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Disclosure to Promote the Right To Information

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Indian Standard

PLANNINGANDDESIGNOFGUIDEBANKS

FORALLUVIALRIVERS-GUIDELINES

Fi rst Revi si on

UDC627 41

: 624 4

QBIS 1994

B U REA U O F I ND I A N S TA ND A RD SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Apri l 1994 PriceGroup 5

( Reaffirmed 1999 )

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River Training and Control Works Sectional Committee, RVD 22

FOREWORD

This Indian Standard ( First Revision was adopted by the Bureau of Indian Standards, after the draftfinalized by the River Training and Control Works Sectional Committee had been approved by theRiver Valley Dtvision Council.

Indian rivers in plains are often shallow and flow in a wide alluvial belt, with meanderingand/orbraiding characteristics. To construct an engineering structure across rivers, it is necessary to narrowdown its section and restrict its course of flow centrally through the structure built over it. This isachieved by construction of heavy embankments, called Guide Banks.

Guide banks are thus meant to confine and guide the river low through the structure without causingdamage to it and its approaches. They also prevent the outflanking of the structure.

Guide banks form one of the major and vital constituent of river training works and often a subs-tantial amount of cost of project is spent on them. Thus it is imperative that they must be designedin the most economic and efficient manner.

As a result of researches conducted by various organizations in India and by the knowledge and

experience gained from the banks constructed in the past, attempt has been made in this standard toevolve more rational criteria of design for guide banks. A number of factors, which have an importantbearing in the design and are still in investigation stage or are not yet universally accepted, have beenkept out of the purview of this standard and should be incorporated in subsequent modifications andrevisions, thereto. Thus the provisions laid down in this standard are recommendatory in nature, andare intended to lay down guidelines for design, where much depends on the experience and ingenuityof engineers involved in design.

This standard was first published in 1983 under the title Criteria for Design of Guide Banks for AlluvialRivers. The revision of the standard has been undertaken to incorporate the latest practices beingfollowed in the field. The important changes in this revision are in respect of design requirements of

pitching stone and incorporation of use of filter fabric.The details regarding construction and main-tenance of guide banks have been covered in IS 12926 : 1990 Construction of guide banks in alluvialrivers Guidelines ( under revision ,

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IS 10751 : 1994

pzdi n

Standard

PLANNING AND DESIGN OF GUIDE BANKS

FOR ALLUVIAL RIVERS GUIDELINES

First Revision

1 SCOPE

This standard covers the planning and designof guide banks used for the various engineeringstructures constructed on the alluvial rivers.

2 REFERENCES

The following Indian Standards are necessaryadjuncts to this standard:

IS No. Ti t le

4410 Glossary of terms relating( Part 3 : 1988 to river valley projects:

Part 3 River and rivertraining f irst revi sion )

8237 1985 Code of practice for pro-tection of slope for reser-voir embankment ( f i r s t revi sion )

3 TERMINOLOGY

For the purpose of this standard, the termsdefined in IS 4410 ( Part 3

:

1988 shall apply.

4 GENERAL DESIGN FEATURES

4.1 Guide banks are constructed in the direc-tion of flow both upstream and downstream ofstructure, on one or both flanks as required.

4.2 Alignment

4.2.1 The alignment, should be such that thepattern of flow is uniform with minimumreturn currents.

4.2.2 The alignment and layout are best decidedbased on model studies.

4.2.3 In case of a head regulator of a canal,constructed adjacent to the main structure, thealignment of the guide bank should furtherendeavour to induce favourable flow conditionsfor the entry of water with minimum silt intothe canal.

4.2.4 In other cases, guide banks should be soaligned that the flow is uniformly distributedacross the waterway as far as possible.

4.3 Classification of Guide Banks

Guide banks can be classified according to:

a) their form in plan, and

b) their geometrical shape.

4.3.1 Accordi ng to Form i n Pl an

Guide banks can be divergent u p s t r e am ,parallel and convergent upstream ( see Fig. 1 .

R I V E R C U R R E N T

D I V E R G E N T U P S T R E A M \

R I V E R C U R R E N T

E M B A Y M E N T

W O R S T P O S S I B L E

EMEAYMENT

C P A R A L L E L

FIG. 1 DIFFBR~T FORMS OF GUIDFBANKS

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IS 10751 : 1994

4.3.1.1 Gui de banks div ergent upstream

They exercise an attracting influence on flowand they may be used where the river hasalready formed a loop and the approachingflow has become oblique to keep flow activein bays adjacent to them. However, theapproach embankment gets relatively lesser

prote ct io n in wor st pos sib le embaymentscompared to equal bank length of parallel guidebanks ( see Fig. 2 .

Divergent guide banks require a longer lengthin comparison to parallel guide banks for thesame degree of protection to approach em-

bankments. However, hydraulically they givebetter distribution of flow across the waterway.

4.3.1.2 Parall el guide banks

Parallel guide banks with suitably curved headshave been found to give uniform flow from thehead of the guide banks to the axis of thestructure.

4.3.1.3 Gui de banks convergent upst ream

Convergent guide banks have disadvantage ofexcessive attack and heavy scour at the headand shoaling all along the bank rendering theend bays inactive.

4.3.2 According to Geometrical Shape

The guide banks can be straight or ellipticalwith a circular or multi-radii curved head( see Fig. 3 . Elliptical guide banks have beenfound more suitable in case of wide flood plainrivers for better hydraulic performance. In caseof elliptical guide banks, the ratio of major

axis to the minor axis is generally in the rangeof 2 to 3.5.

Due to gradual change in curvature in ellipticalguide banks the flow hugs the guide banks all

along its length as against separation of flowoccurring in case of straight guide banks afterthe curved head which leads to obliquity andnon-uniformity of flow.

4.4 Other Type of Guide Banks

Other type of guide banks differing in form

mentioned in 4.3.1 or shape mentionedin 4.3.2 may be provided if warranted by siteconditions and supported by model studies.

4.5 Length of Guide Banks

4.5.1 Upstr eam L ength

4.5.1.1 The general practice is to keep theupstream length of guide banks as I.0Lto 1.5L , where L is the length of structure

between the abutments. For elliptical guidebanks the upstream length ( that is semi majoraxis a is generally kept as 1 OL tol-25L .This practice is generally applicable where thewaterway is within the close range of L that is,Laceys waterway.

4.5.1.2 For wide alluvial belt the length of guidebanks should be decided from two importantconsiderations, namely (a) the maximumobliquity of current ( it is desirable that obli-quity of flow to the river axis should not bemore than 30 , and (b) the limit to which themain channel of the river can be allowed toflow near the approach embankment in the eventof the river developing excessive embaymentbehind the guide bank. The radius of worstpossible loop should be ascertained from thedata of acute loops formed by the river during

past. In case of river where adequate pastsurveys are not available, the radius of worstloop can be determined by dividing the averageradius of loop worked out from the availablesurveys of the river by 2.5 for river having a

\\

W O R S T POSSBLE \

EMBAYMENTS\

I

A PPROA CH B A NK

hlVERGENT

G U I D E VDlSTANCE B E T W E E N T H E

BANK A PPROA CH B A NK A ND THE

WORST POSSIBLE EMBAYMENTS

FIG.

2 EXTENT OF PROTECTION PROVIDED BY PARALLEL AND DIVERGENT G UIDE BANKS

2

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IS 10751 : 1994

0.3 T O O SR

I

3 A S T R A I G H T GUlbE B A N K

R,-0

3B E L L I P T I C A L G U I D E B A N K

FIG. 3 GEOMETRICAL SHAPE OF GUIDE BAN KS

maximum discharge up to 5 000 m3/s and by2 O for discharging above 5 000m3/s.The aboveconsiderations are illustrated in Fig. 4. Thelimit to which the main channel of the rivercan be allowed to flow near approach embank-ment has to be decided based on importanceof structure and local conditions.

4.5.1.3 In cases where the detailed examina-tion in accordance with 4.5.1.2 is difficult forwant of data, as a general guide the upstreamlength of the guide bank may be kept 1 O Lto 1.5

4.5.2 Downstream Length

On the downstream side the river tries to fanout to regain its natural width. The functionof guide bank is to ensure that the river action

does not adversely affect the approachembankment. The downstream length will

therefore, has to be determined so that swirlsand turbulence likely to be caused by fanningout of the flow downstream the guide bank donot endanger the structure and its approach.The length of O 2 ito O 4 L is recommended.

4.5.3 In allimportant cases the lengths, bothupstream and downstream, should be decidedbased on results of model studies incorporatingthe past history of river in the reach where thestructure is proposed.

4.6 Radius of Curved Head and Tail

4.6.1 Function of curved head is to guide riverflow smoothly and axially to the structure,keeping end spans active. A too small radiusgives a kick to river current making it obliqueand therefore larger radius to attract and guidethe flow is needed, but it is uneconomical.Radius should be kept as small as possible

3

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l l

4i

SINGLE MEANDER LOOP

RIVER FLOWA F F L U X /APPROACH

EMBANKMENT

LAUNCHING APRON

l OD

m a x .

DOUBLE

MEANDER LOOP7

? t/rf

,I,UNcHING

\

A PR ON \

RADIUS R

LLAUNCHING

A P R O Nl OD

m a x .

APP RO A CH EM B ANK ME NT

LO*25 TO 0 L

F I G. 4 TYP ICA L LAYOU T OF G UIDE BA N K

consistent with proper functioning of bank.Radius of curve head equal to 0.45L has beenfound to be satisfactory.

5.2 Top Width

4.6.2 Radius of curved tail may be 0.3to 0.5 times the radius of curved head.

4.6.3 Considerable economy consistent withsmoother conditions at the head may beachieved by adopting a composite curve oftwo or three different radius instead of a singlelarge radius. This can be best decided by modelstudies.

The top width should be 6 to 9 m to permit

transport of material. At the nose of guidebanks, the width may be increased suitably toenable vehicles to take turn and for stackingstones.

5.3 Free Board

4.7 Sweep Angle

A free board of 1.0m to 2 O m may be provid-ed above the design flood level. Where heavywave action is apprehended and/or aggrava-tion is anticipated, a hjgher free board may be

provided.The sweep angle is related to the loop forma-tion. For curved head the angle of sweep mayrange from 120 to 145 according to river

curvature. For curved tail it varies from45 to 60.

5.4 Side Slope

5 DESIGN OF GUIDE BANKS

5.1 Material

It

depends on the angle of repose of the

material of guide banks and the height. Sideslopes of 2

:

1 to 3: are generally recom-

mended.

5.5 Protection of Structures

Guide banks may be made of locally available 5.5.1 Curved head is prone to damage due tomaterials from river bed, preferably silt, sand concentration of discharge caused by collectionor sand-cum-gravel. of over bank flow and direct attack of current

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As in the Original Standard, this Page is Intentionally Left Blank

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IS 10751 : 1994

5.6.5.4 At the junction of head and shanknormally high velocities exist. Design scourdepth varies from 2.5D to 1.5D. This transi-tion should be effected in a length of one-fourthof radius of head from the head towards theshank. ( Details have been shown in Fig. 6. )

5.7 Slope Protection

The river side earthen slope of guide banks areprotected against river action by covering themwith dumped or hand placed stones and con-crete blocks. This pitching is intended toremain in its laid position ( see Fig. 6).

5.7.1 The rear slopes of guide banks are notsubjected to direct attack of river and may beprotected against wave splashing by 0.3-0.6mthick cover of spawls or by turfing. In case,however, a parallel or back flow leading toerosive action is likely as evident from modelstudies at the rear face, suitable pitching maybe necessary.

5.7.2 For the design of pitching on the riverside, factors that affect are size or mass of theindividual stone, its shape and gradation,thickness and slope of pitching and type offilter underneath. The predominant flowcharacteristic which affects the stability of

pitching is velocity along the bund. Otherfactors like obliquity of flow, eddy action,waves etc, are indeterminate which could bestudied on models and may be accounted for

by providing adequate margin of safety byincreasing the design mean velocity fordetermining the size and mass of stone.

5.7.2.1 Sizes for hand placed pitching can beless due to interlocking effect which offersgreater resistance to movement of stones.

5.7.3 The thickness of the pitching should beequal to the size of stone determined from thevelocity consideration as indicated in 5.6.1

and 5.6.2. For dumped stone pitching thethickness may be two times the size of stone.In general the following guidelines arefollowed:

a

b

cl

Brick on edge can be adopted up to anaverage velocity of 2 m/s,

Quarryed stones of size 350 mm and/or

weighing 40-70 kg should be used up toan average velocity of 3.5 m/s, and

For higher velocity cement concreteblocks/crated stone could be used.

NOTE Round and smooth boulders should beavoided particularly for hand placing.

5.8 Drainage Arrangement

A system of open paved drains ( Chutes ) alongthe sloping surface terminating in lognitudinalcollecting drains at the junction of berm andslope should be constructed at 30 m centre todrain the rain water. The drains are to beformed of stone pitching or with precast con-

crete section. The crest of guide bank shouldbe sloped : 50 from upstream to downstreamriverside to countryside and longitudinalpaved drams according to approved drawingare to be constructed at downstreamfcountryside edge of the crest. These longitudinal drainsshould drain the rainwater in chute drain.

6 DESIGN OF FILTER

A graded filter generally specifying the standardcriteria conforming to IS 8237 1985 should be

provided below the protection. The filter isrequired below pitching on the slope as well asbelow the apron also. The use of syntheticfilter is preferable from the point of qualitycontrol and convenience of laying. The criteriafor synthetic filter is given in Annex A.A 15 cm thick sand layer should be providedon the filter to prevent the mechanical ruptureof the fabric by armoured layer.

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IS 10751 : 1994

ANNEX A

( Clause 6 )

CRITERIA FOR SELECTION OF FILTER FABRIC

Geotextile filters may be recommended becauseof ease in installation and their proven effective-

ness as an integral part of protection of bedmaterials, may be used to select the correctfilter fabric:

b)a) For granular material containing 50 per-

cent or less fines by weight, the followingratio should be satisfied:

85

passing size of bed material (mm)Equivalent opening size of fabric (mm)

>

1.6

cl

In order to reduce the chances of clogg-ing, no fabric should be specified with anequivalent opening size smaller than 0.149

mm. Thus the equivalent opening size of

fabric should not be smaller than0.149

mm and should be equal to or less

than 85 percent passing size of bedmaterial.

For bed material containing at least50 percent but not more than 85 percentfines by weight, the equivalent openingsize of filter should not be smallerthan O-149 mm and should not be largerthan O-211 mm.

For bed material containing 85 percentor more of particles finer than O-074 mm,it is suggested that use of non-wovengeofabric filter having opening sizecompatible to the equivalent values given

in (a) above may be used.

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Bureau of Indian Standards

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Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are alsoreviewed periodically; a standard along with amendments S reaffirmed when such review indicates thatno changes are needed; if the review indicates that changes are needed, it is taken up for revision.Users of Indian Standards should ascertain that they are in possession of the latest amendments oredition.

This Indian Standard has been developed fromDot : No. RVD 22 97 .

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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