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CE 46-HIGHWAY ENGINEERING

Aim: The objective of the course is to educate the students on the various components of

Highway Engineering. It exposes the students to highway planning, engineering surveys

for highway alignment, Design of eometric Elements of Highways and !rban roads

Objectives:

Introduction to Transportation "ystems Engineering Explaining Transportation #lanning eometric Design of highways #avement Design of highways Explaining Traffic Engineering

Text Book(s):

1. $hanna $ and %usto & E , Highway Engineering, $hanna #ublishers, 'oor(ee,)**+.

). $adiyali ', #rinciples and #ractice of Highway Engineering, $hanna Technical#ublications, Delhi, )***.

Reference Book(s):

+. Transportation Engineering - #lanning, &.". #apacostas, #.D. #revedouros,#rentice Hall of India #vt ltd, )**.). I'& "tandards /I'& 01 2 )**+ - I'& 34 2+55460. 7ureau of Indian "tandards /7I"6 #ublications on Highway 8aterials9. "pecifications for 'oad and 7ridges, 8:'TH /India6

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UNIT 1

Road classification

The roads can be classified in many ays. The classifica!ion based on s"eed andaccessibili!y is !he mos! #eneric one. No!e !ha! as !he accessibili!y of road increases$

!he s"eed red%ces. &'ee fi#%re (). Accordin#ly$ !he roads can be classified as follos in!he order of increased accessibili!y and red%ced s"eeds.

*reeays+ *reeays are access-con!rolled di,ided hi#hays. os! freeaysare fo%r lanes$ !o lanes each direc!ion$ b%! many freeays iden !oincor"ora!e more lanes as !hey en!er %rban areas. Access is con!rolled !hro%#h!he %se of in!erchan#es$ and !he !y"e of in!erchan#e de"ends %"on !he ind ofin!ersec!in# road ay &r%ral roads$ ano!her freeay e!c.)

E/"ressays+ They are s%"erior !y"e of hi#hays and are desi#ned for hi#hs"eeds & (01 m2hr is common)$ hi#h !raffic ,ol%me and safe!y. They are#enerally "ro,ided i!h #rade se"ara!ions a! in!ersec!ions. 3arin#$ loadin#and %nloadin# of #oods and "edes!rian !raffic is no! alloed on e/"ressays.

Hi#hays+ They re"resen! !he s%"erior !y"e of roads in !he co%n!ry. Hi#haysare of !o !y"es - r%ral hi#hays and %rban hi#hays. R%ral hi#hays are !hose"assin# !hro%#h r%ral areas &,illa#es) and %rban hi#hays are !hose "assin#!hro%#h lar#e ci!ies and !ons$ ie. %rban areas.

Ar!erials+ I! is a #eneral !erm deno!in# a s!ree! "rimarily mean! for !hro%#h!raffic %s%ally on a con!in%o%s ro%!e. They are #enerally di,ided hi#hays i!hf%lly or "ar!ially con!rolled access. 3arin#$ loadin# and %nloadin# ac!i,i!ies are%s%ally res!ric!ed and re#%la!ed. 3edes!rians are alloed !o cross only a!in!ersec!ions2desi#na!ed "edes!rian crossin#s.

ocal s!ree!s + A local s!ree! is !he one hich is "rimarily in!ended for access !o

residence$ b%siness or ab%!!in# "ro"er!y. I! does no! normally carry lar#e ,ol%me of!raffic and also i! allos %nres!ric!ed "arin# and "edes!rian mo,emen!s.

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Collec!or s!ree!s+ These are s!ree!s in!ended for collec!in# and dis!rib%!in# !raffic!o and from local s!ree!s and also for "ro,idin# access !o ar!erial s!ree!s.Normally f%ll access is "ro,ided on !hese s!ree!s . There are fe "arin#res!ric!ions e/ce"! d%rin# "ea ho%rs.

i!"re 1: '"eed ,s accessibili!y

FACTORS AFFECTING HIGHWAY ALIGHNMENT

Design speed

5esi#n s"eed is !he sin#le mos! im"or!an! fac!or !ha! affec!s !he #eome!ric desi#n. I!

direc!ly affec!s !he si#h! dis!ance$ horion!al c%r,e$ and !he len#!h of ,er!ical c%r,es.'ince !he s"eed of ,ehicles ,ary i!h dri,er$ !errain e!c$ a desi#n s"eed is ado"!ed forall !he #eome!ric desi#n.

5esi#n s"eed is defined as !he hi#hes! con!in%o%s s"eed a! hich indi,id%al ,ehicles can!ra,el i!h safe!y on !he hi#hay hen ea!her condi!ions are cond%ci,e. 5esi#n s"eedis differen! from !he le#al s"eed limi! hich is !he s"eed limi! im"osed !o c%rb acommon !endency of dri,ers !o !ra,el beyond an acce"!ed safe s"eed. 5esi#n s"eed isalso differen! from !he desired s"eed hich is !he ma/im%m s"eed a! hich a dri,ero%ld !ra,el hen %ncons!rained by ei!her !raffic or local #eome!ry.

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'ince !here are ide ,aria!ions in !he s"eed ado"!ed by differen! dri,ers$ and by differen!!y"es of ,ehicles$ desi#n s"eed sho%ld be selec!ed s%ch !ha! i! sa!isfy nearly all dri,ers.A! !he same !ime$ a hi#her desi#n s"eed has cascadin# effec! in o!her #eome!ric desi#nsand !hereby cos! escala!ion. Therefore$ an 78!h "ercen!ile desi#n s"eed is normallyado"!ed. This s"eed is defined as !ha! s"eed hich is #rea!er !han !he s"eed of 789 ofdri,ers. In some co%n!ries !his is as hi#h as :8 !o :7 "ercen!ile s"eed.

Topography

The ne/! im"or!an! fac!or !ha! affec!s !he #eome!ric desi#n is !he !o"o#ra"hy. I! is easier!o cons!r%c! roads i!h re;%ired s!andards for a "lain !errain. Hoe,er$ for a #i,endesi#n s"eed$ !he cons!r%c!ion cos! increases m%l!iform i!h !he #radien! and !he !errain.Therefore$ #eome!ric desi#n s!andards are differen! for differen! !errain !o ee" !he cos!of cons!r%c!ion and !ime of cons!r%c!ion %nder con!rol. This is charac!eried by shar"erc%r,es and s!ee"er #radien!s.

Other a!tors

In addi!ion !o desi#n s"eed and !o"o#ra"hy$ !here are ,ario%s o!her fac!ors !ha! affec!!he #eome!ric desi#n and !hey are briefly disc%ssed belo+

#e$icle: +The dimensions$ ei#h! of !he a/le and o"era!in# charac!eris!ics of a,ehicle infl%ence !he desi#n as"ec!s s%ch as id!h of !he "a,emen!$ radii of !hec%r,e$ clearances$ "arin# #eome!rics e!c. A design vehiclehich has s!andard

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ei#h!$ dimensions and o"era!in# charac!eris!ics are %sed !o es!ablishhi#hay desi#n con!rols !o accommoda!e ,ehicles of a desi#na!ed !y"e.

%"man: The im"or!an! h%man fac!ors !ha! infl%ence #eome!ric desi#n are !he"hysical$ men!al and "sycholo#ical charac!eris!ics of !he dri,er and"edes!rians lie !he reac!ion !ime.

Traffic: I! ill be %neconomical !o desi#n !he road for "ea !raffic flo. Therefore a reasonable ,al%e of !raffic ,ol%me is selec!ed as !he desi#n ho%rly

,ol%me hich is de!ermined from !he ,ario%s !raffic da!a collec!ed. The#eome!ric desi#n is !h%s based on !his desi#n ,ol%me$ ca"aci!y e!c.

&nvironmental: *ac!ors lie air "oll%!ion$ noise "oll%!ion e!c. sho%ld be#i,end%e considera!ion in !he #eome!ric desi#n of roads.

&conom': The desi#n ado"!ed sho%ld be economical as far as "ossible. I!sho%ldma!ch i!h !he f%nds allo!ed for ca"i!al cos! and main!enance cos!.

Ot$ers: Geome!ric desi#n sho%ld be s%ch !ha! !he aes!he!ics of !he re#ion isno!affec!ed.

Nagp"r !#assii!ation

In Na#"%r road classifica!ion$ all roads ere classified in!o fi,e ca!e#ories as Na!ionalhi#hays$ '!a!e hi#hays$ a

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tate $i!$a's

They are !he ar!erial roads of a s!a!e$ connec!in# %" i!h !he na!ional hi#haysof ad

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?n"a,ed roads+ Roads hich are no! "ro,ided i!h a hard co%rse of a!leas! aWF layer !hey is called %n"a,ed roads. Th%s ear!h and #ra,el roads come%nder !his ca!e#ory.

A#ign$ent

The "osi!ion or !he layo%! of !he cen!ral line of !he hi#hay on !he #ro%nd is called !he

ali#nmen!. Horion!al ali#nmen! incl%des s!rai#h! and c%r,ed "a!hs. er!icalali#nmen! incl%des le,el and #radien!s. Ali#nmen! decision is im"or!an! beca%se a badali#nmen! ill enhance !he cons!r%c!ion$ main!enance and ,ehicle o"era!in# cos!s.=nce an ali#nmen! is fi/ed and cons!r%c!ed$ i! is no! easy !o chan#e i! d%e !o increasein cos! of ad

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o o%n!ain+ While !he ali#nmen! "asses !hro%#h a mo%n!ain$ !he ,ario%sal!erna!i,es are !o ei!her cons!r%c! a !%nnel or !o #o ro%nd !he hills.The s%i!abili!y of !he al!erna!i,e de"ends on fac!ors lie !o"o#ra"hy$si!e condi!ions and cons!r%c!ion and o"era!ion cos!.

o In!ermedia!e !on+ The ali#nmen! may be sli#h!ly de,ia!ed !o connec!an in!ermedia!e !on or ,illa#e nearby.

These ere some of !he obli#a!ory "oin!s !hro%#h hich !he ali#nmen! sho%ld "ass.Comin# !o !he second ca!e#ory$ !ha! is !he "oin!s !hro%#h hich !he ali#nmen! sho%ldno! "ass are+

Reli#io%s "laces+ These ha,e been "ro!ec!ed by !he la from bein# ac;%iredfor any "%r"ose. Therefore$ !hese "oin!s sho%ld be a,oided hile ali#nin#.

ery cos!ly s!r%c!%res+ Ac;%irin# s%ch s!r%c!%res means hea,y com"ensa!ionhich o%ld res%l! in an increase in ini!ial cos!. 'o !he ali#nmen! may be

de,ia!ed no! !o "ass !hro%#h !ha! "oin!. aes2"onds e!c+ The "resence of a lae or "ond on !he ali#nmen! "a!h o%ld

also necessi!a!e de,ia!ion of !he ali#nmen!.

Traffic+ The ali#nmen! sho%ld s%i! !he !raffic re;%iremen!s. Fased on !he ori#in-des!ina!ion da!a of !he area$ !he desire lines sho%ld be dran. The ne ali#nmen! sho%ldbe dran ee"in# in ,ie !he desire lines$ !raffic flo "a!!ern e!c. Geome!ric desi#n+Geome!ric desi#n fac!ors s%ch as #radien!$ radi%s of c%r,e$ si#h! dis!ance e!c. also#o,ern !he ali#nmen! of !he hi#hay. To ee" !he radi%s of c%r,e minim%m$ i! may bere;%ired !o chan#e !he ali#nmen!. The ali#nmen!s sho%ld be finalied s%ch !ha! !heobs!r%c!ions !o ,isibili!y do no! res!ric! !he minim%m re;%iremen!s of si#h! dis!ance. The

desi#n s!andards ,ary i!h !he class of road and !he !errain and accordin#ly !he hi#haysho%ld be ali#ned. Economy+ The ali#nmen! finalied sho%ld be economical. All !he!hree cos!s i.e. cons!r%c!ion$ main!enance$ and o"era!in# cos! sho%ld be minim%m. Thecons!r%c!ion cos! can be decreased m%ch if i! is "ossible !o main!ain a balance be!eenc%!!in# and fillin#. Also !ry !o a,oid ,ery hi#h embanmen!s and ,ery dee" c%!!in#s as!he cons!r%c!ion cos! ill be ,ery hi#her in !hese cases.

+ross sectional elements

Overvie

The fea!%res of !he cross-sec!ion of !he "a,emen! infl%ences !he life of !he "a,emen!as ell as !he ridin# comfor! and safe!y. =f !hese$ "a,emen! s%rface charac!eris!icsaffec! bo!h of !hese. Camber$ erbs$ and #eome!ry of ,ario%s cross-sec!ional elemen!sare im"or!an! as"ec!s !o be considered in !his re#ard. They are e/"lained briefly in !hischa"!er.

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+amber

Camber or can! is !he cross slo"e "ro,ided !o raise middle of !he road s%rface in !he!rans,erse direc!ion !o drain off rain a!er from road s%rface. The ob

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,idt$ of carria!e a'

Wid!h of !he carria#e ay or !he id!h of !he "a,emen! de"ends on !he id!h of!he !raffic lane and n%mber of lanes.

Wid!h of a !raffic lane de"ends on !he id!h of !he ,ehicle and !he clearance.'ide clearance im"ro,es o"era!in# s"eed and safe!y

. The ma/im%m "ermissible id!h of a ,ehicle is -.//and !he desirable side clearance forsin#le lane !raffic is 1.67 m. This re;%ire minim%m of lane id!h of B.8 m for a sin#lelane road &*i#%re (a). Hoe,er$ !he side clearance re;%ired is abo%! 1.8B m$ on ei!herside or (.16 m in !he cen!er.

Therefore$ a !o lane road re;%ire minim%m of B.8 me!er for each lane &*i#%re (b). Thedesirable carria#e ay id!h recommended by IRC is #i,en in Table (

Table 1: IRC '"ecifica!ion for carria#e ay id!h

'in#le lane B.C8

To lane$ no erbs C.1

To lane$ raised erbs C.8

In!ermedia!e carria#e 8.8

%l!i-lane B.8

i!"re 1: ane id!h for sin#le and !o lane roads

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UNIT -

0erbs

erbs indica!e !he bo%ndary be!een !he carria#e ay and !he sho%lder or islandsor foo!"a!hs. 5ifferen! !y"es of erbs are &*i#%re ()+

o or mo%n!able erbs + This !y"e of erbs are "ro,ided s%ch !ha! !heyenco%ra#e !he !raffic !o remain in !he !hro%#h !raffic lanes and also allo !hedri,er !o en!er !he sho%lder area i!h li!!le diffic%l!y. The hei#h! of !his erb isabo%! (1 cm abo,e !he "a,emen! ed#e i!h a slo"e hich allos !he ,ehicle !oclimb easily. This is %s%ally "ro,ided a! medians and channelia!ion schemesand also hel"s in lon#i!%dinal draina#e.

'emi-barrier !y"e erbs + When !he "edes!rian !raffic is hi#h$ !hese erbs are"ro,ided. Their hei#h! is (8 cm abo,e !he "a,emen! ed#e. This !y"e of erb"re,en!s encroachmen! of "arin# ,ehicles$ b%! a! ac%!e emer#ency i! is "ossible!o dri,e o,er !his erb i!h some diffic%l!y.

Farrier !y"e erbs + They are desi#ned !o disco%ra#e ,ehicles from lea,in# !he"a,emen!. They are "ro,ided hen !here is considerable amo%n! of "edes!rian!raffic. They are "laced a! a hei#h! of 01 cm abo,e !he "a,emen! ed#e i!h as!ee" ba!!er.

'%bmer#ed erbs + They are %sed in r%ral roads. The erbs are "ro,ided a!"a,emen! ed#es be!een !he "a,emen! ed#e and sho%lders. They "ro,idela!eral confinemen! and s!abili!y !o !he "a,emen!.

i!"re 1: 5ifferen! !y"es of erbs

Sho"#ders

"houlders are provided along the road edge and are intended for accommodationof stopped vehicles, serve as an emergency lane for vehicles and provide lateralsupport for base and surface courses. The shoulder should

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be strong enough to bear the weight of a fully loaded truc( even in wetconditions. The shoulder width should be ade;uate for giving wor(ing spacearound a stopped vehicle. It is desirable to have a width of 9. m for theshoulders. < minimum width of ).3 m is recommended for )2lane ruralhighways in India.

&ar'ing #anes

3arin# lanes are "ro,ided in %rban lanes for side "arin#. 3arallel "arin# is "referredbeca%se i! is safe for !he ,ehicles mo,in# on !he road. The "arin# lane sho%ld ha,e aminim%m of B.1 m id!h in !he case of "arallel "arin#.

("s)*ays

F%s bays are "ro,ided by recessin# !he erbs for b%s s!o"s. They are "ro,ided so !ha!!hey do no! obs!r%c! !he mo,emen! of ,ehicles in !he carria#e ay. They sho%ld be a!leas! 8 me!ers aay from !he in!ersec!ion so !ha! !he !raffic near !he in!ersec!ions isno! affec!ed by !he b%s-bay.

Ser+i!e roads

'er,ice roads or fron!a#e roads #i,e access !o access con!rolled hi#hays lie freeaysand e/"ressays. They r%n "arallel !o !he hi#hay and ill be %s%ally isola!ed by ase"ara!or and access !o !he hi#hay ill be "ro,ided only a! selec!ed "oin!s. These roadsare "ro,ided !o a,oid con#es!ion in !he e/"ressays and also !he s"eed of !he !raffic in!hose lanes is no! red%ced.

Drainage

The "a,emen! s%rface sho%ld be absol%!ely im"ermeable !o "re,en! see"a#e of a!erin!o !he "a,emen! layers. *%r!her$ bo!h !he #eome!ry and !e/!%re of "a,emen! s%rfacesho%ld hel" in drainin# o%! !he a!er from !he s%rface in less !ime.

Footpath

*oo!"a!hs are e/cl%si,e ri#h! of ay !o "edes!rians$ es"ecially in %rban areas. They are"ro,ided for !he safe!y of !he "edes!rians hen bo!h !he "edes!rian !raffic and ,ehic%lar!raffic is hi#h. inim%m id!h is (.8 me!er and may be increased based on !he !raffic.

The foo!"a!h sho%ld be ei!her as smoo!h as !he "a,emen! or more smoo!her !han !ha!!o ind%ce !he "edes!rian !o %se !he foo!"a!h.

Ri!$t of a'

Ri#h! of ay &R=W) or land id!h is !he id!h of land ac;%ired for !he road$ alon# i!sali#nmen!. I! sho%ld be ade;%a!e !o accommoda!e all !he cross-sec!ional elemen!s of!he hi#hay and may reasonably "ro,ide for f%!%re de,elo"men!. To "re,en! ribbon

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de,elo"men! alon# hi#hays$ con!rol lines and b%ildin# lines may be "ro,ided. Con!rolline is a line hich re"resen!s !he neares! limi!s of f%!%re %ncon!rolled b%ildin# ac!i,i!yin rela!ion !o a road. F%ildin# line re"resen!s a line on ei!her side of !he road$ be!eenhich and !he road no b%ildin# ac!i,i!y is "ermi!!ed a! all. The ri#h! of ay id!h is#o,erned by+

Wid!h of forma!ion+ I! de"ends on !he ca!e#ory of !he hi#hay and id!h ofroaday and road mar#ins.

Hei#h! of embanmen! or de"!h of c%!!in#+ I! is #o,erned by !he !o"o#ra"hyand !he ,er!ical ali#nmen!.

'ide slo"es of embanmen! or c%!!in#+ I! de"ends on !he hei#h! of !he slo"e$soil !y"e e!c.

5raina#e sys!em and !heir sie hich de"ends on rainfall$ !o"o#ra"hy e!c.

'i#h! dis!ance considera!ions + =n c%r,es e!c. !here is res!ric!ion !o !he,isibili!y on !he inner side of !he c%r,e d%e !o !he "resence of someobs!r%c!ions lie b%ildin# s!r%c!%res e!c.

Reser,e land for f%!%re idenin#+ 'ome land has !o be ac;%ired inad,ance an!ici"a!in# f%!%re de,elo"men!s lie idenin# of !he road.

Table 1:Normal ri#h! of ay for o"en areas

Road Roaday id!h in m

classifica!ion 3lain and o%n!aino%s and

rollin# !errain s!ee" !errain

="en areas

NH2'H 48 04

5R 08 (7

=5R (8 (8

R (0 :

F%il!-%" areas

NH2'H B1 01

5R 01 (8

=5R (8 (0

R (1 :

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i!"re 1: A !y"ical Ri#h! of ay &R=W)

The im"or!ance of reser,ed land is em"hasied by !he folloin#. E/!ra id!h of land isa,ailable for !he cons!r%c!ion of roadside facili!ies. and ac;%isi!ion is no! "ossiblela!er$ beca%se !he land may be occ%"ied for ,ario%s o!her "%r"oses &b%ildin#s$ b%sinesse!c.) The normal R=W re;%iremen!s for b%il! %" and o"en areas as s"ecified by IRC is#i,en in Table (A !y"ical cross sec!ion of a R=W is #i,en in *i#%re (.

Overvie

Horion!al ali#nmen! is one of !he mos! im"or!an! fea!%res infl%encin# !he efficiency andsafe!y of a hi#hay. A "oor desi#n ill res%l! in loer s"eeds and res%l!an! red%c!ion inhi#hay "erformance in !erms of safe!y and comfor!. In addi!ion$ i! may increase !hecos! of ,ehicle o"era!ions and loer !he hi#hay ca"aci!y. Horion!al ali#nmen! desi#nin,ol,es !he %nders!andin# on !he desi#n as"ec!s s%ch as desi#n s"eed and !he effec! ofhorion!al c%r,e on !he ,ehicles. The horion!al c%r,e desi#n elemen!s incl%de desi#n ofs%"er ele,a!ion$ e/!ra idenin# a! horion!al c%r,es$ desi#n of !ransi!ion c%r,e$ and se!bac dis!ance. These ill be disc%ssed in !his cha"!er and !he folloin# !o cha"!ers.

esi!n 2eed

The desi#n s"eed$ as no!ed earlier$ is !he sin#le mos! im"or!an! fac!or in !he desi#n ofhorion!al ali#nmen!. The desi#n s"eed also de"ends on !he !y"e of !he road. *or e.#$!he desi#n s"eed e/"ec!ed from a Na!ional hi#hay ill be m%ch hi#her !han a ,illa#eroad$ and hence !he c%r,e #eome!ry ill ,ary si#nifican!ly.

The desi#n s"eed also de"ends on !he !y"e of !errain. A "lain !errain can afford !o ha,eany #eome!ry$ b%! for !he same s!andard in a hilly !errain re;%ires s%bs!an!ial c%!!in#and fillin# im"lyin# e/orbi!an! cos!s as ell as safe!y concern d%e !o %ns!able slo"es.Therefore$ !he desi#n s"eed is normally red%ced for !errains i!h s!ee" slo"es.

*or ins!ance$ Indian Road Con#ress &IRC) has classified !he !errains in!o fo%r ca!e#ories$namely "lain$ rollin#$ mo%n!aino%s$ and s!ee" based on !he cross slo"e as #i,en in !able (.Fased on !he !y"e of road and !y"e of !errain !he desi#n s"eed ,aries. The IRC hass%##es!ed desirable or r%lin# s"eed as ell as minim%m s%##es!ed desi#n s"eed and is!ab%la!ed in !able 0.

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Table 1: Terrain classifica!ion

Terrain classifica!ion Cross slo"e &9)

3lain 1-(1

Rollin# (1-08

o%n!aino%s 08-61

'!ee" 61

The recommended desi#n s"eed is #i,en in Table 0.

Table -: 5esi#n s"eed in as "er IRC &r%lin# and minim%m)

Ty"e 3lain Rollin# Hilly '!ee"

N''H (11-71 71-68 81-41 41-B1

5R 71-68 68-81 41-B1 B1-01

=5R 68-81 81-41 B1-08 08-01

R 81-41 41-B8 08-01 08-01

%ori3ontal c"rve

The "resence of horion!al c%r,e im"ar!s cen!rif%#al force hich is a reac!i,e force ac!in#

o%!ard on a ,ehicle ne#o!ia!in# i!. Cen!rif%#al force de"ends on s"eed and radi%s of !he

horion!al c%r,e and is co%n!erac!ed !o a cer!ain e/!en! by !rans,erse fric!ion be!een !he

!yre and "a,emen! s%rface. =n a c%r,ed road$ !his force !ends !o ca%se !he ,ehicle !o o,err%n

or !o slide o%!ard from !he cen!re of road c%r,a!%re. *or "ro"er desi#n of !he c%r,e$ an

%nders!andin# of !he forces ac!in# on a ,ehicle !ain# a horion!al c%r,e is necessary.

ario%s forces ac!in# on !he ,ehicle are ill%s!ra!ed in !he fi#%re (.

i!"re 1: Effec! of horion!al c%r,e

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The second !endency of !he ,ehicle is for !rans,erse siddin#. i.e. When !he !hecen!rif%#al force is #rea!er !han !he ma/im%m "ossible !rans,erse sid resis!ance d%e !ofric!ion be!een !he "a,emen! s%rface and !yre. The !rans,erse sid resis!ance &*) is#i,en by+

here and is !he frac!ional force a! !yre and $ and is !he reac!ion a!

!yre and $ is !he la!eral coefficien! of fric!ion and is !he ei#h! of !he,ehicle. This is co%n!erac!ed by !he cen!rif%#al force &3)$ and e;%a!in#+

A! e;%ilibri%m$ hen siddin# !aes "lace &from e;%a!ion()

and for safe!y !he folloin# condi!ion m%s! sa!isfy+

&B)

E;%a!ion 0and B#i,e !he s!able condi!ion for desi#n. If e;%a!ion 0is ,iola!ed$ !he ,ehicleill o,er!%rn a! !he horion!al c%r,e and if e;%a!ion Bis ,iola!ed$ !he ,ehicle ill sid a!!he horion!al

c"rveAnal'sis of s"2er4elevation

'%"er-ele,a!ion or can! or banin# is !he !rans,erse slo"e "ro,ided a! horion!al c%r,e !o

co%n!erac! !he cen!rif%#al force$ by raisin# !he o%!er ed#e of !he "a,emen! i!h res"ec! !o!he inner ed#e$ !hro%#ho%! !he len#!h of !he horion!al c%r,e. When !he o%!er ed#e israised$ a com"onen! of !he c%r,e ei#h! ill be com"limen!ed in co%n!erac!in# !he effec!of cen!rif%#al force. In order !o find o%! ho m%ch !his raisin# sho%ld be$ !he folloin#analysis may be done. The forces ac!in# on a ,ehicle hile !ain# a horion!al c%r,ei!h s%"erele,a!ion is shon in fi#%re (.

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i!"re 1: Analysis of s%"er-ele,a!ion

*orces ac!in# on a ,ehicle on horion!al c%r,e of radi%s a! a s"eed of are+

!he cen!rif%#al force ac!in# horion!ally o%!-ards !hro%#h !he cen!er of

#ra,i!y$

!he ei#h! of !he ,ehicle ac!in# don-ards !hro%#h !he cen!er of #ra,i!y$ and

!he fric!ion force be!een !he heels and !he "a,emen!$ alon# !he s%rfaceinard.

A! e;%ilibri%m$ by resol,in# !he forces "arallel !o !he s%rface of !he "a,emen! e #e!$

here is !he ei#h! of !he ,ehicle$ is !he cen!rif%#al force$ is !he coefficien! of

fric!ion$ is !he !rans,erse slo"e d%e !o s%"erele,a!ion. 5i,idin# by $ e #e!+

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&(

)

We ha,e already deri,ed an e/"ression for 32W.Fy s%bs!i!%!in# !his in e;%a!ion ($ e#e!+

&0)

This is an e/ac! e/"ression for s%"erele,a!ion. F%! normally$ and $

and for small $ $ !hen e;%a!ion 0becomes+

&B)

here$ is !he ra!e of s%"er ele,a!ion$ !he coefficien! of la!eral fric!ion $ !he

s"eed of !he ,ehicle in $ !he radi%s of !he c%r,e in and

. Three s"ecific cases !ha! can arise from e;%a!ion Bare as follos+

(

If !here is no fric!ion d%e !o some "rac!ical reasons$ !hen and e;%a!ion B

becomes . This res%l!s in !he si!%a!ion here !he "ress%re on !he o%!er

and inner heels are same re;%irin# ,ery hi#h s%"er-ele,a!ion .

0If !here is no s%"er-ele,a!ion "ro,ided d%e !o some "rac!ical reasons$ !hen

and e;%a!ion Bbecomes . This res%l!s in a ,ery hi#h coefficien!

of fric!ion.

B

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If and !hen for safe !ra,elin# s"eed from e;%a!ion Bis #i,en by

here is !he res!ric!ed s"eed.

Design of super-elevation

*or fas! mo,in# ,ehicles$ "ro,idin# hi#her s%"er ele,a!ion i!ho%! considerin#coefficien! of fric!ion is safe$ i.e. cen!rif%#al force is f%lly co%n!erac!ed by !he ei#h! of!he ,ehicle or s%"er ele,a!ion. *or slo mo,in# ,ehicles$ "ro,idin# loer s%"er ele,a!ionconsiderin# coefficien! of fric!ion is safe$ i.e. cen!rif%#al force is co%n!erac!ed by s%"erele,a!ion and coefficien! of fric!ion. IRC s%##es!s folloin# desi#n "roced%re+'!e" (

*ind for 8 "ercen! of desi#n s"eed$ ne#lec!in# $ i.e .

'!e" 0

If $ !hen $ else if #o !o s!e" B.

'!e" B

*ind for !he desi#n s"eed and ma/ $ i.e . If

$ !hen !he ma/im%m is safe for !he desi#n s"eed$ else #o

!o s!e" 4.

'!e" 4

*ind !he allowable speed for !he ma/im%m and $

If !hen !he desi#n is ade;%a!e$ o!herise %se s"eed ado"!

con!rol meas%res or loo for s"eed con!rol meas%res

Ma,i$"$ and $ini$"$ s"per)e#e+ation

5e"ends on &a) slo mo,in# ,ehicle and &b) hea,y loaded !r%cs i!h hi#h CG. IRCs"ecifies a ma/im%m s%"er-ele,a!ion of "ercen! for "lain and rollin# !errain$ hile !ha!of hilly !errain is (1 "ercen! and %rban road is 4 "ercen!. The minim%m s%"er ele,a!ionis 0-4 "ercen! for draina#e "%r"ose$ es"ecially for lar#e radi%s of !he horion!al c%r,e.

Attain$ent o s"per)e#e+ation

(. Elimina!ion of !he cron of !he cambered sec!ion by+

(. Ro!a!in# !he o%!er ed#e abo%! !he cron + The o%!er half of !he crossslo"e is ro!a!ed abo%! !he cron a! a desired ra!e s%ch !ha! !his s%rfacefalls on !he same "lane as !he inner half.

0. 'hif!in# !he "osi!ion of !he cron+ This me!hod is also non as dia#onalcron me!hod. Here !he "osi!ion of !he cron is "ro#ressi,ely shif!ed

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o%!ards$ !h%s increasin# !he id!h of !he inner half of cross sec!ion"ro#ressi,ely.

0. Ro!a!ion of !he "a,emen! cross sec!ion !o a!!ain f%ll s%"er ele,a!ion by+Thereare !o me!hods of a!!ainin# s%"er ele,a!ion by ro!a!in# !he "a,emen!

(. Ro!a!ion abo%! !he cen!er line + The "a,emen! is ro!a!ed s%ch !ha! !he inner

ed#e is de"ressed and !he o%!er ed#e is raised bo!h by half !he !o!al amo%n!

of s%"er ele,a!ion$ i.e.$ by i!h res"ec! !o !he cen!re.0. Ro!a!ion abo%! !he inner ed#e+ Here !he "a,emen! is ro!a!ed raisin# !he

o%!er ed#e as ell as !he cen!re s%ch !ha! !he o%!er ed#e is raised by!he f%ll amo%n! of s%"er ele,a!ion i!h res"ec! !o !he inner ed#e.

Radi"s of %ori3ontal +"rve

The radi%s of !he horion!al c%r,e is an im"or!an! desi#n as"ec! of !he #eome!ric desi#n.The ma/im%m comfor!able s"eed on a horion!al c%r,e de"ends on !he radi%s of !he c%r,e.Al!ho%#h i! is "ossible !o desi#n !he c%r,e i!h ma/im%m s%"er ele,a!ion and coefficien! offric!ion$ i! is no! desirable beca%se re-ali#nmen! o%ld be re;%ired if !he

desi#n s"eed is increased in f%!%re. Therefore$ a r%lin# minim%m radi%s can bederi,ed by ass%min# ma/im%m s%"er ele,a!ion and coefficien! of fric!ion.

&()

Ideally$ !he radi%s of !he c%r,e sho%ld be hi#her !han . Hoe,er$ ,ery lar#e

c%r,es are also no! desirable. 'e!!in# o%! lar#e c%r,es in !he field becomes diffic%l!.

In addi!ion$ i! also enhances dri,in# s!rain.

E/!ra idenin#

E/!ra idenin# refers !o !he addi!ional id!h of carria#eay !ha! is re;%ired on a c%r,edsec!ion of a road o,er and abo,e !ha! re;%ired on a s!rai#h! ali#nmen!. This idenin# isdone d%e !o !o reasons+ !he firs! and mos! im"or!an! is !he addi!ional id!h re;%ired fora ,ehicle !ain# a horion!al c%r,e and !he second is d%e !o !he !endency of !he dri,ers!o "ly aay from !he ed#e of !he carria#eay as !hey dri,e on a c%r,e. The firs! isreferred as !he mechanical idenin# and !he second is called !he "sycholo#icalidenin#. These are disc%ssed in de!ail belo.

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UNIT45

%ori3ontal Transition +"rves

Transi!ion c%r,e is "ro,ided !o chan#e !he horion!al ali#nmen! from s!rai#h! !ocirc%lar c%r,e #rad%ally and has a radi%s hich decreases from infini!y a! !he s!rai#h!

end &tangent point) !o !he desired radi%s of !he circ%lar c%r,e a! !he o!her end &curvepoint) There are fi,e ob

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Therefore$ !he len#!h of !he !ransi!ion c%r,e in is

&()

here is !he ra!e of chan#e of cen!rif%#al accelera!ion #i,en by an em"iricalform%la s%##es!ed by by IRC as belo+

&0

)

2. Rate of introduction of super-elevation

Raise & ) of !he o%!er ed#e i!h res"ec! !o inner ed#e is #i,en by

. The ra!e of chan#e of !his raise from !o is achie,ed#rad%ally i!h a #radien! of in o,er !he len#!h of !he !ransi!ion c%r,e &!y"ical ran#e

of is 61-(81). Therefore$ !he len#!h of !he !ransi!ion c%r,e is+

&B)

3. By empirical formula

IRC s%##es! !he len#!h of !he !ransi!ion c%r,e is minim%m for a "lain and rollin# !errain+

&4)

and for s!ee" and hilly !errain is+

&8)

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and !he shif! as+

&6)

The len#!h of !he !ransi!ion c%r,e is !he ma/im%m of e;%a!ions ($ Band 4or8$ i.e.

&)

Case (a)

*or sin#le lane roads+

&()

Therefore$

&0)

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i!"re 1: 'e!-bac for sin#le lane roads & )

*or m%l!i lane roads$ if is !he dis!ance be!een cen!erline of !he road and !hecen!erline of !he inner lane$ !hen

&B)

&4)

i!"re -: 'e!-bac for m%l!i-lane roads & )

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Case (a)

*or sin#le lane roads+

&()

Therefore$

&0)

i!"re 1: 'e!-bac for sin#le lane roads & )

*or m%l!i lane roads$ if is !he dis!ance be!een cen!erline of !he road and !hecen!erline of !he inner lane$ !hen

&B)

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&4)

i!"re -: 'e!-bac for m%l!i-lane roads & )

#ertical ali!nment4I

Overvie

The ,er!ical ali#nmen! of a road consis!s of #radien!s&s!rai#h! lines in a ,er!ical "lane) and

,er!ical c%r,es. The ,er!ical ali#nmen! is %s%ally dran as a "rofile$ hich is a #ra"h i!h

ele,a!ion as ,er!ical a/is and !he horion!al dis!ance alon# !he cen!re line of !he road as !he

!he horion!al a/is. >%s! as a circ%lar c%r,e is %sed !o connec! horion!al s!rai#h! s!re!ches of

road$ ,er!ical c%r,es connec! !o #radien!s. When !hese !o c%r,es mee!$ !hey form ei!hercon,e/ or conca,e. The former is called a s%mmi! c%r,e$ hile !he la!!er is called a ,alley

c%r,e. This sec!ion co,ers a disc%ssion on #radien! and s%mmi! c%r,es.

6radient

Gradien! is !he ra!e of rise or fall alon# !he len#!h of !he road i!h res"ec! !o !hehorion!al. While ali#nin# a hi#hay$ !he #radien! is decided for desi#nin# !he ,er!icalc%r,e. Fefore finaliin# !he #radien!s$ !he cons!r%c!ion cos!$ ,ehic%lar o"era!ion cos!and !he "rac!ical "roblems in !he si!e also has !o be considered. ?s%ally s!ee" #radien!sare a,oided as far as "ossible beca%se of !he diffic%l!y !o climb and increase in !he

cons!r%c!ion cos!. ore abo%! #radien!s are disc%ssed belo.

Ee!t o gradient

The effec! of lon# s!ee" #radien! on !he ,ehic%lar s"eed is considerable. This is"ar!ic%larly im"or!an! in roads here !he "ro"or!ion of hea,y ,ehicles is si#nifican!.5%e !o res!ric!i,e si#h! dis!ance a! %"hill #radien!s !he s"eed of !raffic is of!en con!rolledby !hese hea,y ,ehicles. As a res%l!$ no! only !he o"era!in# cos!s of !he ,ehicles are

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increased$ b%! also ca"aci!y of !he roads ill ha,e !o be red%ced. *%r!her$ d%e !o hi#hdifferen!ial s"eed be!een hea,y and li#h! ,ehicles$ and be!een %"hill anddonhill #radien!s$ acciden!s abo%nd in #radien!s.

Representation o gradient

The "osi!i,e #radien! or !he ascendin# #radien! is deno!ed as and !he ne#a!i,e

#radien! as . The de,ia!ion an#le is+ hen !o #rades mee!$ !he an#le hich meas%res

!he chan#e of direc!ion and is #i,en by !he al#ebraic difference be!een !he !o

#rades . E/am"le+ ( in B1 J B.BB9 is a

s!ee" #radien!$ hile ( in 81 J 09 is a fla!!er #radien!. The #radien!

re"resen!a!ion is ill%s!ra!ed in !he fi#%re (.

i!"re 1: Re"resen!a!ion of #radien!

Types o gradient

any s!%dies ha,e shon !ha! #radien! %"!o se,en "ercen! can ha,e considerable effec!on !he s"eeds of !he "assen#er cars. =n !he con!rary$ !he s"eeds of !he hea,y ,ehiclesare considerably red%ced hen lon# #radien!s as fla! as !o "ercen! is ado"!ed.Al!ho%#h$ fla!!er #radien!s are desirable$ i! is e,iden! !ha! !he cos! of cons!r%c!ion illalso be ,ery hi#h. Therefore$ IRC has s"ecified !he desirable #radien!s for each !errain.Hoe,er$ i! may no! be economically ,iable !o ado"! s%ch #radien!s in cer!ain loca!ions$s!ee"er #radien!s are "ermi!!ed for shor! d%ra!ion. 5ifferen! !y"es of #rades are disc%ssedbelo and !he recommended !y"e of #radien!s for each !y"e of !errain and !y"e of#radien! is #i,en in !able (.

Table 1: IRC '"ecifica!ions for #radien!s for differen! roads

Terrain R%lin# imi!in#s E/ce"!ional

3lain2Rollin# B.B 8.1 6.C

Hilly 8.1 6.1 C.1

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'!ee" 6.1 .1 7.1

R%lin# #radien!$ limi!in# #radien!$ e/ce"!ional #radien! and minim%m #radien! aresome !y"es of #radien!s hich are disc%ssed belo.

R"lin! !radient

The r%lin# #radien! or !he desi#n #radien! is !he ma/im%m #radien! i!h hich !hedesi#ner a!!em"!s !o desi#n !he ,er!ical "rofile of !he road. This de"ends on !he !errain$len#!h of !he #rade$ s"eed$ "%llin# "oer of !he ,ehicle and !he "resence of !hehorion!al c%r,e. In fla!!er !errain$ i! may be "ossible !o "ro,ide fla! #radien!s$ b%! in hilly!errain i! is no! economical and some!imes no! "ossible also. The r%lin# #radien! isado"!ed by !he desi#ner by considerin# a "ar!ic%lar s"eed as !he desi#n s"eed and for adesi#n ,ehicle i!h s!andard dimensions. F%! o%r co%n!ry has a he!ero#eneo%s !raffic andhence i! is no! "ossible !o lay don "recise s!andards for !he co%n!ry as a hole. HenceIRC has recommended some ,al%es for r%lin# #radien! for differen! !y"es of !errain.

7imitin! !radient

This #radien! is ado"!ed hen !he r%lin# #radien! res%l!s in enormo%s increase in cos!of cons!r%c!ion. =n rollin# !errain and hilly !errain i! may be fre;%en!ly necessary !oado"! limi!in# #radien!. F%! !he len#!h of !he limi!in# #radien! s!re!ches sho%ld belimi!ed and m%s! be sandiched by ei!her s!rai#h! roads or easier #rades.

&xce2tional !radient

E/ce"!ional #radien! are ,ery s!ee"er #radien!s #i,en a! %na,oidable si!%a!ions. Theysho%ld be limi!ed for shor! s!re!ches no! e/ceedin# abo%! (11 me!res a! a s!re!ch. Inmo%n!aino%s and s!ee" !errain$ s%ccessi,e e/ce"!ional #radien!s m%s! be se"ara!ed by a

minim%m (11 me!re len#!h #en!ler #radien!. A! hair"in bends$ !he #radien! is res!ric!ed!o 0.89.

+ritical len!t$ of t$e !rade

The ma/im%m len#!h of !he ascendin# #radien! hich a loaded !r%c can o"era!ei!ho%! %nd%e red%c!ion in s"eed is called cri!ical len#!h of !he #rade. A s"eed of 08m"h is a reasonable ,al%e. This ,al%e de"ends on !he sie$ "oer$ load$ #rad-abili!y of!he !r%c$ ini!ial s"eed$ final desirable minim%m s"eed

*inim"m !radient

This is im"or!an! only a! loca!ions here s%rface draina#e is im"or!an!. Camber ill

!ae care of !he la!eral draina#e. F%! !he lon#i!%dinal draina#e alon# !he side drainsre;%ire some slo"e for smoo!h flo of a!er. Therefore minim%m #radien! is "ro,idedfor draina#e "%r"ose and i! de"ends on !he rain fall$ !y"e of soil and o!her si!econdi!ions. A minim%m of ( in 811 may be s%fficien! for concre!e drain and ( in 011 foro"en soil drains are fo%nd !o #i,e sa!isfac!ory "erformance.

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UNIT /

"mmit c"rve

'%mmi! c%r,es are ,er!ical c%r,es i!h #radien! %"ards. They are formed hen

!o #radien!s mee! as ill%s!ra!ed in fi#%re (in any of !he folloin# fo%r ays+

(. hen a "osi!i,e #radien! mee!s ano!her "osi!i,e #radien! Kfi#%re (aL.

0. hen "osi!i,e #radien! mee!s a fla! #radien! Kfi#%re (bL. .

B. hen an ascendin# #radien! mee!s a descendin# #radien! Kfi#%re (cL. .4. hen a descendin# #radien! mee!s ano!her descendin# #radien! Kfi#%re (dL. .

Type o S"$$it C"r+e

any c%r,e forms can be %sed i!h sa!isfac!ory res%l!s$ !he common "rac!ice has been!o %se "arabolic c%r,es in s%mmi! c%r,es. This is "rimarily beca%se of !he ease i!h i!can be laid o%! as ell as alloin# a comfor!able !ransi!ion from one #radien! !o ano!her.

Al!ho%#h a circ%lar c%r,e offers e;%al si#h! dis!ance a! e,ery "oin! on !he c%r,e$ for ,erysmall de,ia!ion an#les a circ%lar c%r,e and "arabolic c%r,es are almos! con#r%en!.*%r!hermore$ !he %se of "arabolic c%r,es ere fo%nd !o #i,e e/cellen! ridin# comfor!.

i!"re 1: Ty"es of s%mmi! c%r,es

Design Consideration

In de!erminin# !he !y"e and len#!h of !he ,er!ical c%r,e$ !he desi#n considera!ions arecomfor! and sec%ri!y of !he dri,er$ and !he a""earance of !he "rofile ali#nmen!. Amon#!hese$ si#h! dis!ance re;%iremen!s for !he safe!y are mos! im"or!an! on s%mmi! c%r,es.The s!o""in# si#h! dis!ance or absol%!e minim%m si#h! dis!ance sho%ld be "ro,ided on!hese c%r,es and here o,er!ain# is no! "rohibi!ed$ o,er!ain# si#h! dis!ance or

in!ermedia!e si#h! dis!ance sho%ld be "ro,ided as far as "ossible. When a fas! mo,in#,ehicle !ra,els alon# a s%mmi! c%r,e$ !here is less discomfor! !o !he "assen#ers. This isbeca%se !he cen!rif%#al force ill be ac!in# %"ards hile !he ,ehicle ne#o!ia!es as%mmi! c%r,e hich is a#ains! !he #ra,i!y and hence a "ar! of !he !yre "ress%re isrelie,ed. Also if !he c%r,e is "ro,ided i!h ade;%a!e si#h! dis!ance$ !he len#!h o%ldbe s%fficien! !o ease !he shoc d%e !o chan#e in #radien!. Circ%lar s%mmi! c%r,es areiden!ical since !he radi%s remains same !hro%#ho%! and hence !he si#h! dis!ance. *rom

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!his "oin! of ,ie$ !ransi!ion c%r,es are no! desirable since i! has ,aryin# radi%s and so!he si#h! dis!ance ill also ,ary. The de,ia!ion an#les "ro,ided on s%mmi! c%r,es forhi#hays are ,ery lar#e$ and so !he sim"le "arabola is almos! con#r%en! !o a circ%lar arc$be!een !he same !an#en! "oin!s. 3arabolic c%r,es are easy for com"%!a!ion and also i!had been fo%nd o%! !ha! i! "ro,ides #ood ridin# comfor! !o !he dri,ers. I! is also easy forfield im"lemen!a!ion. 5%e !o all !hese reasons$ a sim"le "arabolic c%r,e is "referred ass%mmi! c%r,e.

Length o the s"$$it !"r+e

The im"or!an! desi#n as"ec! of !he s%mmi! c%r,e is !he de!ermina!ion of !he len#!h of !hec%r,e hich is "arabolic. As no!ed earlier$ !he len#!h of !he c%r,e is #%ided by !he si#h!dis!ance considera!ion. Tha! is$ a dri,er sho%ld be able !o s!o" his ,ehicle safely if !hereis an obs!r%c!ion on !he o!her side of !he road. E;%a!ion of !he "arabola is #i,en by

$ here $ here N is !he de,ia!ion an#le and is !he len#!h of !he In

deri,in# !he len#!h of !he c%r,e$ !o si!%a!ions can arise de"endin# on !he %"hill and

donhill #radien!s hen !he len#!h of !he c%r,e is #rea!er !han !he si#h! dis!ance and

!he len#!h of !he c%r,e is #rea!er !han !he si#h! dis!ance.

e! is !he len#!h of !he s%mmi! c%r,e$ is !he ''52I'52='5$ is !he de,ia!ion an#le$

dri,erMs eye hei#h! &(.0 m)$ and !he hei#h! of !he obs!r%c!ion$ !hen !he len#!h of !hes%mmi! c%r,e can be deri,ed for !he folloin# !o cases. The len#!h of !he s%mmi!

c%r,e can be deri,ed from !he sim"le #eome!ry as shon belo+

+ase a. 7en!t$ of s"mmit c"rve !reater t$an si!$t distance( )

i!"re 1: en#!h of s%mmi! c%r,e & )

The si!%a!ion hen !he si#h! dis!ance is less !han !he len#!h of !he c%r,e is shonin fi#%re (.

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&()

+ase b. 7en!t$ of s"mmit c"rve less t$an si!$t distance

The second case is ill%s!ra!ed in fi#%re (

i!"re 1: en#!h of s%mmi! c%r,e & )

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*rom !he basic #eome!ry$ one can ri!e

&()

Therefore for a #i,en $ and !o #e! minim%m $ differen!ia!e !he abo,e e;%a!ion

i!h res"ec! !o and e;%a!e i! !o ero. Therefore$

'ol,in# !he ;%adra!ic e;%a!ion for $

&0

)

No e can s%bs!i!%!e bac !o #e! !he ,al%e of minim%m ,al%e of for a #i,en $

$ and . Therefore$

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'ol,in# for $

&B

)

&4)

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When s!o""in# si#h! dis!ance is considered !he hei#h! of dri,erMs eye abo,e !he road

s%rface & ) is !aen as (.0 me!res$ and hei#h! of ob

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mo,emen! of ,ehicles a! desi#n s"eed and &0) a,ailabili!y of s!o""in# si#h!dis!ance %nder headli#h! of ,ehicles for ni#h! dri,in#.

*or #rad%ally in!rod%cin# and increasin# !he cen!rif%#al force ac!in# donards$ !hebes! sha"e !ha! co%ld be #i,en for a ,alley c%r,e is a !ransi!ion c%r,e. C%bic "arabola is#enerally "referred in ,er!ical ,alley c%r,es. 'ee fi#%re (.

i!"re 1: alley c%r,e de!ails

5%rin# ni#h!$ %nder headli#h! dri,in# condi!ion$ si#h! dis!ance red%ces and a,ailabili!yof s!o""in# si#h! dis!ance %nder head li#h! is ,ery im"or!an!. The head li#h! si#h!dis!ance sho%ld be a! leas! e;%al !o !he s!o""in# si#h! dis!ance. There is no "roblem ofo,er!ain# si#h! dis!ance a! ni#h! since !he o!her ,ehicles i!h headli#h!s co%ld be seenfrom a considerable dis!ance.

Length o the +a##ey !"r+e

The ,alley c%r,e is made f%lly !ransi!ional by "ro,idin# !o similar !ransi!ion c%r,es of

e;%al len#!h The !ransi!ional c%r,e is se! o%! by a c%bic "arabola here

The len#!h of !he ,alley !ransi!ion c%r,e is desi#ned based on !o cri!eria+

(. comfor! cri!eria !ha! is alloable ra!e of chan#e of cen!rif%#al accelera!ion

is limi!ed !o a comfor!able le,el of abo%! .

0. safe!y cri!eria !ha! is !he dri,er sho%ld ha,e ade;%a!e headli#h! si#h! dis!ancea! any "ar! of !he co%n!ry.

+omfort criteria

The len#!h of !he ,alley c%r,e based on !he ra!e of chan#e of cen!rif%#al accelera!ion!ha! ill ens%re comfor!+ e! is !he ra!e of chan#e of accelera!ion$ !he minim%mradi%s of !he c%r,e$ is !he desi#n s"eed and is !he !ime$ !hen is #i,en as+

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or a c"bic 2arabola8 t$e #al"e afet' criteria

en#!h of !he ,alley c%r,e for headli#h! dis!ance may be de!ermined for !o condi!ions+

&() len#!h of !he ,alley c%r,e #rea!er !han s!o""in# si#h! dis!ance and &0) len#!h of

!he ,alley c%r,e less !han !he s!o""in# si#h! dis!ance. of for len#!h is #i,en by+

+ase 1 7en!t$ of valle' c"rve !reater t$an sto22in! si!$t distance ( )

The !o!al len#!h of ,alley c%r,e is #rea!er !han !he s!o""in# si#h! dis!ance ''5. Thesi#h! dis!ance a,ailable ill be minim%m hen !he ,ehicle is in !he loes! "oin! in !he,alley. This is beca%se !he be#innin# of !he c%r,e ill ha,e infini!e radi%s and !he bo!!omof !he c%r,e ill ha,e minim%m radi%s hich is a "ro"er!y of !he !ransi!ion c%r,e. The

case is shon in fi#%re (.

i!"re 1: alley c%r,e$ case ($*rom !he #eome!ry of !he fi#%re$ e ha,e+

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&()

here is !he de,ia!ion an#le in radians$ is !he hei#h! of headli#h! beam$ is

!he head beam inclina!ion in de#rees and is !he si#h! dis!ance. The inclina!ion is

( de#ree.

+ase - 7en!t$ of valle' c"rve less t$an sto22in! si!$t distance ( )

The len#!h of !he c%r,e is less !han ''5. In !his case !he minim%m si#h! dis!ance isfrom !he be#innin# of !he c%r,e. The im"or!an! "oin!s are !he be#innin# of !he c%r,e

and !he bo!!om mos! "ar! of !he c%r,e. If !he ,ehicle is a! !he bo!!om of !he c%r,e$ !heni!s headli#h! beam ill reach far beyond !he end"oin! of !he c%r,e hereas$ if !he,ehicle is a! !he be#innin# of !he c%r,e$ !hen !he headli#h! beam ill hi!

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i!"re 1: alley c%r,e$ case 0$

No!e !ha! !he abo,e e/"ression is a""ro/ima!e and is sa!isfac!ory beca%se in "rac!ice$!he #radien!s are ,ery small and is acce"!able for all "rac!ical "%r"oses. We ill no! beable !o no "rior !o hich case !o be ado"!ed. Therefore bo!h has !o be calc%la!ed and

!he one hich sa!isfies !he condi!ion is ado"!ed.

(. *le/ible "a,emen!0. Ri#id "a,emen!

F#e,i*#e pa+e$ent-

These "a,emen!s reflec! !he deforma!ion of s%b #rade and !he s%bse;%en! layers !o!he s%rface.

Rigid pa+e$ent-

The ri#id charac!eris!ic of !he "a,emen! are associa!ed i!h ri#idi!y or fle/%rals!ren#!h or slab ac!ion so !he load is dis!rib%!ed o,er a ide area of s%b #rade soil.

F#e,i*#e pa+e$ent- Deinition

These "a,emen!s reflec! !he deforma!ion of s%b #rade and !he s%bse;%en! layers !o!he s%rface. *le/ible$ %s%ally as"hal!$ is laid i!h no reinforcemen! or i!h as"ecialied fabric reinforcemen! !ha! "ermi!s limi!ed flo or re"osi!ionin# of !heroadbed %nder #ro%nd chan#es.

The desi#n of fle/ible "a,emen! is based on load dis!rib%!in# charac!eris!ic of !he

com"onen! layers. The blac !o" "a,emen! incl%din# a!er #ra,el bo%nd macadam fallin !his ca!e#ory.

*le/ible "a,emen! on !he hole has lo or ne#li#ible fle/ible s!ren#!h fle/ible in !heirs!r%c!%ral ac!ion). The fle/ible "a,emen! layers !ransmi! !he ,er!ical or com"ressi,e s!resses!o !he loer layers by #rain !ransfer !hro%#h con!ac! "oin!s of #ran%lar s!r%c!%re.

The ,er!ical com"ressi,e s!ress is ma/im%m on !he "a,emen! s%rface direc!ly %nder!he heel load and is e;%al !o con!ac! "ress%re %nder !he heels. 5%e !o !he abili!y !odis!rib%!e !he s!ress !o lar#e area in !he sha"e of !r%nca!ed cone !he s!resses #e! decreasedin !he loer layer.

As s%ch !he fle/ible "a,emen! may be cons!r%c!ed in a n%mber of layers and !he!o" layer has !o be s!ron#es! as !he hi#hes! com"ressi,e s!resses.

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To be s%s!ained by !his layer$ in addi!ion !o ear and !ear$ !he loer layer ha,e !o !ae%" only lesser ma#ni!%de of s!ress as !here is no direc! earin# ac!ion die !o !rafficloads$ !herefore inferior ma!erial i!h loer cas! can be %sed in !he loer layers.

Rigid pa+e$ent- Deinition

The ri#id charac!eris!ic of !he "a,emen! are associa!ed i!h ri#idi!y or fle/%ral s!ren#!h

or slab ac!ion so !he load is dis!rib%!ed o,er a ide area of s%b #rade soil. Ri#id "a,emen!is laid in slabs i!h s!eel reinforcemen!.

The ri#id "a,emen!s are made of cemen! concre!e ei!her "lan$ reinforced or"res!ressed concre!e.

Cri!ical condi!ion of s!ress in !he ri#id "a,emen! is !he ma/im%m fle/%rals!ress occ%rrin# in !he slab d%e !o heel load and !he !em"era!%re chan#es.

Ri#id "a,emen! is desi#ned and analyed by %sin# !he elas!ic !heory.

Ad+antages o Rigid &a+e$ent

(. Ri#id las!s m%ch$ m%ch lon#er i.e B1D years com"ared !o 8-(1 years offle/ible "a,emen!s.

0. In !he lon# r%n i! is abo%! half !he cos! !o ins!all and main!ain. F%! !he ini!ial cos!sare someha! hi#h.

B. Ri#id "a,emen! has !he abili!y !o brid#e small im"erfec!ions in !he s%b#rade.4. ess ain!enance cos! and Con!in%o%s Traffic and *lo.8. Hi#h efficiency in !erms of f%nc!ionali!y

+om2arison of lexible and Ri!id 9avement

(. 5eforma!ion in !he s%b #rade is!ransferred !o !he %""er layers

0. 5esi#n is based on loaddis!rib%!in# charac!eris!ics of!he com"onen! layers

B. Ha,e lo fle/%ral s!ren#!h

4. oad is !ransferred by #rain !o#rain con!ac!

8. Ha,e lo com"le!ion cos! b%!

re"airin# cos! is hi#h6. Ha,e lo life s"an

. '%rfacin# canno! be laid direc!lyon !he s%b #rade b%! a s%b baseis needed

(. 5eforma!ion in !he s%b #rade is no!!ransferred !o s%bse;%en! layers

0. 5esi#n is based on fle/%ral s!ren#!hor slab ac!ion

B. Ha,e hi#h fle/%ral s!ren#!h

4. No s%ch "henomenon of #rain !o#rain load !ransfer e/is!s

8. Ha,e lo re"airin# cos!b%! com"le!ion cos! is hi#h

6. ife s"an is more as com"are!o fle/ible

. '%rfacin# can be direc!ly laid on !hes%b #rade

7. Thermal s!resses are more ,%lnerable

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7. No !hermal s!resses are ind%ced as !o be ind%ced as !he abili!y !o con!rac!

!he "a,emen! ha,e !he abili!y !o and e/"and is ,ery less in concre!econ!rac! and e/"and freely :. Tha! hy e/"ansion

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i!"re 5: A t'2ical cement concrete batc$ mixin! 2lant

9ro2erties of fres$ concrete

Ideally a fresh concre!e sho%ld be orable$ sho%ld no! se#re#a!e or bleed d%rin#cons!r%c!ion. Cons!i!%en! "ro"er!ies$ !heir "ro"or!ions$ a##re#a!e sha"e and sies$!em"era!%re affec! !he "erformance of fresh mi/. The !es!s !ha! are cond%c!ed on freshconcre!e incl%de orabili!y !es! and air-con!en! !es!. 'ome of !es!s !hro%#h hichorabili!y of can be es!ima!ed are elly ball "ene!ra!ion !es!$ sl%m" !es!$com"ac!in# fac!or !es!$ ee bee !es! and flo !able !es! e!c.

+"rin! of concrete

3resence of ade;%a!e amo%n! of mois!%re$ a! some re;%isi!e !em"era!%re and for a s%i!able"eriod of !ime$ is necessary !o com"le!e !he hydra!ion "rocess of cemen!. This "rocess iscalled c%rin#. The c%rin# condi!ions si#nifican!ly affec! !he final s!ren#!h achie,ed by !heconcre!e. *or "a,emen! cons!r%c!ion$ only in-si!% c%rin# me!hods are a""licable. C%rin#com"o%nds are some!imes a""lied !o re!ain !he mois!%re a#ains! e,a"ora!ion. *or finalc%rin# of concre!e"a,emen!s con!in%o%s "ondin# or mois!ened hessain2 #%nny ba#s are%sed

&roperties o hardened !on!rete

Tes!s are cond%c!ed on hardened concre!e !o es!ima!e "ro"er!ies lie$ com"ressi,es!ren#!h$ !ensile s!ren#!h$ mod%l%s of r%"!%re$ elas!ic mod%l%s$ 3oissonMs ra!io$ cree" andshrina#e "erformance$ d%rabili!y$ !hermal e/"ansion coefficien! e!c. These "arame!ers

are of f%nc!ions of a##re#a!e !y"e$ sha"e and sie$ !y"e and ;%an!i!y of cemen! andadmi/!%res incor"ora!ed$ a!er cemen! ra!io$ c%rin#$ a#e e!c.

Com"ressi,e s!ren#!h of concre!e is !he fail%re com"ressi,e s!ress on c%bical orcylindrical sam"les of concre!e. Com"ressi,e s!ren#!h of concre!e is rela!ed !o !hecombined effec! of !em"era!%re and !ime$ a "arame!er called ma!%ri!y. a!%ri!y of

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concre!e is calc%la!ed as !he !ime of c%rin# &in ho%rs)$ m%l!i"lied by !he !em"era!%re$ &inde#rees) abo,e some s"ecified reference !em"era!%re. ario%s em"irical rela!ionshi"s ares%##es!ed !o ob!ain !he ,ario%s s!ren#!h "arame!ers of concre!e &elas!ic mod%l%s$ !ensiles!ren#!h$ bendin# s!ren#!h e!c.) from !he com"ressi,e s!ren#!h of concre!e.

5irec! !ension !es! on concre!e is "erformed by a""lyin# !ension !o !he cylindrical ord%mble sha"ed sam"les of concre!e. Indirec! !ension is a""lied !o concre!e sam"les bys"li! cylinder !es!.

od%l%s of r%"!%re of concre!e is es!ima!ed by meas%rin# !he ma/im%m bendin# s!resson concre!e beam s%b

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mee! !he demand of s"ecial "%r"ose ma!erials ha,in# s"ecific "ro"er!ies.E/am"le+ hi#h or lo "ermeabili!y$ enhanced shear s!ren#!h e!c

T$ese $ave been disc"ssed f"rt$er "nder to sections as8

binder &bi!%men) modifica!ion

a##re#a!e modifica!ion

esi!n 2arameters

The desi#n "arame!ers can be "rimarily di,ided in!o !hree ca!e#ories$ ma!erial$ !raffic anden,ironmen!al "arame!ers and are disc%ssed in !he folloin#.

*aterial 2arameters

The elastic modulus$ Poisson's ratio$ fatigue life$ modulus of rupture e!c. are !heen#ineerin# "arame!ers %sed for !he s!r%c!%ral desi#n of !he concre!e "a,emen!. The in"%!

"arame!ers are ei!her fo%nd o%! e/"erimen!ally or es!ima!ed from ,ario%srecommenda!ions "ro,ided in !he desi#n #%idelines &ACI 011($ A'T 011B$ I'-486).'!a!is!ically s%i!able desi#n ,al%e is !o be ado"!ed if !here are ,aria!ions in !he in"%!"arame!ers &Charobor!y and 5as 011B). The modulus of subgrade reaction &k) is#enerally %sed for charac!eria!ion of s%b#rade s!ren#!h. kin idealied model re"resen!s!he s"rin# cons!an! of a dense li;%id fo%nda!ion. The k,al%e is ob!ained by "erformin#"la!e load !es! on !he s%b#rade. The IRC+87 &0110) "ro,ides a !able i!h s%##es!ed k,al%es hen CBR ,al%es of s%b#rade are non. Concre!e slab$ in #eneral$ arecons!r%c!ed on bo%nd$ s!abilied$ or %nbo%nd s%b-base layer$ and no! direc!ly ons%b#rade. The s%b-base layer "ro,ided belo !he concre!e "a,emen! ser,es cer!ain"%r"oses &A%s!roads 0114)$ s%ch as$

(. I! "ro,ides %niform s%""or! !o !he concre!e slab.0. I! limi!s "%m"in# a!

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UNIT4;

Traffic 2arameters

esi!n life

5esi#n life is !he n%mber of years &or n%mber of s!andard a/le re"e!i!ions) for hich !he"a,emen! is bein# desi#ned. A "a,emen! is e/"ec!ed !o ser,e sa!isfac!orily i!hin !hedesi#n life. *or concre!e "a,emen!s 01 !o 41 years may be ass%med as !he desi#n life&3CA (:74$ IRC+87 0110).

Basic desi!n 2rinci2le

Tho%#h differen! a""roaches for concre!e "a,emen! desi#n are s%##es!ed in ,ario%s#%idelines$ !he desi#n "rinci"les !end !o remain similar across differen! #%idelines$ fore/am"le$ 3CA &(::4)$ A%s!roads &0114)$NCHR3 &0114)$ IRC+87 &0110)e!c.$ e/ce"! !heAA'HT= &(::B) "ro,isions$ hich is based on em"irical a""roach. The basic s!e"sin,ol,ed in !he desi#n of concre!e "a,emen! me!hod can be s%mmaried as follos+

The de,elo"ed s!ressesd%e !o load for a !rial !hicness of !he concre!e slab arecalc%la!ed for ,ario%s loadin# confi#%ra!ion and !he cri!ical one is chosen. Thea/le loads are #enerally di,ided in!o differen! a/le load #ro%"s and !he loads!resses are calc%la!ed indi,id%ally.

The ra!io be!een !he load s!ress and Modulus of Rupture &=R) is non asstress ratio . The s!ress ra!io de!ermines ho many re"e!i!ions !he "a,emen! cans%s!ain &i.e. allowable traffic repetitions) for !he indi,id%al a/le load #ro%". If !hes!ress ra!io is 1.88 or loer$ i! can i!hs!and ,ir!%ally infini!e n%mber of !rafficre"e!i!ions &3CA (:74).

The ra!io be!een !he alloable re"e!i!ions !o !he epected traffic repetitions is

!he damage fraction. The calc%la!ion "rocess is re"ea!ed for ,ario%s a/le loads&some!imes$ for ,ario%s seasons$ or ,ario%s !imin#s of !he day)$ and !he s%m ofindi,id%al dama#e frac!ions & cumulative fatigue damage) sho%ld be less !hane;%al !o one for "a,emen! desi#n bein# safe. If fo%nd %nsafe$ !he !rial !hicness ischan#ed and !he desi#n "rocess is re"ea!ed.

The desi#n "rocess may also incl%de considera!ions for !em"era!%re s!ress$mois!%re s!resses$ and erosion dis!ress.

A brief disc%ssion on concre!e "a,emen! desi#n a""roaches s%##es!ed by ,ario%s desi#n"rac!ices$ vi!"3CA me!hod &(:74)$ A%s!roads me!hod &0114)$ AA'HT= me!hod &(::B)$NCHR3 mechanis!ic-em"irical me!hod &0114) and !he Indian Roads Con#ress &IRC)me!hod &0110) are "laced in !he folloin#+

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9ortland +ement Association (9+A) *et$od

The 3CA me!hod is based on Wes!er#aard$ 3ice! and RayMs or and f%r!her !heore!icalanalysis by *ini!e Elemen! e!hod &H%an# (::B). The da!a %sed !o de,elo" !he 3CAme!hod is #enera!ed from ,ario%s road !es!s$ lie$ A''H= road !es!$ Arlin#!on !es!&cond%c!ed by 3CA)$ Fa!es !es! road$ and aryland road !es! &3CA (:74). The 3CAdesi#n me!hod is based on !he folloin# !o considera!ions &3CA (:74)+

The fa!i#%e dama#e on !he concre!e slab$ d%e !o re"e!i!i,e a""lica!ion of !rafficload is es!ima!ed. The c%m%la!i,e fa!i#%e dama#e "rinci"le is %sed !o es!ima!e !hedesi#n !hicness of !he slab. Ed#e s!ress be!een !he mid-ay of !he !rans,erse

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i!"re41< c$ematic dia!ram of A"stroads (-==/) c$art for estimation of effectives"b!rade stren!t$

As "er As!roads &0114)$ !he concre!e "a,emen! slab !hicness$ for a #i,en e/"ec!ed!raffic re"e!i!ions$ is desi#ned considerin# !he &i) fle/%ral fa!i#%e of !he concre!e slab and!he &ii) s%b#rade erosion arisin# o%! of re"ea!ed deflec!ions. *or bo!h !he considera!ions$e;%a!ions are s%##es!ed !o calc%la!e !he alloable !raffic re"e!i!ions. If !he alloable!raffic is less !han !he e/"ec!ed !raffic$ !he desi#n is re,ised by increasin# !he slab!hicness. The concre!e sho%lders ado"!ed are of in!e#ral !y"e or s!r%c!%ral !y"e .

AA%TO met$od

The AA'HT= me!hod &(::B) for desi#n of concre!e "a,emen! has e,ol,ed from !heAA'H= road !es! &AA'H= (:60). The AA'HT= "a,emen! desi#n follos an em"iricala""roach. 3a,emen! "erformance in !erms of "resen! ser,iceabili!y inde/ &P#$)$ loss ofser,iceabili!y$ s%b-#rade and s%b-base s!ren#!h$ c%m%la!i,e !raffic$ "ro"er!ies ofconcre!e$

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The NCHR3 &0114) has recen!ly de,elo"ed concre!e "a,emen! desi#n "roced%re based

on mechanis!ic-em"irical &-E) a""roach. This a""roach a!!em"!s !o red%ce !he e/!en! of

em"iricism "re,alen! in !he e/is!in# AA'HT= &(::B) #%idelines. This "ro"osed NCHR3"a,emen! desi#n sys!em is mod%lar in na!%re$ !ha! is$ !he desi#n a""roach can be

modified by "ar!s &as and hen ne noled#e is a,ailable) i!ho%! disr%"!in# !he

o,erall desi#n "roced%re. This a""roach also can !ae care of ,ario%s heel-a/le load

confi#%ra!ion &han%m e! al. 0114). As "er !his a""roach !rial !hicness of !he slab is firs!ass%med$ and !he s!ress$ s!rain and dis"lacemen! ,al%es are ob!ained. *rom !hese ,al%es$

!he "erformance of !he "a,emen! in !erms of dis!resses &s%ch as fa%l!in#$ cracin#) andsmoo!hness and "redic!ed. If !hese "redic!ed "erformance "arame!ers does no! sa!isfy !he

re;%ired "erformance for a #i,en reliabili!y$ !he desi#n re,ised. The desi#n a""roach

incl%des a lar#e da!a-base as in"%! "arame!ers$ for e/am"le$ a,era#e daily !raffic$ !raffic

#ro!h ra!e$ !raffic com"osi!ion$ ho%rly ea!her da!a on air !em"era!%re$ "reci"i!a!ion$ind s"eed$ "ercen!a#e s%nshine$ rela!i,e h%midi!y$ "a,emen! ma!erial en#ineerin#

"arame!ers$ #ro%nd a!er de"!h$ infil!ra!ion$ draina#e$ hydra%lic cond%c!i,i!y$ !hermal

cond%c!i,i!y$ hea! ca"aci!y e!c. The !em"era!%re s!ress is considered in !his me!hod$ b%!!he !em"era!%re "rofile is linearied !o enhance com"%!a!ional efficiency &NCHR3 0114).

Indian Roads +on!ress (IR+) met$od

The Indian Roads Con#ress &IRC) #%idelines$ IRC+87 &0110)$ has ado"!ed !heWes!er#aardMs e;%a!ion !o es!ima!e load s!ress and Frdab%ryMs e;%a!ion !o es!ima!e!em"era!%re s!ress. The load s!ress is hi#hes! a! !he corner of !he slab$ lesser in ed#e andleas! in !he in!erior. The order of ,aria!ion of !em"era!%re s!ress is

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es!ima!ion of corner s!ress d%e !o load$ and !he corner s!ress d%e !o !em"era!%reis ass%med !o be ero.

i!"re4-= c$ematic dia!ram of IR+:;> c$art for estimation of load stress at t$eed!e (IR+:;> -==-)

&stimation of la'er t$icknesses

The !hicness of !he "a,emen! is ad

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i!s !o" s%rface and needs !o be !aen o%! of !he "a,emen! - !his is done by "ro,idin# anin!ernal draina#e sys!em !o !he "a,emen!. Wa!er ill also !ry !o en!er in!o !he "a,emen!from bo!!om d%e !o ca"illary rise or d%e !o rise in a!er !able. A s%i!ably desi#ned s%b-s%rface draina#e sys!em !ries !o a,oid s%ch a "roblem.

9avement t$ickness desi!n c$arts

*or !he desi#n of "a,emen!s !o carry !raffic in !he ran#e of ( !o (1 msa$ %se char! ( andfor !raffic in !he ran#e (1 !o (81 msa$ %se char! 0 of IRC+B 011(. The desi#n c%r,esrela!e "a,emen! !hicness !o !he c%m%la!i,e n%mber of s!andard a/les !o be carried o,er!he desi#n life for differen! s%b-#rade CFR ,al%es ran#in# from 0 9 !o (1 9. The desi#nchar!s ill #i,e !he !o!al !hicness of !he "a,emen! for !he abo,e in"%!s. The !o!al!hicness consis!s of #ran%lar s%b-base$ #ran%lar base and bi!%mino%s s%rfacin#. Theindi,id%al layers are desi#ned based on !he !he recommenda!ions #i,en belo and !hes%bse;%en! !ables.

9avement com2osition

"b4base

'%b-base ma!erials com"rise na!%ral sand$ #ra,el$ la!eri!e$ bric me!al$ cr%sheds!one or combina!ions !hereof mee!in# !he "rescribed #radin# and "hysicalre;%iremen!s. The s%b-base ma!erial sho%ld ha,e a minim%m CFR of 01 9 andB1 9 for !raffic %"!o 0 msa and !raffic e/ceedin# 0 msa res"ec!i,ely. '%b-base%s%ally consis! of #ran%lar or WF and !he !hicness sho%ld no! be less !han (81mm for desi#n !raffic less !han (1 msa and 011 mm for desi#n !raffic of (+1 msaand abo,e.

Base

The recommended desi#ns are for %nbo%nded #ran%lar bases hich com"risecon,en!ional a!er bo%nd macadam &WF) or e! mi/ macadam &W) ore;%i,alen! confirmin# !o ='T s"ecifica!ions. The ma!erials sho%ld be of #ood;%ali!y i!h minim%m !hicness of 008 mm for !raffic %" !o 0 msa an (81 mm for!raffic e/ceedin# 0 msa.

Bit"mino"s s"rfacin!

The s%rfacin# consis!s of a earin# co%rse or a binder co%rse "l%s earin# co%rse.The mos! commonly %sed earin# co%rses are s%rface dressin#$ o"en #raded"remi/ car"e!$ mi/ seal s%rfacin#$ semi-dense bi!%mino%s concre!e and

bi!%mino%s concre!e. *or binder co%rse$ ='T s"ecifies$ i! is desirable !o %sebi!%mino%s macadam &F) for !raffic %"!o o 8 msa and dense bi!%mino%smacadam &5F) for !raffic more !han 8 msa.

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N"merical exam2le

5esi#n !he "a,emen! for cons!r%c!ion of a ne by"ass i!h !he folloin# da!a+

(. To lane carria#e ay

0. Ini!ial !raffic in !he year of com"le!ion of cons!r%c!ion J 411 C35 &s%m of

bo!h direc!ions)B. Traffic #ro!h ra!e J .8 94. 5esi#n life J (8 years

8. ehicle dama#e fac!or based on a/le load s%r,ey J 0.8 s!andard a/le"er commercial ,ehicle

6. 5esi#n CFR of s%b#rade soil J 49.

Solution

(. 5is!rib%!ion fac!or J 1.8

0.

B. To!al "a,emen! !hicness for CFR 49 and !raffic .0 msa from IRC+B011( char!( J 661 mm

4. 3a,emen! com"osi!ion can be ob!ained by in!er"ola!ion from 3a,emen! 5esi#nCa!alo#%e &IRC+B 011().

(. Fi!%mino%s s%rfacin# J 08 mm '5FC D 1 mm 5F0. Road-base J 081 mm WFB. s%b-base J B(8 mm #ran%lar ma!erial of CFR no! less !han B1 9

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i!. / 9ro2a!ation of fati!"e crackin!

o The horion!al !ensile s!ress2 s!rain a! !he bo!!om of bo%nd layer&bi!%mino%s s%rfacin#$ cemen!ed base or concre!e slab$ as !he case maybe) is %sed as !he #o,ernin# "arame!er for fa!i#%e fail%re.

o Con,en!ionally$ for desi#n of concre!e "a,emen! s!ress is %sed as"arame!er$ and for desi#n of bi!%mino%s "a,emen! s!rain is %sed as"arame!er.

o R"ttin!: R%!!in# is !he acc%m%la!ion of "ermanen! deforma!ion. This is!he manifes!a!ion of #rad%al densifica!ion of "a,emen! layers$ and sheardis"lacemen! of !he s%b#rade.

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i! ;. evelo2ment of R"ttin!

o The ,er!ical s!rains on !he "a,emen! layers$ mainly !he ,er!ical s!rain on!he s%b#rade is ass%med !o be #o,ernin# fac!or for r%!!in# fail%re.

o The r%!!in# iss%e is no! considered for concre!e "a,emen! desi#n$ beca%sei! does no! ha,e any "ermanen! deforma!ion.

The fa!i#%e2 r%!!in# e;%a!ions are de,elo"ed from field or labora!ory s!%dies$here fa!i#%e 2 r%!!in# li,es are ob!ained i!h res"ec! !o res"ec!i,e s!ress2 s!rainfor fa!i#%e2 r%!!in#. *or a #i,en desi#n life$ !h%s$ alloable fa!i#%e and r%!!in#s!ress2 s!rains can be es!ima!ed %sin# !he fa!i#%e2 r%!!in# e;%a!ions.

The ,ario%s o!her !y"es of "a,emen! fail%res co%ld be shrina#e$ !hermal fa!i#%e$!o" don cracin# &for bi!%mino%s "a,emen!) e!c.

+oncrete 2avement

Concre!e "a,emen! is$ in #eneral$ consis!s of !hree layers$ s%b#rade$ base layerand !he concre!e slab.

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Generally bo%nd base layers are %sed for concre!e "a,emen! cons!r%c!ion. As "erIndian s"ecifica!ion$ some e/am"le of s%ch base layers are 5ry ean Concre!e&5C)$ Roller Com"ac!ed Concre!e &RCC) &IRC+(8-0110)

The concre!e slab is #enerally of 41 !o 81 #rade of concre!e as "er Indians"ecifica!ions$ and is called as "a,in# ;%ali!y concre!e &3C) &IRC+(8-0110).

Bit"mino"s 2avement

The s%b#rade is a com"ac!ed soil layer.

The base and s%b-base co%rse co%ld be made %" of bo%nd or %nbo%nd #ran%lar layer. As "ers"ecifica!ions &=RTH 011()$ some e/am"les of base or s%b-base layers are+ Gran%lbase&G'F)$ Wa!er Fo%nd acadam &WF)$ We! i/ acadam &W) e!c.

The binder co%rse is made %" bi!%mino%s ma!erial. As "er Indian s"ecifica!ions &=RTHsome e/am"les of binder co%rse are+ Fi!%mino%s acadam &F)$ 5ense Fi!%mino%s &5F) e!c.

The earin# co%rse is !he !o" bi!%mino%s layer hich is comes in con!ac! !o !he ,ehicWearin# co%rse "ro,ides im"ermeabili!y !o !he "a,emen! s%rface a#ains! a!er "erc&Charobor!y and 5as 011B). The binder co%rse and earin# co%rse !o#e!her are called bi!%s%rfacin#.

IR+ *&T%O O 7&?IB7& 9A#&*&NT *I? &I6N

These #%idelines ill a""ly !o desi#n of fle/ible "a,emen!s for E/"ressay$ Na!ionalHi#hays$ '!a!e Hi#hays$ a

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i!hin !he alloable limi!s. *or calc%la!in# !ensile s!rains a! !he bo!!om of !hebi!%mino%s layer$ !he s!iffness of dense bi!%mino%s macadam &5F) layer i!h 6121bi!%men has been %sed in !he analysis.

ail"re +riteria

+ritical locations in 2avement

A and F are !he cri!ical loca!ions for !ensile s!rains . a/im%m ,al%e of !he s!rain is

ado"!ed for desi#n. C is !he cri!ical loca!ion for !he ,er!ical s%b#rade s!rain since !he

ma/im%m ,al%e of !he occ%rs mos!ly a! C.

atigue Criteria(

Fi!%mino%s s%rfacin#s of "a,emen!s dis"lay fle/%ral fa!i#%e cracin# if !he !ensiles!rain a! !he bo!!om of !he bi!%mino%s layer is beyond cer!ain limi!. The rela!ion be!een!he fa!i#%e life of !he "a,emen! and !he !ensile s!rain in !he bo!!om of !he bi!%mino%s

layer as ob!ained as

&()

in hich$ is !he alloable n%mber of load re"e!i!ions !o con!rol fa!i#%e cracin# and

is !he Elas!ic mod%l%s of bi!%mino%s layer. The %se of e;%a!ion (o%ld res%l! in

fa!i#%e cracin# of 019 of !he !o!al area.

Rutting CriteriaThe alloable n%mber of load re"e!i!ions !o con!rol "ermanen! deforma!ion can bee/"ressed as

&0)

is !he n%mber of c%m%la!i,e s!andard a/les !o "rod%ce r%!!in# of 01 mm.

esi!n 2roced"re

Fased on !he "erformance of e/is!in# desi#ns and %sin# analy!ical a""roach$ sim"le desi#nchar!s and a ca!alo#%e of "a,emen! desi#ns are added in !he code. The "a,emen! desi#ns are#i,en for s%b#rade CFR ,al%es ran#in# from 09 !o (19 and desi#n !raffic ran#in# from (msa !o (81 msa for an a,era#e ann%al "a,emen! !em"era!%re of B8 C. The

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la!er !hicnesses ob!ained from !he analysis ha,e been sli#h!ly modified !o ada"! !hedesi#ns !o s!a#e cons!r%c!ion. ?sin# !he folloin# sim"le in"%! "arame!ers$a""ro"ria!e desi#ns co%ld be chosen for !he #i,en !raffic and soil s!ren#!h+

5esi#n !raffic in !erms of c%m%la!i,e n%mber of s!andard a/les and

CFR ,al%e of s%b#rade.

esi!n traffic

The me!hod considers !raffic in !erms of !he c%m%la!i,e n%mber of s!andard a/les&7(61 #) !o be carried by !he "a,emen! d%rin# !he desi#n life. This re;%ires !hefolloin# informa!ion+

(. Ini!ial !raffic in !erms of C35

0. Traffic #ro!h ra!e d%rin# !he desi#n life

B. 5esi#n life in n%mber of years4. ehicle dama#e fac!or &5*)

8. 5is!rib%!ion of commercial !raffic o,er !he carria#e ay.

Initial traffic

Ini!ial !raffic is de!ermined in !erms of commercial ,ehicles "er day &C35). *or !hes!r%c!%ral desi#n of !he "a,emen! only commercial ,ehicles are considered ass%min#laden ei#h! of !hree !onnes or more and !heir a/le loadin# ill be considered.Es!ima!e of !he ini!ial daily a,era#e !raffic flo for any road sho%ld normally be basedon -day 04-ho%r classified !raffic co%n!s &A5T). In case of ne roads$ !raffic es!ima!escan be made on !he basis of "o!en!ial land %se and !raffic on e/is!in# ro%!es in !he area.

Traffic !rot$ rate

Traffic #ro!h ra!es can be es!ima!ed &i) by s!%dyin# !he "as! !rends of !raffic #ro!h$

and &ii) by es!ablishin# econome!ric models. If ade;%a!e da!a is no! a,ailable$ i! isrecommended !ha! an a,era#e ann%al #ro!h ra!e of .8 "ercen! may be ado"!ed.

esi!n life

*or !he "%r"ose of !he "a,emen! desi#n$ !he desi#n life is defined in !erms of !hec%m%la!i,e n%mber of s!andard a/les !ha! can be carried before s!ren#!henin# of !he"a,emen! is necessary. I! is recommended !ha! "a,emen!s for ar!erial roads lie NH$ 'Hsho%ld be desi#ned for a life of (8 years$ EH and %rban roads for 01 years and o!herca!e#ories of roads for (1 !o (8 years.

#e$icle ama!e actor

The ,ehicle dama#e fac!or &5*) is a m%l!i"lier for con,er!in# !he n%mber of commercial,ehicles of differen! a/le loads and a/le confi#%ra!ions !o !he n%mber of s!andard a/le-load

re"e!i!ions. I! is defined as e;%i,alen! n%mber of s!andard a/les "er commercial ,ehicle.The 5* ,aries i!h !he a/le confi#%ra!ion$ a/le loadin#$ !errain$ !y"e of road$ and from

re#ion !o re#ion. The a/le load e;%i,alency fac!ors are %sed !o con,er! differen! a/le loadre"e!i!ions in!o e;%i,alen! s!andard a/le load re"e!i!ions. *or

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!hese e;%i,alency fac!ors refer IRC+B 011(. The e/ac! 5* ,al%es are arri,ed af!ere/!ensi,e field s%r,eys.

#e$icle distrib"tion

A realis!ic assessmen! of dis!rib%!ion of commercial !raffic by direc!ion and by lane isnecessary as i! direc!ly affec!s !he !o!al e;%i,alen! s!andard a/le load a""lica!ion %sed in!he desi#n. ?n!il reliable da!a is a,ailable$ !he folloin# dis!rib%!ion may be ass%med.

in!le lane roads: Traffic !ends !o be more channelied on sin#le roads !han !olane roads and !o allo for !his concen!ra!ion of heel load re"e!i!ions$ !he desi#nsho%ld be based on !o!al n%mber of commercial ,ehicles in bo!h direc!ions.

To4lane sin!le carria!ea' roads: The desi#n sho%ld be based on 8 9 of!hecommercial ,ehicles in bo!h direc!ions.

o"r4lane sin!le carria!ea' roads: The desi#n sho%ld be based on 41 9 of!he!o!al n%mber of commercial ,ehicles in bo!h direc!ions.

"al carria!ea' roads: *or !he desi#n of d%al !o-lane carria#eay roadssho%ld be based on 8 9 of !he n%mber of commercial ,ehicles in eachdirec!ion. *or d%al !hree-lane carria#eay and d%al fo%r-lane carria#eay !hedis!rib%!ion fac!or ill be 61 9 and 48 9 res"ec!i,ely.