Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 12892 (1989): Safety of barrage and weir structures -Guidelines [WRD 22: River Training and Diversion Works]

IS 12192 : 198!1

Indian Standard

SAFETY OF BARRAGE AND WEIRSTRUCTURES - GUIDELINES

"ltrofuf ~

.t~'III' m f~ ~v;l';ml'1 "lft ~lm-q'(.mn f~;gI.<'1

UDC 62782 + 627"43 : 614'8

© BIS 1990

BUREAU OF INDIAN STANDARDSMANAK BHAVAN. 9 BAHADUR SHAH ZAFAR MARO

NEW DELHI II00lI2

AMENDMENT NO. 1 AUGUST 1991TO

IS 1%891: 1989 SAFETY OF BARRAGE AND WEIRSTRUCTURES - GUIDELINES

( h~ 2, c"'ese '.1 (e). (6) J- S.lloIIlUIe 'excessive re'rogress"on' for'IMdeqUIte ~trograsion·.

(RVD20)

Barrages and Weirs Sectional CommiUee, RVD 20

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards on 22 December 1989, after thedraft finalized by the Barrages and Weirs Sectional Committee had been approved by the River ValJeyProjects Division Council.

The safety of barrage and weir structures should be ensured right from the mvestigallon stage andcontinues up to the location. desrgn, construction. operation and maintenance stages. There cannot beany laxity on these aspects. A safe structure should not only be hydraulically and structurally safebut it should also fulfil the function. for which it has been constructed. Fire fighting equipment maybe provided near the barrages

IS 121192 : 198'

Indian Standard

SAFETY OF BARRAGE AND WEIRSTRUCTURES - GUIDELINES

84118 : 1976

7720: 1975

7349: 1989

6532 : 1972

5.1 For a safe and efficient barrage/weir. thelocation of the structure is very Important.Various considerations for locating the structureur tile proper pla~ l$lJall include the course: of thonver, the nature of ailt, condition of the banks,width or the river bed, foundation conditions,confluence of tributaries, bends and rapids in theriver, etc. The following aspects shall be thoro­ughly examined frorn safety considerations.

4 SAFETY ASPECTS ON INVESTIGATIONS

4.1 The investigations should be earned outWithout any laxity as the continued safety andefficient funcnonmg of barrage/weir structure andintegrating It With the master plan of the beemdevelopment depends on the data collected andanalysed. The structure designed based on inade­quate data may suffer an unexpected seriousstructural damage.

4.1 For details of preliminary and detaiJedinvestigations for barrages and weirs. IS 7720:1975 may be referred.

5 SAFETY ASPECfS ON WCATION

a) Course of the River

It shall be studied with survey maps/satelliteimageries that the course of the river has notchanged for many years at the prcspeeetve site ofthe structure. In the case of shifting rivers,proper measures shan be adopted to contain theriver in the desired course.

b) Nature oj SiTI

It shall be examined to determine whether tbesoil through which the canal alignment runs, isable to withstand the velocity of flow which cancarry the silt down the canal. This factor willinfluence the location of the head regulator andalso the overa II cost of the barrage as costly linin,may be required otherwise for safe operation.

c) Condition of the lJanks

It shall be ensured that the banks at the proposedlocation are firm and not easily erodible. Thebank. shall normally be high 80 that the countryareas are not submerged duriDg high DODds.Otherwise. costly flood protective embankmenuwould be necessary.

11130: 1984

11150: 1984

1 SCOPE

1.1 This standard provides guidelines on variousaspects of safety of the barrage and weir struc­tures, such as. investigations. location. design.construction. operation and maintenance.

2.1 The following Indian Standards are necessaryadjuncts to this standard.

IS No. Tille

Code of practice for design.installation, observation andmaintenance of uplift pressurepipes for hydraulic structureson permeable foundations

Guidelines for hydraulicdesign of varrages and. weirs:Part 1 Alluvial reaches (firstrevision )

Guidelines for operation andmaintenance of barrages andweirs (first revision)

Criteria for investigation,planning and layout of bar­rages and weirs

Criteria for river trainingworks for barrages and weirsin alluvium

Criteria for structural designof barrages and weirs

Code of practice for construc­tion of concrete barrages.

3 TERMINOLOGY

2 REFERENCES

6966( Fa,t 1 ).: 1989

3.1 For various terms used in this standard,reference may be made to tbe following IndianStandards,

a) IS 6966 : 1989b} IS 7349: 1989c} IS 7720: 1975d} IS 8408 : 1976e} IS 11130: 1984f} IS 11150: 1984

1

d) Width ofthe Ri..r net!

The width of the river at the pt'oposed locationshall not be too .~ -"'dft inlful:es- iKegular IiJfforming shoals on tile *pstreadt net dbwlbft:teddlland consequent megulat' arut Iikoly orOSI flo_A very narrow width 0' the- ri ...r shtliP eleo geavoided as it 'Would reduce the waterway andinduce hip intensities of flow which wouldnecefsirafe cIoeper ea. ollt' ""d "'lIn'd'atfono 8116protective works to make the arruerure safe ala.iast..sud'ace ff()W,.

e} ~i'" Collrllri_

For .... sllf"'Y ef tIM Ilructllr•• me- rou_co_.s, ""cit ..., 11010.....<tflOCks, ra.ltzo-. ol.yoy lay .... lIiIty loy'" ..,oore.. Iiquof....tion, artisian and quicksand. etc. ,,..11 be' tho,owughly known so that proper foundation treatmentcollfct !Ie effected.

f) Confluence of Tributaries

The location of~ strDCtl!l.... ~ tM mdl1.· 'iYerwith a tributary flowmg parallel and close to therna;. rivor _I be ""_ III ,h_ woulG 1M:possitJi.tiIlle8 at .. later date' of tl. mam riverbreUi,. i".o iIle lr'-J ..., o1ltlllr..king thestrlllrtotodM~ Rodorias: it _ale and infrae­tuo..

g) ClNreetive MeQ6UFes

11 is aof"f"ays very difficatr to select an. ideafsife forthe location tJf a: barrage and' its head regulatorssansfying all tbe requirements Including the safetyaspects. Hence. it oflen becomes eecessery to'select B site satisfying most of the requirementsand rot the ...st, s<Sme eoreecnve n:teasures shalfbe Ulc8'1"Of'tlfed in the 1ay<>1ft and desl/lTI' '8enswe It iaftf ~rute'. Yhese jndade properfl)uJJdatten tfeU1!rtfenl'. prO'fJ'erfy designed flJ'fdebursds, ~. Rood "",,'ecd"e ertt&atlkrtlmt!. pdotchannels, slit excluding de'vices, proper gateregulation, etc.

6 SMETY ASPECTS ON DESI<;.N

6.1 1>«ra1l1e"'~, StJCf\ as, de'iS" flood, pond level,free bdatd'. waterway ,aage-d,iscftarae curve, etc..shaft IJe lJl'dper~ select~d to ecsure safe design oft~e muctu.te arrd gutdefjnea for tlle sa.me aseS'VOOI in til<! followi"ll paras. 1tetereace may alsobe made td l!l ~!l66 ( rart 1 ) : 19t9.

a} Design Floot!

Th~ ltatnIre""'it shan be desilll1ed to oatol.y _a fiaC'd wfih- cOttam return period. U&Ua.Lfy.. i.Ataecase crfba:rraces or minor and normal importaRcejl.he cf~ift flood far "aterway shan ... takeA tohavt< it l'MIUell~of I hI SO years. 14 such c.aoos

2

wfl.er.c. rislls aod hazards are involved. a review offtris criteria based on site conditions may benecessary.

bl Fru JUard

The f_ INlttd oItaH!Ie """"ibM) fixed so that thestructure and abutments are safe for a higherflood With a frequency of I in 500 years. Thelikely accretion of bed on the upstream lJItoo1IIalso be taken mto account while fixing the freebOa1'd. The 101' levet~ of abutmeRt'J dItd pi.rs shal'also- be Ii"ed to _ommodatl: tle 18"'" ill tilernMimut'tl \leNd po9itioO 'moll t1I<n tbese ..... _damaged by ftoatiwg 1'I'eeS". ~.

c) Afflux

The permioaible a4llwt shall be """,ruUy fix"" So'that the waterways of the bacr3.le call be iKdIaccordingly without causing damage to nearbyimportant/populated towns, industries, etc andrisk of outflanking. by breaches of buads; etccould be avoided. Occasionally, floodmg of culti­vated lands in the river bed Islands and the banks,under extreme case of flood above 1 in 100 yearsfrequency, maoy be allowed, Otherwise, the water­way win be unnecessarily too wide which maycause shltAish :ftE:I'VI t1h'ough tbe barrage. shodformation, C'I'€JSI flows. excessive cost oC SUU(:tUle"etc.

d) Waterway

The watorway of <t lIan:'3ge shaH be very carefullyfixed to aveid shoat formali<iJn and excessiveSCOUf.

e) HpuullC Design

The failures of barraplw~its.can be attributed t.the followmg main. CIIUK5,. acung alone Of Incombination. These are (I) undermining throughpipmg, (2) eruption of Ooor caused by upliftexceeOlftf payity foree. 'DOt ill the case of raftfloor ). (3) deep scour i:mmediately upstream and!or downstream oftbe solid floor .. (4) faulty cons­truction, (5} faulty n:guta1ion of gates. and (6)medequate setrcgessiou.

After proper investigation of foundation condi­lions ..c the proposed b_aae -t it. a&utm-.suitable Mundtdfi,oa tr&at:menU. an: _ be ~poMd.

by th~ design or~aniza.tion for improving beat...c.apaclty,. reducing the settlement and avoidmg&iquefactlon. etc. Proposals for preconsohdatfoe;vibrofloatation, compaction piles. groubo' f:IIloose rock, ground anchors, etc, may be prQprerlyanalysed and design tntimated to tbe constructionagency well in advance.

The hydraulic design of tbe barrage,lweir shan becarried out to be safe against eXd sradieo.t, scour

and uplift and settlement of foundation. Forgurdefines for their designs, reference may be madeto IS 69(lj6 : 1989. In general, this would involvesafe design of upstream and downstream cutoffs/sheet piles, energy dissipation arrangements.thickness of floor, flextble protections, etc.

f) Structural Designs

In so far as the structural design is concerned,the various forces and moments Including thosecaused by the earthquake, differential heads.differential settlement etc, shall be taken mtoaccount and the vanous factors, such as, eliding,overturning, etc, shall be arrived at to be wuhmthe permissible limits. Allowable stresses In mate­rials, such as. concrete, masonry. steel, etc, shallnot be exceeded. For gurdehnes for structuraldesign of barrage/weir, reference may be made toIS 11130 : 1984. Proper measures to protect thebarrage crest and floor against abrasion da mageby rolling boulders may be provided. Fenders maybe added where navigation IS expected.

Gale designs

For the safety of the barrages, proper remotecontrol and group control systems of the gateoperation must be provided. Sometimes. after theerection of the gates. some gate leaves VIbrateunder certain hfted condmons. These should beImmediately checked by manufacturers and destg­ners and necessary rectifications carried out.

Occasionally, floating tree trunks hit the under­side of the gate leaves which may seriouslydamage the gates. Whenever such possrbihtyexists, sufficient margm must be allowed abovehigh flood level to allow large Size tree trunksto pass underneath the gates.

Radial gates may be advantageous in barrageswhere flashy flood is expected. These can beoperated 18 a shorter time than vertical gates.

g) River Training Works

Care shall be taken for the safe design of variousriver training works. such as. guide bunds, spurs,etc, and other safety works. namely. afflux buad,margmal and approach embankments. etc. Forguidelines for design of river trammg works.reference may be made to IS 8408 : 1976. Formajor barrages, performance of rtver trainingworks should be reviewed from time to lime. Ifnecessary, it may also be checked in modelsbecause the flow condmons in upstream anddownstream regions of the barrages get consider­ably changed after a few years due to shoal for­matron, bank scour, etc. If necessary. the guidebunds are sometimes required to be extended orits protection works to be strengthened after the

flood. season. Detailed pictures oC the flow condi­tions and their effect on river tl;ainina worksshould be placed before the designers for reviewand reconsideration every year.

h) Design of Other Components

A safe design of fish pass would necessitate pro­per provrsrons fOT the safe passage offish fromupstream to downstream and 'VIce verso. ElI"ectlvc­ness of the fish passes is to be regularly observedboth during the monsoon and past-monsoonperiod. If It is not effective, proper moditicationsin the design and operation method have to berequested from the design organizations. Similarly.the safe design of navigation lock would neeessr­tate proper tilling and emptying arrangements,berthmg arrangements. desittmg arrangements. etc.Whenever ice formation takes place. provision ofde-icing arrangements for proper gate operationshould be ensured.

NOTE - For auidellnes on the deergn of fish pass,na v igaticn lock. trash racks or head regulator, etc,reference may be made to the Publication No. 179Vol II· of ebe Central Board of lrrigatlOa andPower, New Delhi.

7 SAFETY ASPECTS ON CONSTRUCTION

1.1 A good coordination between designing andconstructing agencies shall be estabhshed forbringing our a safe and economical structure. Thefield engineers shall be In the knowledge of theimplications of provisions in the design of variouscomponents. Any change required to be made 00

account of Site condmons or any other reasonwhatsoever, shall not be attempted by him on hisown without evaluating the implications due tosuch changes and the designer shall invariably beconsulted to find out any other economical andsafe alternative thereof. Frequent checks on theconstruction vis-a-vis desrgn provisions and cons­tant quality control shall be ensured for providin.a safe structure.

7.2 For carrying out the construction efficientlyand safely, the following points shall be carefuJlyplanned and data on the same regularly collectedduring the construction period:

a) Sequence of construction of various itemsof the structure including river diversionand de-watering arrangements.

b) Various constraints on different activitiesof construction of the components.

c) Inter-dependence of various items so thatthere is minimum interference in the con­tmuity of progress.

·ManuaJ on bal'raaes and weirs on permeablefoundation.

3

IS usn, 1989

d) Obliptory precautiollO to be tolen for theprotection of season's works from theensuring doods.

e) Special features, if any.

f) Proper lighting arrangements to be pro­vjded at tbe project site.

8) Right type ond capacity of the equipmentrequired for de-watering well. point andpumping. excavanon, machines, sheetpiling equipment; foundatu;)D treatment,plants. sucb. as. vibro-floatation, etc, c?m.paction equipment, concreting plant. rivercrafts. floating cranes, etc to be carefullyplanned and arranged before the CDnstr1:Jc­tion is started. Wrong selection of equip­ment often causes serious bottlenecks inconstruction and even causes accidents.The selection of the above may be gotvetted in the design office including safetyarrangements to be provided for theiroperation.

h) Safety crew includinB divers. with fulldiving kit must be provided at site.

j) First aid kit for accident or emergencyshould be provided wherever necessary.

7.3 Righf {rom the preparatfon of foundation forthe structure, each and every component of thebarrage/weir shall be constructed properly forensuring safety of the structure. For generalguidelines on the construction of barrages/wens.reference may be made to IS JJ150; 1984.

7.4 Safety aspects on the constructIOn. or follow­ing items shall be ensured by the site-in-chargeB8 detailed.

a) Foundatiolf

Foundation preparation is an important itemsince the whole structure is going to rest on thesame. It shall be dressed up to the barrage/weirprofile and excavation shall be carried out care­fuUy without exceeding the tolerance limits. Thefoundation shaH not contain loose pockets ormaterials and they shall be watered and compact­ed to the specified reiattve deneuy. Thrs is appli­cable to those portions of the foundation alsowhicb may become loose during excavation andde-watering operations. Clay pockets shall betreated as specified by the designer includingremoval. re611ing with sand and compacting. Itshall be ensured that proper drainage arrange­ments in the foundation in accordance with thedesign including inverted filter wherever indicatedare provided before concreting work is taken up.To avoid honey-combing of concrete of the floor.proper mudmat of lean concrete usually 50 toISO mm thick ,hall be provided,

4

b) Cut-Off/SM., Pil.

1) Wherever sheetpiles are to be provided,they shall be driven at their correct align­ment without any gaps between them inthe waH. Since it may not always bepossible to drive them at exact plumb,suitable tolerances may be allowed. If thetolerances exceed the permissible limit, theyshall be corrected by taper piles. If thereIII any split in the interlock. additionalpiles In front shall be driven to cover it..Drtvtng of welded sheet piles of more tban8 m length shall not be allowed as the weldmay give way due to excessive drivingstresses. Random checking of sheet pilejomts should be done for leakage by die­injection technique or any other suitabletechnique. Wherever seals are to be jointedto the sheet piles, it shaH be carefully doneby welding and bracing. Smce sheet pilearc designed to have hinge action at thetop. u shall be ensured by the provision ofthe tar paper Wherever two piles rowsare provided side by side, cork mastic filleron top shall be provided to take care ofuneven heights and hinge action.

Sheet pile capmg beams should be castmcnahthrc wuh the barrage raft. Other­wise clean cold joints may form at theinter face, which may cause short circuitingof the seepage flow and even piping alongthrs jomt.

Vrbrostekers should be recommended forpile sinkmg to aVOId mis-alignment, damageof pile head, separation of clutches and tofacrhties quick driving.

2) Wherever concrete/masonry cut offs areprovided, precautions shall be taken toaVOId crack 109 as It may lead to shortcrrcurtmg of seepage path and the eXI'gradrent may be exceeded endaogermg thesafety.

c) Solid Floor

The solid floor shall be constructed carefullyavoiding stratiticatton of concrete which may leadto farlure by blowing off agatnst uplift pressures.Cold joints shall be avoided. The strength ofcement concrete of the raft shall be maintainedin accordance With the specifications so that thestresses III both the concrete and steel reinforce­ment are not exceeded. The mam and dtstnbunoareinforcement of the raft shall be carefully laidin accordance With the specrflcauons and designrequirements. The spacings shall be arranged Insuch a way tha.t proper placements of concreteand vibration are ensured. Reinforcement aroundsiIJ beam grooves shall Dot be omitted. Proper

dowels between first and second stage concrete inthe gate grooves. trestle foundation, etc, must notbe forgotten. The pier reinforcement sball be pro­perly anchored to the raft. Wherever horizontalor vertical construction joints are necessary.proper steps to cut the joint and provision of sealswhen the joint is to be Jeft open for more than3 days, are to be provided.

d) Piers and Gates

In the piers, correct alignment of the gate andstoplog grooves shall be ensured so that no diffi­culty is experienced in therr operation. speciallyduring floods. For inspection and repairs of thegate wheels wherever contemplated. suitable galle­ries ID tbe prers with easy access shaU be provided.

Whtle concreting, the pressure relief pipes instal­led In the piers and their outlets shall not be lostsight of and the open ends of the pipes shall becovered so that the concrete does not fall into thepipes and chokes "them.

In the case of gravity type of floor, the steppedpier footings shalt be concreted up to the barragefloor level and further portion of the pier abovethe bay level shall be concreted simultaneouslyWith. the bay concrete. The steps shalt be soprovided that there is no vertical jomt. In theran type of floor. the bay concreting and pierconcreting shall be done Simultaneously.

e) Abutment

Anchorage of the abutment reinforcement to thebase slab shall be ensured. The abutment wellshall be raised simultaneously aJong wrrh thebackfill and in any case shall not be more thanabout I· 5 m above the compacted back fill. Speci­fied relative density of the backfuli shan beensured by proper compaction. Wherever dram­age 18 to be provided behind the abutment wallsin accordance with the desrgn, the same shall bedone carefulJy so that the saturated water levelof the backfill is not allowed to exceed the designvalues. Inverted filter and sea lrng arrangementsat the junctions of different abutment blocksshall be properly ensured.

High abutments sometimes undergo long termsettlements, in foundations susceptible to settle­ment, at the toe side resulting in gradualtiUmg of the abutment face. As a result. the gategrooves may get jammed It may be desirable 10

such cases to provide extra depth for the verticalgrooves on 'he face of the abutment to allow freemovements of gates even if tilted.

f) Divide Wall

As the divide wall IS the one coming under the di­rect attack of flood flow. proper protection around

5

IS 12119% : 19811

the same in accordance with the design shall beprovided. The change in tbe levels of the bed infront of the sluice and spillway parti"n sball begradually made up and abrupt changes avoided.The junction between the divide wall and thebay concrete shall be done with proper precau­tions.

Sometimes due to the cross-flow at the nose ofthe upstream divide wall, a dtflerentiul scourmay rake place between the two faces of thedrvrde wall. This may even cause tilting of the wall.Regular watch IS necessary. by sounding,. on tbetwo sides of the upstream divide wall. Ifnecessary, boulders in crates may have tobe dumped near the nose if the scour is serious.Jute bags or nylon nets fined with sand may bedumped in deep scour holes and covered withcrated boulders up to 1 m.

g) Downstream Protection

As the downstream inverted fiUer below thecement concrete ( c,c. ) blocks is very importantas a measure against piping, it shall be laid withdue care. The gaps between the c.c. blocks shallalways be filled with small stones or bajrt. Where­ever downstream bed level is higher than thelevel of downstream c.c. block protection, reverseslopes, not steeper than I in S shall be providedand it shall be ensured that some loose stoneprotection is provided for a length of not lessthan 2 m in the higher bed portion after thereverse slope.

Sorneumee, due to error in gate operation andalso due to shoal formation near the barrage.high concentration of flow may generate unsteadyshooting flow over the down stream protectionworks. To prevent any damage due to suchcontmgency, indigenous geofiJters of bamboomattress, etc, can be provided below the mineralfilters, to avoid displacement of the filter niaterralfrom below the c.c, blocks resultmg in the suctionof bed materials underneath.h) Instrumentation

The importance of instrumentation shall beunderstood fully and care shall be taken in theirInstaliarion $0 that wrong data are Dot observedleading to misleading and dangerous conclusions.For guidelines on the instrumentation in barrages!weirs, reference may be made to IS 6532 : 1972.

It may be stressed that often the instruments aresimply forgotten, once the construction is over.Even the locations of the instruments are notremembered. It is desirable to prepare an ex­haustive manual for instruments embedded in thebarrage. with their locations. frequency of obser­vanons, analy sis to be done, importance of theseobservations, etc. This manuaJ may be kept bothin the offices of the Assistant Engineers and

IS 1Z8~2 : 1919

Executive Engmeers in charge of the barrage. asalso in the site control room.The location of each of the instrument may alsobe painted on the face of the piers where the endof the cable pairs emerge out. The actual taplocation may also be mdrcated there by paints.

J1 River Training Works

The materials used in the construction of variousriver training works. such as, gurde bunds, affluxbunds, approach embankments groynes or spurs.etc, and that their construction Itself shall be ofrequired standards so that their failures. impairingthe hydraulic performance and hence the safetyof the drverston structure. 00 not occur. whereverfilters are mdrcated in the design, they snail beprovided Without fall since the stability of thebunds would depend on It. It shall be ensuredthat the afflux: bunds are tied to high grounds toprevent outflanking of the structure and endanger­ing the same wherever the deep channel of theriver hugs th.e gutde bunds and adequate apronshall be provided to avoid scour and consequentfailures.

k) Head Regulator

Head regulator IS also a structure simrlar to themain structure In so far as the general prmclptesof destgn are concerned. Hence, whatever pre­cautions are to be observed In the constructronof the mam structure from safety POint of View,they shall be followed for the head regulatoralso.

Whenever there IS a chance of floating deb-ts,such as, grass logs. tree- trunks, etc, entertng thecanal through the head regulator, log-booms ortrash booms may have to be provided at theupstream of the head regulator.

If heavy silt deposition takes place at the entry ofthe canal, thereby rcducmg the canal capacity, Itmay be necessary to have a small dredger operar­109 in the canal (damage of hning III the canalshould be provided) and clearing the Silt depostt­ed, The dredged material can be dumped oneither side of the bank.m) Damages due to Rolling Stones

Barrages/weirs located 10 the bouJdery reachesface the problem of abraston and damages due toroiling stones thus endangering the safety of thestructure. ]0 order to ensure the safety, measureshke provrsron of richer concrete III the top thick­ness of the floor, paving stones, clading of piernose with steel or stone. etc, shaH be adopted.

While repairing the cavaues on the crest slopeand cistern of the barrage and III the piers, properdowel bars and Wire mesh may be embeddedinside the cavmes before concrete lSI poured Intoit. At the surface, special concrete. namely.

6

haematlte concrete. epoxy concrete. etc, may beused, for a thickness of 150 rom or so.

When big boulders roll over the barrage. steelrails with welded anchors may be fixed on thesurface, so that the boulders cannot damage theconcrete surface.

n) Shearing Off of Pier Reinforcement

When the piers are under construction. the pro­jectmg pier reinforcement shall be properly pro­tected from floods by bending them In the drrec­non of flow. well before the floods and later onstrurghtemng them when the construction isresumed. As some damages could be caused dueto obhque flow or any other reason, the reinforce­ment shall be first checked up before startmg theconstruction after floods whether they are looselysticking out or not. After ensuring its properbendmg With the lower portion, new reinforcementshall be welded on to the old ones. Proper bond­mg of new concrete With the old one shall also beensured. A few welded rods shall also be testchecked for therr strength.

p) Provision of thrust forces, exerted by ice-coversof the pond, with reference to the safety of thestructure should be made. This provision is ofimparlance m sub-Himalayan areas of thecountry.

Provision for safety against uplift forces on thefloor structure that are exerted by the waterseeping down the mountain on h111 slopes (Partt·cularly, durtng rurny seasons) while the floor isunder repairs and no counterweight IS availabledue to diversion of flyer waters.

q) Quabty Control

Safety of the barrages/weirs depends on the soundconstruction With strict quality control. Safetyshall not be compromised for cost or speed ofconstruction. To prevent possible failures, thespots where faulty construction has occurred shallbe Identified by non-destructive tests and SUitablemeasures taken with strict quahty control.

Alkali aggregate reactron sometimes causes ex­pansron of concrete at a much later stage afterconstruction, Somenmes, such expansion In pearsand abutments james the gates. It IS essential thatthe cement and the aggregate proposed to be usedIn the construction of the barrage or the weirsshould be tested In a competent laboratory foralkah-aggregate reactivity. Use of pozzclanamaterial, for example, fly ash, etc, to a consider­able extent (up to 40 percent of the cementquannty ) may reduce the alkali aggregate reacti­vity. AU the cement and aggregates which arcliable to such reaction should be avoided in theconstruction.

r) Stri.. quality ~rtJl duriFfil COR8&nlctioasbould be exeseeed so thar the following ceesrruc­lion defects do not occur and the safety of strec­ture is' en-sured.

11 Stratfficatlon of concrete layers in the saIidfloor and the improper bond between thela.yers of CODCI'ck

2} VariQ\ls COltstFUdion and st1'$turaf designderects.

3) C.adc& ill the downstream gJaed.leading toshort circuiting of seepage path.

4) Improper foundation treatment leading tosubsidence and consequent disturbance In

the a.lipment of gate track and jammmg.5-} Cracking of seals In the joint'S.6) Tearing or sheet piles and. Improper iatee­

locking.7} Improper foundation treatment of imper­

VIOUS layers leading to locked up seepagepressure.

8) Inadequate cover for reinforcement bars.9) Honeycombing or bottom layers of floor

concrete due to omission of inadequatemudmat.

10) Improper cODack IDIX nsed resuttlflj Xlstructural failure, etc.

11) Neekmg Iailuses of flexible concrete cutoff walls.

12) Rigid slteet piles instead of hinged onesdue lO non-prOVISIOO of tar paper, corkmastick, aspbatt. etc.

8 SAFETY ASPECTS ON MAINTENANCEAND OPERATION

8.1 Proper inspection, maintenance and opera­non of the diversion structures are necessaryadjuncts to safe and economical designs. Anyslackness 10 these aspects would lead to failuresand extension of damages, For guideltnes OR thisaspect, reference may be made to IS 7349 , 1989.

8.2 Safety agaInst faulty gate regufatton can beprevented ortly by imparting adequate knowledgeto the' operating personnel about the significanceof the proper regulation and proper maintenanceof the gates and other hoistmg arrangements. TheyshaH also be imparted adequate training in thisregard. These shall form part of the duties of thesue-In-charge. Operation and mamrenance manual01 gates should be updated.

HA group of engineers including the designers,model research officers and maintenance engi­neers may form a committee of gate regulation.This committee may meet twice a year, onceImmediately before the flood and once imme­diately after the flood. The committee shallreview the condition of the nver, both upstream

7

IS JZI9J: 1!lD

aod dOWDStrealll or tile ba_ utililinw t1llrcrcsssecnons taken of tbe rWee. Whcmevcrserious scour is taking place. the couumtteemay adVice repair work by crated bouldersetc. where' kigh shoats have- been formed nearthe barrage. both upstream and downstream.proper deshoahng measures either by dredgers.,.. by dozen duriatl 1M IUln-mOD8OOJ) period.are" to be rKGmm&Rdcd. ADIi baRk SCOUJ' narthe barrago Will also be.carefully suncyecll andremedial measures to be q.ul<:kly de&tttnea.If quick decisions are not t&i.ca., aaJ'C"a'ilrMmay become beyond the control of tbe main..tenance engineers.Sometimes. the under sluice tunnels are chokeddue to heavy silt deposition. ThIS shouJd berC!ufarlY checked after closing the tunnel'gales on the downstream. If necessary, such,"hokag4:i are to be cleaaed by compressed airor ai.r water jets".

8.3 Safety of the barrages against scour damagesreselung from cross. :fWWi. shcal fOimatiQB, vor..tex formation.. etc, ahalk be eMlued by properoperatron of the gates and dredgiRg of shoalswherever necessary.

8.4 The piezometric data shan be regularlychecked, particularly dtlnng and after tlte floodsand saetable action taken if unWiW lKAavioardrfferent from the dei!:ilJ,ll values are obse:rved.Readings of ultmeters insaa..Lled over abwtments,piers and divide walls shall be regularly observedand safety of the structure ensured wheneveradverse behaviour is observed. Similarly.. thereadings of SOil meters and stress meters, whereverprovided, shall be lDIalyscd and suitable actiontaken to ensure safCS:y of the slr1.M.:ttJrc.

8.5 Safety of the trash racks provided sometimesupstream of the gates of the head regulator feed­mg hydel channels shall be ensured by frequentlycleaning the cloged Ol'eDiRgs,. thus enm:iDlltiughigh differential pressures to develop.

8.6 Divide walls aaarysi. of seov holes and yearto year maintenance required :dI:oukl'" examinedfrom hydraulic performance, pte OpeIat1fil&& aMflow phenomenon. If the scoue holes are. deepenedto vortex formation leading to washing of fine duomaterrala and sinking boulders, remedial measuresshould cover treatment of proper fibre filter.

9 MISCELLANEOUS

9.1 For each and every barrage/weir, a record ofits construction features and behaviour, bothhydraulic and structural. shall be kept In the officeof the Divisional Engmeer of the project. Therecord shall also contain the details of Its failures!problems, If any. and remedial measures adoptedfrom time to time. Necessary photographs shallalso be available of the same. These would always

IS llB9Z : .,.,

help for future modification if any, needed for thesafety of tbe structure.

Construction details. design calculations andconstruction drawings of barrages/weirl. etc,should be documented and preserved for futurereference and use.

River plan forms in the vicinity of barrage shouldbe monitored from ground survey as well as fromsateJlitc rmagertes If possible. Model studiesshould be earned out before design and construc­tion of 'DanagtJwe)T.

'.2 Whenever there is any problem or failureof the barrage/weir. a lot of data needs to becollected for study and analysts so that suitableremedial measures could be adopted and safetyensured. A list of such data IS given below:

a) Detailed drawings of the barrage/weir, itshead regulators, guide bunds, afflux bunds,approach bunds, spurs, etc.

b) Detailed note on the damages noticed in ...eluding the history and remedial measurescarried out, If any, so far.

c) Development of the damages.

d) Photograpbs taken, if any.

e) Discharge and water levels at various pointsalong guide bunds, afflux hunds, approachbunds, spurs, abutments, etc.

r) Flow pattern observed. for example. con­eentratron of flow through some bays orotherwise.

I) Sounding data both upstream and down­stream at the ends of the ran. cementconcrete blocks. stone protection arounddivide walls and for a dl:itance of 60 mor so at J5 m interval.

h) Gate operations followed during floods andother times.

j) Any seismicity experienced prior to ordUlinl the ilood'So.

k) Data on settlement of piers, abutments,flank walls, etc, if any.

•

m) Quantity and quality of bed materials andfloating debrrs during the floods.

n) Details of spurs upstream and downstream.

p) Data on traffic over the structure, if any.during the floods.

q) Details of construction materials used in­cludmg quahty of construction for variouscomponents including the different bunds.

r) Instrumentation data available includmg itsana~~~o\'& aM fiw!i.t'o.gB.

s) Details about stages of construction.

t) Details of any field investigation done fordetecting hollows If any and results thereof,

u) Previous history of any damages and reme­dial measures thereof.

v) Recommendations of any Technical Advi­sory Committee from ume to time andcompliance thereof.

w) Notes on hydraulic and structural designswith assumptions made if any (full detailsshall be available WIth the design office ).

y) Any other data relevant to the case underInvestigation.

z) Analysts of discharge. silt charge observa­uons near the barrage and bead regulatorshould be earned out on year to year basis.Gauge discharge relationship and retrogres­sron in the vrcuuty of barrage, if any.should be taken Into consideration forprotection measures and river trainingmeasures.

9.3 Another important point leadmg to the safetyof the barrage/weir structures being planned.designed. constructed and/or operated and main­tamed is that of pubhshmg the cases of failuresof barrages/weirs and remedial measures adoptedin the technical journals for the benefit of thedesigners and the project authorities, This shallbe done wherever feasible subject to orders, ifany, regarding publications on projects classifiedas secret.

StODdard Mark

The use of the Standard Mark: IS governed by the prcvrstons of the Bureau of IndianStandards Act, 1986 and the Rules and Regulations made thereunder. The Standard Mark onproducts covered by an Indian Standard conveys the assurance that they have been producedto comply With the requirements of that standard under a well defined system of inspection.testing and quality control which IS devised and supervised by HIS and operated by theproducer. Standard marked products are also contmuously checked by HIS for conformityto that standard as a further safeguard. Details of conditions under which a licence for theuse of the Standard Mark may be granted to manufacturers or producers may be obtainedfrom the Bureau of Indian Standards.

B....... of fDdian Studards

DIS is a statutory institution established under the Bureau of Indian Standa,ds A.ct. 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.

Copyright

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any form without the prior permission 10 wrrting of BIS. This does not preclude the free use, In thecourse of implementing the standard, of necessary details, such as symbols and sizes, type OT gradedesignations. Enquiries relating to copyright be addressed to the Director ( Puhhcauons ). BIS.

Revision of lndlao Standards

Indian Standards are reviewed perrodicafly and revised, when necessary and amendments, If an)'. areissued from time to time. Users of Indian Standards should ascertain that they are In possession orthe latest amendments or edition Comments on this Indian Standard may be sent to BrS givmg thefollowing reference:

Doc: No RVD 20 (4418 I

Amendments Issued Since Publication

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