-
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.
! $ ' +-Satyanarayan Gangaram Pitroda
Invent a New India Using Knowledge
01 ' 5 Jawaharlal Nehru
Step Out From the Old to the New
1 +, 1 +Mazdoor Kisan Shakti Sangathan
The Right to Information, The Right to Live
! > 0 B BharthariNtiatakam
Knowledge is such a treasure which cannot be stolen
Invent a New India Using Knowledge
IS 5186 (1994): Design of chute and side channel spillways-
Criteria [WRD 9: Dams and Spillways]
-
IS 5186 : 1994
~~ llFfCf1(1)~l?fr ;rrm 3li~ '1T~ >r1l1T~ \j~cmcr ~
f~\if~ Cfir +rID~T - +rT'1~g( 'l~~T ~
-
AMiNDMENT NO.1 OCTOBER 2008TO
IS 5186 : 1994 DESIGN OF CHUTE AND SIDECHANNEL SPILLWAYS -
CRITERIA
( First Revision)
(Page 1, clause 2) - Substitute 'IS 11155 1994 Code of practice
forconstruction of spillways and similar overflow structures (first
revtstoni' for'IS 11155 1984 Code of practice for construction of
spillways and similaroverflow structure'
(Page 9, clause 8.2.6) - Substitute 'IS 11155 1994' for 'IS
111551984'
(WRD9)
ReprographyUmt, BIS, New Deihl, India
-
Spillways Including Energy Dissipators Sectional Committee, RVD
10
FOREWORDThis Indian Standard ( First Revision) was adopted by
the Bureau of Indian Standards, afterthe draft finalized by the
Spillways Including Energy Dissipators Sectional Committee hadbeen
approved by the RIver Valley Division Council.Spillway i~ an
integral part of all river valley project, and is essentially
required to pass down tothe fiver 01 to sorne other natural
drainage, surplus or flood water which cannot be safelyretained
upstream of the storage dam. Provision of a hydraultcally efficient
and structurallystrong spillway I~ very Important for the safety of
the dam and the life and property along thefiver down
below.Generally the spillway can be provided directly over the dam
in case of concrete or masonrydam. But for darns composed of earth
or rock, or for dam, over which it is impossible orundcvrrable, for
special reasons, to pass water, some form of spIllway adjacent to
the dam is to beprovided. These may be either closed conduit or
open channel spillways. In open channel spillwayswater I' conveyed
from the reservoir to the rrver below the dam or to other natural
drainagethrough an excavated and lined open channel with fairly
steep slope and placed either alonga dam abutment or through a
'addle 111 the Tim of the reservoir. These consist of a low
crestand a paved channel on a steep slope on the natural or
excavated earth or rock formation.Generally the control structure
is placed normal or nearly normal to the centre line of the
channeldownstream. Such a spillway IS termed chute spillway. In
narr ow canyons. or otherwise, wherethe site for the control
structure is lrmrtcd in Width, the crest IS placed almost parallel
to thechannel and the spillway IS then called Side channel
spillway. A typical arrangement for chuteand side channel spillway
is shown in Fig. 1.Chute and Side channel spillways can be
constructed on all types of foundat ron materials rangingfrom solid
rock to soft clays. However. If the foundatton materral is
incapable of passing thewater without excessive erosion, It should
alway, be protected by concrete paving. Due topossible usc of large
amounts of spillway excavation in the dam embankment, these
spillwaysgenerally result in overall economy in c.irthfill d.uns,
Theve structures are specially suited insrtuut io ns where sound
rocky foundatrons required for the conventional type of spillways(
vert rca] drop type) are not available. Therefore, due to
simplicity of their design and construe-non, adaptabih ty to
alrnovt any fo undatron condition, these spillways are used with
earthfilldarns more often than any other type.This standard was
first published In 1969. This standard has been revised to update
its contentsbased on the experience gained WIth the use of this
standard. The principal modifications arein respect of design
requirements of outlet channel, floor lining, drainage system and
anchors.Par the purpose of deciding whether a particular
requirement of this standard is complied with,the final value,
observed or calculated, expressing the result of a test or
analysis, should berounded off in accordance with IS 2: 1960 'Rulcs
for roundmg off numerical values (revised)'.The number of
srgruflcant places retained in the rounded off value should be the
same as that ofthe specified value in this standard.
-
IS 5186: 1994
Indian Standard
DESIGN OF CHUTE AND SIDE CHANNELSPILLWAYS - CRITERIA
( First Revision)
2 REFERENCESThe followmg Indian Standards are necessaryadjun e
ts tu this standar d:
1 SCOPETills standard covers the criteria for hydraulicand
structural designs anti othcr general rcquu-e,merits of chute and
side channel spulways.
S.2 Site conditions generally influence thelocation, type, and
components of a spillway.1 he steepness of the ten ain traversed by
thecontrol and discharge channel, the class andamount of excavation
and the possibrlrty forits use as embankment material, the
chancesof scour of tile boundi ,g surfaces a nd the needfor hrung,
the pel meabrlit y ant! bc.mng capacityof the Iounda tion, and the
stabihty of theexcavated slopes should necessarily be consi-dered I
n the selection of layout.
6 HYDRAULIC DESIGN6.1 Chute or side channel spillways in
generalconsist of the following components:
a) An approach channel,b) Control structure,c) Side channel
trough,d) Discharge channel,e) Energy dissipntor and/or terminal
stru-
cture, andf) Outlet chan nel.
6.2 Approach Channel
6.2.1 Where the spillway is located through anabutment, saddle
or ridge, an approach channelIS required to draw water from the
reservoirand convey rt to the control structure.
6.2.2 Approach velocities should be hrmted andchannel curvatures
and transitions should bemade gra-Iual, 111 order to minimize head
lossthrough the channel and to obtrun uniformityof flow over the
spillway CI est. Head loss IIIthe approach channel has the effect
of reduc-ing the spillway discharge. High velocity mayalso
necessitate lining of the channel depend-ing upon the rock. Even
distribution of flowshould be ensured over the spillway crest asfar
as possible.
6.2.3 The approach velocity and depth belowcrest level have
important influence on thedischarge over an overflow crest. Prefer
ablythc depth below the crest may be about half ofthc head over the
crest for gooJ co-efficient ofdischarge.
Title
lJ772 : 1986
11527 : 1985
IS No.4410( Part 9 ) : 1982
Glossary of terms relating tor iver valley projcct s : Pal t
9Spillways and syphons (firstrevIsion)Code of practice for con
stru-ction of spillways and srmrlaroverflow structure
Cntcrra for structural designuf energy dtsstpat or s
ftJrspillways
Guidelines for devign ofdr aruage arrangements ofenergy
dissipators and train-ing walls of spillways
3 TERMINOLOGY
11155: 1984
For the purpose of this standard the definitionsgiven 111 IS
4410 ( Part-9.) : 1982 shall apply.4 GEOLOGICAL
INVESTIGATIONSGeology of the site w rlI he taken into
considera-tion for designing the details of the structure.
5 SPILLWAY LAYOUT5.1 The outflow charactcnstics of a
spillwaydepend o n the particular device selected tocontrol the
dischar gc. After having selected aspillway con trol with certain
dimensions andcrest level, the maxrmurn spillway dischargeand the
maXIl11Um reservoir wat er level may bedetermined by flood routing
for adopted design-ed flood. Other comp iuents of the spillwaymay
the.i be proportioned to conform to therequired capacity,
topography and foundationconditions of the site.
-
18 5186 , 1994
6.3 Control Structure6.3.1 The control structure In chute
sprllwaysIS generally pi aced normal or nearly normal tothe dXIS or
the discharge channel 111 the headreach and In Sl,' e channel
spillways the controlsu ucture 15 placed along the side or
approxi-mately parallel to the upper por uon of thespi llway
lJI~lhdrge channel Control structureIS to limit or prevent outflows
below fixedreservoir leve lv an.l to regulate releases whenthe
reservoir r ises above that level6.3.1 Control st ructure III plan
may be sti arghtsermcircular, or U shaped The crest may begated or
ungat cd The overflow sect ro n maybe agee sh.rpcd, OJ broad
crested
6.3.3 The CIevt p ofile should be leslgncd tosuit the "lll huons
of g ite opei auo I Atpartial gate openings free fl.iw p otlles ar
L likelyto develop neg urve pr cssures In low crestswhu.h Me
usually WIth these types Dr spillwaysthe negauv p essui cs may be
,Ivolded WIthoutany ,tpprell,lble cx tr a cost by adopnng a letflow
plofile fOI J. small galt opening fOI thepart or the crcvt downvu
earn of the gate SillThe co-efficient of divc har ge III tlu s case
ISreduced and can best be WOl ked out on ahydr aulic model6.4 Side
Channel Trough6.4.1 In Side channe l sprllway the controlstructure
IS gene: ally place'! along the stJ e ofor approximately parallel
to the upper portronof the spillway discharge channel Plow overthe
crest falls into a trough, turns appr oxt-mately at a rrght angle
and then continue, Intothe main discharge chan nel The flow into
thetrough may enter only on one SIde 111 the caseof a steep
hrllside location, or on both SIdesand over the end of the trough
if rt IS locatedon a knoll or gently sloping abutment6.4.2
Reduction 10 discharge over the crestdue to submergence, If It
occurs, should betaken into consrderation The vubmci gcncemay be
due to some flow conditions alongthe reach of the trough under
consi leration ora control section or a construction In thechannel
downstream of the trough6.4.3 The crest structure should be
designedas In 6,3,3
6.4.4 Cross-SectIon of TroughThe cross-sectIOnal shape of the
Side channeltrough IS ll1flucncLd by the overllow crest onone SIde
and by bank conditIOns on the oppo.site Side A trapeZOidal
cross-section Withminimum WIdth to depth ratio 15 rccommended(or
the SIde channel trough However, themmlmum WIdth should be
commensurate WIth
2
both pi actrcal and sti uc tura1 aspects If thewidth to depth
ratio IS large, the depth of flow111 the channel Will be shallow,
resulung inpoor diffuvion of mc re.rsing flow WIth thechan nel flow
Moreover, with greater bedWidth the cxcnvauo.i wrll i nc re ase
6.4.4 I Bccau-,e of lUI bule Ices and VIbrationsmhe, C It 'n SI
'L ch mn el 110w the trough shouldbe set w -ll Into the orrgrnal
formation forsafety The sule slope' sho\l\d be tnmmed tothe st
ccpe-t anulc at wl-u.h the mater ral wrllsafely q I rd and hned wu
h corn.r etc anchoredch cctly to the rock
6,4.5 SlopeF0r the sul-crtt rcal -tage In the t i ough t he
mcorn-/ 19 fl iw wrl l not dcvc.I ip high II .msverve
vclocitresbcc.iuvo 01 t h, low drop bcfor e It meets thechan u.l fl
iw thus dfLttlng a good diffusionWith the wucr hulk In the Hough
Suu.e bothth , iucom mg vc lo c i tn s and the channel velo-tlt,.;
Will b ,e'lllv.ly slow, a farr ly completemtci nuughng of the 11
iws will take place,thereby pr uuclng ,Illlmpdldtively smooth
flowIn the side ch.m .c l Where the channel flowI' vupercr r rc t l
t hc ch In lei ve locrtres will behigh a lei the mt c: nux ing of
the high-energyti ans vcr s fI W With t hc c haunc l su , irn WIll
berough and turbulent 1 he n an,verse flowswill tend to S veep t hc
c hanuel flow to the farSide of the ch.mnel, producmg VIOlent
waveactro n With at t e nd mt vibr atrons Thereforefor good
hydraulic pel forman cc the Side channeitrough should have mrld
slope 01 a steep slopeWith 01 cont rol scr tion at the downstream
endof Side channel trough '0 that the flow IS sub-Critical in the
trough The slope depends onsite co nd I t Ions aud should be so
chosen as toreducc the exc avauon to .1 rmrumum6,4.6 Control
Section
The control section IS a sccuon downstream ofSide channel trough
where the depth of flowchange, nom subcritica I to
supercrrtrcalControl section may be provided by constrrct,1l1g the
channel SIdes or elevating the channelbottom The best location of a
control sectionIS usually at point where bed slope has to
besteepened to keep the channel on the groundSpecial coridruons may
require another Iocatron,For example, the sectron may be placed
Im-mediately downstream of the dlschal ge trough.
6.4.7 Water SlIrface ProfileThe water ,urfdce profile on the
Side channeltrough may be determillcd uSll1g the followll1gequat 10
n which IS based on the law of Lonserva-tlOn of Itnear momentum,
assummg that the onlyforces producmg motIOn In the channel
result
-
from the fall In the water surface In the drrectronof the aXI~
and that the entire energy of flow overthe crest I' dissipated
through Its mterminghngwith ih, channel flow and I... therefore of
noassistance .n moving the water along thechannel Ax ral velocity's
produced only afterthe mcormng wat er par trcles JOII1 the ch an ne
lstream
6.=yg, [ (VI ~ V,) J[ev,- V,) 1-V'(Q,_ Q,)]g (Q, +Q.) Q,
wher c6. y = drop in water surface m a small reach
between Section I and Secuon 2 m rn,Q, - dl ... charge at Sccuon
I. In m'h,g = ac celcru m due to gravity In m/s',
V, - vclocrty at Scctron I, In in],V2 - velocny at Scctron 2. In
tnfs, andQ, - disc.harge at Section 2 In m"ls
Q, and Q, may be c il cul tted for a particularreach knowi rg
the d rs charge per unit length ofthe cre-r
6.4.8 Design ProcedureThe fol lowmg steps are recommended for
thedesign of a 'Ide channel trough
a) Dcsrgn the ,Ide channel crest controlled01 uncontrolled, .l~
required The lengthof the ("l est should be deterrruncd by thetota
1 dr-charge to be passed and the sur,chat ge allowed,
b) Choose a surtabl e cross secuon, b iuornprofile and locauon
and the datum ofthe control sect: 1I1,
c) Calculate the crrucal depth of flow at thecout i o l,
d) If the contro I section I' not at the down.srre.irn end of
-trough, calculate thehydraulrc propcr tres of the down ... n
eamend of the trough uSing Bernoulli's t heor-rem and by trial and
error method,
c) Detcrm irie the water surface profile Inthe trough usmg the
equation given In6.4.7,
f) Fit the channel profile to the crest datumby rclatmg the
water surface profile tothe' eservou level such that the ...
ubrner-ge lce of thc overflow IS comlstent withthe condition
a,sumed for eV.lluatlllg thedlsch,uge over the cre~t. and
g) VarIOus ,'esIgn> ,hould be made by,I~sumlng dIfferent
hottom wldth~. dlffc.rent channel ~Iopes and varylllg control
IS 5186: 1994
secttons The most economical designthus achieved by comparing
severalalternatives should be adopted.
6.5 Dlscharge Channel
6.5.1 flow rclea...ed through the control struc-lure I~ conveved
to the ternunal structure orstream bed b~low dam III an open
channelexcavated aIo ig the ground surface, Thepr ofilc of the
channel rn.iy be val rably flat orsteep, the eros..., L'IO 1 I11dy
be var rably rectan-gular or trapezoidal It may be Wide or
narrow,long or short6.52 Di-charge channel duru.nsror, ... arc
gover-ned primarily by hydr.ruh c requrremcnts, butthe velectron of
the p' ofilc, cross sec t.onalshape. etL," mfluen c d by the
geological andtopographn.al charn c i er rvuc-, of the srte Inplan
the ch.mnc] m,ly be ,tI.ught or curved,wuh s ides par allcl , con
vet gent, divergent orcombm.itton of these Where the dischar
gechann. I IS cu.ved , sui table Jtlvepre,sure on the flJIH ,lilt!
,hould beequ.ll to Ol gl L.ltel th,ln I 5,
ci= depth of flow
-
IS 5186 : 1994
6.5.3.3 Concave curve should have a sufficicnt lylong radius of
curvature to mrr muze thedynarmc force on the floor due to
cernrrfugal
force and should not be less than 2 x Wd~,p~
where W I~ Ul11t weight of water, g I~ accelerationdue to
gravity, d I~ depth of flow, V I' velocityand p IS perrrussible
lntensrty of d) narnicpressure In no case the radius should be
lesvthan 10 d except at the toe of the ~I evt where Itmay be 5
d.
6.5.4 Slope6.5.4.1 DIscharge generally passes through thecr
rtrcal stage In the sprll way control
-
6.5.6 CurvesThe centre line of the spillway should be
keptstraight as far a" possible. However. on pl.ice-where It has to
be curved owmg to un.ivordableCircumstances particular attention
should bepaid to the degree of superelevauon to be pro-vided at the
outside of the bend The 'UpCI-elevation should be determined by
hydraulicmodel studies. Sloped SIde" of sprllway ch.m-nel should be
avoided on the outside of sharpbends because they cause a higher
supereleva-tron of water surface than that bv verticalwalls
6.5.7 Free Board6.5.7.1 The tree boar d provided for d
ischargechannel where flow J~ supercrrncal should benot lcs-, tban
that given by the followingformula
Free board ( In m ) = 061 + 0037 8vd" 3where
v = maximum velocity of !low III m/>. andd = depth of flow In
m
6.5.7.2 Where Side wall-, of ~tI11II1g basm arcnot desired to be
overtopped by waves. WI JCS.splash or spray. the free b v ird f ir
the sidewalls III th e basin. In the absence of Illy modeltests,
should be grvcn by the fo llowrug formula
Free board ( In m ) = 0 I (VI + d. )where
VI = mcormng velocity to the basin In ill/",and
d, = conjugate tad water depth In m6.6 Terminal Structure or
Energy Dissrpator
6.6.1 In order to avoid excesvive scour on thedownstream of
discharge channel, the excessiveenergy of water should be
dissipated before thedischarge IS returned to the downstream
rrverchannel6.7 Outlet Channel6.7.1 Outlet channel conveys spillway
flow fromthe terminal structure to the rrver channel belowthe dam
It should be of sufficient size to passthe anticipated flow WIthout
forming a controlwhich WIll affect the tarlwater levels for
energydissrpators6.7.2 The dimension of channel a-id i equn c-ment
of protective measui e-. by lining or riprap should depend upon the
nature of ch mnelbed and the velocny .ichu,vcd after the
energydisstpator 1 he scourmg of channel affectsthe tall water
levels.
s
IS 5186 : 1994
67.'?! The tailwater level in the outlet channelmay be affected
by the scour of channel bed asabove, and by retrogression in the
river beddue to relatively cleat water from the reservo irIn case
the outlet channel I" only a pilorchannel 11l crrodi ble mat crra
l, the errodedmaterral may form Istands or bar" In thc
channeldownsu cam and raive the tarlwatci level sThese hkely
changes III the tailwater levelshould be taken care of In design of
energydiss rpators
6.7.4 Where two or mo re types of energy drss i-pators have been
used for the set vice orauxihary spillwav, adequate CMe should
betaken to assess through model studre-, andtaking Into
considcratron the eflect c f t hceroded materral and It, depovit
ron furt herdownvtream 111 th, ovcr a ll pl mnrng dnd June-tiorung
of l-nergy di ssipator s and otherappurtenant structures such a,
t.ul rave channelsof the power houvcs so thelt the eroded
matcrralor its deposition does not Interfere With
energydtssrp.itor-, or the appui tenant structures
7 HYDRAULIC MODEL TESTS
7.1 Where necessary the de"gn should bechecked by conducuug tevt
s on geo n tr icallysumlar or disto: ted mode Is
7.2 With proper care III hydrauhc studies whei ethe shape of the
crest and ot hcr fc atui ," aresuch that precedent IS avarlablc ,
hydraulicmodel tests may not be necessary However,for unusual
condition, and whc: eVll ther c '" abend In channel, appropriate
model test> shouldbe made
8 STRUClURAL REQUIREMENTS8.1 Side WallsWhere rct ammg wall>
for SIde" of cntran cechannel, discharge channel and stilhng
basmare used, they should be de-igned to wnhvtan dall possible
combmauons of various loadmgs,for example, backfill, earth or ruck
pressure.water pressure, hv e 10id surcharge, upliftpressures and
force, due to horizontal orvertical seismrc accclcrauon
8.2 Floor LiningWhere velocity of 1low and type of bed
rockwarrant protcctro n of bed rock agamvt erosion,the bed rock
vhould be 11l1~d with ~()I11C pro te-clive material wruch generally
t .kc-, the fo t mof concrete 11l1111g The luung may be I cqUl'
cd111 entrance channel, discharge trough 01 channeland strllmg
ba-rn.
-
IS 5186 : 1994
8.2.1 Thickness of LiningDUring spillway flows the floor lmmg I~
sub-jeered to hydrostatic forces due to the weightof the water In
the channel, to boundary cragforces due to frictional resistance
along thesurface to dynamic forces due to flow Impinge-ment, to
uplift forces due to i educt ron ofpressure along the boundary
surface, or to upliftpressure caused by Lakage through JOints
orclack, When there IS no spill, the III1Ing ISsubject to the
action of exp.insron and contrac-tion due to temperature var
ratrons, alternatefreezing and thawing. weatheung and
chemicaldctenoratron, to the eff cts of settlement andbuckling, 01
to uplift pressures due to underseepage or high ground water
condition SInceIt IS not possible to evaluate the v-mous
forceswhich might occur and also not to make thehrung heavy e iough
to resist them the thick-ness of the luung " est ablished on a more
orless ernpmcal basis, and under drains anchors,cut off>, etc,
are provided to st abrhze theIlI1l11g8.2.1.1 The thickness of
IlI1l11g of approachchannel Will depend upon the velocrnes, depthof
flow and poor rOl.kj'OlI cond mons Thethickness (If the order of 15
ern to 30 ernhave been found satisfactory for
normalcircumstances8.2.1.2 In the discharge channel, where
thevelocrty of water I~ usually very high, thedesign of the floor
slab should depend on thefoundation (for example unyielding rock,r
elatrvelv yielding rock or earth), vclocuyand intensity of flow,
uplift head and othersirmlar factors mcludmg the location of
spill-way with respect to dam Probable hydro-stanc uplift forces
under adverse condrt ionmay be considered parttally rchevcd by
thedrainage to make the entrancechannel lining ,t reasonably water
tight upstreamapron to reduce uphft on the control su ucturesWherc
I equired, the JOInts In the IJl11ng shouldbe provided With
waterstops In all the joi ntsThe requu cmcnt of waterstops In the
IJl11ng ofdischarge channel Will depend upon the degreeof water t
rgh tnc.vs required agarnst the cxter iorwater hc-uls Where a laver
of gravel has beenprovrded under the hnmg the prOVISIOn ofwater
stop- m ty not be necessary, other wisewatcrstops should be
provided 111 the longitudi-nal JOInts , and In rransv e: se joints
at theconcave curves Bee.ruse of high velocity flowpassrrig dU"~
the JOint With lin offset( see 8.2.2.2) the povs ibrl rt y of water
scepmgwater the transverse jomts IS very little 1 hedown stops
should not be pi ovided In ti ansvci seJ01l1ts unlcvs complete
water tightness againstexrei ior water hc ads i-, required because
thesetransverve jo m ts should otherwise serve as a reliefagainst
built up of high uphft pressure under thehrung III case of any
povsible chockrng of underdrams Where the foundations are
permeable,waters top, should be provided 111 the j ornts ofstilling
basm floor Irn mg '0 as to avord circu-latrng flow und ci the
1II1Ing due to differentialhead on the JOInts 111 the zone of
hydraulicjump8.2.2.1 The water stops should also be provided111 the
JOints of Side walls where seepage offlow behmd the wall> IS u
idesrrable
8.2.2.2 The transverse jornts should be providedWith 13 mm
offset, as shown In Fig 2 so as toaVOId high velocity flow strrkmg
against theedge of the lower floor cause water to seepthrough the
JOint under a very 11Igh pressureand dtslodge or uplift the lmrng
To furtherensure ag unst this, the lifting of upstream edgeof lower
slab due to drffcrentral settlements orheaving should be checked by
providing cut-off( see 8.2.3 l, especially when the lming IS
found-ed on a layer of gravel or earth
- '
-
IS SI86 : 1994
8.2.2.3 The offset in the downstream slab at thetransverse
joint, as shown in Fig. 2, shouldalso be provided in the joints of
side walls( Fig. 3 ).
..
All dimensions 10 rmllunetrcs.FIG. 3 DETAILS Of JOINTS IN SIDE
WALLS
CONTRACTION JOINT
BURLAP
8.2.3 Cut-offsWhere the lining is placed on earth on a
steepgradient OT the lining is placed on a layer ofgravel and not
anchored to the foundation, acut-off should be provided on the
upstream endof each panel to check the creeping (FIg. 2 ).This
cut-off should also check the lower slablifting above the lower
edge of the upper slab.These cut-offs should also form barriers
againstseepage of water in the gravel layer or amongthe contact of
lining and foundations, anddivert the seepage water to the
transversedrains.
8.2.3.1 Similar small cut-offs should be providedin the
longitudinal jornts as well. where liningis founded on a layer of
gravel as shown inFIg. 4A. Typical joint details for lirung onrock
arc shown in Fig. 4B.
loA JOINT DETAILS FOR LINING ON GRAVEl
CONTRACTION JOINT
BURLAP
125mm SAND
LEAN CONCRETESEWER
PIPE DRAIN WITHOPEN JOINTS
48 JOINT DETAILS FOR lIING ON ROCKAll dimensions in
rmlllmetres.
FlO. 4 DETAILS OF LONGITUDINAL JOINTS
8
-
8.2.3.2 Cut-offs should also be provided at theupstream end of
the spillway to reduce seepageof flow along the hrung, Increase
path of per-colatron, Intercept permeable strata and reduceuphft
under the spr! Iway and adjacent struc-turcs Cut-offs should aha be
provided at thedownstream end r f spillway to check eros ionand
underrmnmg of the su uctures The depthand thickness of such
cut-offs "auld dependupon the nature of the foundations
8.2.4 Drainage SystemA~ mentioned 111 8.2, the stabihty of'flooi
lmmgI' lOCI cased by pr ovrdmg underdrams Thesedrams reduce the
uplift on the hrung Thedrainage f(1J 11 .or hrung, energy
drssipators andtrarrnng wall> of spillways and the drarnage
forbackfill subject to di aw moisture tothe undersrde of the hrung
by capil l.u y action,a conunuou-, gravel blanket should be
providedunder the lirung, e-pecrally where the ar ea I~subject to
fJost 'ictron This blanket shouldserve to insulate the f iundattons
against frostpenetr.uro-i The thickness of gravel layerwould depend
upon the clunite of the ruea andvusccpubihty of the foundauon to
frost heavmg,
8.2.4.2 The gravel blanket should be well gradedto safeguard
against movement of foundationmaterral WIth the seepage flow
8.2.4.3 The drains under the hrung vhouldconsist of a network of
pipe drams which shouldfollow the joints III the hrurig The
dramsshould either be perf01 ated or non-perforatedclay or cement
sewer pipes laid With open JOints111 gi avel and bedded on a mortar
or porousconcrete pad to prevent the foundation materialfrom being
leached into the pipe
8.2.4.4 Where the stratifications III foundationrock are almost
parallel to channel bed, verticaldram ige holes prercing through
the layers ofstratrfic mons, backfilled WIth gravel should
beprovided to I eheve uphft on the layers of foun-dation due to
seepage or gi ound water. Theseholes should be connected to the
pIpe drams.
8.2.4.5 The drains under the discharge channelshould have therr
outlets either In the dischargechannel itself through the Side
walls, or Into
IS ~186 : 1994
drainage gallery in case of wide and longspillway. The outlets
should be connected tothe pipe drains.
8.2.4,6 The drains under the hrung belowmaximum tailwatei level
and strlhng basrnshould have thcrr outlets IJIto the chute blocksof
the basm The dramage system of st ilhngbasrn floor should, however,
be kept separatefrom that of the other floor lmmg8.2.4.7 Sewer pipe
drams WIth open jointsshould also be provided at the toe of the
heelof the Side walls to collect seepage water fromthe backfill and
relteve the Side walls fromwater pressure These pipes should have
theiroutlets In the discharge channel through theSIde walls or
mdependen t outlets elsewhere
8.2,5 AnchorsThe floor of the chute should be anchored tothe
foundation by anchor bars to mcrcase theeffective weight of the
slab against displacementdue to uplift and other forces8,2.5.1 Por
chute spillways on rock foundation,It may be generally sufflcicnt
to provrde norm-nal anchors, say 25 rnm mild steel rounds 3 mlong
at the rate of 15m centre to centre( staggered) 111 the rock With
SUit ib!e drainagearrangement, In the absence of any analys
isAnchors below an I around the energy drssrp.r-non arrangement
should be desrg red acc ordmgto IS 11527 . 19858.2.5.2 The diameter
of hole Into which theanchor bars should be placed and
groutedshould not be less than one and a half tunesthe maximum
transverse dtrnensron of the bar8.2.5.3 Actual pull out tests
should be carriedout at the site to deter mille the depth
andspacing of anchors, diameter of holes and typeof anchors to be
provided82.5.4 In soft rocks where bond bewtcen rockand grout IS
very poor, or III earth, bulbanchors as shown In Fig 5 should be
used8.2.6 Surface FInishBecause of very high velocity of flow rn
chuteor SIde channel spillways, the concrete surfacefinish against
which water should flow, IS ofparamount Importance The abrupt or
gradualirregularrttes for such formed or unformed sur-faces should
be reduced to the rmrumurn andshould conform to the details given
InIS 11155 , 1984
-
IS 5186 : 1994
ENLARGED BOTTOM FORBULB ANCHORAGE
-,
-,,,
ANCHOR BAR
AUGERED HOLE BACKFILLWITHCONCRETE
/I
//'
APPROXIMATE EFFECTIVEADDED WEIGHT OBTAINEDBY ANC.HORAGE
All dimensions in millimetres,
PIG. S DETAILS Of BULB ANCHORS
10
-
Bareaa .r lulu Stuulard.BIS II a statutory msutuuon established
under the Bureau of Indian Standardl Act, 1986 topromote harmonious
development of the acuviues of stadardization, marking and
qualitycertification of goods and attending to connected matters In
the country.
CopyrlgbtSIS has the copyrrght of all Its pubhcauons. No part of
these publications may be reproducedIn any form wrthout the poor
permission In writmg of BIS. This does not preclude the free use,JQ
the course of Implementing the standard, of necessary details, such
as symbols and SIzes, typeor grade designauons. Enqurrres relatmg
to copyrrght be addressed to the Director( Publications), BIS.
B."I.loo of Indian Standard.Amendments are ISsued to standards
as the need arises on the baSIS of comments. Standard.are also
reviewed perrodrcally; a standard along WIth amendments IS
reaffirmed when such reviewiadicates that no changes are needed; If
tile review Indicates that changes are needed, It IS takenup for
revrsron. Users of Indian Standards should ascertain that they are
In possessrou of tbelatest amendments or edition by referring to
the latest Issue of 'BIS Handbook' and Standard.Monthly
Addrnons'.
Th .. Indian Standard bas been developed from Doc: No. RVD 10 (
57 ).
Amendments Issued Since Publication
Amend No. Date of Issue
BUREAU OF INDIAN STANDARDS
Te&t Mected
Headquartera :Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi
110002Telephones: 331 0131, 331 1375 Telegrams: Manaksao.tba
(Common to all Office.)
Northern: SCO 4t5-446, Sector 35-C, CHANDlGAR.H 160036
Soutbern : C. I. T. Campus, IV Cross Road. '\1ADRAS 600113
Rellonal Olllce. :Central: Manak Bhavan, 9 Bahadur Shah Zaf"r
Marg
NEW DELHI 110002Bastern : 1/14 C. I. T. Scheme VII M, V. I. P.
Road, Mamktola
CALCUTTA 700054
Telephone
{331 01 31331 13 7S
{37 8499, 37 85 6137 86 26, 37 86 62
{53 38 43, 53 1640532384
{235 02 16, 235 0442235 15 19, 235 23 15
Western: Manakalaya, E9 MIDC, Marol, Andheri ( East) {632 92 95,
632 78 S8BOMBAY 400093 63278 91, 632 78 92
Brancb: AHMADABAD. BANGALORB. BHOPAL BHUBANESHWAR.
COtMBATOR.B.FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR..
K,ANPURLUCKNQW. PATNA. THIRUVANANTHAPURAM.
Prlolcd al Pr;olwell PTlDlere. Alicarb. Jodla