6=$t\tnginecring

Dep.rrhndnl ol C l

Dclinition of gauge of track:

wq_Ga

ilhw*un Nahar 5i A-/.-ffre-

i I) t}.AIi, GAUGES

The gauge of a raihvay tlack rs defined as the clear minit.ttut.t.t perpendicular distance

bet,r,ccn lnner laccs of Lhe ts.o rails as sho*,n in fig.4-1. Itr ittauy countries, the gauge is

r,easured bet\\,ecn the inncr laces of tlie trvo rails a1 a certaiu vertical distance fron-r top of

rail or rail table. ln Eurol)e, thc gauge is tlleasurecl at 14 tnt.l.t bclorv the rail table; in

Arncrica, it is rtrcasurerl at 15,88 mrll beiow thc rail table and in Japan, it is measured at 16

nrnr belou, thc rail tablc.

Roils

Fro. 4'1!-- -

G:r u gcs in diflcrcnl cottntrics:

It is secl previously thar the fir'sr public railrvay rvas laid in Britain and it is still a matter of

tlispLrtc horv the standard gaugc c.rnle iuto existence. It is believed that George Stephenson

nrcasured tl.re distance betwecn the rvheels of l.ris fam.r cafi hauled by horse tractior.r and

lound this distatrce quite convenient for his early locomotives. Later on, different countries

adopted variotrs gauges. Factors aflecting the choice of a gauge are as follows:

( 1) Trolfic Con itions:

Il tiie intensity of traffic on thc track is Iikely to be more, a gauge wider than the standard

gauge is suitabls. As rviclcr gauge can have larger sized wagous/coaches and has tnore

potcntial for higher specd arld thercby can carry more volurne oftraffic'

(2) Developmenl of Poor arets:Narroru gairges nr" tuia i, certain parts olthe world to develop a poor area and thus link the

poor arca u'ith tltc outsidc clcvclol:cd world.

(3) Casr of trucli:'lhe cost ofraiNvay rrack is dircctly proportional to the widtli of its gauge. Hence, ilthe fund

available is not sufficient to construct a standard gauge, a metre gauge or a nalrow gauge is

prelerred rather than to have no raihvays at all.

(4) \'urure of country: hc,,, r lrxrrow qlrugc o[ tl']e tlrrcli sinc. it,is ilrt''lc

I. rrrorrutaitlorts coLllltl'y' rt ts lJvisnble Io ltlvc"r '"tll)' ?r,i' is t]rc ttr.itr rcrtsott * ltv sJrttc

ii.'i;i.'ili;;,, u'''"..il: llil"'lHIi:i-:i:ll]i,,'J'."^ll,,i;;;,t,.. g..us.. as r):.1ow 35 ortr

inlporr.;ult rails tys' t:t t''l'l j;,,ii;i;,., ,t.o influ.n... r'c choicc of guugcs

rlnt. Morcovcr. [outldat ttltl cc

The <tifferent gauges cirn broadly be dividctl into four categorles:

(l) Broad gauge: Width l676 mm to 1524 rnm or 5'-6" to 5'-0"'

(2) Staudard gauge: Witlth I435 nrm and 1451 rnm or 4'-8 5" and 4'-91/8"'

(3) Merre gauge: Width .l067 nrm' 1000 mm and 915 mm or 3'-6"' 3'-33/E" and 3'-0"'

(-l) Narrorv gaLrge: Width 762 r.nm and 610 mm or 2'-6" and 2'-0"'

TABLE 4.I

RAILWAY GAUGES IN VARIOUS COTNTRIES

Name of couutrtes

Bangladesh, India, Pakistan' Ceylon'

Brazil, Argentine

Spain, Portugal

lreland, South Australia

Russia, Finland

(1)Broutl guuge:

(a) 1676 mm

(b) I670 nint

(c) 1600 mnt

(d) 1524 mtrt

England, U.S A , Canada' TurkeY'

Persia, China. EgYPt' Australia

Europe (excePt Russia' SPain and

PortLrgal)

(2) Standartl guuge:

(a) 143 5 ntnr

(b) 145 I mnt

South Africa, Japan, Java' Australia'

New Zealand

Bangladesh, India, Fr ance' Switzerland'

Argeniine

(3) lvletre guuge:

(a) i 067 ntm

c) 91 5 tnm

India, Britain

lndia, South Afr-ica

(4) Nurrort' guugc:

(a) 762 mrr

(b) 610 mnt

Unifornrity in gauges:

It has bccn gcucrally agreed that a country should have a uuiforut gauge.'l'his I'act has Icd

to scrious thinking in thc coLuttrics lraving nrorc th:rn ot]c gaugc and attclllllts arc bcitlg nratlc to

pass an tct of Got,cntnrent in this connection. Various causes which have arisen due to non-

unilonrity ofgauges are as lollows:

( 1 ) Itrcottvutiencc to passcttgers

At the point rvhere therc is a change ofgauge, passengers are required to move from one

train to the other. This transler involves difficulties such as getting accommodation in the

nqv train, translerring luggage frorr one train to otlier, climbing staircases of overbridges,ctc. Morcovcr'. tftc tirlilgs of thc t',vo trains arc to be correspoudingly adjusted. Sometit]lcs,this ntay rcsult in ntissirrg the train and thell passengers lrave to pass the time orr tl.re

plarforms. Moreover, i:rsanitary condilions will be developed on the platfomrs due to theirconslant usc.

(2) Difficulties for se n irrg gootls

(a) The labour required lor loading and unloading the goods may go on strike and thus

completely dislocate the ntovement olessential goods required for various trades. The

problenr gets lurthcr complicated lor goods sent loose or in bulk such as coal, lime,Iimcstonc, stonc chii)s, ctc. bccausc it is obscrvcd that at cvery transhipnlcnt point.

there arc certain groups of labourers rvhich are specialised in the handling of suclt

matcrials. Flence it becorres difficult to cmploy other labourers in an emergency, even

though there may be cousiderable unemployment in the area.

(b) lt is most likely that delicate goods may be damaged during the process of loading and

unloading.(c) Thcfts or misplacenrent ofgoods nlay occur during the transhipping which may lead to

inconvenicnce to the pclsons concerned and long unnecessary corespondences are

thus unduly created.(d) Large costly yards are to be provided at the junction o[ tl.re two gauges to store the

goods.(c) Onc or nrorc cxlra chargcs rvill have to be paid by thc owncr of the goods rvhich will

result in the increase in cost of the product.

(3) Inefficient use of rolling stock:

It is quite clear that a wagon of metre gauge cannot be used on a broad gauge. Thus.

sometimes, this results in artificial shortage of wagons. Many wagons may be lying idle on

broad gauge line while there may be an acute shortage ofwagons on the metre gauge line.Had there been a unifon.n gauge, sucl.t difficulty would never have arisen.

(4) War time dilficulty :

lfthe gauge is not unilolur tlrroughout the country,by rail lronr one corncr of the country to the otheramount of time.

it becomes difficult to trarlsfer the arn.ty

comer of the country in a very limited

5) !)quipnrent at statiou:A station where two gauges rneet, will have to be provided with duplicate facilities such as

platforms, sanitary arangements, sidings, clocks, ticket offices, etc. This will result in extra

J

Uniformity in gauges:

It has bccn gcncrally agrccd that a country should have a unilbrnr gaugc. 'l'his liLct l.ras led

to scrious thinking irt tlrc countrics having nrolc tlran onc gaugc and tttctttPts arc bcitlg I.tladc [o

pass an act ofGovcntnrent in this connection. Various causes rvhich have arisen due to non-

unilornrity ofgauges are as lbllo*'s:

(l) Incontenicucc lo posscttgcrs

At the point rvfiere therc is a change of gauge, passengers are required to n]ove from one

train to the other. This transfcr involves difficulties such as getting accomn.rodalion in the

nes, train, transferring luggagc lrom one train to other, climbing staircases of overbridges,

ctc. Morcovcr. tlrc tintings of thc trvo lrains arc to bc corrcspondingly adjusted. Sonletittles,thrs uray rcsult ir.r ntissing the train and thcn passengers llave to pass tlie tirle on the

platlonns. Morcover, insanitary condiliorls will be developed on the platlomrs due to their

col)stanI usc.

(2) Dilficultics for serrdittg goois

(a) The labour required lor loading and unloading the goods may go on strike and thus

completely dislocate the nlovenlent of essential goods required lor various trades. The

problem gets lurthcr conrplicated lor goods sent loose or in bulk such as coal, lime,

Iimcstope, stonc chips, ctc. bccausc it is obscrvcd 1ha1 at cvery transhiltrucnt poiltl.

there arc ccrtain groups ol labourers rvhich are specialised in the handling of such

matcrials. Flence it becoures difficult to enrploy other labourers in an emergency, even

though therc rnay L.:e cot.tsiderable unentployment in the area.

(b) It is most likely that delicate goods may be damaged during the process of loading and

unloading.(c) Thefts or misplacenrent of goods may occur during the transhipping which may lead to

inconvenicnce to tlle pcrsons concemed and long unnecessary correspondences are

thus undu ly c reated.(d) Large coslly yards are to be provided at the junction of the two gauges to store the

goods.(c) Onc ol ntorc cxtra clrargcs will have to be paid by thc ownet'of the goods rvhicir rvill

result in the increase in cost of the product.

(3) Incfficient use of rolling stock:

It is quite clear that a wagon of metre gauge cannot be used on a broad gauge. Thus:

sometimes, this results in artificial shortage oiwagons. Many wagons may be lying idle on

broa<l gauge line while there may be an acute shortage ol wagons on the metre gauge line.Had tl.rere been a unifon.u gauge, such difficulty would never have arisen.

(J) war time dilliculty :

If thc gauge is not Lrni fornr throughout the country, it becomes dilficult to trai]sfer the arnlyby rait from one comcr ol'the counl.ry to the otller corner of the country in a. very Iimitedaniount ol tinre.

5) llquipment at station:A station where two gauges rneet, will have to be provided with duplicate facilities such as

platforms, sanitary arrangements, sidings, clocks, ticket ofhces, etc. This will result in extra

?t

{'

,\''t: i'

cxpenditure.

61 llintlcrance ibr futurc corlYcrsiotr:

Itbccot:rcs\,cfydifficultandplacticallyunecollolnlcaltolvidetranexistillgtrackir-rlirturo\\.hctl lleed arises. l.his is Jrc',ro th" tact thar changc in gaugc also involves change in the

climeusions of roiling "ott'

ona other structures such as tunl'Iels' bridges' etc'

1

Rails

Irunction of Rails

Rails are sintilar to steel girders. Thcse are placed end to end to provide continuous and levelsurlacc for the trains to nrove. Thc finishcd or conrpleted track of a railway line is commonlykrrorvn as Peraunu I,Va.1,.

Rails pcrform the following functions:l. The rails provide continuous and level surface for movement oftrains.2. The rails provide a pathway which is smooth and has very less friction. The friction

be[veen steel rvhee] and stecl rail is about l/5th of the friction between the pneumatic tyreaitd metalled road.

3. The rails scrve as a latcral guide for the running ofwheels.'1. The rails bear the strcsses developed due to vertical-loads transmitted to it through axles

anLl rvhecls ol rolling stocli as rvcll as due to braking forces and tl'reflral stresses.5. The rails carry out thc lunction oltransmitting the load to a iarge area of formation tluougl.r

slecpers and ballast.

Types of rails

I . Double hcarlcd rails2. BLrll lreadcd r:r i ls

3. FIat lootcd rails

originally, the rails used were double headed (D.H.) and made of "I" section or Dumb-bellsection (Fig. 5.1.) The idea *,as that when the head was vr'om out during the service, the railcotrld be invertcd and reused. Tl.re expcrience, horvevcr, ihowed that the bottom table of the railwas dcntcd to such an cxtent in scrvice by long and continuous contact with the chairs that itwas nol possible to reuse it. This led to the development of Bull headed (B.H.) rail which hadalmosl a sinrilar shape but with nrore metal in the head to allow for greater wear and tear (Fig.5.2)' This rail scction had orte big dlawback that chairs were required for fixing it to theslcepers.A llat lboted rail, also callcd vigttolc rail (Fig.5.3), having a cross section ofinverted r- typelvas, tltcrcforc, dcvclopccl wltich coLrkl bc fixcd dilcctly (o thc slccpcrs witlr thc lrclp of spikcsctc- Allothcl' advatttogc wilh tlrc flat-looted lail was that it was a morc ccononlical tlcsigngiving grcatcr strcrtgLh arl(l latcral stability to thc track as cornpared to a B.ll. rail lor a givencross sectional area.

\ Adrn,,trgn, of flat looted rails:(i) Chairs: No chairs are required in this fonn ofrails. The foot ofthe rail is directly spiked tothe sleepers. This fact nrakes theur economical.(ii) Stllessr This fonn of rail is stiffer, both vcrtically and laterally than the bull headed railofequal weight. Especially on curves, the lateral stiffness ofrails is vely impofiant.(iii) Rinks: This lbrnr of rail is less liable to develop kinks and it maintains a more regular top

( o-\\a

r

surllce than thc bull headcd rails.(iv) Cosr.'The flat footcd rails are lound

l\') Load distributiott: Thc flat lootedslcepcrs.This results in grcatcr trackmaintenance costs, less rail lailures and

to be clicapcr than the bull headed rails.rail distributes the train load over a great numbei ofstability, longer li[e of rails and sleepers, reducedfew intemrptions to traffic.

LO

,-U

4d^^

I64 nm

,i-

TIIDouble hcadod rail-=-Eo-:E:i--

Bull heoded radls (69. 5-2)..

F<- 64 .nm ---+!

Bull hcadqd railFro.5-2

Flat footcd rail

(2)

T46 z'rr.

!I

I

I

I

+,rg-\r.

!rl.;,,4rl

t47A8

- r3.8e mm I

I,..6 I

------rl

66.68 mm.--

'_?

.,/' , t.ttljL_-..-----13A53min

10.64

Tl45mm

If-.

{

Web

mrn.\+

q

l* TOmm -*l

le 68-55rnn ---t

Fro.5-3

W,;ight of rail and its relation to uxle loadA rail is dcfincd by its rvcight, c.g,,45 kg rail means that rhe weight of rail per rnetre lcng[h is45 kg. Scvc'rai lactors arc to be considered belore deciding the rveight olrail and its sections,the chief aniong tltem are as follorvs:

L hcav icst axle load

2. gauge of track

3. maximum pcnlrissiblc spced

4. type and spacing ofslecpers

5. depth ol ballast cushion

6. nalure of traffic.

Though the weight of the rail and its section depends upon various considerations yet theheaviest axle load which tl.re rail has to carry plays, the most important role. It is lound andvcrificd by cxperinlcnts that the axle loads on locomotives directly depend on the weight ofrails used in thc track.

Tirc lbllorving is thc thu:rib ru)e lor giving the rnaximum axle load with relation to rail section :

Maxintum axle loadFor rril of 90 lb pel yard, rnax. axle loadFor- r-ail of 52kg per n1, ntax. axle load

Requirements for an ideal rail section'

l. The rail should have most economical section consistent with strength, stiffitess andd urab i tity.

2. 'l'hc ccrrtrc olgravity olrail section slrould prelerably be very near to 1he centre ofheight ofrail so that nraxinrurn tcnsilc and conrprcssivc stresses are equal.

'1. A rail prirnarily consists ol a head, web and foot and there should be an economical andbalanced distribution of utetal in its various components so that each of them can fulfil itsrequirernents properly.

The requiremetrts as well as the niain considerations lor design ofideal rail section componentsare given below:

(u1 IIeod:The head olthe rail should have adequatc depth to allow for vgrtical wear. The rail headshould also be sulliciently wide so that not only wider runnirlg sufrdis available toreduce lhe contact strcsscs betwcen the rain and whecl but the rail has the dcsired ]atcralstiffness also,

(b.t Web:The web should be su ffi c.lg1.lI1b@k so as to wirhstand tl.re stresses d.e to the loadscorning on it aft", oli6iil! fonio.rnal conosion.

(c) Foot:The foot should be of sufficient thickness so as to withstand vertical and horizontallorces after allowing for loss due to corrosion. The foot should be wide enough so as tobe stable against over tuming. The design of foot should be such that it can spread theload on a large arca of sleeper.

= 560 x sectional weight of rail in lbs/yard or kg/m: 560 x 90 lbs = 22.5 tons

560 x 52 kg - 29.l2MT

'+

Corrugated or roaring rails:

Mcaning:In certain places, heads of the rails are found not straight but corrugated, i.e., with a rvavy

surlace. Such rails arc knorvn as corrugated or roaring rails and when vehicles pass over such

comrgatcd rails, a fg!.iggnd is created.

Causcs:

Thc plicuorlena ol corrugation of rails is very complex and hence, it is

mcntion specific causes lor the same. However, following are the possible

contribute to the commencenrent and development of corrugation of rails: '

( I ) coning of engine rvheels,

(2) excessive slack or excessive tight gauge,

(3) high speed o f trains,(4) non-urrifonnity olthc diameter of engine wheels,

(5) presencc of high huuridity and dust in the atmosphere,

(6) rigid railrvay track,

(7) slipping of wlrr:cls oIengirtes,

(8) snrall spacing betrvcen driving axles ollhe locornotives,

(9) sudden application o f brakes,

(10) use ofstccl having high nitrogen corltent and high tensile strength, etc.

Occurrtncc:

The corrugatcd rails arc lound norrnally at tlie following places along a track:o At tlre points olstarting and stopping of the trains.o On elcctrificd scction ofa raihvay track.o Where ballast used lor the railway track consists ofbroken bricks.e At long tuinelo At steep gradient

Effects:o The track with corrugated rails produces discomfort to passengers due to rlryUiding

r@"".c Whcn vcl.ricle pass ovcr thc corrugatcd rails, a roaring sound is produced.o This unplcasant and cxccssive noise causes great inconvenience to the passangers.

cr The ruuuiug of trains on corrugatcd rails leads to overall deterioration of the raihvaytrack, loosening of the fastenings, disturbance in ballast bed, loosening of anti-creepdevices, etc.

Rcnrcdy:

The only remedy which is practiced at present to remove corrugation is to grind the corrugationof rails by special machines. A rail-grinding train is run on the affected section at a specifiedspeed and the pioccdure is continued till com.rgations disappear.

not possible tofactors which

Corrosion of rails:

Sonletimes thc rails arc corroded. The phenomena olcorosion of rails is urainly due to theprcscnce ofdamp conditions. It is usually seen in active i.!d*!!r,.I areas, wet tunnels, near ash-Dits. etc.

Follorving are the effects of con osion of rails:e Rail section is gradually reduced.

o The latigue strength ofa rail is lowered.o Therc is considerable increase in wear ofrail and ifcorrosion is not prevented, it may

lead to the lailure of rail.

To prevent corrosion, various ntcasures nray be adopted. Such measures can broadly be dividedinto thc lollorving_!q categorics:

o Quality of rail: For the areas where corrosion is likely to occur, rails prepared fromspecial :tgelor a lloy steels are employed in the construction ofpemranent way.

o Surlace treatlnent: The rail surface is coated with non-corrosive material. For thispurposc, special paints, red lead, birumcn, cqqllsr, etc. have been tried. The surface tobc coatcd is Lhoroughly.i"ffi tr" i5[-rtl" ,f,li-cor ion of coat.

Leugth of rails:

The tendency at present is to adopt a rail olmore length. The marn advantage ofa longer rail isthat:

o it clinrinates joints whicl.r are the weakest part of the track.c less nurrrbcr of ruil fastcnings

c this results in lorv consl.ruction & maintcnance cost

o sntooth running oltrains and comlort to passengers.

The length ofrail is, however, restricted due to the following factors:o Difficulties in manufactLrring very long rails.

ll/car of rails:

The rail head gets lvom out in course of time due too friction between the rail and moving wheels.o ilnpact produced by acceleration, deceleration an<i-braking ofwheels.o abrasion caused by rail-rvheel interaction.o thc eflects of weathering like tenrperature, moisture chainge

o Lack of lacilities for transport, lifting or handling longer rails.o Dilficulties in having

" qg.Cgl"-I3qlgugfgr for long rails.

o At thc fittings heavy inllnBllglnel stresses in long rails.

Depending upon thc above consideration, various countries have adopted different length ofrails. Bangladcsh, India adoptcd 12,80 rn and I I .89 m as stan<.larcl rail lcngths for. B.G. 11dM.c. rcspcctivcly. 'fhc nonral rail lcngths in America, Britain, trance arid Germany are 11.g9m, I 8.30 m, 24 nr and 30 m rcspectively.

Li'!<-\>,Thcsefactorscauseconsidelablervearandtearotrverticalandlateralplanesoniheraillrcad.Eventually, u'lrich results in loss of weight ofrail'

Types of wear on rails:

Dcpcnding upon its location, thc rvcar ol'rails can bc classified as lollows:

o Wear orr top of rail hcad (vcrtical wear)

l Wcar on cnds of thc rails (battering of rail cnds)

c Wear on sitlcs of rail head (lateral wcar)

Each type rvill norv bc described in briel

(t) l\cur ott loP o,' hcutl of rails:

Therrretalfromtltctopofrailtlorvsandlomrsprojections'Theseareknownasbltlgasshownrn fig. S-S. Follorvingare lhe c4trscs lor such type of wear ofrails:

(a) Rails are wonl out on top due to abrasioll olthe roiling wheels over them

(b) The heavy rvliecl loatls are conccntrated on very small areas This results into flow of

metal from toP.

(c) Impact of heal'y loads causcs top ofrail to wear'

(c])Wheelburirscausedbyslippingofthedrivingwheeloflocomotivesontherailsur.faceresulting in a dcpression oll the rail table'

(e) The grinding action of the sgd.pSrtjqes between the rails and wheels help wear of rail

on toP.

({) Conosion olmc(al olrails, especially"tl"giEu, will cause wear of head of rails'

ig) the metat of top o l1a!![g1s during starti])g whcn the wheels slip or rvhen 'brakes are

lpplicd to tltc tlor ittg lrritts'

(2) lVctr al tht tnls of rtils:

This rvear of rails takes place at the ends ofrails and is found to be very much greater than the

*"", u, ,op of rails. At ihe expansion gap, the wheels ofthe vehicle have to take a jump and

Juring ttrii 1ump, they impart i uto* ,J ti.,. ends of the rarts as shown in hg. 5-6. This blow is

,f* "i^i" "uus" of *ror of rails at ends. Due to successive blows, the ends of the rails are

battcrcd and various othcr cflccts are sccn whicl.r further increasc this type of wcar' These

effacts ate as follows:(a) Fish-bolts and fisll-piatcs bdcorne loosc

(b) The colltact surlaces betwecn rails and sleepers are wom ou['

i.j it""p.r, at expansionjoints are depressed due to settlement ofballast at these points.

{

Wear of rail at ton W/

. Fro. 5-5

(2))

(3) Wear on the sides of thc head of rail:

Flc.5-7

Wear on Side of Rail

Wcar of rail at cndsFro. 5'-6

ffiiilr,rg., ""

This is thc rnost dcstructivc typc olwear and occurs rvhen tracks are laid oncurves. The carses of this type of u,ear areas follorvs:(a) Due to curvature, pressure due tocentrifusal force causes grinding action of

the irLner side ol the headofthe outer rail.(b) The vehicles do not bend to the shapeof the curvature while uroving over lcurve. This results into the biting of the

./, \/\,/\

nn,, %'/ 'N outrRoil* A H- tottd/')v7> <<\\\ ';///

Wear of rail on sides rrc. 5-8

inner side of the head of outcr rail by wheel flanges.

ln*r Wred

of rail o#des

.1' ;

v'

(c) The rvear on inner side olhead ofinner rail is mainly due to lhe slipping actlg]lgf w_hgei oncurves. lt is clear liom fig. 5-7 that the outer wheel has to cover a longer distance than the inneru'heel as pg is grcater tiran rr. But due to rigid connections betwcen two wheels, thcy cover thesame distancc and hcnce, the inner whcel slips ovcr the inner rail, resulting in the wcar of innerside oIhcrd of irrncr rail. [:ig. 5-ll sJrorvs thc rvear olrail on sidcs.

Nlcthods adoptcd to reduct rveur of rails:In addition to coning ofrvhcels and super-elevation, various nrethods, as nrentioned below, are

uscd lor the purpose of rcducing rvear of rails:o Use olspecial alloy steel

c Use of heavier rails

o Good nraintenancc of track

o Reduction of expansion gap

o I{eductron ol nunrbcr ofjoints by wcldingo Exchange ofinner and outer rails on curveso lntroducing parallcl clrcck rails (usually wont oul. rails are used as check rail)c Lubrication olgaugc lacc olouter rail in case olcurves. -.

Coning of rvheels:

The flanges ofrvhecls al.c ncver made flat. But they are in shape of a cone with a slope ofaboutI in 20. As the ivhecls are set on the axle, there is some chance for lateral movement belween

the flanges of the wheels and the rails. Hence, without coning, the flanges rvould cause a slightbut sudden shock to the sides of the rails-

Behaviour ofconed rvlrcels on straight and level track is shown in Fig:5-15. In this case, tl.re

llaugcs ol rvhccls have eclual circumlcrence. But the situation is different when the wheels

move along a curve as shown in fig. 5-16. In this case, the outer rail has to cover a greaterflongc Coned ! in 2O

Bchaviour of concd whecls on.lcvel trackFro.5-15

l:20l: f o

lrrret Roll Oulcr

Bchaviour of coned wheels onFro.5-16

Roil

curveS

distance than that of thc inner rail. Also, as the vehicle has a tendency to rnove sidcways

towards tlre outcr rail, thc circLrnrfcrence of thc flange of outer wheel will be greatcr than that

of tlte inncr whcel and this will help the outer rvheel to cover a longer distance than the innerrvht'cl.

Corrrog of s hce ls is nrlirll, dorrc

:r to rnaintain tirc vclriclc in the ccntral position with respect to tl.re track. and thereby

o to avoid f iction bc[rvecu rail and wheel rim

o to mininlize slipping of inner wheel when moving along,a curve

Coning of wheels has tlie lollowing disadvantages:( I ) Smooth riding is produced by the coning of wheels. But the pressure of the horizontal

component near the inner edge olthe rail has a tendency to wear tlie rail quickly.(l) l'he horizontal corlporleuL terlds to tum the rail or.rtwardly and lience, the gauge is

sonletimes r.vidcncd.

(3) If no brsc-platcs arc providcd, slccpcrs undcr the outcr edge olthe rail are damaged.

In ordcr to nrirrir:risc thc above-mentioned disadvantages, tiltittg of rails rs done, wl'rich meansthat the rails are not laid fiat, but they are tilted inwards. The most common method adopted fortilting ofrails is to use inclined base-plates as shown in fig. 5- 17. The slope olthe base-plate isI in 20 which is also the slope ofthe coned surface ofthe wheel. Following are the'adyantagesof rilrirry ol ruils:

'^"u;:1.lTiro'"*

: The tilting of rlils ntain(ains tlie gauge properly.c The u'ear olthc head olthe rail is unifonl due to tilting ofrails.r The tilting of rails increases the lile ofsleepers as well as rails.

Ilogged rai Is:

Rails wliich are bcnt vcrtically at the ends are known as hoggecl rails and they are fonnedduc to wear of rails on cnds. Thc hogging rails causc dcterioratior-r ir.r the running quality of titetrack. -fhis is or.rc of the serious rail delects and the following methods are used to rectily suchdanraged rails:

( l) The hogged rails should be removed and replaced by new rails. However, this will bevery uneconomical. But some economy is achieved by using hogged rails on sofle un-irnponanl. Iines.

(2) The end portion of the rail is cut-off and fresh holes are provided for fish-plates. Thus,the rail is shortened but can be used conveniently. This cutting can be done either atdepot or at site. The fomrer method is tedious and unecononiical as the rails are to betaken to the dcpot, rcpaired and then brought back to the site. In the second method, aportable drilling machine and power saws are used. The rail ends are cut-off at site onlyand then the rails are pulled back corrcsponding to the length ofcut-off. This method is

Slop€ L; )O

{

uscd in U.S.A. aud was provcd to be quite successful

(l) Fioggctl rails can bc inrproved by rvelding the rvom ends of the rails'

(1)Hoggedrailscallalsobeinlprovedbysorrresirrrplcclcvicesuclrasadelnggedntuckinc.' It c-o-nsists of a bottie jack, , lcngtt] of old rail and two sets of clamps. This machine is

uscd ,,vitlt sttcccss in India.

Ilucklittg;

Sonrctinres, lorrlatior.r ol buckles takcs place which nleans that the track has gone out of its

original poiition. This happens on.,,ru.i when expansion ofrails is prevented. The preve.tion

oI erpltision Ittay bc due- to ottc ol'the Ibllowing ,]vo causes:

(l) insulficietlt cx1;attsion gap. antl

(2) excessive tiglitncss of the joint.

Buckles in tracks are serious ancl sonletimes, they are responsible for the derailments of the

trains. Hcncc, propcr ci)rc shoulcl be takelt to avoid buckles. Precautions to be taken are as

follorvs:

i. Expar:sion ga1; shoulcl be sulficicnt.

2. The fish-bolts shor.rld not bc tightcned up to such an extent as to prevenl expansion or

contracl.iott ol' rli ls.

j. The corltact surlaccs bctrveen thc fish-plates and rails should be periodiially lubricated.

hL

i 3i SLEEPERS

I;unctions ol s le cpcr.s

Slccpcrs arc lrlllsycrsc tics ott rvhiclr llrc rails arc laid.'fhe LIain lunctions ofslccDers are ls[o Ilori s:

-.r Llolding rails to corrcct Saugc and alignntcnt.r Civing a finl and evcn support to rails.: To nraintain tltc alignnrcnt and gauge of the track correctlv'r 1'rarrsrcrring rrrc road *'crrry riorr the .ails to r.vider ur.u of ,h. bn r.,.-: Actirrg as u, crastic nrediu, betrveen the rairs and the balrast to absorb the brorvs

arrd r ibratiors ol ntor.ing loatis.-.r l)rovitling iongitLrdirral and latcral stability to pcnlanent wly.r Pror,iding ntcans to rcctify the track gcornetry during its service life.

Requirements ol' an idcal sleeper

Ihc i<leal sleepcr.should nor.nrally lulfil tlie lollou,ing requirements:c Thc initial cost as well as uraintenance cost should be nrinintunr.:: Thc rreight o1'thc sieeper shoukr be nioderate {br ease ofhandiing.= The design of slcepc. a,d faste.ings should be such that it is possibre to fix anil

rcntovc thc rails casily.e fhc slccpcr shoulcl havc sufficient bcaring arca.-"r 1-lrc slc'cpcr srrourd trc sucrr rrrat ir is possibrc to maintain a.d adjusl gatrge properly.:r The rnar'criar o1'sJccpcr urrtr its desrgn shoLrrd be sLrch that the sreeper does noib,.erk

or get damaged rvhile packing below the sleeper.-.r The dcsign olslccpcr shouid be such that rt is posstble-.r 'l'he slccpcr shoLLlti be capabie olresisting vibrations

T1,pes of SleepersDcpcrdi.g upon thc posirio' in a railway track, siccpers may be classilied as''t Longitudinur srecpcrs- I'rrcse are the earry rorm ofsleepers a.d consisted orslabs ofstortes or picces of tinrbcr praced paralrer to the rairs as shown in fig.7-1. At presenrthey are not being used because high cost and poor perlbrmance.e Transverse sreepers - Trarsverse o. cros.-sleepe.s were first introduced in the year

1835 anci rncy arc rrow univcrsally adopted. They have b.."-" ;;;;;;,_; ;;; **renrove ,' Lhc disadvanrages of the rormer type. They are placed at right-ar.rgres to theraiis as shorvn in trg. 7-2.

fast nroving trains.

r The sleepcr should have anti_sabotage and anti_theft

to har e rrack cir.curring.

and shocks due ro passage ol

qualities.

i{

I

t4//

Depctrding Lrpon the rnateriul transverse/cross sleepers may is classified as

-.r \\'oodcn slccpcls-.i Stccl s lccpcrsr Cast iron s lccpersJ Concrctc slccpcrs.

\\'oodcn SleepersWoodcn sleel;er is thc tttost idcal typc ofslecpcr and it is being used universally ahlost evel'sittce tltc invctt(iott of Ilil*.tr,. Its utility hus not tlccrcascd witlr thc passagc of tinrc. Only thcpossiblc sltorl:rgc ol's,ooti ir fittttrc hus lcrl ltr llrc llrirrltirrg ofslccpcrs ol'othcr ntatcrials.

Ihc rvoodcn slcepcr Iras tlte It-rllorvitrg lrrirrn advantagcs arrti rlrsadvurrtrt:es .

Adyflrtl ges

o Cheap arrtl casy Lo ntanLrlacturc.

:: Absorbs shocks lnd Ius gor good ca1:acity to dantpetl the vibrationso Thercby retarns packing rvell.

c Easy harrclling witllout diintagc.

o Suitahlc for track cilcuited sections.

: Suitablc lbr aleas har,ing yielding forntations.u Alignnrent can bc easily corrected.

:: Morc suitable lol rnoclr: rn tncthods of nraintcnancc.Lr Can bc uso(l u,itir or rvithout stone ballast.e Cirn be uscd on blitlgcs and ash pits also.

Disulvuntagasi.: l,csscr iil'c iluc to n,car, dccay and attack by vennin.u Liablc to mcchanical wcar rvitlr bcalcr packing.o Difficulty to nraintain gauge.

o Susceptible to llrc hazards.

tr Scrap value is negligible.

Sr.c.'The size of'sleepers will dependStandard sizes ol- titnber slccpers used

: I;or [].C., 274 cl"r x 254 rnnt xc For M.G., 183 cnr x 203 nrnr x:.t Iror N.G., I 52 cnt x 178 rnrr x

upon the load coming and the quality of wood.are as follo*,s:127 nrnr.

I l4 rnm.

I I 4 nrnr.

,jL

,,1 ::.itrg oJ lllootlctt Sltcpars

Iil order to enablc tile rails to l)c slightly tiltcd inu'ards at a cant of 1 in 20 the Wooden slcpcrs

rc rcqlrircd to bc cut to this slopc at rail scat bcfore laying. This proccss ol- cutting tlrcsoodcn slccpcl at a slopc ol' I in 20 is knorvn as 'Adzing of Woodcrt slccpcr'.It is to bc donc ri ith grcat carc othcnvise the slopc u,ill vary lrom sleepel to sleeper resulting

in roLrgh riding.'fhc adzcd surlacc olrloodcn slccper is treated rvith coal tar or creosote to

cnsLrrc ploper protcction oi'surlitcc. Nonlally adzing olrvooden sleeper is done only when

bcaring platcs arc not provi(lcd.

S teel S lecper-fhc inclcasing shortage ol'tirlircr and otircr ccononrical lactors are urainly responsible ibt the

use of steel slecpers. The stcel sleepers have the lollorving main advantages/disadvantagesover the rvooden sleepers :

Fig. 7.1. Stcal Trouglt Sleeper (8.G.)

Advtnlogesu Longer life.

o Easy to maintain gauge and lesser maintenance problems

c Bertcr lateral rigidity.o Lesser dan:agc dtrring handling and transport.

o Manulacturing proccss is simple.

:.r Vcry good scr:rp r;rltrc.

r Free llonr dccay arrd attack by vcnlin.tr 1\-ot susccptible to llrc hazards.

Disuth'ttrrtngcs--.: l-iabie to corrosion.

-.r Urrsuitable [or track circuitrrrg areas.

-.r t-iablc lo bcconrc ccntrc bound bccausc ol'slopcs itt two cnds

-: Dcve lops cracks at rail scats during scrvice.:.r Can only be used lor rails lor."vhich it is manufactured.

Dasigtt l"oatun:s-l'hc stcel trough slecpcl cssentially consists of a rolled steel plate of about 12mm (1/2")thickness and pressed to suitable trough shapc and rhe rail seat canted to I in 20. The ends ofthe rolled section are flattcned out in the shape of a spade to retain the ballast. Tno

Jf

l4{",.l.- zro .-lSEC. AT A-A

lultcrnativc typcs of slccltcls htrvc bccn designcd lbr each raii section as. per dctails givcll

hclorr:(l) ln otlc t),pc, thc lLrgs or jarvs arc ltlcsscd out ol'thc platc itscll- to irccollll)]ollatc tllc

lbot ol rlrc rail a:rd thc kcy (Fig.7.5). Thele are a lot ol maitttenance problenls with

rlrese llrc'sscd up Iugs its thcy git,c way duc to the utoventeut of thc keys as rvell as due

to the vihrations ancl itrtpact of tlre nloving 1oads.

(2) 11 ordcr to obviatc this dc{cct. auolhcr dcsign ol slcspcl's has bcctl adopted. In this

typc, t\\o hoies ar.c punchcd in the plarc on cither sidc ol the plate to acconlnlodate

specially dcsigned 'Loosc jarvs' (Fig 7.6). Thc rails are l.reld rvith the help of trvo

stantlartl ke;'s tlrivcrr cithcr i:r thc lttcsscti Lt1> lttgs or in the loose-jarvs.

Fig.7.5.Sslcepcr with pressetl- up lugs

'l'he adjustntent of thc gauge to tltc cxteltt oli 3 tunr (1/8") is dole by proper driving of the

keys. In the dolble linc section, the keys are driven in the direction of traffic. The weight of

standard B.G. tlough slccpcr is 81 kg and that ol M G. sleeper is 35 kg approximately. The

stcel Irou,lh slecpcr has iln avcrage lif-e olaboLrt 50 years. It is an acceptable type of sleeper

lbr usc witS long rvcllcd rails bccaLrse of its latcral stability and its adaptability for use u'ith

clastic lastcn ings.

KEY Ki:Y

l;ig. 7.6 Sleqtet' x,itlt loosc.iatt,s irrscrted itr ltoles

^rJ!

."i, l,

Fig, 7-7 Steel sleeper *,ith bolts

PEESSED

LOSEJAW

$$mTEo W

Cast I ron S lecpers

The nrain advantages and disadvantageslollos's:

Adt' ,ttagcs

:l Lcsscr corrosion.-J Lcsser liablc to crack at rail scat.

-r Easi,.'r lo rnlrtttf;.rctttrc.: H igher scrap valuc.

Disa va,iugas

ol C.l. sleepers over stecl trough sleepers are as

r Cauge nlaintcnance is difllcult as tie-: Providcs lcsser lateral stability.o Unsuitable lor track circuited lines.I Not very suitable for mechanical maintenance.: More susccptiblc to breakage.

Cast irort slccpcrs rre uscd irt many coLrntries. Type of C.I. sleepers are

J pot type - corrsists of two oval slrape pots.

tr plate type - consists oItwo plates.

Fro. 7-6

C. f. sleeperFrc. 7-7

bars get bent.

I'ltc cr alLrutron ol corlcrctc slccl)els llas Dcott lltattlly uLlc io

-: Econonric consitlcratiotrs couplcd rr'ith thc clentcnts of chatrging traffic pattem.

:r Morcover, a slceper lor long rvclded track has to be heavy and sturdy and should be

capablc ol'ol'ltrirrg latclll lcsistance to tlrc track. Wooden and stcel slcepers wct'c fbund

to hc llcking in ll)csc re(lllirctllcllts.

I;ig. 7-8 shorvs il lypical prc-strcssctl cottcrctc slccpcr.

Reinlorcemen

66a-:iJ F

259cm*----+r j*Xq.-a

Prc-stressed concrete sleeper for British Railways-Class EFro. 7-8

Advu tuBcsjr Conclcte slcepcrs, being hcavy, lend strength and stability to track.

r Concrete slecpers s,rth clastic fastenings provide a track which can maintain better

gaLlgc. cross icvcl attd aligrtntcttt. lt retains packing also very r'r'ell.

r The concrcte slccpcrs, bccause of thcir ilat bottom, are best suited for modern

nrethods oI track nraintctrancc.

o Concrctc slcepcrs carl bL- used ilt

electlicity.r They are ncither intlarrnrablc nor subjccted to dat.nage by pests or cottosiott in normal

circ ur.ttstances.

The lilc ol'concretc sleepets is very long, probably 40 to 50 years. Rail and sleeper

rcncu'als as such can be rnatched, wltich rs a very big economic advantage.'l hc cotLcrctc slccpcrs cal gcrtcraily bc ttutss ptotluccrl ll'ortr locll lcsoLlrccs.

Disa vutttugcso Handling and laying ol' concrete

Mechanicrl rncthods have to be

considerable initial cxpendittirc.

track circuited areas, being poor conductor of

sleepers is difficult due to their being heavy.

nonnally adopted for handling which involve

c The danrages to coucrete s)cepers is very heavy at the tilne ofderailment.

c There is no scrap value lor the concrete sleepers.

Sleeper Density and Spacing of Sleepers

Tlre nunrber of sleepers used per rail length on a track is known as sleeper density. Sleeper

density mainly depends upon:

o Axle load and spccd,: Type arrd section ofrails,r Typc and strcngth olslecpcrs,,-r Type of ballast and ballast cushion,iJ Naturc of fornration.

The ntorc thc no. olsleepers greater will be the lrteral stability. The no. ofsleepers, horvever,cannot be increased indclrnitely, since a certain minimum spacing is necessary for packingthe ballast.

It isspecifiecl byM+xorN+xwhereMorNisthelengthofrailinmetresoryardsandxislhe n urllber.

In rnetric units, ifslecpcr clcnsity is M + 7 on e Broad Gaugc route and tlte length ofrail is 13

nretrcs, it nlcans tlrat 13 + 7 = 20 sleepcrs will be used per rail. Similaily in F.P.S. Units, ilthc slccpers dcnsity is N + 3 on a M.C. route and the length of rails is 36 11. or 12 yards, thenunrber ofsleepcrs used is l2 + 3 : 15 per rail length.

l'he number ofsleepers in the track can also be specified by indicating the number ofsleepersper kln of track, e.g. 1540 sleepers per km. This becomes more relevant pa(icularly in thosecases rvhere rails are welded and length of the rail does have much bearing.

Spocing naar tht' Joints

'[hc spacing is kept unilornt throughout the rail length but is made closer near the jointso because of thc rveakness ofthejointss to give st.rong support against tl.re impact of the moving loads on it ando to avoid loosening o[ballast due to impact in suspendedjoints

As such, the spacing ol sleepers is not uniform near the joints. Three or four sleepers oneither side of the joints known as shoulder sleepers are kept close together. The details ofthespacing are shown in Table 7.1 and Figure 7.1 .

I

,/--

Cornparison ol cltaractcristics of dilTcrcnt typcs of slecpcrs

Cltu ructcrstics ['l'oolut Stee I slecpers L'.1. s lcapcrs Concrcte slacpcrs

l. Scrvicq lil'c

2. Wcighr lor B.C.

3. Ilandlrng

-l l'r,pc o1'

nrailltenancc

5. Cost ofntailttertance

6. Cauee ad justrncnt

7. Track circLriting

E. Danrage by whitcants and corrosion

9. S uitability lorlastening

10. Suitablility totrack

I l. Track clast ic ity

I 2. Creep

13. Scrap valuc

l2 to l51,rs.

83 kg

M an Lral;

No darl;rgcrvlrilc lt anciling

NIattLral tlrnr cchan izcd

H i_qh

-=GDil'ficLrTh/

Bcsl

Can bc dantagedby white ants

Suitablc lorCF&EF

Suitable lor allfoulcs*

Good

Crcep iscxcess ive

Low scrap valuc

3U to -10 yrs.

179 kr

lu,'nurt ;

lNo danra-ge

lrr h r lc hrnd linu

I

lMrrr,r.il ,,,.

lnrcchanizedI

Mediunr

t-- ._--lEasv

I

lDiificLrlt;I lnsLr Illt ins nads

lrr" n"..rlrrv

No darlage butcorToston rs

possible

Suitable forCF&EF

Suitable lor allroutes

Good

Less creep

Highcr scrapvalue thanwooden sleeper

140 to 50 vrs.

lr, *n

1r,,,1,,,,lLiablc to breakbv ro Lt ult hrnd Iin l

1r"","].,,,

I

Medium

!-.lEasyI

t_--lDl ttl c Ll lt.

llnsuletinB pads are

nec csse ty

Canoe dantaged bycoIroston

Suitable foronly CF

Not suitable 1brhrgh speed routes

High scrap vahre

Good

Less creep

50 to 60 yrs.

267 kg

Mcchanized;Gets dauragedby rough hand lrng

Mechanized only

Low

No adiustmer.rtpossib le

Easy

No damage bywhite ants or '

corrosion

Suitable foronly EF

Suitable for highspeed routes.

Best

Creep isminimum

No scrap value

t Also suitablc lbr track circuititrg, lcvcl crossing and poinrs & Crossings... Large nunrber ol.anchors required to prevent &cessive crrep.CF stands lbl convcntional lastcning & EF stands for elastic fastening.

{/

I

{

'fable 7.1. Spacing of Sleepers (Fig. 7.1)

Spucing of Sleepers Metre Gauge centre locentre spacing in cm

Wooden Metal

2558

70(62)*

82(72)*

3.

Between joint slecpcrs (a)

Between joint sleepers ar.rd the firstshoulder sleeper (b)

Betwecn lst shouldcr slecpcr and 2nd

shoulder slccper (c.1 lbr sleePer

dcnsityM l-4andM+7*Between intcmlediatc sleepers (d) forsleepers density M +' 4 ar.rd M + 7+

+ The spacing is lor slecper density M + 7

Nores .. (i) The spacing lor joint sleeper (a) and the lst shoulder sleeper (b) will always

remain thc sarltc as givcn above for all length of rails and all sleeper densities. The

spacing (d) shoulcl bc rvhole numbcr o1'cr.n aud spacing c should be betwcen b and d.

(ii) In case of long welded rails on BC arld MG, the sleeper spacing is kept 65 cm'

L{I'EIIED ME *#Zf 'p{iZ'l'l9Sl"l3ltl*'#J:i'iJ'S{k'*TH'#fl'

33

58

1t(60) n

8i(64)*

Fig. 7.1. Spacing of Sleepers at Fish Plted Track

Broad Gauge centre to

cetire spacing in cm

30 38

61 61

70 72

(64)* (63)*

84 83

(68)* (68)*

(f nanast

Delin itionBallast is a layer ol'brolicn stone, gravcl or any other granular matenal placed and

packed below and around sleepers for distributing the load from the sleepers to the formationand for providing drainage as wcll as giving longirudinal and lateral stability to rhe track.

SleeperSlope

ofl tolot

t!rc t

Ballast sectionFrc. 8-l

FIC-A,2 BALIAST PROFILE FOR BG SINGL.E UNE FOR FISII PIATED TP./.CT

Functions of Ilrll^st(i) To provide a level and sound foundatron for the sleepers to rest on.(ii) To lrold thc slccpers in position during the passage oftrains(iii) 1'o transfcr and distribute the load from sleepers to a large area of formatiolt.(iv) To provide elasticity and resilience to track for getting proper riding comfort.(v) To provide necessary resistance to track lor longitudinal and lateral stability.(vi) To provide elfective drainage to track and keep the sleepers in dry condition.(vii) To provide effective means ofmaintaining level and alignment ofthe track.(viii)To discourage the growth ofvegetation.

Requirements of good Ballast(i) lt shoLrld be tough and wear resistant.(ii) It should not be brirtle,(iii) tt should be hard enough so that ir is not crushed under the moving loads.

ii

\'

/c c)

'g"--Vo o o ^oo<>" o o

3-3:3'i;.c> o <=, ooolo,

"\ ..

\

(iv) lr shoultl bc dLrrable and should not gct pulvcrized under the weather conditiotls.

(v) lt should be generally cubical in shape with sharp edges so that they can

sufficient grip over the sleepers to prevent their horizontal movelllent'

(vi) It should bc notl-porous and Ilon-absorbcnt of watcr'

(vii) lt should provide good drainage of water.

(viii) lt should be cheap and easily available.

T1'pe of Ballastfoilo*'ing materials are uscd as ballast in a raihvay track:

(i) Broken stone( ii) Gravel(iii) Ashes or cinders(iv) Coarse Sand(u) Kankar(vi) Moorum(vii) Brickbats(viii) Selected earth.

(l) Broket stoua:This is the best material lor perfonning the lunctions of ballast in a railway track.

Almost all the important tracks are provided with stone ballast. The stone to be used as

ballast must be haia, tough, non-porous and should not decompose rvhen exposed to air and

danrpness. Cranite lulfilli these conditions. But due to consideration of availability, quartzite,

sandstorle and linrcstonc arc also used as ballast. Initial cost of the material is high. But itkecps the triick in bctter position, cspccially undcr heavy traflic.

(2) Gruvel:Gravel comes next to broken stone and it is used in many countries. It consists of wom

fragments of rock occurring in natural deposit. It is obtained from river beds or gravel pits

along the track,

Ath,ttnlages:(a) It is cheaper tharr stoue ballast.(b) The drainage property is excellent.

Di.t(l\'0 n ta gc.\:(a) It casily rolls down duc to vibr-ations and the packing under the sleepers gets'loose.

(b) Variation in size is considerablc and hcnce, it requires screening before use

(3) Ashes or ci,tders:The residue from the coal used in locomotives

cinders and this is one of the most universal formsrailway which uses coal as fuel.

and other fumaces, is known as ashes or

of ballast, since it is by-product of every

ti wrntages:(a) - ris nraterial has got fairly good drainage properties.

(b) Handling of tl.ris matcnal is not cumbersome(c) The cost ofnraterial is low.(d) The nraterial is available in large quantities at short notice.

Dr Md. Sha,Jsul Hoque

{

{

Disutlvu tt tuge-s .'

(a) This material is r,ery sofi and it gets easily reduced to powder and heilce, the trackbeconrcs vcry dusly. This is objcctronablc cspecially in dr.y wcather.

(b) This ballast has got conosive qualiry and hence, this is not used where steelsleepers are flxed.

(c) The foot of the rail gets aflected where this type ofballast is used.

(4) Sand:Sand lorns anothcr good ballast nraterial. Coarse sand is to be preferred to fine sand.

.,11t'u rtlctgcs:(a) lf the sand is fiec lronr eiirth and vegetables, it has got excellent propefiies to drair.r

olT wal.er irnntcdiately.(b) This rraterial produces a silent track and has been found very good for packing

casl- irou pot sleepers.(c) It is chcap, ifavailable in nearby locaiity.

D$dlld tagcs;(a) Sar.rd ballast rerluires fi"equent rcnerval as sand can be easily blown off or washed

away(b) Sand is disturbcd casily by vibration and hence, the maintenance oftrack becomes

vcry drlficLr h.(c) Sand gets into the nroving parts of the vehicles and causes friction. This Ieads to

hcavv wcar of vch iclcs.

(5) Kankar:Kankar is found * many places in the fomr of nodules of varying sizes. It is useful

where other suitable uraterial for ballast is not available and also, on light tralfic on metregauge and narrow gauge. Kankar tums down to powder very easily and lrence, thenraintenance of the track becomes very difficuit.

(6) Moontm:Deconrposition of laterite rcsults in the fomlation of moorum. It has a red and sornetimes

a ycllo* co lou r.

,llvuntages..(a) Moorunr can salely be used on newly laid tracks and it will act as soling when the

stone ballast is laid afterwards-(b) Moorum has got good drainage properties.

Disutlvutttuges;(a) Moorum is soft and it turns into dust in very short time.(b) Maintcnancc of rlack laid with this material as ballast becomes vcrv difficult.

(6) IJrickbats:Sometimes, brickbats ofoverburnt bricks are used as ballast.

t? Dr. ltld. Shansul Hoque

,d

Adva lugcs:(a) Brickbats arc uschrl in places where suitable rnaterials lor ballast are not available.

(b) Brickbats havc gr.rt lairly good drainagc propcrtics.

Dis(dru tuges:(a) Brickbats turn dowt'l into powder lorm very easily and

(b) it becoues very difficult to maintain the track inthe track becomes dustY.

good condition where this

ruraterial is used as ballast.(c) Rails are olten corrugated ou the track laid witir ballast ofbrickbats.

(8) Selected earth:For sidings and also for newly laid railway tracks, selected earth is sometimes used as

ballast.

Minimum depth of Ballast Cushion

The depth ol the ballast is dcflncd as the distance between the bottont of sleeper and top ofsubgrade. This depth of ballast is very important in deternlining the carrying capacity of the

track.The loacl conting on the sleeper is transferred through the medium ofballast to the formation.

The pressure distribution of the ballast section depends ripon size and shape of ballast and

dcgree ol consolid:rtior.r etc. Through the lines of equal pressure are in the shape of bulb, yet

foi simplicity, the dispersion of load can be roughly assumed at 45 degree to the vertical. In

order to cnsurc that thc load is translcrrcd cvcnly otr thc lon.ttatiott, the dcpth of ballast should

be cnouglr so that dispcrsion lines do not overlap each othcr.

FIG. A.I MINIMUM DEPTH OF BALIAST CUSHION

It can be proved by a simple geometry that for even distribution of load on the formation, the

depth ofballast is given by the fonnula.

Sleeper spacing: Width ofthe sleeper + 2 x depth ofballast.

Assuming that the track is laid with woodon sleepers to N + 6 slecper densrly, thc slccpcr

spacing is ],5" and width of sieeper is 10", the minimum depth of ballast fi'om the above

consideratioir comes to 7 112'. A rninimum cusliion of 15 to 20 cm. (6" to E") of ballast below

the sleeper bcd is, therefore, nomrally prescribed.

Dt. M.l. Sh.,nsul Lloque

J'1'. '

Y"

Spccification of Stone Ilallast

Pht'sicrtl propartics of btllust:0 Qualit.y of Truck ballusr

fract-Uattait ihould be obrained iiom good quality stone and top layer, if weathered, must

not be used. Track ballast sl.rould consist of hard and rlurable stone and sl.rould confom to the

upproYe<t samples. Track ballast should not contain inorganic or organic residues and must be

lrcc lrorn infcrior and harnilul substances.

(iii) Elongatiort, Flakiness Speciftc gruvitl' and absorption properties

(ii) Si:e untl Gradatiotr of Ballast:a) Retained on 65 mnl square me sh:

b) Retained on 40 nttn square nlesh:

c) Retained on 20 mnl square mesh:

ballest

T)'pe of te sta) Elongation Indcxb) Flakiness lndcxc) Specific gravitYd) Water absorPtion

Meclrunical properlics of ballast:T1'pe of test

a) Aggregate Abrasion valucs

b)Aggrcgllte InlP:rc t tcst

NIL55% to 10%Not less than 100% for machines crushed

Re commended. ValueMaximum 507u

Maxir.num 500%.

Minimum 2.65Maximum 1o%

Reconrmended ValueMaximum 3070

Maximum 207o.

Ballast sectionFrc. B-2

Droin

Ballast sectionFro. B-3

,{::r:t'":"-'i:::b>:.,-'a)

..."=

Subgrade and Formation

Definitionstl SttbgrctLle;strbgradc is rronnally dcfined as thc naturally occurring soil.ri) Intli.ot,ad Suttgr.ude . Natural sirbgrade which can be fLrrther prepared to receive the

b a I last.iii) Formution. The prcpatcd

and rails is callccl tlrcembartknrcnt or a c Ltttin g.

ir,) En ;urtkntcn /r whelt the fbrrnation is in the siiape of raised bank consLructed abovethe natrlral ground, it is callcd an Ernbankment.

v) Cutring'. lV-hen thc formation is at a Ievel below the natural ground, it is called a

culting: Nornrally cuttirlg or excavation is nrade through a hilly or natural ground forprovrding the railway line at the required level below ground level.

Iiunction of FonnationThe fonnation has the following lirnctions:

i) To provide a snrooth and unifomr bed on which track can be laid.ii) To bear the vertical load of moving trains.iii) To rcducc the intcnsity of load at natural sub-grade level.iv) To keep the track above flood Ievel.v) To providc stability to thc track.

Emban knrent Geontett'yo The height of lbrnration depends upon the ground contours, highest flood level (HFL)

and the gradrents adopted.o The width of the lonnation depends upon the number of track'to be laid, gauge and

such other factors.o The side slope of the embankment is dependent upon the shearing strength of the soil

and its angle of repose. To prevent erosion of the side slopes due to rainwater, rvaveactioll e1c., tire side slopes are turled with a thin layer of cohesive soil or alten.rativelywith suitablc tyl.rcs of grass. Sometimes, a toe wall is provided at the bottom of theembankmcnt to plevcnt sliding of soil.

Blanket LayerBlanket can bc deflncd as an intervening layer of superior material rvhich is provided justundcrlcatlr tlre billlast cuslrion. lt is dilfcrent fron sub-ballast rvhich is provided above thelorniation. The [unction ol the blanket are two-fold:

(a) To mrnimisc the puncturing of stone ballast into the formation soil.(b) To reduce the ingrcss o f rainwater in the formation soil.

The blanket should generally cover the entire width of the formation. The depth of theblanket should normally be about 30cm in ordinary clay soil. However, if formation soil isparlicularly wcak, a thicker layer upto 60cm may be necessary depending on the shearpropcrties of thc lormation soil.

'l'cchniques to I rnproYc Embaukment Stability.[-here are varit.rus methods to improve the stability olrailway embanl(ments:i) Flutten sidc slopes: This provides better stability particularly when there is

iailure due to fill nlaterialit) Intprovc tlrainage: -Ihe drainage gets improved by providing surface and sub-

surlace cir:rins.iii) Provisron of sheet piles: Sheet or ordinary piles are provided on either side of

ernbankrnent to cheek the shear failure and improve stability.iv) Scnd drains: This helps in quicker consolidation of ernbankment.

tlat surface, rvhich is rcady to receive the ballast, sleeperslbrnration. 'l'hc tbrntatior.t can be it.t the shape of an

Dr Md. Sh/.trtsul lloque

{

\) Itiver!(tl fittcr. A blarlkct of adequalc thickness or illvetlctl filtcr is providcd\ )

;:ii"";;; 11.,iirt, ,,,.1-*"rr for:'ration to improve stahilitv

,.'i) Ct'rrcrrt s,rotttittg:irrlt]lLUii'i" I*p't"ini tr'" stahiIitv"of the bank'

lii) !;;;;;;,/i;;. :irh"'

';;;J pit'i' (ro"pl"t tlre-soii and pr6vide mechanical support 10

,,,,., tlll*,),1.0,,i-

tt of soir: Che,.rical a,d mechanical srabilization l.ras the potential to

inrurove stability o l' thc entbattknrent'irt Giorett ile,".l,,,,q,l"r li1,iJr.,.ipt 1,,,'i*p.'ing dri'inage and provide resistance to

thc soil bed and thcreby inrprove the slablllly

t"il':.:i:lif;::'lii 3,l,,",,ilji.tjl'li.>oir has rcccnrry been gg.,qlop"a in mrnv :::,il,l::.:,f ,h"

rt.rtrt bv usc ol.Cl-OTE\ I f LLBI iiiir',*'* 'rri.i;,ri " U^i.ullv'rttrdc trp ol polyurcr. irrrd lrrs

uniquc properry ol.ullo$ing r rr?"r, rt"i"ro fasr itriougtr but noi iire soil fines. ceotextiles r.r ork

not only as sepalalors ono "'it" n" il'L a'uin thE water and provide reinforcemellt to the

soil bed.

Allyerofgcotextilclsnorrrtallyl;rideitherdirectlybelowrhehallast.sometimesitrslaidassandu,iched betrvceu rry",. oi'r'",,i'lo iii"i u.ri.r, does nor reir airectty on the ceotextile and

il;1";td;;." of te ar and purlcture gets redr-rced

BALLAST

t-t<;- 9.7 FUNCTIoNs oF aEot'Ex'|-ILES

r!,IOISTUHE

rta. 9.E LIvNA l)l Gtol LrnLEs

MOISTURETBAN9POBTEDALONG PIANEOF FABAIC &THROUGHAALLAST

SOIL FINESRETAINEOSELOW FABRIC