RAILWAYS & TRACKSRAILWAYS & TRACKS

The total width across the two-track alignment will be about 15 The total width across the two-track alignment will be about 15 m (50 ft) for a modern formation.  The "cess" shown each side of m (50 ft) for a modern formation.  The "cess" shown each side of the alignment is the area available for a walkway or refuge for the alignment is the area available for a walkway or refuge for

staff working on the trackstaff working on the track..

Component of TrackComponent of Track 2 main categories:2 main categories:

i) Substructure: Ballast, sub-ballast and sub-i) Substructure: Ballast, sub-ballast and sub-gradesgrades

ii) Superstructure: Rails, Fastening systems, ii) Superstructure: Rails, Fastening systems, sleeperssleepers

RailRail : act as girder to transmit load to sleeper : act as girder to transmit load to sleeper

SleeperSleeper : hold the rails to a proper tilt, gauge and : hold the rails to a proper tilt, gauge and level and transmit load to ballastlevel and transmit load to ballast

Ballast: Ballast: distributes the load over the formation distributes the load over the formation and holds the sleeper in positionand holds the sleeper in position

Types of railTypes of rail

Various types of rail are produced, ranging Various types of rail are produced, ranging from standard 'flat bottom' rail to special from standard 'flat bottom' rail to special rails for mining wagons and electric trains rails for mining wagons and electric trains

Two types of rail used are :Two types of rail used are :i)i) Flat-bottom Flat-bottom ii)ii) Bullhead; Bullhead;

These are available in various weights. These are available in various weights.

Figure : Types of railFigure : Types of rail

Bullhead/ Flat BottomBullhead/ Flat Bottom

Types of railTypes of rail The The Flat-bottomFlat-bottom rail has, to a great extent, rail has, to a great extent,

superseded the Bullhead rail because it is superseded the Bullhead rail because it is better suited to heavier and faster traffic. better suited to heavier and faster traffic.

Weight for weight, the Weight for weight, the Flat-bottom railFlat-bottom rail is is considerably stiffer than the Bullhead considerably stiffer than the Bullhead section; this has resulted in longer track-life, section; this has resulted in longer track-life, greater stability and reduced maintenance. greater stability and reduced maintenance.

However, Bullhead rails are easy to fix and However, Bullhead rails are easy to fix and unfix to the sleeper, and therefore still used unfix to the sleeper, and therefore still used in situations where traffic intensity in situations where traffic intensity necessitates frequent replacement.necessitates frequent replacement.

Types of railTypes of rail The rails are supported by sleepers of The rails are supported by sleepers of

timber, pre-stressed concrete or in some timber, pre-stressed concrete or in some cases steel, which in turn are supported by cases steel, which in turn are supported by a ballast foundation.a ballast foundation.

The standard gauge for main lines is 1.435 The standard gauge for main lines is 1.435 m or 1.432 m for main lines with continuous m or 1.432 m for main lines with continuous welded rails on concrete sleepers. welded rails on concrete sleepers.

The gauge is the distance between the inner The gauge is the distance between the inner faces of the heads of the rails, measured at faces of the heads of the rails, measured at 14 mm below the top of the rail. 14 mm below the top of the rail.

The acceptable tolerance in standard gauge The acceptable tolerance in standard gauge for safe operation is +8 mm and -5 mm but for safe operation is +8 mm and -5 mm but railway engineering authorities may insist railway engineering authorities may insist on closer tolerances than this, depending on closer tolerances than this, depending upon the importance of the track.upon the importance of the track.

Types of railTypes of rail Rails are fixed to the sleepers in various Rails are fixed to the sleepers in various

ways. The bullhead rail is fixed in a 'chair' by ways. The bullhead rail is fixed in a 'chair' by a high-tensile spring key (Figure 1.1) a high-tensile spring key (Figure 1.1)

The Flat-bottom rail is fixed with or without a The Flat-bottom rail is fixed with or without a base plate, depending on the type of sleeper base plate, depending on the type of sleeper (Figure 1.2). (Figure 1.2).

Chairs for Bullhead rails are made to give the Chairs for Bullhead rails are made to give the rail an inward tilt of 1 in 20, thus bringing the rail an inward tilt of 1 in 20, thus bringing the upper surface of the rail into line with the upper surface of the rail into line with the coned tread of the wheels. coned tread of the wheels.

Types of railTypes of rail

The same facility is achieved with Flat-The same facility is achieved with Flat-bottom rails by incorporating tapered base bottom rails by incorporating tapered base plates or by forming a bevel on the sleeper. plates or by forming a bevel on the sleeper.

Both chairs and base plates are now fixed to Both chairs and base plates are now fixed to the sleepers by bolts, coach screws or lock the sleepers by bolts, coach screws or lock spikes, or alternatively the base plate may spikes, or alternatively the base plate may be cast in place. be cast in place.

The spring-spike fixing is falling into disuse The spring-spike fixing is falling into disuse with the development of concrete sleepers.with the development of concrete sleepers.

Figure 1.1 : types of rail with traditional fixings to timber and Figure 1.1 : types of rail with traditional fixings to timber and concreteconcrete

Figure 1.2 : Flat bottom rail using traditional fixingsFigure 1.2 : Flat bottom rail using traditional fixings

Figure : The flat bottom rails had been cut out of Figure : The flat bottom rails had been cut out of continuous welded lengths by use of gas-cutting continuous welded lengths by use of gas-cutting

torchestorches

Figure : Laying out concrete sleepersFigure : Laying out concrete sleepers

Jointing of rail/Fastening Jointing of rail/Fastening SystemSystem Rails are jointed either by Rails are jointed either by

i)i) fish-plates fish-plates ii)ii) weldingwelding

The The fish-platesfish-plates,, 450 mm long and 25 mm 450 mm long and 25 mm thick, are bolted to each rail with two bolts; thick, are bolted to each rail with two bolts; this type-of connection permits expansion. this type-of connection permits expansion.

WeldedWelded rail is being increasingly used on rail is being increasingly used on main lines, which can be supplied in pre-main lines, which can be supplied in pre-welded lengths of 220 m from the factory.welded lengths of 220 m from the factory.

The expansion and contraction is confined to The expansion and contraction is confined to relatively short lengths at each end of the relatively short lengths at each end of the track, where a special 'adjustment switch' is track, where a special 'adjustment switch' is used to allow the welded rails to expand and used to allow the welded rails to expand and contract.contract.

Figure : Fish plates/ Welding/ ClipsFigure : Fish plates/ Welding/ Clips

Pandrol rail clipsPandrol rail clips Pandrol rail clips are manufactured from Pandrol rail clips are manufactured from

high quality silicon-manganese steelhigh quality silicon-manganese steel In the case of timber sleepers the base In the case of timber sleepers the base

plate is fixed to the sleeper with 'Lock plate is fixed to the sleeper with 'Lock spike' base plate fastenings or with spike' base plate fastenings or with screws, depending on the type of base screws, depending on the type of base plate, plate,

whereas concrete sleepers are fitted whereas concrete sleepers are fitted with malleable iron shoulders, the latter with malleable iron shoulders, the latter being cast in during the manufacturing being cast in during the manufacturing process.process.

Figure 1.2 : Flat bottom rail using traditional fixingsFigure 1.2 : Flat bottom rail using traditional fixings

Pandrol rail clipsPandrol rail clips

When insulation is necessary for track When insulation is necessary for track circuiting purposes, an insulator of hard circuiting purposes, an insulator of hard nylon or other similar material is placed nylon or other similar material is placed between the shoulders and the edge of the between the shoulders and the edge of the rail toof (Figure 1.3).rail toof (Figure 1.3).

'An extension of the insulator on top of the 'An extension of the insulator on top of the foot rail beneath the 'Pandrol' rail clip.foot rail beneath the 'Pandrol' rail clip.

For severe conditions, eg very sharp For severe conditions, eg very sharp curves, a composite insulator is available, curves, a composite insulator is available, consisting of a nylon insulating piece consisting of a nylon insulating piece protected by a cover of malleable iron.protected by a cover of malleable iron.

Figure 1.3 : Various parts of the Figure 1.3 : Various parts of the pandrol clippandrol clip

Figure : Pandrol rail clipsFigure : Pandrol rail clips

Pandrol rail clipsPandrol rail clips Where concrete sleepers are used, Where concrete sleepers are used,

insulation is also provided between the rail insulation is also provided between the rail and the sleeper in the form of a 'rail pad' and the sleeper in the form of a 'rail pad' (Figure 1.3). (Figure 1.3).

This resilient pad provides electrical This resilient pad provides electrical insulation where required, but its primary insulation where required, but its primary function is to dampen the impact forces function is to dampen the impact forces between the rail and the sleeper. between the rail and the sleeper.

The pad, made- from- suitable grades of The pad, made- from- suitable grades of polyurethane or thermoplastic elastomer, polyurethane or thermoplastic elastomer, are commonly 5 mm thick although other are commonly 5 mm thick although other thicknesses are available.thicknesses are available.

Pandrol rail clipsPandrol rail clips The latest development in rail clips is the The latest development in rail clips is the

'Pandrol Fastclip' , which is fully captive, pre-'Pandrol Fastclip' , which is fully captive, pre-assembled, unthreaded rail fastening. assembled, unthreaded rail fastening.

All components of the fastening are assembled All components of the fastening are assembled on concrete sleepers at the sleeper factory and on concrete sleepers at the sleeper factory and remain captive throughout the service life in remain captive throughout the service life in the track. the track.

This eliminates the handling of loose This eliminates the handling of loose components during track maintenance components during track maintenance operations. operations.

Tensioning and de-tensioning of the clips is Tensioning and de-tensioning of the clips is carried out by means of a track-mounted carried out by means of a track-mounted machine, or by hand toolsmachine, or by hand tools

Timber sleepersTimber sleepers It is normal practice to lay 24 sleepers per It is normal practice to lay 24 sleepers per

18.3 m of track, although this may be 18.3 m of track, although this may be increased to 28 per 18.3 m for weak increased to 28 per 18.3 m for weak formations, curves and continuous welded rail.formations, curves and continuous welded rail.

Timber sleepers have been used in the past Timber sleepers have been used in the past but are being replaced by concrete on all but are being replaced by concrete on all permanent lines.permanent lines.

Timber sleepers have a life of approximately Timber sleepers have a life of approximately twenty years on secondary lines, and are twenty years on secondary lines, and are suitable for temporary track work suitable for temporary track work

Figure : Timber sleepersFigure : Timber sleepers

Concrete sleepersConcrete sleepers Concrete sleepers are produced in various Concrete sleepers are produced in various

classes for general use, and a special sleeper classes for general use, and a special sleeper for use on heavily trafficked main lines.for use on heavily trafficked main lines.

These sleepers are pre-stressed and, apart These sleepers are pre-stressed and, apart from being more durable, their extra weight from being more durable, their extra weight increases the stability of the track. increases the stability of the track.

These advantages, together with the fact These advantages, together with the fact that concrete sleepers can be readily formed that concrete sleepers can be readily formed to receive the various types of track fixings, to receive the various types of track fixings, have proved that this material is superior to have proved that this material is superior to others being used. others being used.

For increased track stability, 'wing' sleepers For increased track stability, 'wing' sleepers are available (Figure 1.4)are available (Figure 1.4)

Figure 1.4 : Details of concrete sleepers, formation & Figure 1.4 : Details of concrete sleepers, formation & drainagedrainage

Figure : Concrete sleepersFigure : Concrete sleepers

Steel sleepers are also now used on more lightly Steel sleepers are also now used on more lightly used roads, but they are regarded as suitable only used roads, but they are regarded as suitable only where speeds are 100 mi/h (160 km/h) or less.where speeds are 100 mi/h (160 km/h) or less.

Steel sleepers have been used for some time but are Steel sleepers have been used for some time but are unsuitable on electrified lines, due to increased unsuitable on electrified lines, due to increased leakage of the return current.leakage of the return current.

They are used by corporations undertaking work that They are used by corporations undertaking work that could seriously affect concrete and timber sleepers, could seriously affect concrete and timber sleepers, such hot metal processing and chemical spillage. such hot metal processing and chemical spillage.

They have the advantage of low overall life cost, low They have the advantage of low overall life cost, low transportation and handling costs, low installation transportation and handling costs, low installation costs, and high strength to weight ratio. costs, and high strength to weight ratio.

They are made of steel plate, formed into an They are made of steel plate, formed into an inverted trough with flanged ends; this shape is inverted trough with flanged ends; this shape is suitable for strength but creates some difficulty if suitable for strength but creates some difficulty if realignment of the track is necessary.realignment of the track is necessary.

Steel sleepersSteel sleepers

Figure : Steel sleepersFigure : Steel sleepers

Twin-block sleepersTwin-block sleepers

With the advent of light transport systems a With the advent of light transport systems a new concept of sleeper has been developed, new concept of sleeper has been developed, this is known as the twin-block sleeper this is known as the twin-block sleeper

This system is much easier to install than This system is much easier to install than traditional sleepers and gives an enhanced traditional sleepers and gives an enhanced appearance, in keeping with the aesthetic appearance, in keeping with the aesthetic demands of towns and city centres.demands of towns and city centres.

The design consists of two concrete blocks The design consists of two concrete blocks joined by a steel bar.  It is 30% lighter than joined by a steel bar.  It is 30% lighter than a regular concrete sleeper, allowing it to be a regular concrete sleeper, allowing it to be moved manually. moved manually. 

Figure: The twin-block sleepers recessed into a base slabFigure: The twin-block sleepers recessed into a base slab

Formation and drainageFormation and drainage New works are designed by adopting New works are designed by adopting

appropriate alignments and gradients so that appropriate alignments and gradients so that the amount of excavation (cut) will balance the amount of excavation (cut) will balance the amount of 'fill' in embankments.the amount of 'fill' in embankments.

If the soil is suitable, side slopes (batter) of If the soil is suitable, side slopes (batter) of 1.5 to 1 are commonly used; however, the 1.5 to 1 are commonly used; however, the side slope must be designed to suit the side slope must be designed to suit the material. material.

The top surface of the formation should be The top surface of the formation should be sloped outwards from a center crown, to sloped outwards from a center crown, to provide drainage to the track. provide drainage to the track.

The water is channeled away by ditch or The water is channeled away by ditch or other type of drain (Figure 1.4)other type of drain (Figure 1.4)

Formation and drainageFormation and drainage The formation consists of a clay fill or The formation consists of a clay fill or

formation it should be protected against formation it should be protected against ingress of surface water: clay becomes ingress of surface water: clay becomes plastic when wet and the rolling stock may plastic when wet and the rolling stock may then force the ballast into the clay. then force the ballast into the clay.

The protection may consist of a layer of The protection may consist of a layer of sand, stone-dust or ashes 150 mm to 350 sand, stone-dust or ashes 150 mm to 350 mm thick, laid directly on the formation mm thick, laid directly on the formation and covered with polythene sheeting prior and covered with polythene sheeting prior to the placing of ballast.to the placing of ballast.

Figure : Formation and drainageFigure : Formation and drainage

Ballast consists of crushed stone, eg granite or Ballast consists of crushed stone, eg granite or limestone and is used as a base for the sleepers.limestone and is used as a base for the sleepers.

The main function of ballast is to distribute the The main function of ballast is to distribute the loads, it also absorbs vibration, provides track loads, it also absorbs vibration, provides track drainage and prevents the movement of drainage and prevents the movement of sleepers. sleepers.

It is laid to a depth of between 225 mm and 300 It is laid to a depth of between 225 mm and 300 mm, depending on the traffic load; mm, depending on the traffic load;

The ballast is filled to the top of the sleepers and The ballast is filled to the top of the sleepers and out beyond the end of the sleeper to a distance out beyond the end of the sleeper to a distance of between 250 mm and 500 mm, the latter of between 250 mm and 500 mm, the latter forming a shoulder to the outer edge of the track forming a shoulder to the outer edge of the track to restrain lateral movement.to restrain lateral movement.

BallastBallast

Figure: Ballasting constructionFigure: Ballasting construction

ballast

Modern TrackModern Track There are now a range of modern track forms There are now a range of modern track forms

using a concrete base.  They are generally used using a concrete base.  They are generally used in special locations such as tunnels or bridges in special locations such as tunnels or bridges where a rigid base is required to ensure track where a rigid base is required to ensure track stability in relation to the surrounding stability in relation to the surrounding structures.  This type of track, usually called structures.  This type of track, usually called "slab track" or "non-ballasted" track"slab track" or "non-ballasted" track

The The earth mat earth mat is a steel mesh screen provided is a steel mesh screen provided on electrified railways to try to keep stray on electrified railways to try to keep stray return currents from connecting to utilities return currents from connecting to utilities pipes and nearby steel structures. pipes and nearby steel structures. 

Modern TrackModern Track

TurnoutTurnout

In the railway "trade", turnouts are In the railway "trade", turnouts are referred to as "switch and crossing referred to as "switch and crossing work". work". 

Types of TurnoutTypes of Turnout

CrossingsCrossings

CrossingsCrossings

CrossingsCrossings

Sequence of WorksSequence of Works1. 1. Earthwork and Ground Earthwork and Ground

ImprovementImprovement: Soil improvement, : Soil improvement, Undertrack Crossing, Embankment and Undertrack Crossing, Embankment and Slope stabilisation.Slope stabilisation.

2. 2. Drainage and External WorksDrainage and External Works: : Drainage,Culvert, utilities relocation, Drainage,Culvert, utilities relocation, security fencingsecurity fencing

3. 3. TrackworksTrackworks: Track laying, bottom : Track laying, bottom ballast, sleeper distribution, rail laying, ballast, sleeper distribution, rail laying, welding rail, distressing, tamping welding rail, distressing, tamping (allignment, correction, packing (allignment, correction, packing ballast), compactingballast), compacting

Plants and MachineriesPlants and Machineries

Tamping Machines Ballast Cleaning Machine Ballast Tamping Machines Ballast Cleaning Machine Ballast Excavator MachineExcavator Machine

Dynamic Track StabilisersDynamic Track Stabilisers Track Laying Machine Track Laying Machine Rail GrindersRail Grinders