5. hill roads 073.pptx

7/25/2019 5. Hill Roads 073.pptx

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5. Hill Roads

80 @ 10% = 8 Marks


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Topics As Per Syllabus

5.1 Introduction

5.2 Special Consideration in Hill Roads

5.2.1 Alignment of Hill Road Design: General ConRoute ocation in Hills, Gradient, Design and !"#in $ends, Di%erent !"pes of Hill Road Cross&sec

5.' Special Structures in Hill Roads

5.'.1 !"pes of Retaining Structures, Ri(er !raining andslide Sta)ili*ation Structures and GulStructures


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1. I!roduc!io

A +ill road is usuall" dened on t+e )asis of terrain.

As per -RS t+e cross slope ma" )e classied as:

Hill road&one +ic+ passes t+roug+ terrain it+ cros25/ or more i.e. mountainous or steep.

!+ere are sections along +ill road it+ cross slope le

25/, esp. +en t+e road follos ri(er route.


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"#y Hill Road i $epal

-epal area 0 1, s3. 4m appro.


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,0% popula!io reside i #illy areas ad depa-ro produc!s.


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r(ays* Rail(ays* Air(ays 'e $o! Possible o


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Hilly Re-ios !re+es o2 3li+a!ic 34icul! ad Haardous Terrai* Topo-rap#yHi-# Al!i!ude Areas


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3#alle-es o2 Hilly Areas6 7loods* aSo(2all* e!c. 7airly "ea!#ered Roads Poss


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9u! Hilly Areas Ric#6 i $a!ural Resources* 7l7aua I+por!a! !o lauc# de'elop+e! Pr;e.-. Hydropo(er* e!c.


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7or Traspor!* coo+y* Social Reasos 3os!ruc!io o2 Hill Roads i !#e Hilly Re-io


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re Tuels* /iaduc! Possible bu! $o! coo+i


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"#y Hill Road i $epal

-epal area 0 1, s3. 4m appro.

66/ co(ered it+ t+inl"7sparsel" populated +ills, mountains. 8/ population reside in +ill" areas and depends on agro produc

9atera"s, raila"s, aira"s dicult

Hill" Regions ;tremes of Climatic Conditions, Dicult an!errain, !opograp+" and ects ?e.g. H"dropoer, etc.@, tourism, et

=or !ransport, ;conom", Social Reasons ustif" t+e ConstrRoads in t+e Hill" Regions.

9+ere !unnels,


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5.> Special 3osidera!ioHill Roads


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5.>.1 4esi- ad 3os!ruc!io ProbleHill Roads

C+aracteri*ed )" a +ig+l" )ro4en relief it+ idel" di%erinand steep slopes, deep gorges and se(eral ateunnecessaril" increase in road lengt+

Comple geolog" di%erent roc4 )ed geolog" di%ers fplace assessment for road foundation is not eas"

;n(ironmental impact remo(al of (egetation etc. sta)c+ange to unsta)le slope after road construction

Great


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1. 3#arac!eried by a #i-#ly broke relie2 (i4i?eri- le'a!ios ad S!eep Slopes* 4eead Se'eral "a!ercourses ecessarilyi Road e-!#


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>. 3o+ple eolo-y 4i?ere! Rock 9ed eolo-y place !o place Assess+e! 2or road 2ouda!io i


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B. 'iro+e!al i+pac! re+o'al o2 'e-e!a!s!able slope +ay c#a-e !o us!able slope acos!ruc!io


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C. rea! /aria!io i #ydrolo-ical codi!io place !o place ladslides* soil erosio +da+a-es a2!er road cos!ruc!io

5 $ !# Dll 2 d b k !


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5. $e( ear!# Dll 2or road e+bak+e! +ay o'erela!i'ely (eak uderlyi- soil layer o #ill slo!ri--er e( ad recurre! slides


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&. ReEuires is!alla!io o2 'arious !ypes 'arious road s!ruc!ures cos! +ay rise up!o 5!o!al cos!ruc!io


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G. S!eep slopes #i-# speed o2 sur2ace pro'isio o2 erosio pro!ec!io (orks


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8. 3os!ruc!io alo- rela!i'ely s+all s!re!c#es di?ere! cos!ruc!io !ec#olo-eeded

, $ d 2 i l 2 ! !i d i


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,. $eed o2 special sa2e!y precau!io duri-cos!ruc!io


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10. 7reEue! blas!i-

11 4 i 2 # i i b d ! ! # i #!


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11. 4esi- o2 #airpi beds !o -e! #ei-#!s

5 > 1 4 i d 3 ! !i P bl


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5.>.1 4esi- ad 3os!ruc!io ProbleHill Roads

1. C+aracteri*ed )" a +ig+l" )ro4en relief it+ idel" di%erinand steep slopes, deep gorges and se(eral ate

unnecessaril" increase in road lengt+

2. Comple geolog" di%erent roc4 )ed geolog" di%ers fplace assessment for road foundation is not eas"

'. ;n(ironmental impact remo(al of (egetation etc. ma" c+ange to unsta)le slope after road construction

. Great


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6. Re3uires installation of (arious t"pes of special 'arious ros!ruc!ures cost ma" rise upto 5 & 6/ of total constructi

. Steep slopes +ig+ speed of surface runo% pro(ision of

protection or4s

E. Construction along relati(el" small approac+ stretc+es dconstruction tec+nolog" ma" )e needed

8. -eed of special safet" precaution during +ill road construct

1.


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!" #$% %& ' *+ ) ,, - .%) /#

+ttp:77)it.l"71#E-rd2


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5.>.> Special 3osidera!io i Hill R

1. Selection of Road Alignment

2. Special Geometric Standards ?Gradient and Hari #

'. Cross&section Design

. Design of Drainage Structures ?Special StructuresRe3uire@

5. Sta)ilit" of Slopes


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1. Selec!io o2 Road Ali-+e!

Alignment t+roug+ +ill" areas is slig+tl" di%erent from aligniFat terrain.

=or t+e purpose of ecient and safe operation of (e+icles t+terrain special care s+ould )e ta4en +ile aligning t+e +ig+a"

Aim of Hill Roads: Alignment s+ould )e & s+ort, eas", econoline of communication )eteen t+e o)ligator" points conp+"sical features of t+e region and trac needs as distur)ance to eco&s"stem

Ideal Road Alignment: one +ic+ ill cause t+e least o(erall tcost ta4ing into account t+e costs of construction, mainrecurring cost of (e+icle operation.


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Re3uirement of +ill roads: decided )ased on: AdmDe(elopmental, Strategic, t+er -eeds and t+e #oints to )e connected )" t+e road.

Control points )eteen t+e )ligator" #oints: #asseRi(er Crossings,


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Route s+ould a(oid t+e introduction of +air pin )as possi)le.

If suc+ a situation )ecomes ine(ita)le, t+e num+airpin )ends s+ould )e reduced to a)solute mint+e ine(ita)ilt" of eac+ +airpin )end s+ould )e rt+e reconnaissance report.

Hair pin )ends s+ould )e located on sta)le and Faand t+eir location in (alle"s s+ould )e a(oided.

A series of +air pin )ends on t+e same face of t+e

)e a(oided.


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d G d f i +i l


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Adopt ;as" Grades: econom" of operating (e+icles

Jinimi*e Rise and =all: )" folloing a direct line

possi)le )eteen t+e o)ligator" points

S+ortest Distance is an Important =actor: it ma" sacriced in order to o)tain eas" cur(atures and ga(oid pro+i)iti(e cuts and lls and long ri(er crossi

;(en a longer road lengt+ to eas" gradient and cresult in a more economical operating cost.


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SeEueces o2 Sur'ey Me!#od i Hill R

a@ Jap Stud"

)@ Reconnaissance

c@ #reliminar" Sur(e"

d@ Determination of =inal Center ine

e@ =inal ocation Sur(e"Aerial Sur(e", #+otogrammetr" and Remote Sensita4en to facilitate sur(e"ing for selection of alignment


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Alignment survey

Reconnaissance&

!entati(e alignment after map stud"&topograp+igeological and meteorological

!race cut&

route selected in step 1 is translated on t+e groupro(ide an access for su)se3uent detailed sur(e1.2 m ide trac4 is constructed it+ easier grad


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Detailed survey

=iing of )enc+ mar4s

Cross section and longitudinal sections K 15 m on sm at s+arp cur(es

Design of +ori*ontal cur(es and +air pin )ends

Soil in(estigation, geolog", +"drolog" stud"

7ac!ors A?ec!i- Selec!io o2 Ali-+e


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7ac!ors A?ec!i- Selec!io o2 Ali-+eMou!aious ad Hilly Areas

=olloing points to )e considered +ile aligning t+e +ill roads:

i< Te+pera!ure

)!emperature of air (aries in(ersel" it+ altitude Air temperature t+an in


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ii< Rai2all

) Amount of rainfall in +ill" region is in(ersel" proportional to tAs t+e ele(ation increases rainfall also increases.

) In +ill" regions, ind often Fos along t+e (alle" and

conse3uence of +ic+ t+e rainfall in t+e (alle" is su)stantialon +ig+&lands and ater&s+eds.

) Also, maimum rainfall occurs in fe mont+s onl". So t+esituation create t+e pro)lem in construction and maintenanc

) Jaimum rainfall

o)

Lone of intensi(e cloud formation ?15 25 m a)o(e tle(el@

o) 6 mm increase in rainfall for e(er" 1 m of ele(ation

) In summer t+ere is (er" +ea(" rainfall +a(ing serious construction and maintenance of roads

iii< A! # i P d "i d


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iii< A!+osp#eric Pressure ad "ids

Atmosp+eric pressure is in(ersel" proportional to adecreases it+ increase in ele(ation

At +ig+ altitudes ?' m@:o9ind (elocit" is fre3uentl" coming at 25 ' m7s

o=ree*ing temperatures

oDept+ of frost penetration 1.5 2. m

!+e c+ange in c+aracter of ind is due to di%erence of atmosp+eric pressure in (alle"s and opasses.

!+erefore, t+ere is intensi(e roc4 eat+ering and alcontri)utes to t+e damage of lo cost road pa(emen

i'< eolo-ical 3odi!ios


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i'< eolo-ical 3odi!ios

Hori*ontal or almost (ertical stratication of roc4

!+e tendenc" of sedimentar" roc4s is to slip

inFuence of force parallel to t+e la"er.!+e degree of sta)ilit" of +ill slopes depends upon roc4, t+e degree of strata inclination or dip, t+e occla" seem, t+e +ardness of roc4 and presence of gro

!+e insta)ilit" of road ma" )e due to ground ater

and unsta)le folds.

!+erefore e s+ould follo t+e sta)le slope it+ater and t+e alignment s+ould pass t+roug+ t+e t+e dip of strata is as small as possi)le.

'< Rou!e loca!io


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omsom ?nepal@, annapurnas, cli%, dirt roa


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3#arac!eris!ics

1 ocation: along a ri(er (alle"


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1. ocation: along a ri(er (alle"

2. Jost fre3uent case of +ill road alignment

'. Comparati(el" gentle gradient

Meri!s

a. Ser(es t+e rural settlement

). o (e+icle operating cost, a(aila)ilit" of ater and ot+er constrmaterials

4e+eri!s

c. -umerous +ori*ontal cur(es

d. Construction of special retaining and protection of alls on t+e +

e. ;tensi(e eart+or4

f. Construction of large num)er of cross drainage structures

g. Steep sloping +ill side ma" )e insucientl" sta)le

+. Jassi(e ri(er training and protection or4s on t+e ri(er side.

b< Rid-e Rou!e


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b< Rid-e Rou!e

A ridge route is c+aracteri*ed )" (er" steepnumerous s+arp cur(es including +air pin )end

epensi(e roc4 or4s.& !+e road usuall" follos t+e top section of t+e +ill crosses successi(el" mountain pass.

& Geologicall" sta)le and comparati(el" mild slope sselected for t+e articial de(elopment of t+e route.


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arge num)er of s+arp cur(es including +airpin )e

;tensi(e roc4 or4s

Construction of special structures

-ecessit" of long lengt+ aa" from t+e air route

Geologicall" sta)le and comparati(el" mild slope sselected


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Ri'er Rou!e

Ser(es rural settlement situated Rid-e Rou!


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Ser(es rural settlement situatednet to t+e ater course

o (e+icle operation cost

A(aila)ilit" of constructionmaterial and ater

In(ol(es numerous +ori*ontalcur(es, construction of large)ridges

Special retaining protection on+ill sides

Ri(er training or4s ma" )eetensi(e& toe cutting, etc.

-

Steep gradient, s+arp cur(e

;pensi(e roc4 o

Route clim)s up contin(alle" till mountain pas

Construction of special strus

Are mo

>. eo+e!ric S!adards


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Geometric standards folloed in +ill" areas are di%erent from

plain terrain. Roads in t+e +ill" areas re3uire special attention in ing up t

for geometric design )ecause of (arious factors: t"pes of (e+icroads, total dail" tonnage, dicult" in construction, t"pe of spro(ided, topograp+" of t+e area, etc.

Alignment c+osen s+ould ena)le t+e ruling gradient to )eminimum of t+e lengt+, minimi*ing steep gradient, +airpinneedless rise and fall.

Hill roads +a(e to negotiate t+roug+ dicult topograp+", in+ospita)le terclimatic conditions.


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!+erefore geometric design standards of +ill roads s+ould )e decided considesafet" and free Fo of trac and for t+is uniform design standard s+ould )e fo

!+e use of optimum design standards ill reduce t+e possi)ilit" of earl" o)facilities.

Geometric features of a +ig+a" ecept cross sectional elements do nconstruction.

Impro(ement of features li4e grade and cur(ature at a later date can )e (esometimes )e impossi)le.

It is t+erefore necessar" t+at ultimate geometric re3uirements of +ill roads at+e )eginning.

De(elopment of cross section in stages is tec+nicall" feasi)le )ut t+is s+oulafter careful consideration since +ill roads need a lot of protecti(e and drretaining alls, )reast alls, drains of (arious categories, etc. consistentsometimes t+e road ma" +a(e to )e altoget+er re)uilt +en same is upgraded

If stage construction is una(oida)le it is )etter to use dr" masonr" and7or cdrains, )reast alls, pitc+ing, etc. locate t+e intercepting drains ell )ac4 at pro(ide cul(erts to full idt+ of formation7roada" to a(id t+e need fsu)se3uentl".


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Si-#! 4is!ace


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- n +ill roads stopping sig+t distance is a)solute

from safet" angle and must )e ensured regardlot+er considerations.

It ould )e a good practice if t+is (alue can )e e(isi)ilit" corresponding to intermediate sig+pro(ided in as muc+ lengt+ of road as possi)le.

If t+is is t+e case t+en t+e dri(er ill )e a)le to get

opportunities to o(erta4e it+ caution and d)ecomes muc+ easier.

It is not normall" feasi)le or practica)le on +ipro(ide o(erta4ing sig+t distance.


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3a+ber


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Cross fall for eac+ s+oulder s+ould )e at least t+an t+e pa(ements cam)er su)>ect to a minimum

If t+e s+oulders are pa(ed, cross fall appropriate tof pa(ed surface as gi(en in t+e ta)le a)o(e is pro(

n super ele(ated sections, t+e s+oulders s+oul+a(e t+e same cross fall as t+e pa(ement.


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a!eral 3learacei i l di ) +


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Jinimum clearance distance )eteen t+e etret+e carriagea" and t+e face of t+structure7o)struction s+ould )e e3ual to norm

idt+.

n loer categor" roads in +ill areas +a(ing conarro s+oulders, it ill )e desira)le to increase t

idt+ at underpasses to a certain etent.


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/er!ical 3learace


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Jinimum (ertical clearance of 5 m s+ould )e gi(eentire roada" at all underpasses and sio(er+anging cli%s and semi tunnel sections.

Jeasured from t+e +ig+est point of carriagea" i.esuper ele(ated edge to t+e loest point of structures7roc4 outcrop.

Horio!al Ali-+e!


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S+ould )e Fuent and )lend ell it+ t+e surrounding topograp+".

!+e Foing alignment conforming natural contours is aest+eticall" prefe

!+e +ori*ontal alignment s+ould )e coordinated carefull" it+ t+e longitu

$rea4s in t+e +ori*ontal alignment at cross drainage structures and s+aend of t+e long tangents s+ould )e a(oided.

S+ort cur(es for small deFection angles s+ould )e a(oided.

!+e cur(es s+ould )e sucientl" long and +a(e suita)le transitions to appearance.

Cur(e lengt+ s+ould )e at least 15 m for a deFection angle of 5 an

increased )" ' m for eac+ degree decrease in t+e deFection angle. =or deFection angles less t+an one degree, no cur(e is re3uired to )e des

$ro4en )ac4 cur(es s+ould )e a(oided ad far as possi)le in t+e interest osafet" and replaced )" a single cur(e.

If t+is is not feasi)le, a tangent lengt+ corresponding to 1 seconds tra(least )e ensured )eteen t+e to cur(es.


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Superele'a!io


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!+e limiting (alue of super ele(ation is as under:

a@ In sno )ound areas 0 /

)@ In +ill" areas not )ound )" sno 0 1/

)In attaining t+e re3uired super ele(ation, it s+ould t+at t+e longitudinal slope of t+e pa(ement edge ct+e center line ?i.e. t+e rate of c+ange of super e

not steeper t+an 1 in 15 for roads in plain and roand 1 in 6 in mountainous and steep terrain.


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Geometric design re3uirements for +ill roads are!+ d i i d id i


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!+e design is made considering:

a@ Compleit" of t+e terrain

)@ Hig+ altitude factorsc@ t+er pro)lems in t+e design and construction

radie!

In +ill roads gradients are selected close to ma imum t


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In +ill roads gradients are selected close to maimum troad lengt+ and eart+or4.

!+e tracti(e poer of t+e (e+icles decreases it+ t+e a

!+is reduction in poer output is due to c+anges in pressure, temperature and air densit".

=or t+is detailed (e+icle performance stud" s+ould )eit+ t+e +elp of d"namic factor or speed c+art.

Hig+ altitude factors include reduced densit" oatmosp+eric pressure, lo )oiling point of ater andind pressure.

In lo atmosp+eric pressure, t+ere ill )elo ater resulting a)normal engine cooling conditions.

A stud" on d"namic c+aracteristics for t+e truct+at:


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If gradient is / t+e speed is 2 4mp+

If gradient is 6/ t+e speed is '2 4mp+

If gradient is E/ t+e speed is 2 4mp+

If t+e gradient c+osen is / instead of E/, t+e rdou)le in lengt+ )ut t+e speed ill increase onl" !+is indicates in spite of decrease in gradient t+erin tra(el time.

!+oug+ steep gradient +elps in reducing eart+or4of road, it also causes increased fuel consum


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,reduction in operating speed as t+e (e+icles illgears for +ig+er poer output.

!+e distri)ution of t+e load on t+e (e+icle ales une3ual t+ere)" causing o(erloading and ecess

tires and t+e (e+icle engine.

Hence careful >udgment is re3uired to meet t+e

i

;ceptional gradients are meant to )e adopted odicult situations and for s+ort lengt+s not ecee


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gat a stretc+.

Successi(e stretc+es of eceptional gradientsseparated )" a minimum of 1 m +a(ing Fatter gr

!+e cumulati(e rise7fall in ele(ation o(er 2 4m lengeceed 1 m in mountainous terrain and 12 terrain.

/er!ical 3ur'e

Designed as s3uare para)ola


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Designed as s3uare para)ola.

engt+ of (ertical cur(e is controlled )" sig+t distance )ut cur(es it+ greater lengt+ are aest+eticall" )etter.

Cur(es s+ould )e pro(ided at all grade c+ange eceindicated in t+e ta)le )elo and for satisfactor" appearan

9+ere +ori*ontal and summit7crest cur(e o(erlap, t+e dpro(ide for t+e re3uired sig+t distance )ot+ in t+e (ertalong t+e pa(ement and in t+e +ori*ontal direction on t+ecur(e.


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Passi- Places Re3uired on single lane +ill roads to facilitate


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Re3uired on single lane +ill roads to facilitate (e+icles approac+ing from t+e opposite direction aside a disa)led (e+icle so t+at it does not o)struct

#ro(ided at t+e rate of 2&' per 4m.


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Inner and outer edges of t+e roada" s+ould )e conrespect to t+e center line of t+e pa(ement


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respect to t+e center line of t+e pa(ement.

9+ere a num)er of +air pin )ends +a(e to )e inminimum inter(ening distance of 6 m s+ould ))eteen t+e successi(e )ends to ena)le t+e dri(er tt+e alignment smoot+l".

At +air pin )ends prefera)l" t+e full roada" idtsurfaced.

Types o2 Hair Pi 9eds

1@ S"mmetrical Hair #in $end


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2@ As"mmetrical Hari #in $end

C 0 total lengt+ of main cur(e, C r 0 lengt+ of re(ersecur(es, and m 0 tangent ?straig+ts@

P 0 acute angle of )end

R 0 radius of main cur(e


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Q 0 angle su)tends at t+e center

#oints NAO and N$O are located at t+e apices of t+e

re(erse cur(es. $eteen t+e ends of t+e re(erse cur(es and t+e

main cur(e of t+e )end tangents must )e introducedfor t+e transitions of t+e super ele(ation and etraidt+ in t+e cur(e.

=or t+e design and la"out of +airpin )ends elementsuc+ as radii of t+e main and re(erse cur(es ?R and

r@ and lengt+ of t+e tangent ?m@ are initiall" selected)ased on t+e site situation in conformit" it+ t+ere3uired geometric standard.

!+e design of +air pin )ends t+en )asicall" consistsof esta)lis+ing t+e (alue of t+e turning angle Q atpoint NAO and N$O +ic+ satises t+e selectedparameters of t+e )end.

Simple epression ma" )e deri(ed )ased on t+e ge

pressio 2or Hair Pi 9e


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+air pin )ends.


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/arious 3oD-ura!ios o2 Hill Road 3Sec!ios

1 Cut and ll


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1. Cut and ll

2. $enc+ t"pe

'. $o cutting

. ;m)an4ment it+ retaining alls

5. Semi )ridge

6. Semi tunnel

. #latforms

1< 3u! ad 7ill 9it+ a +ill side slope of o(er 2/, a cut and ll road )ed is t+e c+eaper a

friendl" t"pe of construction.

!+e ll mass is o)tained from t+e cut material at t+e same location or


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!+e ll mass is o)tained from t+e cut material at t+e same location or distance.

!o ensure ade3uate sta)ilit" of em)an4ment, )enc+es are made on t+e sside it+ a +eig+t of .5 m and a lengt+ (ar"ing 1.5 m to '. m dependin

!+e settlement of t+e ll portion of road )ed sometimes causes t+elongitudinal crac4s in t+e pa(ement.

!+at is +" it is recommended to locate roads on sta)le +ills cross slope

entirel" in a cutting at t+e +ig+er cost of ma4ing full )enc+. Roads it+ +ard and costl" pa(ement structures are to )e prefera)l" loca

+ile t+ose it+ lo cost surface ?9$J, gra(el, eart+en@ )e made it+ )ed.


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>< 9ec# Type

A cross section of t+e )enc+ t"pe alt+oug+ entailing som


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A cross section of t+e )enc+ t"pe alt+oug+ entailing someart+or4 ensures t+e complete sta)ilit" of t+e road )ed, ifis sta)le.


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B< 9o 3u!!i- 9+en t+e location of road )ed is unsta)le or unsta)le along

due to one or ot+er reason, t+e road )ed is designed as tr


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, gcross section.

!+is t"pe of road )ed increases eart+or4 to a large etent.

It is introduced in order to meet t+e geometric design sgi(en categor" of road.

9+en a road is ascending up t+e grade is reduced su)raising formation line at t+e )eginning it+ ll and loeringt+e folloing section it+ )o cutting.

!+is a", t+e lengt+ of road ma" )e su)stantiall" reduced.

C< +bak+e! (i!# Re!aii- "a

n steep slopes o(er '&'5 degrees, t+e eart+or4


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n steep slopes o(er ' '5 degrees, t+e eart+or4constructing t+e em)an4ment slope line meets t+e natural gan acute angle far aa" from t+e center line of t+e road.

In t+e rst case of retaining all is pro(ided to reduceeart+or4 and to increase t+e sta)ilit" of em)an4ment.

9+en t+e original ground slope is steeper t+an t+e em)at+ese to slope lines ne(er meet don +ill.

In t+e second case retaining alls are necessar" to em)an4ment soil on steep ground at t+e edge if t+e road its

An em)an4ment it+ retaining all +as a greater sta)ilit" apreferred.

Retaining alls are also constructed on a less steep groincrease t+e sta)ilit" of road )ed.


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5< Se+i 9rid-e

If t+e road is located across a steep +ill slope retaining to )e of su)stantial +eig+t.


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g

In suc+ cases, in order to reduce t+e 3uantities of or4, rosemi )ridge t"pe of structure ma" )e constructed.

#art of t+e roada" is accommodated on )enc+ cut and par)ridge.

&< Se+i Tuel 9+en cutting into steep +ills in sta)le roc4 faces t+e ro

permitted to o(er+ang t+e road, reducing roc4 or4s.


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Suc+ a cross section is called a semi tunnel.

Road in +alf tunneling is ad(antageous for +ig+ altitude +t+e" do not get )loc4ed )" snos.

G< Pla!2or+ n t+e precipitous7(er" steep slopes, +ere s+ifting of t+e route into t+e

to enormous roc4 or4, +ic+ ould su)stantiall" increase t+e cost of and +ere semi tunnel cannot )e constructed due to t+e geological con


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and +ere semi tunnel cannot )e constructed due to t+e geological conare usuall" cantile(ered out of t+e roc4 on +ic+ road a" is partiall" loca

9+en cross slope of t+e +ill is (er" small, road ma" )e in full em)an4men

=illing ma" )e small or +ea(".

In case of +ea(" lling, retaining alls s+ould )e constructed on )ot+formation.

C. Hill Side 4raia-e


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Ade3uate drainage facilit" s+ould )e pro(ided

road. Attempts s+ould )e made to align t+e roads in

+ere t+e num)er of cross drainage structures rminimum.

!+is ill reduce t+e construction cost.


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5. S!abili!y o2 Slopes

=or +ill" areas t+e road s+ould )e aligned t+roug


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=or +ill" areas, t+e road s+ould )e aligned t+rougof t+e +ill t+at is sta)le.

!+e common pro)lem it+ +ill" areas is t+at of lan

;cessi(e cutting and lling for road constructionsto steepening of slopes +ic+ in turn ill a%ect t+e

5.B Special S!ruc!ures i Hill Roa

Construction of +ill roads in(ol(es man" special stru


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!+ese ma" include ide range of structures +ic+

retain soil mass to increase sta)ilit" of road emslopes as ell as natural +ill slopes to accommodatin steep slope to penetrate deep t+roug+ mountaiso on.

Special structures are also re3uired to dissipate

surface ater in t+e +ill road drainage s"stem to pra(alanc+e control and protection s"stem, ri(er terosion control to pre(ent scour under cutting and )" t+e ri(er.

!+e folloing t"pes of special structures are most used in t+e +ill road in -epal:


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1. Retaining Structures

2. Ri(er !raining Structures

'. andslide Sta)ili*ation Structures7Slope Structures7Slope Sta)ili*ation Structures

. ;rosion and Gull" Control Structures

5. Drainage Structures

1. Re!aii- S!ruc!ures


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3lassiDca!io o2 Re!aii- "alls

a< 9ased o Ma!erials sed6


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i@ Dr" stone masonr"

ii@ Stone lled ga)ion ire cratesiii@ Stone masonr" it+ cement sand mortar

i(@ Composite ?Dr" Stone Jasonr" =illed in Cement Sand JJasonr" =rame@

(@ #lain Cement Concrete

(i@ Reinforced Cement Concrete

(ii@!im)er or Steel

b< 9ased o oca!io (i!# Respec! !o !#e Road(ay

i@ Hill Side or


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iii@ Cut o% 9alls

i(@ Re(etment 9alls or $reast 9alls, etc.

Re(etment alls are 4non as $reast 9alls. !+e" are nta4e t+e road and retain t+e soil mass )ut to pre(ent tof ll slope made of loose eroding soils from furt+er slip

!+ese alls are sloped toards cut or ll slope and are nto resist o(erturning or sliding.

ses o2 eosy!#e!ics

G t+ ti +i + i l d


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Geos"nt+etics +ic+ include:

Geotetile Geogrids

Geonets

Geomem)ranes

Geocomposites

Can )e used in (arious applications of road and or4s.

Some of t+e areas and t+eir functions are:

c< 9ased o S!ruc!ural Sc#e+e ;Pricipal TypeRe!aii- "alls. Ri'er Traii- S!ruc!ures

Guide $an4 S"stem

Gro"nes or Spurs


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e(ees or Jarginal ;m)an4ment or d"4es7di4es

$an4 #rotection And #itc+ed $an4s #itc+ed Islands

Re(etments

Cut&o%s

Jiscellaneous Jet+ods

Ri(er !raining 9it+out ;m)an4ment $andalling


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uide 9ak Sys!e+


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Types o2 royes or Spurs

1. Accordi- To T#e Ma!erialssed6

# )l G


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#ermea)le Gro"ne

Solid Impermea)le Gro"ne


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>. Accordi- To I!s Hei-#! 9elo( Hi-# "a!er6

Su)merged Gro"ne

-on& Su)merged Gro"ne


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B. Accordi- To T#e 7uc!io I! Ser'es6 Straig+t or -ormal or Sedimenting Gro"ne

Repelling Gro"ne

Attracting Gro"ne


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Attracting Gro"ne

DeFecting Gro"ne


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C. Special Types 2 royes6 Hoc4e" !"pe Gro"ne or $urma !"pe

Gro"ne In(erted Hoc4e" Gro"ne Dene+"Os !&+eaded Gro"ne


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Dene+" s ! +eaded Gro"ne &Headed Gro"ne Slotted Gro"ne

e'ees or Mar-ial +bak+e!


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e'ee alo- !#e Rap!i Ri'er i $epal


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9ak Pro!ec!io Ad Pi!c#ed 9aks


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Rock Rip Rap Re'e!+e!


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Pi!c#ed Islads


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Re'e!+e!s


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Miscellaeous Me!#ods Ri(er !raining 9it+out ;m)an4ment $andalling


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B. adslide S!abilia!io S!ruc!ures)Slope Pro!ec!ioS!ruc!ures)Slope S!abilia!io S!ruc!ures


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C. rosio ad ully 3o!rol S!ruc!ures


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5. 4raia-e S!ruc!ures


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1. Re!aii- S!ruc!ures A retaining structure is usuall" a all constructed for t+e purpose o

retaining a (ertical or nearl" (ertical eart+ )an4 +ic+ in turn(ertical loads.

It pro(ides ade3uate sta)ilit" to t+e roada" and to t+e slope.


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Retaining alls are constructed on t+e (alle" side on t+e roada" cut +ill side to pre(ent slide toards t+e roada".

!+e" are also pro(ided to retain t+e eart+ mass for ele(ated and d+ere t+e em)an4ment slope or cut slope cannot )e etended )e"

Generall" for +ill slopes it+ gentle slope retaining alls ma" not )

=or steeper slopes relati(e econom" of cost of eart+ cutting and

+as to )e compared.

t+er situations re3uiring t+e construction of ralls are:


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alls are:

i@ #laces +ere t+e (alle" side surfaces gets sin t+e monsoons and is li4el" to result in slip part of road it+ it.

ii@ Ii@ places +ere undercutting )" a stream

ater course causes damage to t+e (alle" st+e road

iii@ Iii@ in (alle" point +ere ater Fos o(er t+e r

i(@ I(@ to ac+ie(e roada" idt+, +ere cutting in

Re(etment or )reast alls are pro(ided on t+e inner side of t+e roadsupport to t+e loose and unrelia)le soil of t+e cut up +ill side.


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!+e em)an4ment slopes are normall" protected it+ roug+ stone p

a)out ' cm t+ic4 in order to a(oid erosion due to Fo of ater. Suc+ alls perform t+e folloing functions:

a@ eep t+e road edge dened and also protect t+e drain to some e

)@ !+e +ill slope to t+e etent of )reast all +eig+t ill remain protecslips and an" slide a)o(e t+is +eig+t ill Fo o(er t+e top of t+e )

c@ It ould not allo continuit" of t+e Foing mass of soil and ould

facilitate t+e clearance of slides.

d@ Assistance in drainage fro +ill slope t+roug+ eep +oles in )reast t+e side drain in front of all.

$all" Re(etments:

In ea4 7et sliding area, re(etments of )allies7)am)oos dri(en (ertic+ori*ontall" in ros parallel to t+e road along t+e +ill slopes a)o(e anformation le(el to pro(ide t+e temporar" sta)ilit" to t+e slope


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formation le(el to pro(ide t+e temporar" sta)ilit" to t+e slope.

!+ese can )e replaced )" )reast alls of masonr" or crated in due course. At times t+e temporar" re(etment is enoug+ to sta)ili*e t+e slopes perma

are pro(ided.

If t+e re(etment is made it+ selected (arieties of fres+ cut )allies, +ic3uic4l" under et conditions, it pro(ides (egetation co(er and adds to stslope.

If t+e sloping lengt+ is too long it is prefera)le to construct a toe all as to

em)an4ment. 9+ere t+e cutting slope is steep and contains loose soils, slto occur.

In suc+ locations, re(etment alls of dr" stone masonr" are constructed soil on t+e cutting side to pre(ent occurrence of an" suc+ slip.

Gra(it" alls are made of Dr" Stone Jasonr", Ga)ion, Stone JaCement Jortar or Concrete. -o pro)lem of )ac4ll drainage


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Dr" Stone or Ga)ion $o Retaining 9alls

9eeps Holes are pro(ided at specic inter(al to facilitate )ac4in case of Stone Jasonr" in Cement Jortar oint

Compacted $ac4ll it+ crus+ed aggregates or ri(er gra(el are p)ac4ll to pre(ent c+o4ing of eep +oles.

Anot+er met+od of retaining t+e +ill side can )e )" using ire cit+ stones and used as )reast all.

!+e suggested specication for crate all is ' m 1.5 m si*e, c15 cm 15 cm si*e s3uare mes+ of 1 gauge GI ire intero(enin one or to tiers as re3uired.

In roc4" stretc+esDr" Stone 9alls7Re(etments ma" )e pro(ided at naand re&entrants to pro(ide additional idt+ for mo(ement of trac ta4inconstruction materials to site till t+e road is idened


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construction materials to site till t+e road is idened.

#roper dressing and le(eling of foundation sloping toards +ill side is es Dr" stone masonr" is preferred to masonr" in mortar as it +elps eas" dr

seeping ater.

!+ese are Fei)le and +elp sta)ili*ation of slope.

!+e design of retaining alls is )ased on t+e t+um) rules and suggestedof retaining alls s+ould )e not less t+an .5 m of +eig+t and a minimumof .5 m to .6 m and a front )atter of 1 in it+ t+e rear side (ertica

=or +eig+ts greater t+an 6 m, sections of ?. H .'@ to ?.5H .6@ madopted it+ a top idt+ of .5 m.

Also )ands of coursed ru))le masonr" in cement mortar at (ertical and inter(als of a)out ' m eac+ are constructed for added sta)ilit".

9+en cul(erts7scuppers are constructed and a)o(e t+e retaining alls on t+e (alle" sid


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a)o(e t+e retaining alls on t+e (alle" sid

considera)le +eig+t, in t+e form of free fall, considera)le erosion at t+e toe of t+e retaining

In order to c+ec4 t+is, one or a series of toe constructed in order to )rea4 t+e ater force so retaining all does not get eroded.

In some cases, similar structures called C+ec4 9re3uired in t+e stream )ed on t+e upstream sidroad to reduce t+e Fo of de)ris +ic+ )loc4s t+

Reinforced Soil 9alls

It is a composite construction material in +ic+ t+e strengten+anced t+roug+ addition of inetensi)le tensile reinforcement f t i + t id t til


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of strips, s+eets, grids or geotetiles.

!+e tec+ni3ue of construction is 3uite suita)le for +ill" areas mat+e folloing reasons:

i@ !+e ll materials +ic+ consists of mainl" granular materiaa(aila)le in all parts of t+e +ill" areas from cutting of +ill sconstruction of roads.

ii@ !+ese in(ol(e minimum alteration in natural slopes since t+e e

on a(oiding t+e cutting of natural slope.

iii@ !+e land idt+ or actual em)an4ment idt+ re3uired is less.

i(@ !+is is cost e%ecti(e and en(ironment friendl".


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5. hill roads 073.pptx

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