.No.

Load Combination UpstreamStress(T/sq.m)

DownstreamStress(T/sq.m)

Factor ofSafety inSliding

PermissibleTensileStress(T/sq.m)

1 A 84.369 11.897 -- ---

2 B 16.288 67.077 7.204 No Tension

3 C 16.526 58.915 7.336 0.01 fc(20)4 D 97.177 1.505 112.2695 E -3.098 84.048 8.726 0.02 fc(40)6 F -2.445 57.050 19.167 0.02 fc(40)7 G -23.067 82.085 15.637 0.04 fc (80)

Chasmandva Dam

The overflow blocks of spillway consist of 3 spillway bays of 12 mwidth and 2 piers of 4.0 m thickness. Thus the total length of the spillwaycomes to 44 m. A spillway bridge with a roadway width of 10.0 m has beenprovided. The spillway has its crest at EL.202.00m and comprises ofstandard ogee profile with upstream slope of 0.1H:1V and downstreamslope of 0.9H:1V. It has 3 Nos. of 12 m x12 m radial gates. The foundationlevel has been kept at EL.184.00m. With crest level at EL.202.00 m, themaximum height of the overflow section is 18 m.

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Following data have been used for stability analysis of overflow section:

1. Radial gate trunnion elevation level = El. 205.067 m2. Bridge weight = 10 t/m run (Aprox.)3. Bridge width = 10.0 m4. Width of block =16 m5. Elevation of T.P. = El. 190.73 m 6. Bridge road level =El. 222.0 m7. Cm = 0.7308. Spillway crest =El. 202.00 m9. Foundation level = El.184 m

Results of Stability analysis of spillway are furnished in Table – 6.23 below:

Table – 6.23Results of Stability Analysis of Spillway

Sr.No.

LoadCombination

UpstreamStress (T/sq.m)

DownstreamStress(T/sq.m)

Factor ofSafety inSliding

PermissibleTensileStress(T/sq.m)

1 A 122.409 9.659 -- ----

2 B 38.904 67.124 6.901 No Tension

3 C 31.321 60.886 7.147 0.01 fc (20)4 D 138.33 -2.961 96.0185 E 22.235 80.490 8.894 0.02 fc (40)6 F 12.420 58.161 19.058 0.02fc (40)7 G -0.919 77.152 16.117 0.04 fc (80)

Chikkar Dam

The overflow blocks of spillway consist of 4 spillway bays of 15 mwidth and 3 piers of 4.0 m thickness. Thus the total length of the spillwaycomes to 72 m. A spillway bridge with a roadway width of 7.0 m has beenprovided. The spillway has its crest at EL.198.00m and comprises ofstandard Ogee profile with upstream slope of 0.1H:1V and downstreamslope of 0.9H:1V. It has 4 Nos. of 15 m x12 m radial gates. The foundation

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level has been kept at EL.170.00m. With crest level at EL.198.00 m, themaximum height of the overflow section is 28 m.

Following data have been used for stability analysis of overflow section:

1. Radial gate trunnion elevation level = El. 202.00 m2. Bridge weight = 10 t/m run (Aprox.)3. Bridge width = 7.0 m4. Width of block =19 m5. Elevation of T.P. = El. 188.63 m 6. Bridge road level =El. 222.0 m7. Cm = 0.7308. Spillway crest =El. 198.00 m9. Foundation level = El.170.0 m

Results of Stability analysis of spillway are furnished in Table – 6.24 below:

Table – 6.24Results of Stability Analysis of Spillway

Sr.No.

LoadCombination

UpstreamStress (T/sq.m)

DownstreamStress (T/sq.m)

Factor ofSafety inSliding

PermissibleTensile Stress(T/Sq.m)

1 A 86.462 12.590 -- ----

2 B 20.255 60.791 1.845 No Tension

3 C 17.398 57.065 1.793 0.01 fc (20)4 D 96.526 69.194 33.9355 E 9.754 80.490 2.346 0.02 fc (40)6 F 2.276 53.909 4.091 0.02 fc (40)7 G -5.572 65.996 3.789 0.04 fc (80)

Dabdar Dam

The overflow blocks of spillway consist of 5 spillway bays of 15 mwidth and 4 piers of 4.0 m thickness. Thus the total length of the spillwaycomes to 91 m. A spillway bridge with a roadway width of 7.0 m has beenprovided. The spillway has its crest at EL.157.00 m and comprises ofstandard ogee profile with upstream slope of 0.1H:1V and downstream

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slope of 0.9H:1V. It has 5 Nos. of 12 m x12 m radial gates. The foundationlevel has been kept at EL.132.00 m. With crest level at EL.157.00 m, themaximum height of the overflow section is 25 m.

Following data have been used for stability analysis of overflow section:

1. Radial gate trunnion elevation level = El. 161.00 m2. Bridge weight = 10 t/m run (Aprox.)3. Bridge width = 7.0 m4. Width of block =19 m5. Elevation of T.P. = El. 148.310 m 6. Bridge road level =El. 177.0 m7. Cm = 0.7308. Spillway crest =El. 157.00 m9. Foundation level = El.132.0 m

Results of Stability analysis of spillway are furnished in Table – 6.25 below:

Table – 6.25Results of Stability Analysis of Spillway

Sr.No.

LoadCombination

UpstreamStress(T/sq.m)

DownstreamStress(T/sq.m)

Factor ofSafety inSliding

PermissibleStress(T/sq.m)

1 A 144.867 0.318 -- ----

2 B 41.841 80.573 1.592 No Tension

3 C 37.756 74.595 1.542 0.01 fc (20)4 D 164.255 -15.439 23.4305 E 21.526 97.257 1.939 0.02 fc (40)6 F 8.880 71.745 3.186 0.02 fc (40)7 G -9.450 94.20 2.871 0.04 fc (80)

Kelwan Dam

The overflow blocks of spillway consist of 5 spillway bays of 15 mwidth and 4 piers of 4.0 m thickness. Thus the total length of the spillwaycomes to 91 m. A spillway bridge with a roadway width of 7.0 m has beenprovided. The spillway has its crest at EL.152.00m and comprises of

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standard ogee profile with upstream slope of 0.1H:1V and downstreamslope of 0.8H:1V. It has 5 Nos. of 15 m x12 m radial gates. The foundationlevel has been kept at EL.123.00 m. With crest level at EL.152.00 m, themaximum height of the overflow section is 29 m.

Following data have been used for stability analysis of overflow section:

1. Radial gate trunnion elevation level = El. 156.00 m2. Bridge weight = 10 t/m run (Aprox.)3. Bridge width = 7.0 m4. Width of block =19 m5. Elevation of T.P. = El. 142.63 m 6. Bridge road level =El. 174.0 m7. Cm = 0.7308. Spillway crest =El. 152.00 m9. Foundation level = El.123.00 m

Results of Stability analysis of spillway are furnished in Table – 6.26 below:

Table – 6.26Results of Stability Analysis of Spillway

Sr.No.

LoadCombination

UpstreamStress(T/sq.m)

DownstreamStress (T/sq.m)

Factor ofSafety inSliding

PermissibleTensile Stress(T/sq.m)

1 A 32.244 20.933 -- ---

2 B 5.000 45.125 3.197 No Tension

3 C 6.427 34.891 3.464 0.01 fc (20)4 D 41.146 13.730 35.1555 E -8.095 56.489 3.612 0.02 fc (40)6 F -1.686 32.779 8.715 0.02 fc (40)7 G -16.064 54.414 6.260 0.04 fc (80)

Permissible Values of Tensile Stress as per IS.6512 are:

1. 40t/sq.m for load condition as enumerated under E2. 40t/sq.m for load condition as enumerated under F

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3. 80t/sq.m for load condition as enumerated under G

The stresses obtained are within permissible limit and the factor ofsafety against sliding under all condition of loading is much more than 1.0(the minimum of the specified requirement under different combination ofloading as per IS.6512). Hence, the stability is in order.

The details of Overflow sections of Jheri, Paikhed, Chasmandva,Chikkar, Dabdar and Kelwan concrete dams are at Drawing Nos. PTNL-5900-P-3046, 3006, 3026 and 3066(Plates – 6.15, 6.38, 6.61 and 6.85) inVolume –VIII (A) and Drawing Nos. PTNL-5900-P-3086 and 3106(Plates –6.109 and6.133) in Volume –VIII(B).

6.2.2.4.5 Chute Spillway

A Spillway chute channel has been proposed below the spillwayglacis for all the 6 dams. It will envisage excavation in rock to reach desiredlevels/grades. A tentative thickness of 1500mm has been proposed for theconcrete including 500mm thick rich concrete (M50) for the floor of thechute. The aeration arrangements have not been designed. They will bedesigned in the next stage of designs and studied in detail on a hydraulicmodel for ensuring that cavitation will not take place. The LongitudinalSections of Chute Spillways of the six dams are at Drawing Nos. PTNL-5900-P-3042, 3002, 3022 and3062 (Plates – 6.21, 6.44, 6.67and 6.91) inVolume –VIII (A) and Drawing Nos. PTNL-5900-P-3082 and 3102 (Plates– 6.115and 6.139) in Volume –VIII (B).

Water surface elevations at different sections (section A-A, sectionB-B) as shown in Drawing Nos. PTNL-5900-P-3055, 3014, 3015, 3029,3075 (Plates – 6.22, 6.45, 6.46, 6.68and 6.92 in Volume –VIII (A)) andDrawing Nos. PTNL-5900-P-3095and 3115 (Plates – 6.116and 6.140 inVolume –VIII (B)), have been calculated taking into account the dischargeintensity, height of fall and the existing ground slope. Based on these watersurface elevations, the maximum height of the chute channel wall has beenfixed after considering sufficient freeboard. The chute walls have beendesigned as retaining wall having junctions at the floor from both sides. The

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Chute profile is tentative and subject to confirmation of satisfactoryperformance through physical model studies.

6.2.2.4.6 Energy Dissipation Arrangement

The dissipation of the kinetic energy after flow through chute channelis necessary for bringing the flow into downstream river to pre-damcondition. The factors that govern the type of energy dissipater to be usedare:

a) Hydraulic considerationsb) Topographyc) Geologyd) Type of dame) Economic considerations etc.

In all the 6 dams, Ski jump type Energy dissipation has been proposeddue to:

i) The bed of the river channel downstream comprises sound rockcapable of withstanding the impact of high jet.

ii) Depth of tail water is insufficient for the formation of hydraulicjump.

The details of the principal features in the design of Ski jump energydissipation for all the 6 dams are given in Table – 6.27 below:

Table – 6.27Principal Features in the Design of Ski Jump Energy Dissipation

Sl.No

Dam RadiusofBucket(in m)

InvertLevel ofBucket

TWL Lip Level LipAngle (inDegrees)

1 Jheri 30 176 m 178 m 182 m 352 Paikhed 30 160 m 190 m 182 m 353 Chasmandva 30 178 m 190 m 155 m 30

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4 Chikkar 30 151 m 153 m 180 m 305 Dabdar 30 114 m 123 m 125 m 306 Kelwan 30 115 m 132 m 130 m 30

6.2.2.4.7 Curtain and Consolidation Grouting

Grouting shall be done under close guidance of Geologist andprocedure adopted at site should conform to IS 6066(latest edition).Anyshear, fault plane or other geological features encountered in the foundationshall be suitably treated in consultation with the Geologist.

Curtain Grouting under spillway at u/s may be carried out as per IS6066 in consultation with the Geologist. The spacing, depth and inclinationof grout holes may be modified depending upon the State of foundation rockafter excavation and based on the results of grout acceptance tests done inconsultation with the Geologist.

Consolidation grouting shall be done in 100 % of the base width inthe foundation area of overflow and Non-Overflow portion. Minimumdiameter of consolidation grouting holes shall be 38 mm.

6.2.2.4.8 Spillway GatesA. Jheri Dam:i) Spillway Radial Gates and Hoists

Spillway crest radial gates (5 nos.) of opening size 15.0 m wide x12.0 m high shall be provided to control the discharge through the gatedportion of the spillway. Each gate shall be operated by means of twinHydraulic Hoist of 200 t (2x100 t for each gate) capacity (tentative)mounted on pier through cardanic support at EL 248.40 m. The sill of thegate is located at EL 233.78 m. The radial gate shall be designed for a headcorresponding to FRL i.e. EL 246.00 m. The gates shall be operated underwater head between elevations EL 247.00 m (MWL) to EL 233.78 m. Thewater load on the gate is transferred from gate through radial arms totrunnion brackets and finally to concrete piers through anchorage or to thetrunnion girder and finally to the pier through un-bonded conventionalanchorages. The anchors shall be designed to cater for loads imposed due togate being at any position for different water heads. The gate has been

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designed to close under its own weight for all operating conditions. Theoverall design of Radial Gates shall confirm to IS: 4623-2000. The generalinstallation of Spillway Radial Gate is at Drawing No. PTNL-5900-JHD-1501 (Plate No.6.23) in Volume –VIII (A).

The salient features of Spillway Radial Gate are furnished inAnnexure – 6.1.

ii) Stop logs for Radial Gates

One set of sliding type stop logs has been envisaged to cater formaintenance requirement of 5 nos. of dam spillway radial gates. The stoplog set for opening size of 15.0 m wide x 12.60 m high shall be fabricated insix units with height of each unit 2100 mm i.e., one non- interchangeablebottom unit and five nos. interchangeable units. The stop logs shall havedownstream skin plate and downstream sealing, fitted with sliding pads andadequate structural members. The element is also fitted with side guiderollers for guiding the elements under operation. The stop logs shall bedesigned for head corresponding to FRL of 246.0 m (sill 233.78 m). Thestop log units shall be operated under balanced head condition by means ofa gantry crane of adequate capacity with the help of a lifting beam, exceptthe top unit, which shall be raised under unbalanced head condition. Fourelements are proposed to be stored in the storage bay and remaining twoelements shall be stored in right/left NOF section of dam when not in use.The general installation of Spillway Stop log Gate is at Drawing No. PTNL-5900-JHD-1502 (Plate No.6.24 in Volume –VIII (A)).

The salient features of Spillway Stop log Gate are furnished inAnnexure – 6.2 in Volume-II.

iii) Gantry crane for Spillway Stop logs

A class-II gantry crane conforming to IS: 807 having wheel gauge of6.0 m (Tentative) and wheel base of 10.0 m (Tentative) is proposed to beinstalled at the spillway road bridge at EL: 253.0 m. This gantry will servethe purpose of operation of spillway stop logs.

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iv) Instruments and Remote Control

The main items of control and equipment of Jheri Dam Project shallcomprise the following:

a) Control and operation of all gates.b) Gate position indication and monitoring of all gates.c) Water level indication and monitoring along with necessary alarms

provided.d) Monitoring and indication of discharge measurements for discharge

through all gates and hoist.

All the necessary transducers and instrumentation, terminals,contacts, cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

One uninterruptible power supply (UPS) of suitable capacity to provideback up (minimum 1 hour) to the system in case of failure of main powersupply to equipment shall also be provided.

v) Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment atthe dam site. The diesel generating set shall be located in the dam toprovide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

vi) Weight Estimate for Gates and Operating Equipment

Tentative estimate of weights in respect of complete hydro-mechanical equipment as envisaged is worked out and presented inAnnexure - 6.3 in Volume-II. The weight estimates are based on standardempirical formulae and also the hydro-mechanical works actually executedby various State Government / agencies.

B. Paikhed Dam:i) Spillway Radial Gates and Hoists

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Spillway crest radial gates (4 nos.) of opening size 15.0 m wide x12.0 m high shall be provided to control the discharge through the gatedportion of the spillway. Each gate shall be operated by means of hydraulichoist of 200 t (2 x 100 t) capacity (tentative). The sill of the gate is locatedat EL 235.65 m. The radial gate shall be designed for a head correspondingto FRL i.e. EL 248.00 m. The gates shall be operated under water headbetween elevations EL 249.00 m to EL 235.60 m. The water load on thegate is transferred from gate through radial arms to trunnion brackets andfinally to concrete piers through anchorage or to the trunnion girder andfinally to the pier through un bonded conventional anchorages. The anchorsshall be designed to cater for loads imposed due to gate being at anyposition for different water heads. The gate shall be designed to close underits own weight for all operating conditions. The overall design of RadialGates shall confirm to IS: 4623-2000.The overall design of Radial Gatesshall confirm to IS: 4623-2000. The general installation of Spillway RadialGate is at Drawing No. PTNL-5900-PKD-1501 (Plate No.6.47) in Volume –VIII (A).

The salient features of Spillway Radial Gate are furnished inAnnexure – 6.4 in Annexure Volume-II.

ii) Stop logs for Radial Gates

One set of sliding type stop logs has been envisaged to cater formaintenance requirement of 4 nos. of dam spillway radial gates. The stoplogs set for opening size of 15 m wide x 12 m high shall be fabricated in sixunits with height of each unit 2100 mm i.e., one non- interchangeablebottom unit and five nos. interchangeable units. The stop logs shall havedownstream skin plate and downstream sealing, fitted with sliding pads andadequate structural members. The element is also fitted with side guiderollers for guiding the elements under operation. The stop logs shall bedesigned for head corresponding to FRL of EL 248.00 m (sill EL 235.84 m).The stop log units shall be operated under balanced head condition bymeans of a gantry crane of 40 t capacity (tentative) with the help of anautomatic engaging and disengaging lifting beam, except the top unit, whichshall be raised under unbalanced head condition. The elements are proposedto be stored in the storage bay located on the right/left NOF section of dam

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when not in use. The general installation of Spillway Stop log Gate is atDrawing No. PTNL-5900-PKD-1502 (Plate No.6.48) in Volume –VIII (A).

The salient features of Spillway Stop log Gate are furnished inAnnexure – 6.5 in Annexure Volume-II.

iii) Gantry Crane for Spillway Stop logs

A class-II gantry crane conforming to IS: 807 having wheel gauge of6.0 m (Tentative) and wheel base of 10.0 m (Tentative) is proposed to beinstalled at the spillway road bridge at EL 255.0 m. This gantry will servethe purpose of operation of spillway stop logs.

iv) Instruments and Remote Control

The main items of control and equipment of Paikhed Dam Projectshall comprise the following:

a) Control and operation of all gates.b) Gate position indication and monitoring of all gates.c) Water level indication and monitoring along with necessary alarms

provided.d) Monitoring and indication of discharge measurements for discharge

through all gates and hoist.

All the necessary transducers and instrumentation, terminals,contacts, cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

One uninterruptible power supply (UPS) of suitable capacity toprovide back up (minimum 1 hour) to the system in case of failure of mainpower supply to equipment shall also be provided.

v) Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment at

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the dam site. The diesel generating set shall be located in the dam toprovide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

vi) Weight Estimate for Gates and Operating Equipment

Tentative estimate of weights in respect of complete hydro-mechanical equipment as envisaged is worked out and presented inAnnexure-6.6 in Annexure Volume-II. The weight estimates are based onstandard empirical formulae and also the hydro-mechanical works actuallyexecuted by various State Government / agencies.

C. Chasmandva Dam:i) Spillway Radial Gates and Hoists

Spillway crest radial gates (three nos.) of opening size 12.0 m wide x12.0 m high shall be provided to control the discharge through the gatedportion of the spillway. Each gate shall be operated by means of twinhydraulic hoist of 180t (2x90t) capacity (tentative) mounted on pier at EL216.30 m. The sill of the gate is located at EL 201.65 m. The radial gateshall be designed for a head corresponding to FRL i.e. EL 214.00 m. Thegates shall be operated under water head between elevations EL 215.00 m toEL 201.65 m. The water load on the gate is transferred from gate throughradial arms to trunnion brackets and finally to concrete piers throughanchorage or to the trunnion girder and finally to the pier through unbondedconventional anchorages. The anchors shall be designed to cater for loadsimposed due to gate being at any position for different water heads. The gateshall be designed to close under its own weight for all operating conditions.The overall design of Radial Gates shall confirm to IS: 4623-2000. Thegeneral installation of Spillway Radial Gate is at Drawing No. PTNL-5900-CHVD-1501 (Plate No.6.69) in Volume –VIII (A).

The salient features of Spillway Radial Gate are furnished inAnnexure – 6.7 in Annexure Volume-II.

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ii) Stop logs for Radial Gates

One set of sliding type stop logs has been envisaged to cater formaintenance requirement of 3 nos. of dam spillway radial gates. Thestop log set for opening size of 12 m wide x 12.30 m high shall befabricated in six units with height of each unit 2050 mm i.e., one non-interchangeable bottom unit and five nos. interchangeable units. The stoplogs shall have downstream skin plate and downstream sealing, fittedwith sliding pads and adequate structural members. The element is alsofitted with side guide rollers for guiding the elements under operation.The stop logs shall be designed for head corresponding to FRL of EL214.00 m (sill EL 201.86 m). The stop log units shall be operated underbalanced head condition by means of a gantry crane of 35t capacity(tentative) with the help of a lifting beam, except the top unit, which shallbe raised under unbalanced head condition. The elements are proposed tobe stored in the storage bay located on the left/right bank of NOF sectionwhen not in use. The general installation of Spillway Stop log Gate is atDrawing No. PTNL-5900-CHVD-1502 (Plate No.6.70 in Volume –VIII(A)).

The salient features of Spillway Stop log Gate are furnished atAnnexure – 6.8 in Annexure Volume-II.

iii) Gantry Crane for Spillway Stop logs

A class-II gantry crane conforming to IS: 807 having wheel gauge of6 m (Tentative) and wheel base of 10.0 m (Tentative) is proposed to beinstalled at the spillway road bridge at EL: 222.0 m. This gantry will servethe purpose of operation of spillway stop logs.

iv) Instruments and Remote Control

The main items of control and equipment of Chasmandva DamProject shall comprise the following:

a) Control and operation of all gates.b) Gate position indication and monitoring of all gates.

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c) Water level indication and monitoring along with necessary alarmsprovided.

d) Monitoring and indication of discharge measurements for dischargethrough all gates and hoist.

All the necessary transducers and instrumentation, terminals, contacts,cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

One uninterruptible power supply (UPS) of suitable capacity to provideback up (minimum 1 hour) to the system in case of failure of main powersupply to equipment shall also be provided.

v) Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment atthe dam site. The diesel generating set shall be located in the dam toprovide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

vi) Weight Estimate for Gates and Operating Equipment

Tentative estimate of weights in respect of complete hydro-mechanicalequipment as envisaged is worked out and presented at Annexure – 6.9 inAnnexure Volume-II. The weight estimates are based on standard empiricalformulae and also the hydro-mechanical works actually executed by variousState Government / agencies.

D. Chikkar Dam:i) Spillway Radial Gates and Hoists

Spillway crest radial gates (4 nos.) of opening size 15.0 m wide x12.0 m high shall be provided to control the discharge through the gatedportion of the spillway. Each gate shall be operated by means of twinHydraulic Hoist of 200t (2x100t) capacity (tentative) mounted on pierthrough cardanic at EL 222.25 m. The sill of the gate is located at EL197.80 m. The radial gate shall be designed for a head corresponding to

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FRL i.e. EL 210.00 m. The gates shall be operated under water headbetween elevations EL 212.00 m (MWL) to EL 197.80 m. The water load onthe gate is transferred from gate through radial arms to trunnion bracketsand finally to concrete piers through anchorage or to the trunnion girder andfinally to the pier through unbonded conventional anchorages. The anchorsshall be designed to cater for loads imposed due to gate being at anyposition for different water heads. The gate has been designed to close underits own weight for all operating conditions. The overall design of RadialGates shall confirm to IS: 4623-2000.The general installation of SpillwayRadial Gate is at Drawing No. PTNL-5900-CKD-1501 (Plate No.6.93) inVolume –VIII (A).

The salient features of Spillway Radial Gate are furnished atAnnexure – 6.10 in Annexure Volume-II.

ii) Stop logs for Radial Gates

One set of sliding type stop logs has been envisaged to cater formaintenance requirement of 4 nos. of dam spillway radial gates. The stoplog set for opening size of 15.0 m wide x 12.90 m high shall be fabricated insix units with height of each unit 2150 mm i.e., one non- interchangeablebottom unit and five nos. interchangeable units. The stop logs shall havedownstream skin plate and downstream sealing, fitted with sliding pads andadequate structural members. The element is also fitted with side guiderollers for guiding the elements under operation. The stop logs shall bedesigned for head corresponding to FRL of EL 210.0 m (sill EL 197.30).The stoplog units shall be operated under balanced head condition by meansof a gantry crane of adequate capacity with the help of a lifting beam, exceptthe top unit, which shall be raised under unbalanced head condition. Fourelements are proposed to be stored in the storage bay and remaining twoelements shall be stored in right/left NOF section of dam when not in use.The general installation of Spillway Stop log Gate is at Drawing No. PTNL-5900-CKD-1502 (Plate No.6.94) in Volume –VIII (A).

The salient features of Spillway Stop log Gate are furnished at Annexure-6.11 in Annexure Volume-II.

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iii) Gantry Crane for Spillway Stop logs

A class-II gantry crane conforming to IS: 807 having wheel gauge of6.0 m (Tentative) and wheel base of 10.0 m (Tentative) is proposed to beinstalled at the spillway bridge at EL: 217.0 m. This gantry will serve thepurpose of operation of spillway stop logs.

iv) Instruments and Remote Control

The main items of control and equipment of Chikkar Dam Project shallcomprise the following:

a. Control and operation of all gates.b. Gate position indication and monitoring of all gates.c. Water level indication and monitoring along with necessary alarms

provided.d. Monitoring and indication of discharge measurements for discharge

through all gates and hoist.

All the necessary transducers and instrumentation, terminals, contacts,cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

One uninterruptible power supply (UPS) of suitable capacity to provideback up (minimum 1 hour) to the system in case of failure of main powersupply to equipment shall also be provided.

v) Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment atthe dam site. The diesel generating set shall be located in the dam toprovide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

vi) Weight Estimate for Gates and Operating Equipment

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Tentative estimate of weights in respect of complete hydro-mechanical equipment as envisaged is worked out and presented Annexure-6.12 in Annexure Volume-II. The weight estimates are based on standardempirical formulae and also the hydro-mechanical works actually executedby various State Government / agencies.

E. Dabdar dam:i Spillway Radial Gates and Hoists

Spillway crest radial gates (5 nos.) of opening size 15.0 m wide x12.0 m high shall be provided to control the discharge through the gatedportion of the spillway. Each gate shall be operated by means of twinHydraulic Hoist of 200t (2 x100 t) capacity (tentative) mounted on pierthrough cardanic at EL 171.40 m. The sill of the gate is located at EL156.78 m. The radial gate shall be designed for a head corresponding toFRL i.e. EL 169.00 m. The gates shall be operated under water headbetween elevations EL 170.00 m (MWL) to EL 156.78 m. The water load onthe gate is transferred from gate through radial arms to trunnion bracketsand finally to concrete piers through anchorage or to the trunnion girder andfinally to the pier through unbonded conventional anchorages. The anchorsshall be designed to cater for loads imposed due to gate being at anyposition for different water heads. The gate shall be designed to close underits own weight for all operating conditions. The overall design of RadialGates shall confirm to IS: 4623-2000. The general installation of SpillwayRadial Gate is at Drawing No. PTNL-5900-DBD-1501 (Plate No.6.117) inVolume –VIII (B).

The salient features of Spillway Radial Gate are furnished atAnnexure – 6.13 in Annexure Volume-II.

i) Stop logs for Radial Gates

One set of sliding type stop logs has been envisaged to cater formaintenance requirement of 4 nos. of dam spillway radial gates. The stoplog set for opening size of 15.0 m wide x 12.60 m high shall be fabricated insix units with height of each unit 2100 mm i.e., one non- interchangeablebottom unit and five nos. interchangeable units. The stop logs shall havedownstream skin plate and downstream sealing, fitted with sliding pads and

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adequate structural members. The element is also fitted with side guiderollers for guiding the elements under operation. The stop logs shall bedesigned for head corresponding to FRL of EL 169.0 m (sill EL 156.73 m).The stop log units shall be operated under balanced head condition bymeans of a gantry crane of adequate capacity with the help of a lifting beam,except the top unit, which shall be raised under unbalanced head condition.Four elements are proposed to be stored in the storage bay and remainingtwo elements shall be stored in right/left NOF section of dam when not inuse. The general installation of Spillway Stop log Gate is at Drawing No.PTNL-5900-DBD-1502 (Plate No.6.118) in Volume –VIII (B).

The salient features of Spillway Stop log Gate are furnished atAnnexure 6.14 in Annexure Volume-II.

iii) Gantry Crane for Spillway Stoplogs

A class-II gantry crane conforming to IS: 807 having wheel gauge of6 m (Tentative) and wheel base of 10.0 m (Tentative) is proposed to beinstalled at the spillway bridge at EL: 177.0 m. This gantry will serve thepurpose of operation of spillway stop logs.

iv) Instruments and Remote Control

The main items of control and equipment of Dabdar Dam Project shallcomprise the following:

a. Control and operation of all gates.b. Gate position indication and monitoring of all gates.c. Water level indication and monitoring along with necessary alarms

provided.d. Monitoring and indication of discharge measurements for discharge

through all gates and hoist.

All the necessary transducers and instrumentation, terminals, contacts,cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

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One uninterruptible power supply (UPS) of suitable capacity to provideback up (minimum 1 hour) to the system in case of failure of main powersupply to equipment shall also be provided.

v) Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment atthe dam site. The diesel generating set shall be located in the dam toprovide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

vi) Weight Estimate for Gates and Operating Equipment

Tentative estimate of weights in respect of complete hydro-mechanicalequipment as envisaged is worked out and presented at Annexure- 6.15 inAnnexure Volume-II. The weight estimates are based on standard empiricalformulae and also the hydro-mechanical works actually executed by variousState Government / agencies.

F. Kelwan dam:i) Spillway Radial Gates and Hoists

Spillway crest radial gates (5 nos.) of opening size 15.0 m wide x12.0 m high shall be provided to control the discharge through the gatedportion of the spillway. Each gate shall be operated by means of twinHydraulic Hoist of 200 t (2 x 100 t) capacity (tentative) mounted on pierthrough cardanic at EL 166.40 m. The sill of the gate is located at EL151.80 m. The radial gate shall be designed for a head corresponding toFRL i.e. EL 164.00 m. The gates shall be operated under water headbetween elevations EL 166.00 m (MWL) to EL 151.80 m. The water load onthe gate is transferred from gate through radial arms to trunnion bracketsand finally to concrete piers through anchorage or to the trunnion girder andfinally to the pier through un bonded conventional anchorages. The anchorsshall be designed to cater for loads imposed due to gate being at anyposition for different water heads. The gate has been designed to close underits own weight for all operating conditions. The overall design of Radial

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Gates shall confirm to IS: 4623-2000. The general installation of SpillwayRadial Gate is at Drawing No. PTNL-5900-KLD-1501 (Plate No.6.141 inVolume –VIII (B)).

The salient features of Spillway Radial Gate are furnished atAnnexure – 6.16 in Annexure Volume-II.

ii) Stoplogs for Radial Gates

One set of sliding type stop logs has been envisaged to cater formaintenance requirement of 5 nos. of dam spillway radial gates. The stoplog set for opening size of 15.0 m wide x 12.60 m high shall be fabricated insix units with height of each unit 2100 mm i.e., one non- interchangeablebottom unit and five nos. interchangeable units. The stop logs shall havedownstream skin plate and downstream sealing, fitted with sliding pads andadequate structural members. The element is also fitted with side guiderollers for guiding the elements under operation. The stop logs shall bedesigned for head corresponding to FRL of EL 164.0 m (sill EL 151.82 m).The stop log units shall be operated under balanced head condition bymeans of a gantry crane of adequate capacity with the help of a lifting beam,except the top unit, which shall be raised under unbalanced head condition.Four elements are proposed to be stored in the storage bay and remainingtwo elements shall be stored in right/left NOF section of dam when not inuse. The general installation of Spillway Stop log Gate is at Drawing No.PTNL-5900-KLD-1502 (Plate No.6.142 in Volume –VIII (B)).

The salient features of Spillway Stop log Gate are furnished atAnnexure – 6.17 in Annexure Volume-II.

iii) Gantry Crane for Spillway Stop logs

A class-II gantry crane conforming to IS: 807 having wheel gauge of6 m (Tentative) and wheel base of 10.0 m (Tentative) is proposed to beinstalled at the spillway road bridge at EL: 174.0 m. This gantry will servethe purpose of operation of spillway stop logs.

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iv) Instruments and Remote Control

The main items of control and equipment of Kelwan Dam Projectshall comprise the following:

a. Control and operation of all gates.b. Gate position indication and monitoring of all gates.c. Water level indication and monitoring along with necessary alarms

provided.d. Monitoring and indication of discharge measurements for discharge

through all gates and hoist.

All the necessary transducers and instrumentation, terminals,contacts, cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

One uninterruptible power supply (UPS) of suitable capacity toprovide back up (minimum 1 hour) to the system in case of failure of mainpower supply to equipment shall also be provided.

v) Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment atthe dam site. The diesel generating set shall be located in the dam toprovide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

vi) Weight Estimate for Gates and Operating Equipment

Tentative estimate of weights in respect of complete hydro-mechanicalequipment as envisaged is worked out and presented at Annexure – 6.18 inAnnexure Volume-II. The weight estimates are based on standard empiricalformulae and also the hydro-mechanical works actually executed by variousState Government / agencies.

6.2.2.5 Opening through Dams

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6.2.2.5.1 Gallery

The common purposes for which galleries are provided in ConcreteDam body are:

i. To provide drainage way for water seeping through the u/s face ofthe dam and from the foundation,

ii. To provide space for drilling holes and grouting the foundation inorder to provide a grout curtain,

iii. To provide access to the interior of the dam for observing itsbehaviour after completion, and

iv. To provide access to chambers like Hoist chamber, Pumpchamber, Sump well, Instrument niches etc.

To accomplish the above objectives, a foundation gallery of size 2.0m x 2.25 m running along full length of the dam spillways at 5.25 m(average)from the upstream face of the Dam has been proposed. It has beenlocated as per guidelines in accordance with IS: 12966 (part1).

6.2.2.5.2 Water Stop, Air Vent and Internal Drainage

The water stop shall be installed as per IS 12200.No block out shallbe left around water stop. The water stop shall be raised along with lifts ofconcrete for the dam IS 15058 should be referred for specifications of PVCwater stops. Water stop details of Overflow and Non-overflow sections ofthe six dams are shown in Drawing Nos. PTNL-5900-P-3047, 3050, 3053,3007, 3012, 3027, 3032, 3067, 3070 and 3073 (Plates – 6.17, 6.13, 6.14,6.40, 6.37, 6.63, 6.60, 6.87, 6.84and 6.83) in Volume –VIII (A) and DrawingNos. PTNL-5900-P-3087, 3090, 3093, 3107, 3110 and 3113 (Plates – 6.111,6.108, 6.107, 6.135, 6.131and 6.132) in Volume –VIII (B),

Ventilation pipes/holes of 300 mm diameter have been provided inevery alternate dam blocks from the galleries. However, where adits are notprovided, ventilation shafts of about 1 m diameter may be provided, oneeach near either end of the gallery to maintain a draft of air. The ventilationarrangements should conform to IS 12966.

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200 mm dia. formed concrete drain (vertical) @ 3m c/c has beenprovided in all 6 dams as per IS 10135-1985. Elevation of the joints of thepipe joining the gallery with trap drain shall be suitably located in order tohave proper drainage.

6.3 Barrages and Head Regulators

To divert the surplus waters into Par-Tapi-Narmada Link Canal fromPaikhed Reservoir and Chasmandva Reservoir, two barrages, namelyPaikhed Barrage and Chasmandva Barrage are proposed. These barrageshave been designed as per provisions contained in IS codes 6966(Part 1)1989, I S 7720 1991, IS 7365-1985,IS 10137 1982,IS 11130 1984, IS11527-1985. I S 10751 etc. Originally in F R Stage weirs were proposed fordiversion of water to the link canal but for better control and regulationBarrages have been considered instead.

For design of barrages complete set of data could not be collected dueto public hindrance at the project site, therefore suitable assumptions weremade while designing the barrages. No geological investigation / soilinvestigation were carried out. Therefore it was assumed that competentfoundation strata of sufficient bearing capacity, is available at reasonabledepth to provide gravity type of barrage floor with independent pierfoundation.

Suitable head regulators for the control of flow in the canals are alsoproposed on both the barrages. The details of head regulator and flared outwall details of Paikhed and Chasmandva head regulator are at Drawing No.PTNL-5900-P-2505 and 2510 (Plate No.6.232 and 6.241) in Volume –VIII(B).

Design aspects of both the barrages are discussed in brief in following

paragraphs.

6.3.1 Selection of Barrage Site

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Barrage location has been finalized on the basis of FSL of canal offtaking from Barrage, topography etc. Paikhed and Chasmandva barragesare located on the D/S of Paikhed Dam and Chasmandva Dam respectively.The river reach is straight at these locations and the banks are well defined.The area on either flank of barrage (bank side) shall be developed to suitableelevation so that water is safely contained in the barrage pondage. Generallayout plans and detailed layout plans of Paikhed and Chasmandva barragesare at Drawing No. PTNL-5900-P-2501, 2502, 2506 and 2507 (PlateNo.6.228, 6.229, 6.237 and 6.238) in Volume –VIII (B).

6.3.2 Design FloodA) Paikhed Barrage

Paikhed barrage has been designed for 1:100 design flood i.e. 2223cumecs and free board has been checked for discharge corresponding to 1 in500 years (3606 cumecs). Due to proximity of dam on upstream, free boardhas been checked for PMF (5307 cumecs) as well. The top of pier andabutments were kept at 152.00 m.

B) Chasmandva Barrage

Chasmandva barrage has been designed for 1:100 design flood of1571 cumecs and free board has been checked for discharge correspondingto 1 in 500 yrs (2072 cumecs). Due to proximity of dam on the upstream,free board has been checked for PMF (2578 cumecs) as well. The top of pierand abutments were kept at 133.00 m.

6.3.3 River Diversion for Paikhed and Chasmandva Barrage

The Paikhed barrage is proposed to be constructed in two unitsseparated by a double pier, one having four bays and second having threebays of 15 m each. The Chasmandva barrage is proposed to be constructedin two units each having four bays of 12 m each. The diversion can be easilydone by making a coffer dam to cordon off the work area. It is furtherproposed to restrict the working period to non-monsoon season only. Thecoffer dam shall be rebuilt after every monsoon. As work involves deep

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excavation, provision shall be made for keeping the work area dry by wellpoint system of pumping.

6.3.4 Silt Factor

Silt factor is required to access the depth of scour. In the present caseas barrage is founded on RBM, till specific values are obtained silt factorvalue has been taken as 1.

6.3.5 Assumed Retrogression at Maximum and Minimum Discharges

Suitable value of retrogression were assumed to vary from 0.3 to 0.5m at high discharges to 1.0 at low discharges.

6.3.6 Pond Level

Pond levels were fixed based on the FSL of off taking canals. Pondlevels adopted in case of Paikhed and Chasmandva Barrages are 143.50 mand 131.00 m respectively.

6.3.7 Waterway and HFL

For Paikhed Barrage 7 number bays are provided each with 15 mclear waterway. As there is a deep pond on the u/s of Head regulator, thecrest level for all the bays is kept at EL 136.0 m (average river bed level) tohave better control over sedimentation.

For Chasmandva barrage 8 number bays are provided each with 12 mclear waterway. As there is a deep pond on the u/s of head regulator, thecrest level for all the bays is kept at EL 123.0 m (average river bed level) tohave better control over sedimentation.

The waterway provided is checked for 1 in 100 year flood , 1 in 500year flood and spillway capacity of the main dam on the U/S. Fordetermination of u/s affluxed HFL, it is assumed that all the gates are fullyopen while passing the floods and discharge coefficient is based onMallikpur curves.

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6.3.8 Energy Dissipation Arrangement

To dissipate the energy of water coming out from the barrage spillwayso that it may not cause excessive scour immediately downstream ofbarrage, a stilling basin type arrangement has been proposed. Dimensions(i.e. depth and length) of stilling basin are best determined on the basis ofmodel studies. However as per relevant provisions of IS 6966, calculationsare made to determine the cistern level and length of stilling basin such thatthe hydraulic jump formed under various possible flow conditions, iscontained within the stilling basin.

6.3.9 Drainage and Anchorage Arrangements

The barrages are supposed to rest on rock foundation. Therefore upliftpressures are partly resisted by weight of barrage floor and partly byelaborate arrangement of Rock anchors under stilling basin portion. Toreduce uplift pressures drainage arrangement in form of drainage holes andhalf round tile drains has also been proposed. The longitudinal and crosssection and stilling basin plans (anchorage and drainage details) of Paikhedand Chasmandva barrage are at Drawing No. PTNL-5900-P-2503, 2504,2508 and 2509 (Plates -6.231, 6.232, 6.239 and 6.240) of Volume-VIII(B).

6.3.10 Barrage Spillway Gates6.3.10.1 Paikhed Barrage

Seven (7) nos. of spillway radial gate of size 15.0 m wide x 7.0 mhigh shall be provided to control the discharge through gated portion ofbarrage. The sill of the gate is located at EL 136.0 m. The radial gates aredesigned for the head of 14 m corresponding to Upper Pond Level ofEL 150.0 m. The gates can be operated under water head between sill levelsof EL 136 m to Upper pond level of EL 150.0 m.

The water load on the gate is transferred from gate leaf structurethrough radial arms to trunnion bracket and finally to concrete piers throughanchorage arrangement. The anchorage will be designed to cater to the loadsimposed due to gate being at any position at different water heads.

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Each gate will be operated by means of 160 t capacity (2 x 80 t)(tentative) twin hydraulic hoists mounted on cardanic supports. The generalinstallation of Barrage Spillway Radial Gate is at Drawing No. PTNL-5900-PKB-1501 (Plate No.6.233) in Volume –VIII (B).

The salient features of Paikhed Barrage Spillway Radial Gate arefurnished at Annexure – 6.19 in Annexure Volume-II.

6.3.10.2 Chasmandva Barrage

Fixed wheel vertical lift gate (Eight nos.) for opening size 12.0mwide x 8.0m high shall be provided to control the discharge through gatedportion of barrage. Each gate shall be operated under unbalanced headcondition by means of electrically operated rope drum hoist of 60t capacity(Tentative), mounted on Hoist Bridge, supported on trestles fixed on top ofpier EL133.0m.

The sill of the gate is located at EI 123.0 m. The gates are designedfor the head corresponding to Pond Level of EL 131.0 m and checked foraffluxed HFL of 131.456m. The gates can be operated under water headbetween EI 131.456 m to EI 123.0 m. Gates shall be stored/ maintainedabove top of pier EL 133.0m.The general installation of Barrage SpillwayRadial Gate is at Drawing No. PTNL-5900-CHB-1501 (Plate No.6.242) inVolume –VIII (B).

The salient features of Chasmandva Barrage Spillway Radial Gate arefurnished at Annexure – 6.20 in Annexure Volume-II.

6.3.11 Barrage Spillway Stoplogs6.3.11.1 Paikhed Barrage

Stop logs are proposed for maintenance of barrage spillway radialgates. One set of sliding type stop logs of size 15.0 m x 9.1 m (over allheight) for spillway (consisting of 4 units of 2.275 m high each) isproposed. Each unit shall be 15.0 m x 2.275 m. All four units of stop logsshall be interchangeable with the openings of barrage spillway. These unitsshall be designed for maximum water head corresponding to Upper Pond

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level of EL 150.0 m (sill EL 136.0 m). Each stop log units is provided withd/s skin plate and d/s sealing arrangement with music note type Tefloncladded side seal and wedge type rubber seal at the bottom shall beprovided.

Top unit shall be provided with adequate capacity filling valves tofacilitate lifting of stop logs in balanced head condition. The stop logs unitsshall be lowered and lifted under balanced head conditions and shall beoperated by means of a gantry crane of 50t capacity (Tentative) traveling onbarrage spillway bridge on top of piers, with the help of one set of liftingbeam of adequate capacity with automatic engaging/disengaging device.The stop log units shall be stored at top of the pier at EL 152.0 m throughsuitable latches. The general installation of Paikhed Barrage Spillway Stoplog Gate is at Drawing No. PTNL-5900-PKB-1502 (Plate No.6.234) inVolume –VIII (B).

The salient features of Paikhed barrage Spillway Stop log Gate arefurnished at Annexure – 6.21 in Annexure Volume-II.

6.3.11.2 Chasmandva Barrage

Stop logs are proposed for maintenance of service gates of spillway.One set of sliding type stop logs for spillway (consisting of 5 units of 1.65mhigh each) is proposed. Each unit shall be 12.0m x 1.65m. Stop logs shallbe interchangeable with the openings of barrage spillway. These units shallbe designed for maximum water head corresponding to Pond Level of EL131.0m (sill EL 123.0 m). The stop logs shall be operated by means of agantry crane of adequate capacity traveling on Road Bridge provided at topof the piers, with the help of one set of lifting beam of adequate capacitywith automatic engaging/disengaging device. Each stop log units isprovided with d/s skin plate and d/s sealing arrangement with music notetype Teflon cladded side seal and wedge type rubber seal at the bottom shallbe provided.

Top unit shall be lifted under unbalanced condition by crack openingfor creating balanced head condition. The stop logs units shall be loweredand lifted under balanced head conditions and shall be operated by means of

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a gantry crane of 25t capacity (Tentative) traveling on barrage spillwaybridge on top of piers EL 133.0 m, with the help of one set of lifting beamof adequate capacity with automatic engaging/disengaging device. The stoplog units shall be stored in the stop log grooves when not in use. The generalinstallation of Chasmandva Barrage Spillway Stop log Gate is at DrawingNo. PTNL-5900-CHB-1502 (Plate No.6.243) in Volume –VIII (B).

The salient features of Chasmandva barrage Spillway Stop log Gateare furnished at Annexure – 6.22 in Annexure Volume-II.

6.3.12 Gantry Crane for Stoplogs6.3.12.1 Paikhed Barrage

A class-II gantry crane conforming to IS: 807, for Operation ofBarrage spillway stop logs having wheel gauge of 6 m (Tentative) andwheel base of 10.0 m (tentative) is proposed to be installed at top of pier atEL: 154.50 m.

6.3.12.2 Chasmandva Barrage

A class-II gantry crane conforming to IS: 807, for Operation ofBarrage spillway stop logs having wheel gauge of 6 m (Tentative) andwheel base of 10 m (Tentative) is proposed to be installed at the spillwayroad bridge at EL: 135.50m.

6.3.13 Road-Cum-Gantry Bridge, Trestle, etc.

Pier top of Paikhed and Chasmandva Barrages have been provided at152 m and 133 m respectively. A road–cum-Gantry Bridge has beenproposed with deck level at 154.5 m and 135.5 m respectively. Thisapproach bridge shall continue on either flank of the barrage. The bridgeshall support gantry crane provided for operation of stop-logs and also thetwo lanes of class A vehicle loading/one lane of 70 R loading. Trestles foroperation of service gates of barrage are provided at pier top level. It isproposed to store the stop-log units, when not in use, in a stop-log pit.

6.3.14 Instruments and Remote Control

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The remote control system which is microprocessor controlled basedshall consist of one operator station located at top of Paikhed andChasmandva Barrages and shall be supplemented by an indication statusstations at powerhouse control room.

The main items of control and equipment of Paikhed andChasmandva barrages shall comprise the following:

a) Control and operation of all gates.b) Gate position indication and monitoring of all gates.c) Water level indication and monitoring along with necessary

alarms provided.d) Monitoring and indication of discharge measurements for

discharge through all gates and hoist.

All the necessary transducers and instrumentation, terminals,contacts, cabling etc for the above at various locations shall beprovided and incorporated in the remote control system.

One uninterruptible power supply (UPS) of suitable capacity toprovide back up (minimum 1 hour) to the system in case of failure ofmain power supply to equipment shall also be provided.

6.3.15 Diesel Generating Set

One, three- phase synchronous type diesel generating set of adequatecapacity is envisaged for the emergency operations of the HM equipment atthe each barrage site. The diesel generating set shall be located at thebarrages to provide back-up supply to gate operating equipment and to thecomputerized control system in case of power failure.

6.3.16 Weight Estimate for Gates and Operating Equipment

Tentative estimate of weights in respect of complete hydro-mechanical equipment as envisaged is worked out and presented below.The weight estimates are based on standard empirical formulae and also the

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hydro-mechanical works actually executed by various State Government /agencies.

Tentative weight estimate for Paikhed and Chasmandva barrages areat Annexure – 6.23(a) and 6.23 (b) and head regulator down stream of Ukaidam at Annexure 6.24 in Annexure Volume-II.

6.3.17 Protection Works

Flexible protection work in the form of CC blocks, and launchingapron are proposed at downstream as well as at upstream as shown inrelevant drawings as per relevant provisions of IS 6966. The extent andother details of Flexible protection work may be finalized as per siteconditions through model studies, at the time of construction stage planning.

Minimum weight of stone to be used in protection work should besuch as to resist a flow velocity of 5 m/s or 50 kg whichever is more. Iffound economical wire crates may also be used in place of stones.

6.3.18 Seepage Control

Considering rock foundation, RCC cutoffs of design depths areproposed on upstream and downstream to prevent damage due to piping andscour by ensuring safe exit gradient.

The salient features of barrages are given in Table – 6.28 below.

Table – 6.28Salient Features of Barrages

Sr.No.

Description Paikhed Barrage ChasmandvaBarrage

1 Design FloodDischarge

2223 cumecs 1571 cumecs

2 Total Length 68.320 m 63.350 m3 Total Waterway 138.500 m 122.000 m4 Top level of

pier/abut.152.000 m 133.000 m

5 Crest Level 136.000 m 123.000 m

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6 Cistern Level 131.500 m 118.500 m7 Pond Level 143.500 m/ 150.00 m 131.000 m8 HFL (1 in 100) 140.529 m 127.446 m9 HFL (1 in 500) 141.936 m 128.240 m10 Width of Pier 4.500 m 3.000 m11 Clear Width of

each span15.000 m 12.000 m

6.3.19 Head Regulator, Service Gate and Stoplogs and Hoists6.3.19.1 Paikhed Barrage

Head regulators with 3 bays, 3.0 m wide each are proposed.Identical vertical lift type fixed wheel service gate in each bay for openingsize of 3.0 m wide x 3.0 m high, are proposed to control the discharge incanals. Sill level / Crest level is EL 140.00 m. The gate shall be designed forwater head corresponding Upper Pond Level EL 150 m. These gates will beoperated by means of rope drum hoist of 12 t capacity (tentative) mountedon steel bridge supported on trestles above top of pier EL 152 m. Thegeneral installation of Head Regulator Service Gate is at Drawing No.PTNL-5900-PKB-1503 (Plate No.6.235) in Volume –VIII (B).

The salient features of Paikhed Head Regulator Service Gate are atAnnexure – 6.25 in Annexure Volume-II.

One set of wheel type stop logs of size 3.0 m x 10.05 m (over allheight) for spillway (consisting of 3 units of 3.35 m high each) is proposed.Each unit shall be 3.0 m x 3.35 m. The units of stop logs shall beinterchangeable with the openings of barrage spillway. These units shall bedesigned for maximum water head corresponding to Upper Pond level of EL150.0 m (sill EL 140.0 m). Each stop log units is provided with u/s skinplate and u/s sealing arrangement with music note type Teflon cladded sideseal and wedge type rubber seal at the bottom. Balanced head shall becreated by crack opening of top unit.

The stop logs units shall be lowered and lifted under balanced headconditions and shall be operated by means of a monorail crane of 12tcapacity (tentative), with automatic engaging/disengaging device. The stoplogs units shall be stored at top of pier at EL 152.0m through suitable

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latches. The general installation of Stop logs for Head Regulator ServiceGate is at Drawing No. PTNL-5900-PKB-1504 (Plate No.6.236) in Volume–VIII (B).

The salient features of Stop logs of Paikhed Head Regulator ServiceGate are at Annexure – 6.26 in Annexure Volume-II.

6.3.19.2 Chasmandva Barrage

Head regulators with 3 bays, 3.0 m wide each are proposed. Identicalvertical lift type fixed wheel service gate in each bay for opening size of3.0m wide x 1.0m high, are proposed to control the discharge in canals. Silllevel is 130.0 m. The gate shall be designed for water head correspondingPond level EL 131.0m. These gates will be operated by means of rope drumhoist of 5t capacity (Tentative) mounted on steel bridge supported on trestlesabove top of pier. These gates will be closed when water rises above pondlevel of 131.0m.The general installation of Head Regulator Service Gate isat Drawing No. PTNL-5900-CHB-1503 (Plate No.6.244) in Volume –VIII(B).

The salient features of Chasmandva Head Regulator Service Gate areat Annexure – 6.27 in Annexure Volume-II.

Stop log is proposed for maintenance of service gates. One set ofsliding type stop logs for head regulator service gate (consisting of 1 unitsof 1.2m high) is proposed. The Stop log shall be operated under unbalancedhead with the help of a under slung monorail crane hoist of adequatecapacity (5t tentative), with the help of one set of lifting beam of adequatecapacity with automatic engaging/disengaging device. Stop log unit isprovided with u/s skin plate and u/s sealing arrangement with music notetype Teflon cladded side seal and wedge type rubber seal at the bottom. Thegeneral installation of Stop logs for Head Regulator Service Gate is atDrawing No. PTNL-5900-CHB-1504 (Plate No.6.245) in Volume –VIII (B).

The salient features of Stop logs of Chasmandva Head RegulatorService Gate are Annexure – 6.28 in Annexure Volume-II.6.4 Jheri – Paikhed Link Tunnel

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The Jheri and Paikhed reservoirs are proposed to be linked by 12.70km long concrete lined tunnel of 3.0m diameter (D- shaped) and watercarrying capacity of 11.60 cumecs.

6.4.1 Layout of Link Tunnel

The alignment of the link tunnel and one construction adit has beenfinalized by CWC on the basis of contour maps and data supplied byNWDA. The general Layout plans of the tunnel, Alternative and Final areat Drawing Nos. PTNL-5900-DPR-1001 and 1002 (Plate Nos. 6.143 and144) of Volume – VIII (B).

6.4.2 Hydraulic Design of the Link Tunnel

The layout and hydraulic design of the link tunnel has been carriedout for conveying 11.60 cumecs of water from Jheri to Paikhed reservoir.The size and the slope of the link tunnel have been worked out for supplyingthe design discharge under all possible combinations of water levels at thelinked reservoirs under pressure flow conditions. The value of Manning’scoefficient adopted for design varies from 0.012 to 0.016 for the concretelined tunnel.

Following assumptions have been considered for the hydraulicdesigns of link tunnels:

a. The minor losses occurring in the link tunnel e.g. entrance losses,trash rack loss, transition loss, exit loss; bend losses, gate groovelosses, etc. are of negligible amount in comparison to the frictionlosses occurring in the link tunnels and therefore not taken intoconsideration.

b. The flow through the tunnel is under pressure and driven by the headdifference between the upper and lower reservoirs linked throughtunnel

c. The gates installed at the intake and outfall of link tunnels are meantfor regulating the discharge as well as for maintenance purpose.

The sizes of the link tunnels have been worked out in two steps:

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STEP- I Different range of tunnel diameter are tried under maximum andminimum driving head between the linked reservoirs by adoptingmaximum and minimum value of Manning’s coefficient withenvisaged value of diversion discharge. This gives a range oftunnel sizes capable of carrying the design discharge which isfound by equating the major friction losses occurring in thesystem with the driving head under all possible heads. Differentshapes of the tunnel were also considered.

STEP- II The tunnel diameter is then fixed on the basis of values obtainedfrom STEP- I. The adequacy of tunnel for its discharge capacityis checked under all prevailing head conditions by adoptingmaximum and minimum value of manning’s coefficient under alldriving heads. The major friction losses are equated with thedriving head to know the discharging capacity of tunnel under allpossible variation of head.

Different alternatives of tunnel alignments, tunnel shape, like DShape, Circular and Modified horse shoe were attempted for the finalizationof the shape and diameter of tunnel. The L-Section along Jheri-PaikhedTunnel is at Drawing No. PTNL-5900-DPR-1003 (Plate Nos. 6.145) ofVolume – VIII (B).

6.4.3 Intake structure at Jheri Reservoir

The layout of the intake structure has been planned based on thegeological and topographical data received from NWDA and the alignmentof Jheri to Paikhed Link Tunnel. The intake structure is designed, so as toproduce an adequate acceleration of water from reservoir into the linktunnel. This is achieved by means of smooth entrance at the intake havingelliptical bell mouth shape and also by placing intake below the minimumreservoir level for ensuring optimum submergence to avoid formation ofvortices. Metallic trash racks are provided in front of intake structure toprevent entry of floating debris into the system. The water flows at a smallvelocity through trash rack provided in the front of intake structure. Thecenter to center spacing between the trash bars is provided as 100mm.

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Submergence of the intake centre line, below the minimum reservoirlevel (MDDL) has been checked as per the provisions of IS-9761: 1995. Thehydraulic design of the intake, its dimensioning and sizing has also beencarried out as per the provisions of IS-9761:1995.

The control structure of the intake is located in a vertical shaftdownstream of the intake structure. The vertical shaft consists of groovesfor accommodating service and emergency gates. Suitable transitions havealso been provided for transition from rectangular intake opening to D-shaped tunnel.

The service gate proposed will be of regulating type to supply therequired water demand. High velocities in the gate area and hydraulic jumpformation are expected depending upon the extent of gate opening. Toprotect the concrete tunnel lining from abrasion, steel lining may also beprovided downstream of service gate for an appropriate distance which is tobe firmed up based on model studies. Hydraulic model studies are to becarried out at detailed design stage for firming up the hydraulic details ofintake and its location in the reservoir.

The hydraulic hoisting arrangement for operation of gates has beenprovided. The portion of tunnel in between the intake structure and controlshaft is provided with RCC lining of M25 grade of concrete as per BIS-456:2000. Appropriate rock support system for control shaft structure hasalso been provided for its structural stability. The Intake and Trash rackdetails are at Drawing Nos.PTNL-5900-DPR-1004 and 1005 (Plate Nos.6.146 and 147) of Volume – VIII (B).

6.4.4 Jheri to Paikhed Link Tunnel Details

Location Jheri Dam Paikhed Dam FRL (m) EL. 246.00 EL. 248.00MDDL (m) EL. 204.00 EL. 190.00Diversion discharge 11.60 cumecs

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Link Tunnel

Length of tunnel : 12700m Dia of tunnel : 3.0m, D-shaped Invert Level : EL. 199.50 at inlet Invert level : EL. 185.00 at out fall

Adit

Length of Adit : 408.60m Size : 6.0mx6.0m, D-Shaped Invert level : EL. 210.00m

A 3.0 m diameter D- shaped concrete link tunnel of length 12.70 kmlong has been provided between Jheri and Paikhed reservoirs. The slope ofthe Jheri – Paikhed tunnel works out to be 1 in 875. One construction aditof size 6mx6m (D- shaped) has been provided at RD 6160.00 m forexcavation of the link tunnel. The link tunnel is provided with 250 mm thickPCC lining of M25 grade concrete for ensuring smooth surface forconveyance of envisaged discharge. The lining shall be of RCC at junctionswith shafts in very poor rock strata and any other specified reachesidentified during construction. The lining has been designed to resist theexternal and internal water pressure. The entire rock load is assumed to becarried by the rock support system consisting of rock bolts, steel fibrereinforced shotcrete (SFRS) and steel ribs. The link tunnel is proposed to beexcavated by conventional drill and blast method (DBM) and the design ofrock support system has been carried out by Barton’s Q method.

The rock mass classification according to Bartons ‘Q’ is shown below.

Q value Classification100-40 Very Good40-10 Good10-4 Fair4-1 Poor1-0.1 Very Poor

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The rock support system may need appropriate modificationsdepending upon the actual rock mass encountered. Also, the design of rocksupport system is not meant for shear zones, weak zones, cavities and verylow cover zones at junctions with adits /vertical shafts, etc. of the tunneland the design in these zones require special consideration. Further, thedesign of the tunnel is valid for full face excavation of tunneling withconventional drill and blast method (DBM). The typical excavation androck support system is shown in Drawing No. PTNL-5900-DPR-1006(Plate Nos. 6.148) of Volume – VIII (B).

A typical scheme of contact and consolidation grouting has beenproposed. The contact grouting in the tunnel is proposed to fully pack upthe space between the concrete lining and the rock surface caused byshrinkage of concrete lining. The consolidation grouting is proposed to fillup the joints and discontinuity in the rock upto a desired depth. The contactgrouting and consolidating grouting shall be carried out as per theprovisions of BIS-5878(Part-VII). The typical concrete lining and groutingdetails are shown in Drawing No. PTNL-5900-DPR-1007 (Plate Nos.6.149) of Volume – VIII (B).

One construction adit (6mx6m D- shape, 408.60 m long) has beenprovided with appropriate rock support system to facilitate construction oflink tunnel by providing additional faces for excavation. The adit will beprovided with access gate in the tunnel plug for carrying out any futuremaintenance. The portal location for adit has been selected based onlimited data and shall be firmed up based on the actual site conditions inconsultation with geologist. Typical portal details of the construction adithave been shown in the drawing Nos.PTNL-5900-DPR-1008 and 1009(Plate Nos. 6.150 and 6.151) of Volume – VIII (B).

6.4.5 Outfall Structure at Paikhed Reservoir

For discharge of water at the end of the tunnel from Jheri to PaikhedReservoir, an out fall structure has been provided keeping in view thetopography and geology at the outfall location of Paikhed Reservoir. Acontrol gate shaft upstream of the outfall structure has been provided withprovisions of Service and Emergency gates.

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6.4.6 Hydro-Mechanical Equipment for Jheri-Paikhed Tunnel

Hydro–mechanical equipment as under have been envisaged for thefollowing components of Jheri-Paikhed Link Tunnel.

Intake at Jheri Reservoir

Outfall at Paikhed Reservoir

Detailed descriptions for the proposed equipment are as under:

6.4.6.1 Intake in Jheri Reservoir

(A) Service Gate and Emergency Gate and Hoists

Fixed wheel type gate (one no) for opening size of 3.0 m wide x 3.0m high shall be provided at Jheri reservoir Intake. The sill of the gate islocated at EL 199.50 m. The gate is to be designed for a head correspondingto FRL 246.0 m and operated under unbalanced head condition. The gateshall have downstream skin plate and downstream sealing. The gate shall beoperated by means of double acting hydraulic hoist of 50 t capacity(Tentative). Power pack of hydraulic hoist shall be located at the top of pierat EL 248.0 m. Maintenance chamber shall be provided at EL 207.00 m. Thesalient features of the Service Gate are at Annexure – 6.29 in AnnexureVolume-II.

For maintenance of intake service gate, a fixed wheel type emergencygate of 3.0 m wide x 3.0 m wide is proposed. The gate is to be designed fora head corresponding to FRL 246.0 m and operated under unbalanced headcondition. The gate shall have downstream skin plate and downstreamsealing. The gate shall be operated by means of double acting hydraulichoist of 50 t (Tentative) capacity. Power pack of hydraulic hoist shall belocated at the top of pier at EL 248.0 m. Maintenance chamber shall beprovided at EL 207.0m. General installation details of Service gate andemergency Gate at Jheri are shown in Drawing Nos. PTNL-5900-JPLT-1501and 1502 (Plate Nos. 6.152 and 6.153) in Volume-VIII(B).

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The salient features of the Emergency Gate are at Annexure – 6.30 inAnnexure Volume-II.

6.4.6.2 Outfall in Paikhed Reservoir(A) Service Gate and Emergency Gate and Hoists

Fixed wheel type gate (one no) for opening size of 3.0 m wide x 3.0m high shall be provided at Paikhed reservoir outfall. The sill of the gate islocated at EL 185.0 m. The gate is to be designed for a head correspondingto FRL 248.0 m and operated under unbalanced head condition. The gateshall have downstream skin plate and downstream sealing. The gate shall beoperated by means of double acting hydraulic hoist of 70 t capacity(Tentative). Power pack of hydraulic hoist shall be located at the top of pierat EL 250.0 m. Maintenance chamber shall be provided at EL 194.0m.Thesalient features of the Service Gate are at Annexure – 6.31 in AnnexureVolume-II.

For maintenance of outfall service gate, a fixed wheel type emergencygate of 3.0 m wide x 3.0 m wide is proposed. The sill of the gate is locatedat EL 185.0 m. The gate is to be designed for a head corresponding to FRL248.0 m and operated under unbalanced head condition. The gate shall havedownstream skin plate and downstream sealing. The gate shall be operatedby means of double acting hydraulic hoist of 70 t capacity (Tentative).Power pack of hydraulic hoist shall be located at the top of pier at EL 250.0m. Maintenance chamber shall be provided at EL 194.0 m. Generalinstallation details of Service gate and emergency Gate at Paikhed areshown in Drawing Nos. PTNL-5900-JPLT-1503 and 1504 (Plate Nos. 6.154and 6.155) in Volume-VIIIB).

The salient features of the Emergency Gate are at Annexure – 6.32 inAnnexure Volume-II.

6.4.6.3 Instruments and Remote Control

The remote control system which is microprocessor controlledbased shall consist of one operator stations located at top of pier of Jheri-

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Paikhed Link Tunnel and shall be supplemented by an indication statusstations at powerhouse control room.

The main items of control and equipment of Jheri-Paikhed LinkTunnel shall comprise the following:

a) Control and operation of all gates.b) Gate position indication and monitoring of all gates.c) Water level indication and monitoring along with necessary alarms

provided.d) Monitoring and indication of discharge measurements for discharge

through all gates and hoist.

All the necessary transducers and instrumentation, terminals,contacts, cabling etc for the above at various locations shall be provided andincorporated in the remote control system.

The system shall include various instruments like water leveltransmitters, sensors for opening indication of spillway gates, and intakegate and height (opening) measurements.

One uninterruptible power supply (UPS) of suitable capacity toprovide back up (minimum 1 hour) to the system in case of failure of mainpower supply to equipment shall also be provided.

6.4.6.4 Diesel Generating Set

Two, three- phase synchronous type diesel generating set ofadequate capacity is envisaged for the emergency operations of the HMequipment at Link Tunnel. The diesel generating set shall be located on thetop of pier of Jheri Dam for Jheri Intake side and of Paikhed Dam forPaikhed Intake side respectively, to provide back-up supply to gateoperating equipment and to the computerized control system in case ofpower failure.

6.4.6.5 Weight Estimate for Gates and Operating Equipment

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Detailed estimate of weights in respect of complete hydro-mechanical equipment as envisaged is worked out and is at Annexure – 6.33in Annexure Volume-II. The tentative weight estimates are based onstandard empirical formulae and also the hydro-mechanical works actuallyexecuted by various State government / agencies.

6.5 Canals In planing and design of Canal systems of Par-Tapi-Narmada link projectboth Open canal and Underground pipe line systems are studied to minimisethe Land requirement for canal construction. It was opined that replacing theMain canal by the pipe line system is not viable, techno-economically, dueto the topographical constraints. Hence, it is decided to replace the fourFeeder canals that were planned in the DPR of PTN link project byPipelines.

6.5.1 Open canalsThe proposed Par – Tapi – Narmada link canal project has three

main parts. These are as follows:

i) Par–Tapi reach of Par–Tapi - Narmada link off-taking from proposedPaikhed Barrage across river Nar, and terminating in the existing Ukaireservoir on river Tapi (177.736 km).

ii) Tapi – Narmada reach of Par–Tapi - Narmada link off-taking from Ukaireservoir and terminating at Miyagam branch canal of Narmada MainCanal system after crossing Narmada River (191.307 km).

6.5.2 Feeder Pipe lines

Details of Feeder pipe lines are dicribed below

i) Feeder Pipe lines: There are three main feeder Pipe line emanating fromChasmandva Barrage, Tail Race Channels of Dabdar Dam power Houseand Kelwan Dam Power House feeding main canal in Par to Tapi reach.The lengths of these feeder Pipe line are 2.859 km, 12.258 km, and 7.62km respectively.

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ii) One interlinking feeder Pipe line connecting Chikkar Dam and DabdarDam reservoirs to transfer 6.46 Cumecs of discharge from Chikkar Damto Dabdar Dam. This feeder Pipe line is of 14.342 km length.

6.5.3 Tunnels:

To avoid lengthy traverse of canal and heavy cutting, Five D- shaped, linedtunnels are proposed in the Par-Tapi reach of the reach of Par–Tapi –Narmada link canal. The details of these tunnels are as follows;

Details of Tunnels Proposed in Par–Tapi – Narmada LinkSN

TunnelNo.

RD From (m)

RD To (m)

Length(m)

Diameter(m)

1 Tunnel 1 14650 14750 100 5.5

2 Tunnel 2 24000 24350 350 5.5

3 Tunnel 3 32350 32550 200 5.5

4 Tunnel 4 37750 37800 50 5.5

5 Tunnel 5 51500 51950 450 5.5

Typical excavation and rock support details of tunnels are shown inDrawing No.PTNL-5900-P-2678 (Plate No.6.413) in Volume-VIII (C).Typical concrete lining and grouting details are shown in DrawingNo.PTNL-5900-P-2679 (Plate No.6.414) in Volume-VIII (C). Typical tunnelportal support details of Entry and Exit portal are shown in Drawing No.PTNL-5900-P-2680 (Plate No.6.415) in Volume-VIII (C).

6.5.1 Description of Canal System6.5.1.1 Canal Capacity

The 369.043 km long Par–Tapi-Narmada link canal, off takes fromPaikhed Barrage with the FSL of 142.800 m. In the initial reaches startingfrom Paikhed Barrage, the canal has a carrying capacity of 38.17 cumecs.As the canal moves northwards, water from other reservoirs is addedthrough the feeder pipe lines. Thus the capacity of canal increases at therespective RDs where the feeder pipe lines contributes to the discharge ofmain canal. Maximum discharge after sparing the State’s requirement of

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command area of State Government proposed projects, enroute commandon left side of link canal by gravity and right side of link canal by lift, thecapacity of the canal becomes 63.69 cumecs at the tail before falling inUkai, after traversing a length of 177.736 km in first reach, i.e Par-Tapi-Reach.

The canal capacity of Tapi-Narmada reach at off take from Ukaireservoir is 46.64 cumecs and after meeting en route and target arearequirements, the canal capacity at the tail end reduces to 17.26 cumecs.The hydraulic details and design parameters of Tapi – Narmada portion oflink are given in the Table below and in the the drawings.

Typical Canal sections at different reaches of Main Canal and Feederpipe lines are shown in Drawing No.PTNL-5900-P-2511 (Plate No.6.246and modified sections in plate no.6.426 (a)) in Volume-VIII (C). Typicalcanal sections in cutting and filling are shown in Drawing No.PTNL-5900-P-2512 (Plate No.6.247) in Volume-VIII (C).

6.5.1.2 Canal Alignment

The alignment of the proposed Par –Tapi link canal and feeders Pipeline, finalized on the basis of field surveys have been marked on toposheets.Canal was aligned as contour canal. The canal off take with FSL of 142.800m from Head Regulator at Paikhed Barrage. Thereafter the Chasmandvafeeder Pipe line which off takes from Chasmandva barrage at FSL of130.600 m joins the main canal at RD 62.072 km at FSL of 129.244 m.

Similarly, the Dabdar feeder Pipe line which off takes from the maindam at FSL 136.960 m joins the main canal at RD 108.25 km at FSL of119.217 m and Kelwan feeder Pipe line, also off taking from main dam atFSL 135.46 m joins the main canal at RD 129.600 km at FSL of 114.418 m.

In view of the fact that the FRL of the terminal reservoir at Ukai isRL 105.150 m and that the length of the Par-Tapi canal is about 177.736 km,the off take level at Paikhed Barrage has been kept at RL142.800 m therebygiving working head of 38.35 m . The bed gradient of the Main canal fromPar to Tapi is different from reach to reach and it varies from 1 in 7,500 to 1in 8500.

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The main canal has to cross the ridges between various basins andsub-basins where in deep cuts are involved and also to cross many riversand streams requiring construction of cross drainage works. Five tunnels ofhave been proposed to avoid circuitous route and deep cutting.

For feeders Pipe lines the off take levels are considered keeping inview the corresponding FSL of main canal where the feeder pipe line joinsthe link. Economy in case of feeder pipe lines from Dam/ Barrage ofChikkar and Chasmandva diversion points and MDDL at off take diversionpoint for feeder pipe lines from Kelwan and Dabdar has been kept in view.

The Par-Tapi-Narmada link canal is predominantly contour canal andtraverses a total length of 369.043 km. In the first reach of 177.736 km,canal off takes from Head regulator of Paikhed Barrage and falls into Ukaireservoir in second reach of canal of 191.310 km off takes from UkaiReservoir and outfalls into Miyagam branch canal of Narmada main canal.It crosses several streams, minor/major Rivers and several roads and railwaylines. Each reach has different slope and cross section elements. Thealignment has been marked on the strip survey contour sheet for every 3.0km along with the corresponding longitudinal section. Total 136 No ofsheets for canal alignment have been prepared. Following data has beenprovided as Longitudinal Section table with every Drawing:

1 CHAINAGE R.D (metre)2 NSL3 Canal Bed Level4 Bed Slope (nH:1V)5 Design Discharge (Cumecs)6 FSL7 FSD 8 Bed Width9 Head Loss (CD Structure)10 Side Slope 11 Free Board12 Canal Top Level13 Depth of Cutting 14 Depth of Filling

Variables have been tabulated at every 50 m interval and data whichdo not change frequently are clubbed together at the top row of the table.

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All the 136 sheets containing the L.S. and strip contour maps of Par-Tapi-Narmada link canal are given as PTNL-5900-P-2515 to 2650 (PlateNos. 6.250 to 6.385 in Volume-VIII (C)). The alignment consists of straightlines and circular curves as per Clause 6.4 of IS 5968: ‘Guidelines forplanning and layout of canal system’. The range of radius are given in atable below.

Radii of curves for canalsDischarge (m3/s) Radius, Min( m)280 and above 900 Less than 280 to 200 750 Less „ 200 to 140 600 Less „ 140 to 70 450 Less ,, 70 to 40 300 Less ,, 40 to 10 200 Less „ 10 to 3 150 Less „ 3 to 0.3 100 Less „ 0.3 50

Accordingly effort was made to keep all the curves in the Par-Tapi-Narmada link canals within specified limits of 200 to 300 m. But due tohilly terrain in initial reaches it was practically not possible to comply withthese limits as such curves of smaller radius, than depicted above, have alsobeen introduced at such reaches; however canal bed has to be super elevatedon those curves.

6.5.1.3 Details of Lining Provided

Lining is provided for the entire length of main Canal to minimizeseepage. Lining with CC 1:4:8 is proposed in canal bed as well as in sideslopes. The thickness of lining varies according to canal capacity as per IScode 3873-1978: Laying cement concrete/stone slab lining on canals.However lining of 75 mm thickness is assumed for most of the reaches.Typical cross section of lining of canal is indicated in the drawings. Atplaces where ground water table or otherwise water table is higher suitabledrainage arrangement has been suggested including provision of non-returnvalves, in staggered pattern, at the rate of 1 pressure release valve (PRV)for every 40 m2 of lining along the side slopes and at every 100 m2 of lining

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in canal bed. Typical details of canal lining and drainage arrangement underthe lining are shown in Drawing Nos.PTNL-5900-P-2513 and 2514 (PlateNo.6.248 and 6.249) in Volume-VIII (C).

6.5.1.4 Transmission Losses

Unforeseen losses and demands have been taken care of by increasingthe discharges provided with the cut-off Statement for Par-Tapi reach by20% and Tapi-Narmada reach by 10%.

6.5.1.5 Sections and Reaches

As the length of canal increases from the starting point, morereservoirs and the command area are added and so the section of the canalneeds change. It is not practical to change the section of the canal at eachand every off take point. Hence the canal is divided into suitable reachesand canal sections are designed to carry the required discharges in theparticular reaches. The Statements showing the hydraulic particulars for thevarious reaches of the canal are at Annexure – 6.34 and 6.35 in AnnexureVolume-II.

6.5.1.6 Shape

The shape has been selected as trapezoidal with rounded corners asper provisions of IS 10430. The bed width increases from head to tail withno change in the water depth so that intended flow velocity is generated forthe Par-Tapi reach of canal and constant bed width with varying FSD is keptfor the Tapi-Narmada reach.

6.5.1.7 Design Calculation for Adequacy of Canal Section(a) Open canal

To prevent losses and to reduce the required section of canal, plaincement concrete lined canal is proposed throughout the reaches of Par-Tapi-Narmada link project. The canal section is designed using Manning’sformula. In absence of soil and sub soil data a trapezoidal section with 1.5:1(H:V) side slope, both in cutting and filling , has been assumed for design ofcanal section. As the available head for the main canals was inadequate,

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effort was made to make the canal section as hydraulically efficient aspossible. Therefore trapezoidal lined canal with rounded corners wasprovided to improve hydraulic radius of section. Longitudinal slopes forcanal were targeted to be around 1 in 8000 however other factors liketopography, available head between various reaches and expected headlosses due to canal and various cross drainage structures along the length ofcanal were deciding factors in finalizing the slopes.

For V = 1/n R 2/3 S ½

Where V = Velocity in m/secN = Rugosity coefficient or Manning’s n , 0.018 for RCC lined canalS = Bed slope of canal

Velocity to be adopted depends upon the type of lining andmaximum / minimum permissible velocities for the section. Effort was tokeep critical velocity ratio as unity or slightly higher than unity and to keepvelocities sub-critical, for assumed set of parameters. Due to restraint ofavailable head, steeper slopes to provide higher velocities near topermissible velocity in cement concrete lining and thereby avail the benefitof cement concrete lining could not be made. For the initial Par – Tapi linkapproach of equal FSD in all the reaches was considered, with thisassumption different bed width were obtained for different reaches , withB/D ratio ranging from approximately 2 to 8. Whereas Tapi to Narmadareach was designed for constant width to allow for uniform width of canal,thereby equal size of CD structures and bridges.

Details of design of typical canal section on various reaches are:

The velocity ranges between 0.95 m/sec to 1.05 m/sec, which isbelow 2.7 m/sec the limiting velocity as per IS code 10430-1982 for C.C.lining.

The critical velocity ratio is found to be ranging from 0.87 to 0.99 inmain canal.

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The full supply depth of main canal is 2.800 m in Par-Tapi reach and2.65 m to 3.22 m in Tapi – Narmada reach. The free board of 0.75 m and0.600 m are provided as per IS code 10430-1982. Effort was made to keepratio of bed width to depth within 2 to 8.

Certain fixed values of Loss of head have been assumed at canalstructures or cross drainage structures for designing the longitudinal sectionof canal which are as follows.

1.Aqueducts and Culvert: 140 mm (52 mm in Tapito Narmada Reach for allthe drainage crossingsdue to many crossingsand most of them mayincur little head loss)

2.Road and Rly Bridges, Superpassages 40 mm and 10mm3.Cross regulator cum HR/Escape 150 mm4.Tunnels 140 mm at entry and exit and 40 mm for every 50 m

In Par – Tapi reach the section of canal at head is 8.5 X 2.8 m and attail end is 16.5 X 2.80 m, while in Tapi – Narmada reach the section at headis 8.8 X 3.22 m and at tail end is 5.0 X 2.65 m. Typical sections for canal infull cutting, partial banking and partial cutting and full banking are given inthe drawing Nos. PTNL-5900-P-2511and 2512 (Plate No.6.246 and 6.247)in Volume-VIII (C).

(b) Pipe line Design

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Where:V= Mean velocity in meters per secondn = Mannings coefficient of roughnessR = Hydraulic radius in meters ( The cross-sectional area of flow divided by

the wetted perimeter)S = Hydraulic slope in meters per meter. This is the indication of the loss of

head in system. Q = Quantity of flow in cubic meters per second A = Cross-sectional area of flow in square meters

Solving for hydraulic radius of a fully, filled pipe.

For flow >/= Radious

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1circular segment height

2central angle

3circular segment area

4arc length5 flow area6wetted perimeter

7hydraulic radius

Hydraulic details of Main canalSl. No. Reach Designed

dischargeof canal

Bed Slope Bedwidth

FullSupplyDepth

From To

Km Km cumec m m1 2 3 4 5 6 7

Par - Tapi Reach 1 00.00 62.072 38.17 1 in 7500 8.50 2.802 62.072 108.250 46.64 1 in 7500 10.50 2.803 108.250 129.600 46.64 1 in 8000 10.95 2.804 129.600 177.470 63.69 1 in 8500 16.50 2.80

Tapi - Narmada Reach 1 0.00 51.043 46.64 1 in 10000 8.80 3.222 51.043 69.150 36.40 1 in 10000 7.50 3.123 69.150 82.171 31.80 1 in 10000 5.60 3.064 82.171 191.31 17.26 1 in 10000 5.00 2.65

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Hydraulic details of Feeder Pipe line

Sl.No.

Feeder pipe line Lengthin Km

Bedslope

DesignedDischargein cumec

Dia.of

Pipe

Nos.of pipe

1 2 3 4 5 61 Feeder Pipe line from

Chasmandva weir to Main Canal

2.859 1 in5500

8.50 2.6 m 2

2 Feeder Pipe line interconnecting Chikkar and Dabdar Reservoirs

14.342 1 in7500

6.40 2.5m 2

3 Feeder Pipe line from Dabdar Reservoir to main canal

12.258 1 in5000

17.00 2.9m 3

4 Feeder Pipe line from Kelwan Reservoir to main canal

7.616 1 in5500

17.00 2.6m 4

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6.5.1.8 Canal Operation

The main Canal and feeder Pipe lines will be in operation throughoutthe year with a peak discharge of 63.69 cumec.

6.5.2 Canal Structures6.5.2.1 Cross Drainage Works / Regulators

As per available data, various canal structures, Bridges and Crossdrainage structures have been proposed. Their reach wise number ofstructures is given in the Table – 6.29 below:

Table – 6.29Details of Structures

S N Type of Structure Par-Tapi

Tapi-Narmada

Total

1 Aqueduct 37 36 552 Super Passage 1 75 693 Syphon Aqueduct 2 30 324 Canal Syphon 3 24 275 Culverts 3 13 166 SLRB 39 93 1327 DLRB 14 6 208 RLY B 2 5 079 Escapes 0410 Cross Regulator 3 8 1111 Head Regulator 23 23 46

Total 444

There are 25 no. of river/nallas in the reach of feeder pipe lines.Bridges will be proposed for crossing the feeder pipe line over river/nallas,Detailed designs of these bridge crossings for feeder pipe lines will be doneat the time of construction.6.5.2.1.1 Layout and Foundation

Detailed laboratory tests for finding the suitability of soils forfoundations of cross drainage works have not been carried out. However,based on the soil samples collected it is inferred that hard rock can be metwith at reasonable depths below the stream bed levels. This is required to beconfirmed at pre construction stage.

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6.5.2.1.2 Cross Drainage

The type of cross drainage structure to be provided depends on thephysical features of the stream crossed such as position of bed level ofstream in relation to canal bed level. Canal syphons are proposed whencanal bed level is below the stream bed level but FSL is higher, therebynecessitating canal water to be siphoned below the drainage.

(A) Aqueducts and Culverts

Aqueducts have been proposed along the link canal at the crossings ofmajor streams where the bed level of the link canal is above the highestflood level of the drain. 37 aqueducts and 3 culverts are proposed in Par-Tapi portion and 36 aqueducts and 13 culverts are proposed in Tapi-Narmada portion. Actually small drainages were not delineated in the mapavailable in Par to Tapi Reach as such all the structures are termed asaqueducts in this reach. Loss of head of 140 mm (52 mm in Tapi toNarmada reach) is assumed at each aqueduct. Though head loss in aqueductmainly depend upon the length and fluming adopted, more the length andfluming more is the head loss. Therefore in initial three reaches of Par toTapi link where the base width of canal are 5.5 m, 8.5 m and 15.0 mrespectively aqueducts is not flumed to preserve valuable head at the cost ofstructure , but in the last reach where the canal width is 21.800 m fluming isresorted to achieve economy in cost of structure.

Heights of piers vary from few meters to about 35 m depending uponthe depth of drainage bed from bottom of aqueduct. However consideringaverage conditions, RCC Piers of 1.5 m width with spread footing withfooting depth of min 2.5 m and average height of 10 m were assumed inanalysis. Since aqueduct portion were not flumed, length of piers withassumed width were sufficient enough to keep foundation pressures quitelow. General layout of Aqueducts and culverts in Par-Tapi and Tapi-Narmada reaches is shown in Drawing Nos. PTNL-5900-P-2651 and 2652(Plate Nos.6.386 and 6.387) in Volume-VIII (C) and Typical details ofAqueducts are shown in Drawing Nos.PTNL-5900-P-2667 to 2670 (PlateNo.6.402 to 6.405) in Volume-VIII (C).

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(B) Cross Regulators

Cross regulators are provided at regular intervals in order to ensureeffective water regulation. There are 3 cross regulators in Par-Tapi portionand 8 cross regulators in Tapi-Narmada portion proposed along the linkcanal. The loss of head of 150 mm is considered at each regulator. TypicalCross regulator cum head regulator for Tapi to Narmada reach wheredischarge varies with change of depth was done and indicated in thedrawing. The general layout and typical details of Cross regulators areshown in Drawing No.PTNL-5900-P-2654 and 2676 (Plate Nos.6.389 and6.411) in Volume-VIII (C).

(C) Head Regulators

There are 23 head regulators proposed on main and feeder canals ofPar-Tapi portion and 23 head regulators proposed in Tapi-Narmada portion.A typical design of head regulator has been carried out at RD 164.37 km inPar-Tapi portion. The typical details of Head Regulator are shown inDrawing No.PTNL-5900-P-2677 (Plate Nos.6.412 in Volume-VIII (C)).

(D) Syphon Aqueducts

Two Syphon aqueducts are proposed in Par-Tapi portion and 30syphon aqueducts are proposed in Tapi-Narmada portion of link canal.Particulars of Syphon Aqueducts of Par-Tapi and Tapi-Narmada portion aregiven in Drawing No. PTNL-5900-P-2655 and 2656. Typical details ofSyphon Aqueduct are shown in drawing No. PTNL-5900-P-2672 (PlateNo.6.407) in Volume-VIII (C).

(E) Super Passages

There is one Super Passage proposed in Par-Tapi portion and 75 onTapi to Narmada reach. Seven Super Passages are proposed on FeederCanals. General layout of Super Passages is shown in Drawing No. PTNL-5900-P-2653 (Plate No.6.388) in Volume-VIII (C). Typical details areshown in Drawing No. PTNL-5900-P-2671 (Plate No.6.406) in Volume-VIII (C).

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(F) Canal Syphons

There are three Canal Syphons proposed in Par-Tapi portion and 24on Tapi to Narmada reach. Design of canal Syphon requires calculation ofhead loss when canal is passed below the natural drainage and proportioningof length, breadth, height and thickness of walls of barrels. Slopes of inletand outlet portion of Syphon are proposed as 1 in 5 (V:H). General layout ofCanal Syphons is shown in Drawing Nos. PTNL-5900-P-2655 and 2656(Plate No.6.390 and 6.391) in Volume-VIII (C). Typical details are shown inDrawing No. PTNL-5900-P-2673 (Plate No.6.408) in Volume-VIII (C).

(G) Escapes

Escapes are usually to be provided at the U/S of Aqueducts or at theU/S of HR/CR junction. A typical section of the escape is given at DrawingNo.PTNL-5900-P-2677 (Plate Nos.6.412) in Volume-VIII (C).

(H) Bridges and Culverts

Thirty nine SLRB, 14 DLRB and two Railway Bridge, overall 55bridges are proposed along the length of the canal in Par to Tapi Reach. 93SLRB, 6 DLRB and 5 Railway Bridge, overall 104 bridges are proposedalong the length of the canal in Tapi to Narmada Reach. Loss of head of0.03 m is considered at each bridge mainly due to pier because the canal isnot flumed at bridge sites to preserve head available. Typical designs anddrawings published by IRC for T-beam RCC bridges having spans largerthan 10.5 m have been adopted. Foundations of pier shall be at depths equalto greater than scour depth as per strata available. General layout of RoadBridges and Railway Bridges shown in Drawing Nos. PTNL-5900-P-2657and 2658 (Plate Nos.6.392 and 6.393) in Volume-VIII (C). Typical details ofBridges are shown in Drawing Nos. PTNL-5900-P-2659 to 2666 (PlateNo.6.394) to 6.401 in Volume-VIII (C).

(I) Falls

Due to deficiency of available head there is no provision of canal fallin the main canal, however canal falls are provided at the junctions of feeder

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canal and main canal as Residual head was available in all the feeder canalsafter finalizing the longitudinal slope of these canals.

6.5.3 Study of Integrated Network of Canal System and itsOperation

The canal system will be operated in an integrated network alongwith the proposed reservoirs for optimum utilization of available waters.The simulation studies carried out with integrated network of canals andreservoirs are furnished in Appendix-3.5 of Volume-IV: Appendices –Hydrology and Water Assessment.

6.5.4 Description of Soil Profile along the Canal Alignment

No soil samples could be collected along the Link Canal alignmentby digging Pits or drilling Auger holes due to public hindrance in the projectarea. Necessary Pits/Auger holes shall be dug at pre-construction stage.

6.5.5 Broad Outline of Canal Automation and Branch Canals upto 8Cumec

The canal automation technology adopted for Sardar Sarovar Projectcanal system shall be adopted for the Link Canal system also.

6.6 Power Houses

Five dam toe power houses and one canal power house have beenplanned in Par –Tapi- Narmada link project as mentioned below.

Sl.No. Name of Power House Installed capacity1. Paikhed Dam Toe Power House 3 x 3000 KW2. Chasmandva Dam Toe Power House 2 x 1000 KW3. Chikkar Dam Toe Power House 2 x 1000 KW4. Dabdar Dam Toe Power House 2 x 1600 KW5. Kelwan Dam Toe Power House 2 x 1250 KW6. Kelwan feeder Pipe line Power

House 2 x 1000 KW

Total 207300 KW

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Say 21 MW

The design of hydel civil components (six power houses) are based onlimited/ preliminary data available in the form of topographical maps,geological investigation, power potential studies, electro-mechanical drawingsand feasibility reports. Detailed investigations could not be carried out due topublic hindrance at the project sites. Layout of the power houses designs needsto be confirmed after carrying out detailed investigations and topographicalsurvey.

6.6.1 Surface Power House at Paikhed Dam

A surface Power house of size 45.32m (L) x 16.43m (W) x 93.0m (H) hasbeen provided to house three numbers of horizontal Frances turbines of3000KW each. The centre line of the machine has been kept at elevationEL.164.40m. The structure comprises of RCC columns and beams designed tocarry the loads due to various electro-mechanical equipment.

The location of surface power house has been selected by studying thelimited contour details available as no site visit could be made to ascertain thesuitability of the strata. Hence the Power House location shall be confirmedafter site inspection and in consultation with geologist.

The Power House plan at EL. 167.92 m and Cross Section are shownin Drawing Nos.PTNL-5900-DPR-2010 and 2011 (Plate Nos. 6.165 and6.166) in Volume VIII (B).

Salient features of the project are shown below:

Sl.no Project details Particular1 MWL EL. 249.00 m2 FRL EL. 248.00m3 MDDL EL. 190.00m

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4 Design Head 56.53 m5 Design Discharge 7.40 m3/sec6 Penstock (steel) 2.5m dia ( one number)7 Branch penstock after

bifurcation (steel) 1.6m dia, (3 numbers)

8 Installed capacity 3x3000 KW 9 No of units 3 10 Type of power house Dam toe surface power house 11 Size of power house 45.32m (L) x16.43m(W)x 19.0m

(H)12 Type of turbine Horizontal Francis 13 Average tail water level EL. 172.00m14 Minimum tail water level EL. 170.50m

A Dam toe Surface Power House is planned on the right flank ofPaikhed dam across Nar river. The intake structure is provided adjacent tothe main spillway also termed as “Power Block”. The power block monolithaccommodates an intake structure and a steel penstock (main) of 2.5m dialaid within the body of the spillway. The penstock emanates horizontallyfrom the intake structure and inclined to attain centre line elevation ofEL.164.40 of turbines installed in the power house. The general layout planof Power House, both alternative and final alignments and L-section ofwater conductor system are shown in Drawing Nos. PTNL-5900-DPR-2001,2002 and 2003 (Plate Nos. 6.156, 6.157 and 6.158) in Volume VIII (B).

The main penstock of 2.5m diameter trifurcates thrice near the powerhouse into three units penstocks of 1.6m diameter each to lead the water tothree generating units house in surface power house. The water from thedraft tube is lead back to river through an open tail race channel. Three drafttubes with separate gates have been provided

The power potential study has been carried out by THDC India Ltd.The rated discharge through each unit of the power house is 7.4 cumec. Thedesign head is 56.53m. The installed capacity proposed for this power houseis 9000 KW comprising of 3units each of 3000 KW with 20% COL. Theturbine is of horizontal Francis turbine.

The main components of the scheme comprise of:

i) Intake Structureii) Pressure shaft / Penstock

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iii) Surface Power House iv) Tail Race Channel

6.6.1.1 Intake Structure

The intake structure is designed to ensure smooth entry of water fromthe reservoir into the water conductor system. The required minimumsubmergence from MDDL has been checked as per IS-9761: 1995. Thecentre line of intake has been kept at EL 186.25 to avoid formation ofvortices and the entry of air into the water conductor system. Forminimizing the losses, the profile of the intake roof and sides have beenstreamlined and bell mouth entry has been provided. The plan and section ofIntake and Trash rack details (metal work) are shown in Drawing Nos.PTNL-5900-DPR-2004 and 2005 (Plate Nos. 6.159 and 6.160) in VolumeVIII (B).

6.6.1.2 Pressure Shaft /Penstock

After the bell mouth intake and gate structure, a transition has beenprovided from rectangular [1.8m (w) x 2.5m(l)] to circular (2.5m dia). Thesteel penstock of 2.5m dia, starting from the point, has been embedded inthe dam body for about 25 m and beyond this, steel lined pressure shaft of2.5 m dia has been provided upto the power house. Pressure shaft isprovided with 300 mm thick PCC (M25) grade backfill concrete with steelliner. The lining has been designed to resist full external and internal waterpressure including water hammer. The pressure tunnel is proposed to beexcavated by conventional drill and blast method (DBM) and the design ofrock support system is carried out using Barton’s Q method.

The rock mass classification according to Bartons ‘Q’ is shownbelow.

Q value Classification100-40 Very Good40-10 Good10-4 Fair4-1 Poor1-0.1 Very Poor

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The penstock (2.5m dia) is trifurcated twice near the power house intothree branch penstocks (1.6 m dia) for feeding water to three turbines. Thesteel for penstock is IS-2002(grade 3) and the thickness of steel is 16mm for2.5mdia and 14mm for 1.6m dia. Typical excavation and rock supportdetails, Typical concrete lining and grouting details, Penstock steel liningdetails and Penstock steel lining ferrule details are shown in Drawing Nos.PTNL-5900-DPR-2006, 2007, 2008 and 2009 (Plate Nos. 6.161, 6.162,6.163 and 6.164) in Volume VIII (B) respectively.

6.6.1.3 Tail Race Pool / Tail Race Channel

The water is led back into Nar River through an open tail racechannel provided after the tail race pool (RCC) of 26.0 m wide. The bottomslope of the tail race pool has been provided with a gradient of 1(V): 4.0(H)sloping upwards up to its meting point of the tail race pool /river, as the tailrace channel needs to be suitably provided to join the river based on theactual site conditions.

6.6.1.4 Power Intake Service and Emergency Gate

Fixed wheel type gate (one no) for opening size of 1.8 m wide x 2.5m high shall be provided at the downstream of the Intake having bell mouthshape with elliptical profile. The sill of the gate is located at EL 185.0 m.The gate is to be designed for a head corresponding to FRL 248.0 m andoperated under unbalanced head condition. The gate shall have downstreamskin plate and downstream sealing. The gate shall be operated by means ofdouble acting hydraulic hoist of 50 t (tentative) capacity. Power pack ofhydraulic hoist shall be located at the top of pier at EL 255.0 m. Generalinstallation of Power Intake service gate is shown in Drawing No.PTNL-5900-PKPH-1501 (Plate Nos. 6.167 in Volume VIII (B)).

Salient features of Power Intake Service Gate are at Annexure – 6.36in Annexure Volume-II.

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For maintenance of power intake service gate, a fixed wheel typeemergency gate of 1.8 m wide x 2.5 m wide is proposed. This gate shall beoperated under balanced head condition created by crack opening. The gateshall be capable of lowering in flowing water condition in case of anyemergency. The gate shall be operated by means of double acting hydraulichoist of adequate capacity.

Salient features of Power Intake Emergency Gate are at Annexure –6.37 in Annexure Volume-II.

6.6.1.5 Draft Tube Gates

Slide type gates (three nos.) have been envisaged at the draft tubestructure on the tailrace side. The clear opening is 4.02 m wide x 2.30 mhigh. The gates shall be designed for a head corresponding to average tailwater level of 172.0 m and checked for water level corresponding tomaximum flood level 174.0 m (sill EL 159.40 m).

The gate shall be lifted under balanced head conditions created byfilling valve. The gate shall be operated by means of independent ropedrum hoist of 15 t capacity (tentative) mounted on trestle at deck level of EL167.80 m. General installation of Draft Tube Gate is shown in DrawingNo.PTNL-5900-PKPH-1502 (Plate Nos. 6.168) in Volume VIII (B).

Salient features of Draft Tube Gate are at Annexure – 6.38 inAnnexure Volume-II.

6.6.2 Surface Power House at Chasmandva Dam

A surface Power house of size 32.70m (L) x 13.90m (W) x 19.6m (H)has been provided to house two numbers of horizontal Francis turbines of1000KW each. The centre line of the machine has been kept at elevationEL.171.02m. The structure comprises of RCC columns and beams designedto bear the loads coming from various electro-mechanical equipment.

408

The location of Surface Power House has been selected by studyingthe limited contour details available as no site visit could be made toascertain the suitability of the strata. Hence the Power House location shallbe confirmed after site inspection and in consultation with geologist. ThePower House plan at EL. 175.12 m, Cross Section and Longitudinal Sectionare shown in Drawing Nos.PTNL-5900-DPR-3009, 3010 and 3011 (PlateNos. 6.177, 6.178 and 6.179) in Volume VIII (B).

Salient features of the Power House are tabulated below:

Sl.no Project details Particulars 1 MWL EL. 215.00 m2 FRL EL. 214.00m3 MDDL EL. 190.00m4 Design Head 32.78m5 Design discharge 3.64 m³/sec/unit6 Penstock 1.8m, circular, one number7 Branch penstock 1.2m, circular , 2 nos8 Type of liner Steel lined, IS 2002( grade 3 )9 Installed capacity 2x1000KW 10 No of units 2 units11 Type of power house Dam toe surface power house 12 Size of power house 32.70m (L)x13.90m (W)x 19.60m(H)13 Type of turbine Horizontal Francis 14 Average tail water level EL. 173.02m15 Minimum tail water level EL. 171.52m

A Dam toe Surface Power House is planned on the right bank of TanRiver. The intake structure is provided adjacent to the main spillway alsotermed as “Power Block”. The power block monolith accommodates anintake structure and a steel penstock (main) of 1.8m dia laid within the bodyof the spillway. The penstock emanates horizontally from the intakestructure and after two vertical bends it reaches EL.169.93m to meet theturbine center line of EL.171.02m. The main penstock of 1.8m diameterbifurcates near the power house into two unit penstocks of 1.2m diametereach to lead the water to two generating units in surface power house. Thewater from the draft tube is lead back to river through an open tail racechannel. Two draft tubes with separate gates have been provided. Thegeneral layout plan of Power House, both alternative and final alignments,

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layout plan of water conductor system are shown in Drawing Nos. PTNL-5900-DPR-3001, 3002 and 3003 (Plate Nos. 6.169, 6.170 and 6.171) inVolume VIII (B).

The power potential study has been carried out by THDC India Ltd.The rated discharge through each unit of the power house is 3.64 m³ /sec.The design head is 32.78 m. The installed capacity for this power house is2000 KW comprising of 2 units each of 1000 KW of horizontal Francisturbine.

The main components of the schemes comprise of:

i) Intake Structureii) Penstockiii) Surface Power House iv) Tail Race Channel

6.6.2.1 Intake Structure

The intake structure is designed to ensure smooth entry of water fromthe reservoir into the water conductor system. The required minimumsubmergence from MDDL has been checked as per IS-9761: 1995. Thecentre line of intake has been kept at EL 186.40m to avoid formation ofvortices and the entry of air into the water conductor system. Forminimizing the losses, the profile of the intake roof and sides have beenstreamlined and bell mouth entry has been provided. After the gate atransition from rectangular [(1.42m (w) x1.8m (h)] to circular (1.8m dia) hasbeen provided. The plan and section of Intake and Trash rack details (metalwork) are shown in Drawing Nos. PTNL-5900-DPR-3004 and (Plate Nos.6.172and 6.173) in Volume VIII (B).

6.6.2.2 Penstock

The steel penstock of 1.8 m dia has been provided in the dam body.The penstock is bifurcated into two branch penstocks of 1.2m dia forfeeding water to individual turbines. The penstock is designed to withstandmaximum internal pressure including pressure rise due to water hammer.

410

The steel for penstock is IS-2002(grade 3) and the thickness of steel is12mm. Trash rack details, Penstock steel lining details and Penstock steellining ferrule details are shown in Drawing Nos. PTNL-5900-DPR-3006,3007 and 3008 (Plate Nos. 6.174, 6.175 and 6.176) in Volume VIII (B)respectively.

6.6.2.3 Tail Race Pool / Channel

The water is led back into the Tan River through an open tail racechannel (5m wide) excavated along its alignment. The bottom slope of thetail race pool has been provided with a gradient of 1(V): 4.5(H) slopingupwards upto its meeting point of tail race channel.

6.6.2.4 Power Intake Service and Emergency Gate

Fixed wheel type gate (one no.) for opening size of 1.42 m wide x 1.8m high shall be provided at the downstream of the Intake having bell mouthshape with elliptical profile. The sill of the gate is located at EL 185.50 m.The gate is to be designed for a head corresponding to FRL 214.0 m andoperated under unbalanced head condition. The gate shall have downstreamskin plate and downstream sealing. The gate shall be operated by means ofdouble acting hydraulic hoist of 25 t (Tentative) capacity. Power pack ofhydraulic hoist shall be located at the top of pier at EL 222.0 m. Generalinstallation of Power Intake service gate is shown in Drawing No.PTNL-5900-CHPH-1501 (Plate Nos. 6.180 in Volume VIII (B)).

Salient features of Power Intake Service Gate are at Annexure – 6.39in Annexure Volume-II.

For maintenance of power intake service gate, a fixed wheel typeemergency gate of 1.42 m wide x 1.8 m wide is proposed. This gate shall beoperated under balanced head condition created by crack opening. The gateshall be capable of lowering in flowing water condition in case of anyemergency.

Salient features of Power Intake Emergency Gate are at Annexure –6.40 in Annexure Volume-II.

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6.6.2.5 Draft Tube Gates

Slide type gates (two nos.) have been envisaged at the draft tubestructure on the tailrace side. The clear opening is 3.40 m wide x 2.34 mhigh. The gates shall be designed for a head corresponding to average tailwater level of 173.02 m (sill EL166.51 m) and checked for water levelcorresponding to maximum flood level 175.12 m.

The gate shall be lifted under balanced head conditions created byfilling valve. The gate shall be operated by means of independent ropedrum hoist of 15t capacity (Tentative) mounted on trestle at deck level of EL175.12 m. General installation of Draft Tube Gate is shown in DrawingNo.PTNL-5900-CHPH-1502 (Plate Nos. 6.181) in Volume VIII (B).

Salient features of Draft Tube Gate are at Annexure – 6.41 inAnnexure Volume-II.

6.6.3 Surface Power House at Chikkar Dam

A surface power house of size 32.70m (L) x 13.90m (W) x 17.62m(H) has been provided to house two numbers of horizontal Frances turbinesof 1000KW each. The centre line of the machine has been kept at EL.168.80m.The structure comprises of RCC columns and beams designed tocarry the loads coming from various electro-mechanical equipment. ThePower House plan at EL. 167.92 m, Longitudinal Section and Cross Sectionare shown in Drawing Nos.PTNL-5900-DPR-4008, 4009 and 4010 (PlateNos. 6.189, 6.190 and 6.191) in Volume VIII (B).

The location of surface power house has been selected by studyingthe limited contour details available as no site visit could be made toascertain the suitability of the strata. Hence the power house location shallbe confirmed after site inspection and in consultation with geologist.

Salient features of the Power House are tabulated below:

Sl.no Project details Particulars 1 MWL EL. 212.00 m2 FRL EL. 210.00m

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3 MDDL EL. 179.00m4 Design Head 27.47m5 Design discharge 4.97m³/sec6 Penstock 1.8m, circular, one number7 Branch penstock 1.2m, circular , 2 nos8 Type of liner Steel lined, IS 2002 ( grade 3) 9 Installed capacity 2x1000KW 10 No of units 2 11 Type of power house Dam toe surface power house 12 Size of power house 32.70m (L)x13.90m (W)x

17.62m (H)13 Type of turbine Horizontal Francis 14 Average tail water level EL. 171.50m15 Minimum tail water level EL. 170.00

A Dam toe Surface Power House is planned on the right bank ofAmbica River downstream of Chikkar Dam. The intake structure isprovided adjacent to the main spillway also termed as “Power Block”. Thepower block monolith accommodates an intake structure and a steelpenstock (main) of 1.8 m dia laid within the body of the dam. The penstockemanates horizontally from the intake structure with c/l EL. 175.4 m andafter vertical bends reaches EL. 167.71m. to meet the turbine c/l ofEL168.8m in the power house. The main penstock of 1.8m diameterbifurcates near the power house into two branch penstocks of 1.2m diametereach to lead the water to two turbines. The water from the power house willbe lead in to Chikkar – Dabdar Inter-connecting canal. Two draft tubes withseparate gates have been provided. The general layout plan of Power House,both alternative and final alignments, layout plan of water conductor systemare shown in Drawing Nos. PTNL-5900-DPR-4001, 4002 and 4003 (PlateNos. 6.182, 6.183and 6.184) in Volume VIII (B).

The power potential study has been carried out by THDC India Ltd.The rated discharge through each unit of the power house is 4.97 m³ /sec.The design head is 27.47m. The installed capacity proposed for this powerhouse is 1800 KW comprising 2 units 900 KW each. The turbine ishorizontal Francis type.

The main components of the schemes comprise of:

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i) Intake Structureii) Penstockiii) Surface Power House iv) Tail Race Channel

6.6.3.1 Intake Structure

The intake structure is designed to ensure smooth entry of water fromthe reservoir into the water conductor system. The required minimumsubmergence from MDDL has been checked as per IS-9761: 1995. 8.0 mwide and 270 m long approach channel has been provided to carry the waterupto intake. The centre line of intake has been kept at EL 175.40m to avoidformation of vortices and the entry of air into the water conductor system.For minimizing the losses, the profile of the intake roof and sides have beenstreamlined and bell mouth entry has been provided. After the gate atransition from rectangular [(1.42 m (w)x1.8m (h)] to circular (1.8m dia) hasbeen provided. The plan and section of Intake and Trash rack details (metalwork) are shown in Drawing Nos. PTNL-5900-DPR-4004 and 4005 (PlateNos. 6.185 and 6.186) in Volume VIII (B).

6.6.3.2 Penstock

The steel penstock of 1.8 m dia has been provided in the dam body.The penstock is bifurcated into two branch penstocks of 1.2m dia forfeeding water to individual turbines. The penstock is designed to withstandmaximum internal pressure including pressure rise due to water hammer.The steel for penstock is IS-2002(grade 3) and the thickness of steel is12mm. Penstock steel lining details and Penstock steel lining ferrule detailsare shown in Drawing Nos. PTNL-5900-DPR-4006 and 4007 (Plate Nos.6.187 and6.188) in Volume VIII (B) respectively.

6.6.3.3 Tail Race Pool /Channel

After power generation the water will be lead in to the Chikkar-Dabdar inter-connecting canal through an open tail race channel (5.0 mwide) excavated along its alignment. The bottom slope of the tail race poolhas been provided with an approximate gradient of 1(V): 4.0(H) slopingupwards upto its meeting point of the tail race channel.

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6.6.3.4 Power Intake Service and Emergency Gate

Fixed wheel type gate (one no) for opening size of 1.42 m wide x 1.8m high shall be provided at the downstream of the Intake having bell mouthshape with elliptical profile. The sill of the gate is located at EL 174.50 m.The gate is to be designed for a head corresponding to FRL 210.0 m andoperated under unbalanced head condition. The gate shall have downstreamskin plate and downstream sealing. The gate shall be operated by means ofdouble acting hydraulic hoist of 30 t (Tentative) capacity. Power pack ofhydraulic hoist shall be located at the top of pier at EL 217.0 m. Generalinstallation of Power Intake service gate is shown in Drawing No.PTNL-5900-CKPH-1501 (Plate Nos. 6.192) in Volume VIII (B).

Salient features of Power Intake Service Gate are at Annexure – 6.42in Annexure Volume-II.

For maintenance of power intake service gate, a fixed wheel typeemergency gate of 1.42 m wide x 1.8 m wide is proposed. This gate shall beoperated under balanced head condition created by crack opening. The gateshall be capable of lowering in flowing water condition in case of anyemergency. The gate shall be operated by means of double acting hydraulichoist of adequate capacity.

Salient features of Power Intake Emergency Gate are at Annexure –6.43 in Annexure Volume-II.

6.6.3.5 Draft Tube Gate

Slide type gates (two nos.) have been envisaged at the draft tubestructure on the tailrace side. The clear opening is 3.4 m wide x 2.34 mhigh. The gates shall be designed for a head corresponding to average tailwater level of 171.50 m (sill EL 164.28 m).

The gate shall be lifted under balanced head conditions created byfilling valve. The gate shall be operated by means of independent ropedrum hoist of 15t capacity (Tentative) mounted on trestle at deck level of EL

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171.80 m. General installation of Draft Tube Gate is shown in DrawingNo.PTNL-5900-CKPH-1502 (Plate Nos. 6.193 in Volume VIII (B)).

Salient features of Draft Tube Gate are at Annexure – 6.44 inAnnexure Volume-II.

6.6.4 Surface Power House at Dabdar Dam

A surface Power house of size 49.05m (L) x 20.85m (W) x 17.61m(H) has been provided to house two numbers of horizontal Frances turbinesof 1600KW each. The centre line of the machine has been kept atEL.136.70m. The structure comprises of RCC columns and beams designedto carry the loads coming from various electro-mechanical equipment.

The location of Surface Power House has been selected by studyingthe limited contour details provided by NWDA as no site visit has beenmade to ascertain the suitability of the strata. Hence the power houselocation shall be confirmed after site inspection and in consultation withgeologist. The Power House plan, Cross Section and Longitudinal Sectionare shown in Drawing Nos.PTNL-5900-DPR-5007, 5008 and 5009 (PlateNos. 6.200, 6.201 and 6.202) in Volume VIII (B).

Salient features of the Power House are tabulated below:

Sl.no Project Details Particulars 1 MWL EL.170.00 m2 FRL EL.169.00m3 MDDL EL.139.00m4 Design Head 24.49m5 Design discharge 4.92m³/sec6 Penstock 2.5m, circular, one number7 Branch penstock after

bifurcation 1.6m, circular , 2 nos

8 Type of liner Steel lined, IS 2002 ( latest )Class 3 9 Installed capacity 2x1600KW 10 No of units 2 11 Type of power house Dam toe surface power house 12 Size of power house 49.05m (L)x20.85m (W)x 17.61m (H)

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13 Type of turbine Horizontal Francis 14 Normal tail water level EL.136.96m15 Minimum tail water level EL.134.00m

A dam toe Surface Power House is planned on the right bank ofKhapri River downstream of Dabdar Dam. The intake structure is providedadjacent to the main spillway also termed as “Power Block”. The powerblock monolith accommodates an intake structure and a steel lined penstock(main) of 2.5m dia laid within the body of the dam spillway. The penstockemanates horizontally from the intake structure with centre line EL.135.62m in the power house. The turbine c/l is at EL. 136.70m. The mainsteel lined penstock of 2.5m diameter bifurcates near the power house intotwo branch penstocks of 1.6m diameter each to lead the water to twoturbines. The water from the draft tube is lead back to river through an opentail race channel 5.0m wide. Two draft tubes with separate gates have beenprovided. The general layout plan of Power House and L-Section of waterconductor system are shown in Drawing Nos. PTNL-5900-DPR-5001 and5002 (Plate Nos. 6.194 and 6.195) in Volume VIII (B).

The power potential study has been carried out by THDC India Ltd.The rated discharge through each unit of the power house is 4.92 m³ /sec.The design head is 27.47m. The installed capacity proposed for this powerhouse is 3200 KW comprising of 2units each of 1600 KW. The turbine is ofhorizontal Francis type.

The main components of the schemes comprise of:

i) Intake Structureii) Penstockiii) Surface Power House iv) Tail Race Channel

6.6.4.1 Intake Structure

The intake structure is designed to ensure smooth entry of water fromthe reservoir into the water conductor system. The required minimumsubmergence from MDDL has been checked as per IS-9761: 1995. Thecentre line of intake has been kept at EL 135.62m to avoid formation of

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vortices and the entry of air into the water conductor system. Forminimizing the losses, the profile of the intake roof and sides have beenstreamlined and bell mouth entry has been provided. After the gate atransition from rectangular [(2.0m (w)x2.5m (h)] to circular ( 2.5m dia) hasbeen provided. The plan and section of Intake and Trash rack details (metalwork) are shown in Drawing Nos. PTNL-5900-DPR-5003 and 5004 (PlateNos. 6.196 and 6.197) in Volume VIII (B).

6.6.4.2 Penstock

The steel penstock of 2.5 m dia has been provided in the dam body.The penstock is bifurcated into two branch penstocks of 1.6m dia forfeeding water to individual turbines. The penstock is designed to withstandmaximum internal pressure including pressure rise due to water hammer.The steel for penstock is IS-2002(grade 3) and the thickness of steel is14mm (for 2.5 m dia.) and 12mm (for 1.6 m dia.). Penstock steel liningdetails and Penstock steel lining ferrule details are shown in Drawing Nos.PTNL-5900-DPR-5005 and 5006 (Plate Nos. 6.198 and 6.199) in VolumeVIII (B) respectively.

6 .6.4.3 Tail Race Pool / Channel

The water will be lead in to Dabdar Feeder canal to join the LinkCanal through an open tail race channel 5.0m wide excavated along itsalignment. The bottom slope of the tail race pool has been provided with anapproximate gradient of 1(V): 4.0(H) sloping upwards up to its meetingpoint with the Feeder.

6.6.4.4 Power Intake Service and Emergency Gate

Fixed wheel type gate (one no.) for opening size of 2.0 m wide x 2.5m high shall be provided at the downstream of the Intake having bell mouthshape with elliptical profile. The sill of the gate is located at EL 134.37 m.The gate is to be designed for a head corresponding to FRL 169.0 m andoperated under unbalanced head condition. The gate shall have downstreamskin plate and downstream sealing. The gate shall be operated by means ofdouble acting hydraulic hoist of 30t (Tentative) capacity. Power pack of

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hydraulic hoist shall be located at the top of pier at EL 177.0 m. Generalinstallation of Power Intake service gate is shown in Drawing No.PTNL-5900-DBPH-1501 (Plate Nos. 6.203) in Volume VIII (B).

Salient features of Power Intake Service Gate are at Annexure – 6.45in Annexure Volume-II.

For maintenance of power intake service gate, a fixed wheel typeemergency gate of 2.0 m wide x 2.5 m wide is proposed. This gate shall beoperated under balanced head condition created by crack opening. The gateshall be capable of lowering in flowing water condition in case of anyemergency. The gate shall be operated by means of double acting hydraulichoist of adequate capacity.

Salient features of Power Intake Emergency Gate are at Annexure –6.46 in Annexure Volume-II.

6.6.4.5 Draft Tube Gates

Slide type gates (two nos.) have been envisaged at the draft tubestructure on the tailrace side. The clear opening is 5.10 m wide x 2.34 mhigh. The gates shall be designed for a head corresponding to average tailwater level of EL 136.96 m (sill EL 132.19 m).

The gate shall be lifted under balanced head conditions created byfilling valve. The gate shall be operated by means of independent ropedrum hoist of 15t capacity (Tentative) mounted on trestle at deck level of EL139.80 m. General installation of Draft Tube Gate is shown in DrawingNo.PTNL-5900-DBPH-1502 (Plate Nos. 6.204 in Volume VIII (B)). Salientfeatures of Draft Tube Gate are at Annexure – 6.47 in Annexure Volume-II.

6.6.5 Surface Power House at Kelwan Dam

A Surface Power house of size 32.70m (L) x 13.88m(W) x 18.62m(H)has been provided to house two numbers of horizontal Frances turbines of1250KW each. The centre line of the machine has been kept at EL.135.70m.The structure comprises of RCC columns and beams designed tocarry the loads coming from various electro-mechanical equipment. ThePower House plan, Cross Section and Longitudinal Section are shown in

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Drawing Nos.PTNL-5900-DPR-6007, 6008 and 6009 (Plate Nos. 6.211,6.212 and 6.213) in Volume VIII (B).

The location of surface power house has been selected by studyingthe limited contour details available as no site visit could be made toascertain the suitability of the strata. Hence the power house location shallbe confirmed after site inspection and in consultation with geologist.

Salient features of the Power House are tabulated below:

Sl.no Project details Particulars1 MWL EL.166.00 m2 FRL EL.164.00m3 MDDL EL.136.00m4 MDDL for power generation EL.141.00m4 Design Head 22.16 m5 Design discharge 7.72 m³/sec6 Penstock 2.5m, circular, one number7 Branch penstock after

bifurcation1.6m, circular , 2 nos

8 Type of liner Steel lined, IS 2002 ( latest )Class 3 9 Installed capacity 2x1250KW 10 No of units 2 11 Type of power house Dam toe surface power house 12 Size of power house 32.70m (L)x13.88m (W)x 18.62m

(H)13 Type of turbine Horizontal Francis 14 Normal tail water level EL.135.46m15 Minimum tail water level EL.134.00m

A Dam toe Surface Power House is planned on the left bank of PurnaRiver downstream of Kelwan Dam. The intake structure is providedadjacent to the main spillway also termed as “Power Block”. The powerblock monolith accommodates an intake structure and a steel penstock(main) of 2.5 m dia laid within the body of the dam spillway. The penstockemanates horizontally from the intake structure with centre line elevation ofEL.134.62 m. The centre line of machine is EL. 135.70 m. The mainpenstock of 2.5 m diameter bifurcates near the power house into two branch

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penstocks of 1.6 m diameter each to lead the water to two turbines. Thewater from the draft tube is lead back in to Kelwan Feeder Canal through anopen tail race channel (5m wide). Two draft tubes with separate gates havebeen provided. The general layout plan of Power House and L-Section ofwater conductor system are shown in Drawing Nos. PTNL-5900-DPR-6001and 6002 (Plate Nos. 6.205 and 6.206) in Volume VIII (B).

The power potential study has been carried out by THDC India Ltd.The rated discharge through each unit of the power house is 7.72 m³ /sec.The design head is 22.16 m. The installed capacity for this power house is2500 KW comprising of 2 units of 1250 KW each. The turbine is horizontalFrancis type.

The main components of the schemes comprise of:

i) Intake Structureii) Penstockiii) Surface Power House iv) Tail Race Channel

6.6.5.1 Intake Structure

The intake structure is designed to ensure smooth entry of water fromthe reservoir into the water conductor system. The required minimumsubmergence from MDDL has been checked as per IS-9761: 1995. Thecentre line of intake has been kept at EL 134.62 m to avoid formation ofvortices and the entry of air into the water conductor system. Forminimizing the losses, the profile of the intake roof and sides have beenstreamlined and bell mouth entry has been provided. After the gate, atransition from rectangular [(1.8m (w)x2.5m (h)] to circular ( 2.5m dia) hasbeen provided. The Intake details and Trash rack details (metal work) areshown in Drawing Nos. PTNL-5900-DPR-6003 and 6004 (Plate Nos. 6.207and 6.208) in Volume VIII (B).

6.6.5.2 Penstock

The steel penstock of 2.5 m dia has been provided in the dam body.The penstock is bifurcated into two branch penstocks of 1.6 m dia for

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feeding water to individual turbines. The penstock is designed to withstandmaximum internal pressure including pressure rise due to water hammer.The steel for penstock is IS-2002(grade 3) and the thickness of steel is14mm (for 2.5 m dia.) and 12mm (for 1.6 m dia.). Penstock steel liningdetails and Penstock steel lining ferrule details are shown in Drawing Nos.PTNL-5900-DPR-6005 and 6006 (Plate Nos. 6.209 and 6.210) in VolumeVIII (B) respectively.

6.6.5.3 Tail Race Pool / Channel

After power generation the water is led back into the feeder canalthrough an open tail race channel 5.0 m wide excavated along its alignment.The bottom slope of the tail race pool has been provided with anapproximate gradient of 1(V): 4.0(H) sloping upwards upto its meetingpoint of the feeder canal.

6.6.5.4 Power Intake Service and Emergency Gate

Fixed wheel type gate (one no.) for opening size of 1.8 m wide x 2.5m high shall be provided at the downstream of the Intake having bell mouthshape with elliptical profile. The sill of the gate is located at EL 133.37 m.The gate is to be designed for a head corresponding to FRL 164.0 m andoperated under unbalanced head condition. The gate shall have downstreamskin plate and downstream sealing. The gate shall be operated by means ofdouble acting hydraulic hoist of 25 t (Tentative) capacity. Power pack ofhydraulic hoist shall be located at the top of pier at EL 174.0 m. Generalinstallation of Power Intake service gate is shown in Drawing No.PTNL-5900-KEPH-1501 (Plate Nos. 6.214) in Volume VIII (B).

Salient features of Power Intake Service Gate are at Annexure – 6.48in Annexure Volume-II.

For maintenance of power intake service gate, a fixed wheel typeemergency gate of 1.8 m wide x 2.5 m wide is proposed. This gate shall beoperated under balanced head condition created by crack opening. The gateshall be capable of lowering in flowing water condition in case of anyemergency. The gate shall be operated by means of double acting hydraulic

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hoist of adequate capacity. The salient features of Power Intake EmergencyGate are at Annexure – 6.49 in Annexure Volume-II.

6.6.5.5 Draft Tube Gates

Slide type gates (two nos.) have been envisaged at the draft tubestructure on the tailrace side. The clear opening is 3.40 m wide x 2.34 mhigh. The gates shall be designed for a head corresponding to average tailwater level of 135.46 m (sill EL 131.19 m).

The gate shall be lifted under balanced head conditions created byfilling valve. The gate shall be operated by means of independent ropedrum hoist of 12t (Tentative) capacity mounted on trestle at deck level of EL138.80 m. General installation of Draft Tube Gate is shown in DrawingNo.PTNL-5900-KEPH-1502 (Plate Nos. 6.215 in Volume VIII (B)). Salientfeatures of Draft Tube Gate are at Annexure – 6.50 in Annexure Volume-II.6.6.6 Surface Power House of Kelwan Feeder Pipe line

A Surface Power House of size 19.00 m (L) x 14.75m (W) x 19.0 m(H) has been provided to house two numbers of vertical Kaplan turbines of1000KW each. The centre line of the machine has been kept at elevationEL.115.399 m. The structure comprises of RCC columns and beamsdesigned to carry the loads coming from various electro-mechanicalequipment. A steel roof truss has been provided at top of the power house.The Power House plan at EL. 118.180 m, Cross Section and Power HouseRoof Truss details are shown in Drawing Nos.PTNL-5900-DPR-7007, 7008and 7009 (Plate Nos. 6.222, 6.223 and 6.224) in Volume VIII (B).

The location of surface power house has been selected by studyingthe limited contour details available as no site visit could be made toascertain the suitability of the strata. Hence the power house location shallbe confirmed after site inspection and in consultation with geologist.

Salient features of the Power House are tabulated below:

Sl.no. Project Details Particulars1 Top of canal EL.134.69m2 FSL in canal EL.133.94m3 Design Head 15.97m

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4 Design discharge 7.55m³/sec5 Penstock 2.5m, circular, one number6 Branch penstock after bifurcation 1.6m, circular , 2 nos7 Type of liner Steel lined, IS 2002 ( grade 3 )9 Installed capacity 2x1000KW 10 No of units 2 units11 Type of power house Canal power house 12 Size of power house 19.00m (L)x14.70m (W) x16.5m (H)13 Type of turbine Vertical Kaplan turbine 14 Normal tail water level El.117.77m15 Minimum tail water level El.116.57m

A canal Power House is planned in the feeder canal. The intakestructure is provided in the feeder canal after transition from 3.5 m widemain canal to 13.5 m wide fore-bay. The penstock emanates horizontallyfrom the intake structure with C/L EL. 129.05 m and after the vertical bendsreaches EL.115.399 m of the turbine. The main penstock of 2.5 m diameterbifurcates near the power house into two branch penstocks of 1.6m diametereach to feed the two turbines. Water from the draft tube is led back to thecanal after an open tail race pool. Two draft tubes with separate gates havebeen provided. Bye- pass arrangement has also been provided to allow thewater discharge downstream during shutdown of the power house. Thegeneral layout plan of Power House and L-Section of water conductorsystem are shown in Drawing Nos. PTNL-5900-DPR-7001 and 7002 (PlateNos. 6.216 and 6.217) in Volume VIII (B).

The power potential study has been carried out by THDC India Ltd.The rated discharge through each unit of the power house is 7.55 m³ /sec.The design head is 15.97 m. The installed capacity for this power house is2000 KW comprising of 2 units each of 1000 KW of vertical Kaplan turbinetype.

The main components of the schemes comprise of:i) Intake Structureii) Penstockiii) Surface Power House iv) Tail Race Pool

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Necessary modification in the design and layout of proposed power house on Kelwan feeder pipe line due to replacement of open feeder canal by pipe line will be taken care at the construction stage.

6.6.6.1 Intake Structure

The intake structure is designed to ensure smooth entry of water fromthe forebay into the water conductor system. The required minimumsubmergence from FSL has been checked as per IS-9761: 1995. The centreline of intake has been kept at EL 129.05m to avoid formation of vorticesand the entry of air into the water conductor system. For minimizing thelosses, the profile of the intake roof and sides have been streamlined andbell mouth entry has been provided. After the gate a transition fromrectangular [(2.0 m (w)x2.5 m (h)] to circular (2.5 m dia) has been provided.The Intake details and Trash rack details (metal work) are shown inDrawing Nos. PTNL-5900-DPR-7003 and 7004 (Plate Nos. 6.218 and6.219) in Volume VIII (B).

6.6.6.2 Penstock

The steel penstock of 2.5 m dia has been provided in the dam body.The penstock is bifurcated into two branch penstocks of 1.6 m dia forfeeding water to individual turbines. The penstock is designed to withstandmaximum internal pressure including pressure rise due to water hammer.The steel for penstock is IS-2002 (grade 3) and the thickness of steel is 14mm (for 2. 5 dia.) and 12 mm (for 1.6 m dia.). Penstock steel lining detailsand Penstock steel lining ferrule details are shown in Drawing Nos. PTNL-5900-DPR-7005 and 7006 (Plate Nos. 6.220 and 6.221) in Volume VIII (B)respectively.

6.6.6.3 Tail Race Pool

The water is led back to the feeder Pipe line after an open tail racepool. The bottom slope of the tail race pool has been provided with anapproximate gradient of 1(V): 4.0(H) sloping upwards upto its meetingpoint of the feeder canal.

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6.6.6.4 Feeder Pipe line Power House Intake Service and Emergency Gate

Fixed wheel type gate (one no.) for opening size of 2.0 m wide x 2.5m high shall be provided at the downstream of the Intake having bell mouthshape with elliptical profile. The sill of the gate is located at EL 127.80 m.The gate is to be designed for a head corresponding to FSL 133.94 m andoperated under unbalanced head condition. The gate shall have downstreamskin plate and downstream sealing. The gate shall be operated by means ofrope drum hoist of adequate capacity. Provision of removable guide shall bemade in trestles, when not in use. The gate shall be stored at deck level EL135.00 m supported by dogging beam. General installation of Power Intakeservice gate is shown in Drawing No.PTNL-5900-KFCPH-1501 (Plate Nos.6.225) in Volume VIII (B).

Salient features of Power Intake Service Gate are at Annexure – 6.51in Annexure Volume-II.

For maintenance of power intake service gate, a fixed wheel typeemergency gate of 2.0 m wide x 2.5 m wide is proposed. The sill of the gateis located at EL 127.80 m. The gate is to be designed for a headcorresponding to FSL 133.94 m. The gate shall have upstream skin plate andupstream sealing. The gate shall be operated by means of rope drum hoist of12t (Tentative) capacity. This gate shall be operated under balanced headcondition created by crack opening. The gate shall be capable of lowering inflowing water condition in case of any emergency. General Installation ofPower Intake Emergency Gate is shown in Drawing No.PTNL-5900-KFCPH-1502 (Plate No.6.225) in Volume-VIII(B). Salient features ofFeeder Pipe line Power Intake Emergency Gate are at Annexure – 6.52 inAnnexure Volume-II.

6.6.6.5 Feeder Pipe line Draft Tube Gates

Slide type gates (two nos.) have been envisaged at the draft tubestructure on the tailrace side. The clear opening is 2.652 m wide x 1.50 mhigh. The gates shall be designed for a head corresponding to average tailwater level of 117.77 m (sill EL 112.271 m).

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The gate shall be lifted under balanced head conditions created byfilling valve. The gate shall be operated by means of independent ropedrum hoist of 10t (Tentative) capacity mounted on trestle at deck level of EL118.78 m. General installation of Draft Tube Gate is shown in DrawingNo.PTNL-5900-KFCPH-1503 (Plate Nos. 6.226) in Volume VIII (B).Salient features of Feeder Pipe line Draft Tube Gate are at Annexure – 6.53in Annexure Volume-II.

6.7 Instrumentation

The requirement of special instruments for the construction of dams,tunnels and Power Houses are described in Chapter – 10 “ConstructionProgram, Manpower and Plant Planning”.

6.8 Other Studies

The studies required at DPR stage have been carried out and includedin the report. The other studies which are not covered in the DPR will becarried out at preconstruction stage.

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