Lecture 6 Culvert Design

7/25/2019 Lecture 6 Culvert Design

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CVNG 2003- Design II

Culvert Design

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CVNG2003Culvert Basics

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Objectives

Know the basic denition and t!"es

Know the basic t!"es o# c$%ve&t 'ow

Know how to dete&(ine )* de"th #o&in%et cont&o%

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C$%ve&t +esi,n

Cond$it "%aced $nde& a &oad to ca&&!wate& #&o( one side to the othe&

+esi,ned to "ass a desi,n 'owwitho$t ove&to""in, the &oad

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Introduction

-e%ection o& desi,n sho$%d be based on )!d&a$%ic "&inci"%es

Econo(!

.ini(a% eects onadjacent "&o"e&t! b! headwate& de"th

and o$t%et ve%ocit!

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Other considerations

is o# "&o"e&t! da(a,e

Const&$ction and (aintenance costs

&a4c sa#et! Envi&on(enta% conside&ations

iss o# #ai%$&e and

esthetic conside&ations

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Culvert Flow

Comle! P&ess$&e 'ow

O"en channe% 'ow

Co(bination Varia"les

-%o"e

Pi"e +ia(ete& 7en,th and o$,hness

Ent&ance +esi,n

E8it +esi,n

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C$%ve&t -ha"es

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#eadwater $#%o&

+e"th o# $"st&ea( wate& s$ace(eas$&ed #&o( invert o'culvertoutlet

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Invert( 9nve&t &e#e&s to the inside botto( o# the

c$%ve&t


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#eadwater $#%& +e"th o# $"st&ea( wate&

-ho$%d not e8ceed ed,e o# sho$%de&e%evation :acco$nt #o& #&eeboa&d;

-ho$%d not be so hi,h as to ca$se'oodin, "&ob%e(s

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ai%wate& :*;

+e"th o# downst&ea( wate& s$ace(eas$&ed #&o( invert o' culvertoutlet


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Inlet )*es

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Inlet Control

9n%et cont&o%s :o& %i(its; the 'ow

)a&de& #o& 'ow to ,et th&o$,h theent&ance o# the c$%ve&t than it is to'ow th&o$,h the &e(ainde& o# thec$%ve&t

+u"merged inlets( have aheadwate& ,&eate& than 12 ti(es thedia(ete& o# the c$%ve&t o& ba&&e%hei,ht

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Inlet control

he cont&o% is$"st&ea(

he headwate& andin%et con,$&ation

aects c$%ve&t"eo&(ance

Gene&a%%! the in%et#ace a&ea is the sa(eas ba&&e% a&ea b$t itcan be ta"e&ed

Cont&o% section is atthe th&oat

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Flow asses thecritical deth ,ustdownstream o' theentrance

Flow is suer critical

Flows artiall* 'ull

Downstream end o'

the culvert goes tonormal ow1=


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Inlet Control .B

Flow d/s of inlet is supercritical (below critical dept!

"#draulic $u%p occurs in te barrel

&ote tat sub%er'ence of outlet does not assure outlet

control

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Inlet Control .C

)arrel flow is partl# full and supercritical (below critical dept!

*ritical dept occurs $ust d/s of cul+ert entrance

Flow approaces nor%al dept , outlet end

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Inlet Control .D $rare&

-edian drain pro+ides +entilation/stable conditions

"#draulic $u%p occurs in te barrel

&ote tat full.flow doesnt occur e+en tou' inlet/outlet are

sub%er'ed

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Outlet control

%% o# the #acto&s that in'$ences in%et

cont&o% a%so in'$ences o$t%et cont&o% >a&&e% cha&acte&istics :&o$,hness

a&ea sha"e %en,th s%o"e; and

tai%wate& e%evation aect o$t%etcont&o%

.annin, n va%$e

Below classic outlet controlcondition

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Outlet Control

O$t%et cont&o%@ invo%ves the additiona%

conside&ations ove& the in%et cont&o% o# the

e%evation o# the tai%wate& s%o"e &o$,hnessand %en,th o# the c$%ve&t

O$t%et cont&o%s :o& %i(its; the 'ow

)a&de& #o& 'ow to ne,otiate %en,th o# c$%ve&t

than it is to ,et th&o$,h the in%et :ent&ance;

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Outlet Control ./ $rare&

ressure Flow

Full Flow

-ost cul+erts dont operate tis wa#

nlet/utlet ub%er'ed

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Outlet Control .B

Full Flow

nlet not full# sub%er'ed

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Outlet Control .Cub%er'ed inlet / unsub%er'ed outlet

euires i' "6

utlet +elocities usuall# i'

euires etre%el# i' eadwater to %aintain full

barrel flow wit no tailwater

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Outlet Control .D$)*ical&nlet sub%er'ed

utlet unsub%er'ed

*ritical dept occurs $ust u/s of outlet

ow 6

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Outlet control

!"ica% condition

Pa&t%! #$%% ove& the enti&e %en,th

A%ow is s$bc&itica% 9n%et and o$t%et a&e $ns$b(e&,ed

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)erms

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Bacwater@ const&iction o# 'ow ca$ses a &ise in the

no&(a% wate& s$ace e%evation $"st&ea(he (a,nit$de o# the &ise is the bacwate&

25


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#*draulic er'ormance

Inlet control

conve!in, (o&e 'ow than the in%et wi%% acce"t

"ossib%e when the c$%ve&t s%o"e is h!d&a$%ica%%!stee" :dc B d$;

c&itica% de"th occ$&s at o& nea& the ent&ance h!d&a$%ic j$(" (a! occ$&


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Inlet control

-$b(e&,ence o#the o$t%et end

A%ow downst&ea(o# in%et is

s$"e&c&itica% Ao&(s a j$(" in

the ba&&e%

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Inlet control

!"ica% desi,n sit$ation 9n%et s$b(e&,ed o$t%et end 'ows #&ee%!

A%ow s$"e&c&itica%

A%ows "a&t%! #$%% o# the %en,th

C&itica% de"th j$st downst&ea( o# c$%ve&tent&ance

A%ow a""&oaches no&(a% de"th at the

downst&ea( end

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)!d&a$%icsEne&,! E$ation:EG7; )* and * de"ths and e%evations

Ve%ocit! head :$/s F d/s;

)ead %osses A&iction %oss th&o$,h the ba&&e% Ent&ance/E8it %osses

>end/J$nction/G&ate %osses

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De1nitions( #ead$Friction& osses )eent&ance %oss

)##&iction %oss th&o$,h the ba&&e%

)oe8it %oss

Othe& "otentia% %osses d$e to bendsj$nctions and ,&ates

dd %osses $" to ca%c$%ated the tota%ene&,! &e$i&ed to "$shH wate& th&o$,hthe ba&&e%

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#*draulic er'ormance

Outlet control

the c$%ve&t ba&&e% is not ca"ab%e o# conve!in,as ($ch 'ow as the in%et o"enin, wi%% acce"t

the h!d&a$%ic ,&ade %ine inside the c$%ve&t at

the ent&ance e8ceeds c&itica% de"th c$%ve&t is on a (i%d s%o"e :dnB dc;

9t is a%so "ossib%e to e8"e&ience o$t%et

cont&o% with a c$%ve&t on a stee" s%o"e :dnIdc; with a hi,h tai%wate& s$ch that s$bc&itica%

'ow o& #$%% 'ow e8ists in the c$%ve&t

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nerg* anal*sis o' culverts and owe4uations

3=


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Flow control e4uations

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ngineeringconsiderations

Flood 're4uenc* 25!& sto&( sho$%d be &o$ted

100 !& sto&( sho$%d be checed #o&

'oodin, o# ho$ses o& co((e&cia%b$i%din,s

Velocit* limitations

1(/s =5(/s

Buo*ance rotection $geotech&

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+ite criteria

7en,th and s%o"e

+eb&is and si%tation cont&o%

C$%ve&t ba&&e% bends

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Design limitations

)eadwate& %i(itations

ai%wate& conditions

-to&a,e te("o&a&! o& "e&(anent

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Other design otions

C$%ve&t in%ets

9n%ets with headwa%%s

*in,wa%%s and a"&ons

9("&oved in%ets .ate&ia% se%ection

C$%ve&t sews

C$%ve&t sies and sha"es

win "i"es se"a&ation :ve&tica% and ho&ionta%

C$%ve&t c%ea&ances

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O h d i


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Other designconsiderations

*ee" ho%es

O$t%et "&otection

E&osion and sedi(entation cont&o%

Envi&on(enta% conside&ations

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MC9

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Identi'*ing the catchment$)he 5/6&

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heCH

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/reciating the site

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)!d&a$%ic "eo&(ance c$%ve&t

cont&o%

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Velocities

.ini($(

.a8i($(

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Culvert grade "&o"e& c$%ve&t ,&ade is needed #o& sa#e #$nctionin,

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C l t d


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Culvert grade"&od$ces neithe& si%tin, no& e8cessive ve%ocities and sco$&

,ives sho&test %en,th#o& eas! &e"%ace(ent

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#eadwalls

7a* "e used 'or

9nc&easin, e4cienc! o# the in%et

P&ovidin, e(ban(ent stabi%it!

P&otect the e(ban(ent a,ainste&osion

P&otection #&o( b$o!anc!

-ho&tenin, the %en,th o# the &e$i&edst&$ct$&e

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8rotection

-o$& and e&osion

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Inlets with


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Inlets withheadwalls

)eadwa%%s (a! be $sed #o& a va&iet! o# &easons@

9nc&easin, the e4cienc! o# the in%et

P&ovidin, e(ban(ent stabi%it! P&ovidin, e(ban(ent "&otection a,ainst

e&osion

P&ovidin, "&otection #&o( b$o!anc!

-ho&tenin, the %en,th o# the &e$i&ed st&$ct$&e he &e%ative

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%ingwalls and arons

*in,wa%%s a&e $sed whe&e the side s%o"es o# the channe%adjacent to the ent&ance a&e $nstab%e o& whe&e the c$%ve&t issewed to the no&(a% channe% 'ow

7itt%e inc&ease in h!d&a$%ic e4cienc! is &ea%ied with the $se o#no&(a% win,wa%%s &e,a&d%ess o# the "i"e (ate&ia% $sed and

the&e#o&e the $se sho$%d be j$stied #o& othe& &easons *in,wa%%s can be $sed to inc&ease h!d&a$%ic e4cienc! i#

desi,ned as a sideta"e&ed in%et

9# hi,h headwate& de"ths a&e to be enco$nte&ed o& thea""&oach ve%ocit! in the channe% wi%% ca$se sco$& a sho&t

channe% a"&on sho$%d be "&ovided at the toe o# the headwa%% his a"&on sho$%d e8tend at %east one "i"e dia(ete& $"st&ea(

#&o( the ent&ance and the to" o# the a"&on sho$%d not"&ot&$de above the no&(a% st&ea(bed e%evation

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8rotection

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8rotection

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Other rotection

Gated bo8 c$%ve&t

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Velocities and


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Velocities andsedimentation

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*hat conside&ation #o&


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*hat conside&ation #o&deb&is

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%ee holes

*ee" ho%es a&e o"enin,s %e#t in s$ch thin,sas i("e&(eab%e wa%%s &evet(ents a"&ons

%inin,s o& #o$ndations to &e%ieve the ne$t&a%st&ess o& "o&e wate& "&ess$&e and "e&(it

d&aina,e 9# wee" ho%es a&e $sed to &e%ieve$"%i#t "&ess$&e the! sho$%d be desi,ned ina

(anne& si(i%a& to $nde&d&ain s!ste(s

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/lignment

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/lignment

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/lignment

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oadwa! Ove&to""in,

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9oadwa* )oing

*ate& 'ows ove& the &oad andth&o$,h the c$%ve&t

A%ow ove& the &oad b&oad c&ested

wei&

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nvironmental considerations

9n addition to cont&o%%in, e&osion si%tation and

deb&is at the c$%ve&t site ca&e ($st bee8e&cised in se%ectin, the %ocation o# the c$%ve&tsite

Envi&on(enta% conside&ations a&e an i("o&tant

as"ect o# the c$%ve&t desi,n


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/ssignment

Groups of two (same as part 3)

$i&he #o%%owin, data is "&ovided #o& the desi,n o# a c$%ve&t +esi,nboth a ci&c$%a& and a bo8 c$%ve&t #o& this in#o&(ation Give a%%ass$("tions (ade

*hat s"ecia% #eat$&es wo$%d !o$ conside& to inc%$de in the desi,n

+ischa&,e #o& 25!& 'ood is =0(3/s +ischa&,e #o& 50 !ea& 'ood is D0(3/s

+ischa&,e #o& 100!& 'ood 1D6(3/s

7en,th o# the c$%ve&t 25(

Nat$&a% channe% inve&t e%evations @ in%et 1=50( and o$t%et 1=35(

C$%ve&t s%o"e 00015(/( -oi% t!"e sand! %oa(

Given Oct 2; 20

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Lecture 6 Culvert Design

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