Rails

TOPIC-

NAMEENROLL NO.PATEL JIMI131100106029PATEL MILIND131100106035PATEL VIRAJ131100106040PATEL YASH131100106042SHAH ASHIT131100106051

GUIDED BY: Prof. Rajan lad Prof. Nilesh Rathod

Rail failures - ReasonsSometimes rails fail suddenly without any notice. Factors that influence the failure are as follows.Axle load of locomotiveConstant reversal of stressesDefects in manufactureDesign of rail jointsFatigue caused by shearing stressesFrequency of rail renewalMaintenance of rail joints

Rail lengthRail qualityRail sectionRail weldingSpeed of trains etc.,The above are some of the main reasons of the rail failure

Rail failures - TypesCrushed headTransverse fissureSplit headHorizontal fissureSquare of angular breaks

Crushed headHead gets crushed, metal flows on the head of railDefects in manufacture, flat spots on wheels, slipping of wheels, week support at the rail end etc.,Skidding causes flat spots, loose fish bolts cause week support at endsTransverse fissureFissure or hole in the headIn the form of a cross wire crack starts inside head and spreads graduallyPoor manufacture, excessive strainingVery dangerous, rail breaks with out any sign often

Split headHead is split into 2 partsIf the surface of crack appears smooth and dark, it is called as piped railFormed due to cavity during manufacture, or shrinkage of metalHorizontal fissureA fissure developed keeps on increasingOutcome of worn fish plates or insufficient ballastSquare or angular breaksRail breaks either in vertical plane or angular plane

Creep of railsLongitudinal movement of rails in a track is termed as creepCommon to all railway tracksValue changes from 0 to 130mm per month

Creep - causesBrakesDue to forces while starting or stoppingStarting rails pushed backwardStopping rails pushed forwardWave motion of wheelsDue to wheel loads rails deflect as continuous beamCrests at supports (i.e., sleepers)Changes in temperatureUnequal expansion and contractionHappens more during hot weather

Creep on rails

Creep - causesFollowing are some of the minor causesrails not tightly fixedBad quality sleepersBad drainageNo proper consolidation of the bed of trackGauge maintained tightImproper super elevation at curvesOver capacity of traffic on railsBad joints due to poor maintenance

Allowance of rail expansion jointsDecaying sleepersUneven spacing of sleepersDefective packingInsufficient ballastImproper usage of brakes

Factors determining the magnitude of creepAlignment of trackGreater on the curvesGradient of trackMore on down gradientDirection of motion of trainsOne way or 2 way, no of lanes, load of trainsEmbankmentsCreep more on newly constructed embankmentsWeight and type of railLight weight rails creep more than heavy weight rails

Results of creepSleepers move out of positionGauge disturbanceGap variation at joints and other parts, results in uneven stressesPoints and crossings will be disturbedDifficult to refix rail with creepInterlocking mechanism also gets disturbedBallast gets disturbed

Measurement of creepMeasured using creep indicatorOn the side of bottom flange of rail on either sides, a mark is made by chiselTwo posts of rail are driven in the formation and their tops are in level with top of sleeperString fastened to the post and passed through markings towards railDistance between string and the marks on the bottom of rails will indicate creep during a course of time

Creep measurement

Methods for correcting creepPulling back of rails methodRails are pulled back equal to the amount of creepManually or using jacksSleeper fittings are made loose, fish bolts are removed at one end while at the other end are made looseAt the other end a liner is placed and the rail is pushed or pulled as requiredFollowing points should be notedTrack should be packed properly after pushing/pullingFacility should be there to avoid restrictions to existing trafficLabour should be procuredAll fish plates, bolts should be cleaned, oiled and refixedGood to adjust creep before summer

Usage of Creep anchorsPulling back method is tedious, costly75% decreased using creep anchorCreep anchor is a cast iron piece which is made to grip the railThe arrangement of anchors prevent the movement of rails there by creep, because the sleepers which are embedded in the ballast should move for movement to take place

Methods for correcting creepDifferent types of anchors are availableFollowing points should be kept in mind while using creep anchorsCreep anchor should be strong enough to resist stressesNo of anchors are determined by the intensity of creep. 4 anchors per rail are provided for a creep of 7.5 to 15cmCreep anchors should be placed at points where the creep originatesShould be avoided on railway bridges

Methods for correcting creepAdditional creep anchors should be provided on level crossings, at places where heavy brake applications are madeDefective creep anchors should be replacedAnchors fixed to rails by using clamping, wedging and other methodsCreep anchors should be fixed to good and sound sleepers

Methods for correcting creepUse of steel sleepersUse of steel sleepers on a track minimizes creepSleepers are provided with fittings which do not easily allow the creep to occurThey will also have a good grip with ballast to resist their movement in ballastIncrease in number of sleepers will also help in prevention of sleep.

Rail jointsRail joint are necessary to hold together the adjoining ends of rails in the correct position to ensure continuity. Joint form the weakest part of the track.It is observed that strength of a rail joints is only 50%of the strength of a rail.

Requirements of Ideal JointRail joint should hold the two ends of the rails as nearly as possible. The two ends should be at the same level and in the same straight line.Rail joint should have same strength and stiffness as rails which it joinsJoint should provide space for the expansion and contraction of railsJoint should be such that any rail can be taken out easily or disconnected without disconnecting entire trackFishplates, rail contact surfaces wear gradually. Joints should be able to cope up with this adjustment.

Ideal joint should be cheap and economical for setting up and maintenance.It should be durableShould provide sufficient elasticity so that vibrations and shocks can be absorbed.It should provide resistance to longitudinal forces developed due to acceleration, deceleration to reduce creeping effect.Joints should be universal type so that they can be used for all type of sleepers.

Avoidance of jointsIn order to obtain better and smooth running of trains joints are avoided at the following situations.Bridge spans of 6m and belowLevel crossingsWithin 3m of approach of the bridge abutment

Types of Rail JointsTypes according to position of jointsSquare jointsStaggered jointsTypes according to position of sleepersSuspended jointsSupported jointsBridge joints

Square jointsWhen a joint in one rail is exactly opposite to the joint in the parallel rail it is called as square joint.Very common type of joint in straight track.Also most preferred.Staggered jointsWhen a joint in one rail is exactly opposite to the center of the parallel rail length it is called as staggered joint.

Advantages of staggered jointsCentrifugal force has a tendency to push the track out of line. Since the joints are weakest points they are more vulnerable. But staggered joints resist them to a great extent.More uniform vertical continuity of the track is formedProduce more smooth running than square jointsPossibility of forming kinks will be decreases

Decreases the vertical disturbance of wheelsNumber of impacts at joints are doubled but intensity is halvedNumber sleepers per rail length will be increased by one.Staggered joints are more adopted on sharp curves and not favoured on straight track.It is not a rigid rule to fix the rail exactly at the center.

Suspended JointsThe rail joint when placed at the center of 2 consecutive sleepers is known as suspended joint.Load is equally distributed on sleepersWhen the joint is pressed down both the rail ends are pressed down evenly.More commonly adoptedProvide greater elasticity to the trackCause less disturbance to the wave motion of trackRequire more maintenance

Supported JointsSleeper is placed exactly below the jointIt appears like rails are supported at weakest part.These are not used at presentSupported joint did not give sufficient support to the heavy axle loadsIf the joint is packed too hard it prevents it from settling at timesIt leads to the battering of rails as wave motion is not carried uniformly.

Bridge jointsIt is similar to suspended joint. Difference is here, a sufficient length of metal is used to connect the ends of 2 rails, so that there is no bending stress in the rail.Bridge is placed at bottom of rails and rests on sleepersSleepers at the end will have to be notched out at the sides or will have to be placed at a lower level than other sleepers to accommodate bridge.

Bridge jointsThe end sleepers are supposed to work as unyielding fixed supports.But practically they are not working as fixed unyielding supports.As a compromise between supported and bridge joints Indian railways provide semi-supported joints.Sleepers at rail joints are bought close here in this case.

Rail fastenings:A rail fastening system is a means of fixing rails to railroad ties. The terms rail anchors, tie plates, chairs and track fasteners are used to refer to parts or all of a rail fastening system. Various types of fastening have been used over the years.

Requirements of ideal fasteningGood fastening connecting rail and sleeper plays a vital role in improving the efficiency of railway track.Following are some of the requirements of ideal fastenings.Capable of absorbing shocks and vibrationsCapable of giving protection to the sleeper against different forcesProvide insulation in case of electrified tracks

Requirements of ideal fasteningCapable of resisting the creepCapable of securing the correct gaugeShould be economicalConsist minimum equipmentShould be durableShould be easy to fix and adjustShould be non corrosiveShould have sufficient strength to resist damage due to derailment

Requirements of ideal fasteningShould be possible to remove only using special toolsShould safe guard the alignment in all aspectsShould not adversely affect the rail and sleepersShould not be too rigidAdequate strength to resist lateral forcesShould possess high torque resistance

Fastening for railsFollowing are the fastenings which are used to keep the rails in their correct position.Fish platesSpikes, fang-bolts and hook-boltsChairs and keysBearing plates

Fish platesPurpose: connecting the rails at the endsHoles are drilled through web and rails and fish bolts, nuts are provided in these holes.When bolts, nuts are tightened it forms a continuous trackDesign: The pair of fish plates should have the same strength in bending as the original rail. This can be achieved by improving section of fish plate or by using high tension steels. For details, types and failures: refer text book

Spikes, fang-bolts, hook-boltsPurpose: Spikes are required to hold the rails to the wooden sleepers.Dog spikesScrew spikesRound spikesElastic spikes

Chairs and keysFor double headed and bull headed rails chairs are required to hold them in position.These are made of cast iron and help in distributing the load from rails to sleepers.Chairs are fixed with sleepers by means of spikes.Keys are required to keep the rail in proper position.

Welding of railsTo join two rails and thus increase the length of railTo repair the worn out or damaged rails and thus increase their lifeTo built up the damaged components of points and crossings

Advantages of WeldingIncreases the life of rails due to decrease in wear at endsDecrease in maintenance cost to 25%Smooth functioning of trackDecrease in creepWelded rails better for electrified tracksBetter for large bridges as rails of length equal to each span give better performance and reduce the effect of impact

Welding of rails result in decrease in construction cost due to less number of jointsFast and heavy traffic can be permitted on the trackTractive effort is reduced due to elimination of energy losses at jointsRisks of sabotages and accidents are reducedMore stability in lateral, longitudinal, vertical directions of track

Welding of RailsWelding methodsGas pressure weldingElectric arc welding/Metal arc weldingFlash butt weldingThermit weldingLooking at the advantages, requirements and facilities available one of the methods is chosen.

Gas Pressure Welding2 different types of gases oxygen, acetyleneKept in 2 different cylindersBurned at 1200C temperatureMetal rails butted together and welding done.Metal flows from rails to form a single sectionCheaper, good quality but limited outputs

Electric Arc Welding2 rails are treated as 2 different terminals.Electric current is passed across the gap of butted rails using different techniques.Insert plate techniqueScheron processEnclosed space techniqueCurrent produces heat to melt the electrode kept in the gapElectrode will have same metal composition as railThis method can also be used for repair works

SleepersFunctions : in a railway track sleepers add to the stability of the pavement. Following are the functions.Supports the rails firmlyMaintains the uniform gauge on trackDistributes the weight coming on the rails over a sufficiently large area of ballastActs as an elastic medium between rails and ballast to absorb vibrations of trainsProvides for easy replacement of rail fastenings without disturbing traffic

SleepersFunctionscontd.Permits insulation of track for electrified sectionsMaintain the track at proper grade by allowing raising of the rails and tamping the required quantity of ballastTo maintain the alignment of trackTransfers the load from rails to ballast

Requirement of sleepersFollowing are the requirement of good sleepersThey should maintain correct gaugeRails should be easily fixed and taken out from the sleepers without moving themSleepers should provide sufficient bearing area for the railSleepers should provide sufficient weight for the stabilityThey should be sufficiently strong to act as a beam under loadsThey should provide sufficient effective bearing area on the ballastThey should not be pushed out easily of their position in any direction even under the maximum forces of moving trains

Requirement of sleeperscontd..Design should be such that packing and tamping should not damage themShould be economical in initial as well as in maintenance costFittings of the sleepers should be such that rails can be easily adjusted during maintenance operationsIf track circuiting is required, it should be possible to insulate them from railsThey should be able to bear the stressesShould not be too heavy, nor too lightDesign and spacing should be such that ballast packing can be done easily and effectively in less time.

Types of SleepersDepending upon the position in a railway track, the sleepers may be classified as followsLongitudinal sleepersTransverse sleepersTimber or Wooden sleepersSteel sleepersCast iron sleepersConcrete sleepers

Longitudinal sleepersEarly form of sleepersConsisted of slabs of stones or pieces of timber placed parallel to railsCross pieces were provided at intervals to maintain the correct gauge of trackAt present these sleepers are not in use because,Running of train not smoothCost is moreMore noise is createdEtc.,

Transverse sleepersAlso called as cross-sleepersFirst introduced in UK in year 1835Highly popular, and most used in railways at presentMost of the disadvantages of longitudinal sleepers are taken careDepending on the type of material used for manufacturing these sleepers, classified into different types:Timber sleepersSteel sleepersCast iron sleepersConcrete sleepers

Timber sleepersAlso called as wooden sleepersFulfils most of the requirements of ideal sleeperUsed universallyBut due to high cost, mainly used as sleepers for girder bridgesSalwood, Deodar, fir and chirwood are used as alternatives where those are easily availableAt present usage and manufacturing decreased because of the advent of new type of sleepers

Timber Sleepers - FeaturesUtility:Very much useful for heavy loads and high speedsLife:Depends on various factors such as climatic conditions, intensity and nature of traffic, quality of wood, method of packing, type of fastening, protection against mechanical wear etc.,Treatment:Liable to be attacked by vermins hence treatment required to have more resistance.Preservatives are used for this purpose.Solutions used for timber sleepers are zinc chloride, creosote solution, salt solution or bi chloride of mercury salt.

Timber sleepers - FeaturesThe methods of zinc chloride solution and mercury salt solutions are known as burnettising and kyanizing respectively.Some times sleepers are just painted.Corrosion:Not corrodedInsulation:Ideal for track circuited section as they are good insulatorsSize:Depends on the load coming and quality of wood.Depending on the treatment i.e., treated or not, size of wooden sleepers are standardized by Indian railways.

However, longer sleepers upto length 488cm are used for bridges with open flooring, points and crossings.Section of sleepers is also increased by 300x160mm.Rectangular, half round shapes are used often.

Timber sleepers - FeaturesDriving of spikes:spikes should be driven carefully through the sleeperElse damaged, gauge will be disturbedName and year:Name of wood used and year of laying the sleepers is normally marked on the top surface of sleeper.Normally nails with letters and markings were used before but not used these daysAdzing: Wooden sleepers are adzed or cut at rail seat to get a slope of 1 in 20 when un canted bearing plates are used.

Timber sleepers - FeaturesAdzed surface will be treated normally with tar or creosoteImproper adzing leads to uneven surface for the rails.Further creeping and other types of damage will occurStorage:Large area exposed to air and ventilation is normally usedCare will be taken so that sun do not fall directly on the sleepersStack is some times covered with earth to prevent fire accidentsGround on which sleepers stack are placed should be above ground on platform supported by moisture proof surface.

Timber Sleepers as Bridge sleepersThicker than standard sleepers. Minimum depth of sleepers without fastenings should be 150, 125 and 125 mm for BG, MG and NG respectivelyLength of sleepers is D+30 cm. D is out side distance between edges of parallel girdersShould not be adzedNecessary to provide bearing platesShould be placed sufficiently close to prevent the wheels of derailed train falling through the space between the adjacent sleepers. Max space is 50, 30, 25 cm for BG, MG and NG respectively.

Composite Sleeper Index (CSI)Forest research institute, Dehradun arrived at a formula taking different strength parameters into account for the use of timber for sleepersAn index number is worked out using this formula with which we can identify whether a timber can be used or not for sleeperChir 54Deodar 63Fir 58Sal 112Teak - 82

Composite Sleeper Index (CSI)Minimum CSI values for different sleepers are as followsBridge sleepers 1455Crossing sleepers 1352Track sleepers 783Bearing plates are used in case timber has a CSI value less than 82.CSI = (S+10H)/20S = strength index of timber at 12% moistureH = Hardness index of timber at 12% moisture

Timber Sleepers - AdvantagesLess no of fittingsSimplistic designSuitable for all types of ballastEasy to lay, relay, pack, lift and maintainLess noisy trackEconomical overallObtained in different sized and lengths for easy adoptability at certain locations viz., bridges, crossings etc

Permits track circuitingDamage during derailments is lessCan be placed on yielding formations because of more bearing areaPossible to widen the gauge easily with wooden sleepers

Timber Sleepers - DisadvantagesDifficult to maintain gaugeHigh maintenance costLess useful periodEasily disturbed from their positionsEasily subjected to wear and decay due to various forces and causesRequire special treatment for protectionPossess less scrap value

Steel SleepersExtensively used in Indian railwaysConsist of steel troughs made of 6mm thick steel sheetsBoth ends bent down to check the running out of ballast2 types1. Jaws or lugs pressed out of metal and keys are used for holding the rail. At the time of pressing cant of 1 in 20 is also provided for the rails2. holes are made in the sleepers and clips, bolts are used for fixing the rail. For fixing the rails, first rails are inserted into the lugs and wedges/keys are fixed on both sides of rails. Gauge can be adjusted with the help of keys.

Steel Sleepers

Steel Sleepers - CharacteristicsLife:Useful life of steel sleepers is taken as 30 to 40 years on a normal routeOn high density traffic routes it can be taken as about 20 yearsTrack provide with steel sleepers doesnt require much attention as renewal is not frequent.Corrosion:Steel sleepers not liable to be attacked by verminsBut easily corroded due to moisture. Hence, treatment is done to protect against corrosion.

Steel Sleepers - CharacteristicsInsulation:Cannot be used in electrification of track. As they are not good insulators.Details:Consist of a trough or channel made of steel plate about 6mm thick.Ends bent down to prevent running of ballastRails are fixed with steel sleepers by the help of keys to the pressed up lugs.

Steel Sleepers - RequirementsShould be possible to fix the rails easily in sleepers with out disturbing the sleepersShould be possible to insulate them easily incase at place where track circuiting exists.Rail should have enough bearing areaThickness and shape should be such that they will be strong as beamsCapable of maintaining correct gaugeShould be designed in such a way that tamping or packing should not damage the edges

Steel Sleepers - RequirementsShould be sufficiently heavy for the purpose of stabilityShould have effective bearing area on the ballastShould not be capable of being easily pushed out of position.Etc.,

Steel Sleepers - AdvantagesLess fastenings, simple in natureMaintenance and adjustment of gauge are easy with steel sleepersManufacturing process of steel sleepers is simple in design and operationAre available in one piecePossess good scrap valueLight in weight, easy handlingMeets requirement of long welded track in casesGood anti creep sleeperBehaves better in the case of yielding formation.

Steel Sleepers - DisadvantagesCost of steel sleepers is highCracks develop at rail seatRounded ends of sleepers prevent lateral shiftLiable to corrosionAre not good insulatorsExcess damage during derailmentSteel sleepers are difficult to pack at the rail joints because of their close spacing.Leads to battering of rails

Cast-iron sleepersWere adopted on indian railways since 1870More than 50 % of the sleepers are made of cast iron as of 2000They are generally of the following typesPot sleepersPlate sleepersBox sleepersC.S.T.- 9 sleepersDuplex sleepers

Pot sleepers are in the form of two bowls placed under each rail and connected together by a tie-barTotal effective area of the both pot sleepers is kept 0.46sq.m which is equal to effective bearing area of a wooden sleeper.Two holes are provided under each sleeper for inspection and packing ballastAnd the rail seat is given a slope of 1 in 20.Both the pots are connected together with a tie bar with necessary fittings such as keys, gibs and cotters.

Plate sleepers consist of a plate of 851x254mm in dimensions, with 254mm side parallel to the rails.Both sleepers provide an effective bearing area of 0.46sq.m under each rail.Plate is provided with projecting rib in the bottom to provide a grip in the ballast to check the lateral movement of sleeper.At the top plate stiffeners are provided to increase the strength.Sleeper plates are connected by means of a tie rod.

C.S.T. 9 Sleepers: These are more satisfactory than other type of CI sleepers.It is actually a combination of plate, pot and box sleeper.It essentially consists of a triangular inverted pot on either side of the rail seat.Suitable rail seat or rail chair is provided at the top to hold rails at 1 in 20 cant.Two pieces of sleeper are connected by means of a tie rod.

Cast-iron sleepers - characteristicsDetails:C.I sleepers consists of 2 pots or plates with ribs below and connected by a wrought iron tie bar of section of about 51x13mm. Each pot or plate is placed below each rail.Shape of pot or plate is used to be circular prior. But present, oval shape with larger diameter 610mm and smaller diameter 508mm is preferred.Each pot is provided with holes for packing ballast and inspection.Plate sleepers consist of rectangular plates of size about 864x305mm.The projecting ribs are kept below for their lateral stability.Tie bars can be fixed by keys, gibs, cotters and distance pieces.

Cast-iron sleepers - characteristicsScrap value:Possess considerable scrap value. Broken pots and plates can be melted and reused for preparing new pots and plates.Maintenance of gauge:In case of CI sleepers there is no rigid connection between 2 separate supports. Hence difficult to maintain the correct gauge.Fittings:The cast iron sleepers require a large number of fittings than any other type of sleepers.

Cast-iron sleepers - characteristicsHandling:The C.I. Sleepers are liable to be broken and seriously damaged, if roughly handled.Life:The usual life of C.I. Sleepers may be taken as 35 to 50 years in normal routes.15 to 20 years in heavy traffic routes.The service life can be increased by proper packing , clean ballast, providing coal tar to tie-bar etc.

Cast-iron sleepers - AdvantagesIt can be easily dismantled and assembled. Hence, transport is easy even though it is heavy.Can tolerate certain amount of rough handling.Possess high scrap valueGood longitudinal and lateral resistanceShape is well suited for ballast packing and skill required for its maintenance is minimumAdjustment in gauge can be done ( about 5mm) with help of cotters in case if it is needed.Sleeper is not affected by the random or irregular dropping of fire by the steam engines.

Cast-iron sleepers - DisadvantagesDuring derailment damage is excessive and it requires more time for restoration.Not suitable for circuiting of track.Leads to early wear of sleeper because of small bearing area at the rail seat.Not suitable for modern methods of maintenancePossess poor ability to retain the packing due to its rigid fastenings.It takes about 6 months for proper consolidation after complete track renewal and sleeper renewal.When these sleepers are used, rails have longer unsupported length and may therefore lead to battering of rails.

Concrete Sleepers - characteristicsType:Can be made of R.C.C or pre-stressed concrete.Weight:Weight of concrete sleepers varies from 150 to 300kg which is more than wooden or metal sleepers.This provides more stability to track.Life:Good durabilityUseful life of about 30 to 25 years on high density routes

Concrete sleepers - characteristicsSuitability:Most suitable for welded tracksDead weight of entire track assembly including sleepers play an important role in the design of welded rail track.Since, weight is more they perform better under welded railsFastenings:Should firmly hold the rail to resist creepShould be easily dis-engaged and re-engagedDifferent types of fastening equipment is available for concrete sleepers.Ideal fastenings for sleepers and rails will differ according to the type of track, type of traffic and the climatic conditions.

Concrete sleepers - characteristicsSpecial PSC sleepers have been developed to meet with the special requirement of different locations such as sharp curves, level crossings with facilities for providing check rails, guard rails etc.,Mass production:Mass production techniques are to be adopted for the design and manufacture of sleepers.Economical production of concrete of high strength, handling of sleepers, good plant design, accelerated hardening of sleepers etc., have to be taken care off.Initial cost of concrete sleepers will be very high, but maintenance and other things will be economical because of long life.

Concrete sleepers - characteristicsEnvironmental protection:These PSC sleepers are environmental friendly.Conserves forest.Structural advantages:Have lot of structural advantagesCenter to center distance can be increased by 20% compared to timber sleepersDeflection under loading is much lessImproves lateral, longitudinal and vertical stabilityReduced bending stresses, reduced wear of rolling track, less chance of derailment, reduction in tractive effort etc.

Concrete sleepers - AdvantagesHigh electrical resistanceGood resistance to abrasionIncreased bond resulting in shorter transmission length.Increased impermeabilityReduction in loss of pre-stress due to reduction in shrinkage, creep and elastic shorteningVery high fatigue strength.

Concrete sleepers - DrawbacksThe damage during derailment is excessivePossess no scrap valueRequire complete mechanization in handlingRequires use of superior and costly technology for manufacture.

Sleeper DensityNo of sleepers present in a given length of railSpacing of sleepers is indicated by formula n+xn = length of railx = no of sleepers more than n.Sleepers density depends on several factors:Lateral thrust of locomotives to which the track is subjectedAxle load which the track is expected to carrySleepers density cannot be increased indefinitely minimum spacing is required for packing ballast and maintenance.Wooden sleepers 300mm (for BG), 250mm (for MG)Metal sleepers 380mm (for BG), 330mm (for MG)

Sleeper densityIn case of staggered joints an extra sleeper is requiredSleepers are placed nearer at rail joints compared to other locations.In n+x expression, x value is fixed by indian railway considering the following:Axle load and speedType of ballast and ballast cushionType and section of railsType of sleeper and its bearing area on the ballast.

BallastMaterial placed between the sleeper and top of the formation is known as ballast.Load from the wheels will be taken up by the ballast through rails and sleepers.Ballast serves as foundation of railway track and is present just below the sleepers.

Ballast - FunctionsTo provide a hard and smooth surface for the ballast to rest onHold the sleepers in place during the passage of trainsTo transmit and distribute the load from sleepers to formationAllow for maintaining correct track levels without disturbing the rail road bed.Protect the surface of formation from direct exposure to sun, frost or rain.To form an elastic bed

Ballast - FunctionsTo drain the water immediately and keep the sleepers in dry conditionTo discourage the growth of vegetationTo resist lateral, longitudinal and vertical displacement of track.

Requirements of ideal material for ballastShould be possible to main uniform depth of material for uniformly distributing the load to formationShould provide sufficient grip over the sleepers to prevent their movementBallast should not be too rigid, it should be elastic in nature.Material of ballast should not be brittle, should possess required compressive strength.Should provide good drainage facility.Should be cheap and easily available.Should not have any chemical action on rail and metal sleepersShould be durable and abrasion resistant

Ballast MaterialsBroken stoneGravelAshes or cindersSandKankarMoorumBrickbatsSelected earth

Broken stoneOne of the best material, but expensive.Many important tracks are having stone ballastIt has good interlocking characteristics, due to that it holds track in correct alignment and gradientIt is resistant to abrasion, provides good drainage.Stones which are non-porous, hard and tough should be used as ballast

GravelIt is next best material after broken stone. It consists of smooth rounded fragments obtained from river beds and other natural deposits.Washing should be done for the material obtained from pitsUniform and required size of aggregates should be used.Rounded pieces are sometimes broken to improve interlocking properties.Advantages:Cheaper than stone ballastGood drainage propertyDisadvantages:Easily rolls down due to vibrationScreening is required because of non uniformity in size

Ashes or CindersThe residue from the coal used in locomotives and other furnaces is known as the ashes or cinders.It is by product of railway systems which are run by coal fuel

SandCoarse sand is preferred to fine sandNot used in main and branch lines. Used only in some unimportant lines, sidings, yards.

KankarFound in many placesSuitable only if other types of material is not available and if the traffic is less on metre gauge and narrow gaugeIt becomes powder very easily and hence not preferedMore maintenance is required if used

MoorumDecomposition of laterite results in the formation of moorumPresent in red/yellow colourUsed for unimportant lines and sidings

Brick batsOver burnt bricks are broken into suitable sizes and used as ballastAdvantages:Useful at places where suitable material is not availableGood drainage propertiesDisadvantages:Turns into powder form very easilyTrack becomes dusty and high maintenance is required.

Selected earthFor sidings and newly constructed tracks, selected earth of suitable quantity is sometimes used as ballastThe main purpose of using earth on new formation is to prevent the loss of valuable and expensive ballast sinking into the soft formation.

Specifications of Stone ballastQuality:Should be durable, hard, resilient to impact and free from adherent coatings. Should not contain more than 10% by weight of quarry dust, rubbish or any other matter which passes through 5mm sieveFaces of ballast should result from crushing, only one smooth surface is allowedSize:20 to 50mm size with reasonable proportion of intermediate sizes.50mm wooden and CI spot sleepers40mm CST -9 sleepers25mm points and crossing

Specifications of stone ballastgrading:Ballast should be well gradedSampling:Sample of ballast is collected at the rate of 1cu.m per 2000cu.m.Over sized ballast:When more than 10% of ballast retains on nominal size sieve it is called over sized ballastStacking:Ballast should be stacked along the quarry siding.Height of stack should not be less than 120cm.

Depth of Ballast SectionDepth of ballast section can be calculated by using the below formulaD = (S-b)/2Where D depth of ballast sectionS sleeper spacingb width of sleeperNormally the value ranges in between 20 to 25cm from the above formula.

Section of Ballast