Highway 3rd Sem Lecture Note

Lecture Notes for BCECCE 601R01 Highway and Railway Engineering

Prepared by Dr.G.Dhinakaran/Professor/SoCE/SASTRA UNIVERSITY 69

Geometric Design of Railway Track

A railway track laid along a straight line is said to be an ideal track. But due to general

topography of the area and some other factors, it becomes necessary to deviate from straight

alignment. Hence a curve for or a combination of curves is inserted between straights. Proper

design of component parts of the curve constitutes the geometric design of the track.

Horizontal curves:

The use of curves in railway track is warranted in the following situations:

• To bypass the neutral and artificial obstacles

• To provide easier gradients by diverting the straight track alignment

• To connect the area of potentialities

Locations where curves to be avoided:

Bridges, tunnels, viaduct, steep gradient, stations and yards, level crossings and deep cuttings.

Classification of horizontal curve:

Simple curve: Horizontal curve with single arc of a circle

Compound curve: Horizontal curve which consists of two or more arcs with different radii

having different centers on the same side of the common tangent and bending in the same

direction.

Reverse curve: Horizontal curve which consists of two arcs with different circles of the same or

different radii bending in the opposite direction with a common tangent at the junction.

Transition curve: Horizontal curve of varying radii introduced between a straight and a circular

curve.

Radius and degree of a curve:

The radius of the curve is some times represented by degree of the curve.

Degree of a railway curve: The angle subtended at the centre of the curve by a chord of length

30.5 m length.

Relationship between the radius and degree of a curve: D = 1750/R

Effect of curves on tracks:

Length of trains is to be restricted

Use of heavy locomotives is to be restricted

Unequal distribution of load and hence running of train will not be smooth

Extra track fittings are needed



Rails get bent due to rigid wheel base

Operation and maintenance cost is more

Super elevation:

The difference in elevation of outer rail with respect to inner rail to counter balance the

centrifugal force is called super elevation or cant and is equal to GV2/127R, where G is the

dynamic gauge, V is the speed of the train and R is the radius of the curve.

Cant deficiency: It is the difference between the cant necessary for the maximum permissible

speed on a curve and the actual cant provided.

Cant excess: It is the difference between the equilibrium cant and the theoretical cant required

for the given lower speed.

Cant gradient: It is the amount by which cant is increased or decreased in a given length of the

transition curve.

Rate of change of cant: It is the amount by which cant is increased or decreased per second.

Safe speed on curves: It is the maximum speed of train based on the type of gauge, amount of

super elevation, provision or absence of transition of curve at the ends and weight of the trains.

Maximum sanctioned speed for the section: It is the speed for the section determined by the

factors such as track conditions, standard of locking, type of locomotives etc.

Negative super elevation or Negative cant: When branch line meets main line on curve, outer

rail of one line and the inner rail of the other line should be at the same level and it is called as

negative cant.

Gradients:

The rate of change of slope in the longitudinal direction is called grade or gradient. When a

track rises in the direction of movement of trains, it is known as a up-gradient or positive

gradient, where as a down gradient or falling gradient is the one when the railway track loses

elevation in the direction of the movement of trains.

Gradients are provided in the railway track for the following purposes:

• To reach the stations at different elevations

• To reduce the cost of earth work

• To provide a uniform rate of rise or fall as far as possible



Classification of gradients:

Ruling gradient: It is the gradient which determines the maximum weight of a train, which can

be pulled by a locomotive along a particular section of a track.

Momentum gradient: It is the up gradient which exceeds the ruling gradient along which the

increased load of the train may be hauled by the locomotive after gaining momentum during

descending a falling gradient.

Pusher or helper gradient: It is the steep gradient along which an additional locomotive is

required to push the train up the gradient.

Gradients in station yards: As far as possible the track along the stations and yards should be

level. But, in level track in stations and yards, complex drainage problem is created. To

overcome the drainage problem, Indian railways have prescribed a normal gradient of 1 in 1000

in station yards.

Grade compensation: whenever train is pulled along a curve, an additional tractive force is

required. In order to avoid the total resistance beyond the permissible ruling gradient, the

gradient is reduced on curves and is called as grade compensation. For BG track – 0.04% per

degree, MG track – 0.03% per degree and NG track – 0.02% per degree.



UNIT IV Railway Operation, Control, Construction and Maintenance Points and Crossings:

Turn Outs: The assembly of various components which enables trains to move from one track

to any other track either parallel to or diverging from the first track is called turn out or points

and crossing.

Points:

Stock rails: Rails of the main line track

Tongue rails: The tapered rails whose thicker ends known as heel are fixed to the main track

and thinner ends known as the toe of the switch to obtain a snug fit with respective stock rails.

Switch: Combination of stock rail and its respective tongue rail

Heel blocks: The block which connects the heel of the tongue to the stock rail with a pair of

ordinary fish plates and fish bolts.

Sliding plates: The metal plates, which are provided for supporting and sliding tongue rail to

obtain a snug fit against stock rail.

Stretcher bar: Bars which are used to connect the ends of the tongue rails to ensure the

movement of both the tongues through the same distance.

Throw of switch: The distance through which the tongue rails move at the toe of the switch.

Crossing:

The arrangement of rails, which is provided to enable the flanges of wheels to cross the rails of

the other track.



Important terms used in Points and Crossing:

Types of Crossings:

1. Classification based on the shape of crossing

(a) Acute angle crossing or V crossing or Frog

(b) Obtuse angle crossing or diamond crossing

(c) Square crossing

2. Classification based on the assembly of crossing

(a) Spring or movable wing crossing

(b) Ramped crossing

3. Classification based on manufacturing purposes

(a) Built up crossing

(b) Cast steel crossing

(c) Combined rail and cast crossing



Number of Crossing:

It is the ratio of the spread of the crossing to the length of the crossing from theoretical nose of

crossing.

Number of crossing = Distance of straight rail from toe to heel in feet/Sum of spreads at each

end equal to one foot



Types of Switches:

(ii) Split Switch

These consist of a pair of stock rails and a pair of tongue rails. Split switches may again of two

types. Loose heel type and Fixed heel type.

Loose heel type: In this type, the switch or tongue rail finishes at the heel of the switch to

enable movement of the free end of the tongue rail. The fish plates holding the tongue rail may

be straight or slightly bent. The tongue rail is fastened to the stock rail with the help of a fishing

fit block and four bolts. All the fish bolts in the lead rail are tightened while those in the tongue

rail are kept loose to allow free movement of the tongue,

Fixed heel type: In this type, the switch or tongue rail does not end at the heel of the switch but

extends further and is rigidly connected. The movement at the toe of the switch is made

possible on account of the flexibility of the tongue rail.



Design of Turnouts:

Curve lead = Switch Lead + Crossing Lead = SL + Cl

Track Junctions and Simple track layouts:

1. Turnout of similar flexure

2. Turnout of contrary flexure

3. Symmetrical split

4. Three throw switch

5. Double turnout

6. Cross over

7. Diamond crossing, Diamond crossing with Single slip and double slip

8. Scissors cross over

9. Gauntleted track



10. Gathering line

11. Triangle

12. Double Junctions

STATIONS AND YARDS:

Site selection for railway stations:

Acquisition of adequate land

Level ground with good drainage

Availability of water

Availability of space on both sides

Alignment of the track

Approach road to the station site

Easy accessibility

Basic requirements of a railway station:

1. Public requirements: Waiting rooms, retiring rooms, sanitary arrangements,

refreshment rooms, bath rooms, drinking water, passenger platforms, STD booths,

water coolers, boards for station name at suitable positions, enquiry office etc.

2. Traffic requirements: Station master’s office, telecommunication office, staff rooms,

signal cabins, signals, sufficient number of sidings and platforms.

3. Requirements of locomotives: Sufficient water for locomotives, arrangement for

cleaning and examining locomotives, facilities for inspection and repair, loco shed,

turn table, triangle, inspection pit etc.

4. General requirements: Approach roads, installation of clocks, boards indicating

platform numbers, availability of authorized coolies etc.

Classification of railway stations:

1. Based on operational characteristics

Block stations – Class A, B and C stations in the descending order of their importance

A driver of a train has to obtain a permission to approach an authority to proceed is called block

station. (Min. requirements: Home signal, starter signal and Warner signal)

Non-block stations – Class D or flag stations

Special class stations: The stations which are not covered under the above categories



2. Based o functional characteristics

Way side stations: The stations where movement of train is only two directional. It may be

further classified as

Halt stations: It is usually provided with rail level platform. Neither a building nor a booking

office is provided. Tickets will be issued in train by TTE. Train will stop for a while to permit

entraining/detraining of passengers.

Flag stations: It is more important than halt stations. It is provided with station building and

staff. It will be provided with telegraph or telephone facility.

Crossing stations: An arrangement is provided to permit trains from opposite directions to pass

one another.

Junction Stations: The stations where a branch line joins a main line. A facility to interchange

the traffic from main line to branch line, a loco workshop for repair of locomotives, an

arrangement of changing the direction engine will be available.

Terminal Stations: A railway line or one of its branch lines terminates. The reception line

terminates at a dead end. Facilities for reversing engine, repair of wagons, locomotives,

hydraulic buffer, building with booking office etc.

Platforms:

1. Passenger platforms: Min. length: 61 m, width: 3.66 m, ends with ramp, light

arrangement, drinking water, toilets at either end, suitable length with shelter.

2. Goods platforms: Goods shed, proper drainage facility, easy accessibility, weighing

equipments, trolleys etc.

Yards:

A system of tracks laid within definite limits for sorting out and dispatching, making up of

trains.

Types of railway yards:

Passenger yards: To provide the safe movement of passengers during entraining and

detraining. It has to accommodate passenger trains.

Goods yards: For loading and unloading the goods and also for the movement of goods

vehicles. Facilities like over head cranes, cranes traveling on rails, fixed or gantry rails and

cranes mounted on road vehicles should be available. Weigh bridge and loading gauge also

should be available.



Marshalling yards: Meant for sorting out of wagons according to traffic requirements.

Salient features: Reception sidings, Sorting sidings and departure sidings.

Types of marshalling yard:

Flat yard: All sorting is done by locomotives

Gravitational yard: The tracks are laid over suitable gradient so that wagons can move of their

own under the action of gravity.

Hump yard: Artificially built humps are provided and wagons are pushed upon the hump by an

engine and further running will be due to gravity.

Locomotive yards: They are meant for accommodating the locomotives for watering, repairing,

oiling, cleaning, servicing etc.

SIGNALLING:

A signal is a mechanical or electrical device erected beside a railway line to pass information relating to

the state of the line ahead to train/engine drivers. The driver interprets the signal's indication and acts

accordingly. Typically, a signal might inform the driver of the speed at which the train may safely

proceed or it may instruct the driver to stop.

Originally, signals displayed simple stop/proceed indications. As traffic density increased, this proved to

be too limiting and refinements were added. One such refinement was the addition of distant signals on

the approach to stop signals. The distant signal gave the driver warning that he was approaching a signal

which might require a stop. This allowed for an increase in speed, since trains no longer needed to be

able to stop within sighting distance of the stop signal. Under timetable and train order operation, the

signals did not directly convey orders to the train crew. Instead, they directed the crew to pick up orders,

possibly stopping to do so if the order warranted it.

Signals are used to indicate one or more of the following:

• that the line ahead is clear (free of any obstruction) or blocked.

• that the driver has permission to proceed.

• that points (also called switch or turnout in the US) are set correctly.

• which way points are set.

• the speed the train may travel.

• the state of the next signal.

• that the train orders are to be picked up by the crew.

Signals can be placed:

• at the start of a section of track.

• on the approach to a movable item of infrastructure, such as points/switches or a swingbridge.



• in advance of other signals.

• on the approach to a level crossing.

• at a switch or turnout.

• ahead of platforms or other places that trains are likely to be stopped.

• at train order stations.

'Running lines' are usually continuously signalled. Each line of a double track railway is normally

signalled in one direction only, with all signals facing the same direction on either line. Where 'bi-

directional' signalling is installed, signals face in both directions on both tracks (sometimes known as

'reversible working' where lines are not normally used for bi-directional working). Signals are generally

not provided for controlling movements within sidings or yard areas.

Classification of Signals:

Audible Signals:

Audible signals such as detonators and fog signals are used in cloudy or foggy weather when

hand or flag signals are not visible. The sound can immediately attract the attention of drivers.

These detonators are kept 90 m ahead of a signal to indicate the presence of signal to the

drivers.

Visible Signals: Hand Signals - flags, lamps, bells, and whistles

Hand signals include signals given by hand, or by flags or lamps used by the signalman,

drivers, guards, or station staff. At most stations and signal box cabins, it is still customary to

use hand-held flags (green and red) to signal trains. In many cases these confirm the semaphore

or colour-light signals, but can be used to override them. At night hand-held lamps (red or

green) are used instead. The all-right signal refers to the display of green flags by station

masters (or other staff), lineside workers, level crossing gatekeepers, and others, to passing

trains, or for the driver of one train to another passing train (see drivers' signals below), or from

the signal cabin to the driver or guard of a passing train. It indicates a few different things. For

trains passing stations, it is a confirmation that the train is allowed to be passing through as the

semaphore or colour light signal indicates. The station staff person also keeps a watch for

problems such as hot axles, derailed bogies or dragging equipment, or parted couplers, and the

green flag indicates there are no such problems observed. Customarily, the green flag is held in

the left hand, and the red flag is kept ready to be displayed in case of a problem in the right

hand - the custom arose from the idea that the right hand is usually the more vigorous one for

most people and the red danger signal could be shown more promptly in case of a problem.



Fixed Signals:

Semaphore Signal:

The semaphore arm consists of two parts: A movable arm pivoted in a vertical post through a

horizontal pin as shown in Figure. The arm of the semaphore signal on the side facing the

driver painted red with vertical white stripe. The other side of the signal is painted with black

vertical stripe. The complete mechanical assembly of the signal consists of an arm, a pivot, a

counter weight spring stop etc., and is housed on the top of a tubular or lattice post. A spectacle

holding coloured lenses which move in front of a lamp in order to provide indications at night.

arm projects horizontally in its most restrictive aspect; other angles indicate less restrictive

aspects. Lower quadrant and upper quadrant: Semaphores come in lower quadrant and upper

quadrant forms. In a lower quadrant signal, the arm pivots downwards for the less restrictive

(known as "off") indication. Upper quadrant signals, as the name implies, pivot the arm upward

for "off".

Calling on Signal:

This consists of a small arm fixed on a home signal post below the main semaphore signal arm.

When the main home signal is in the horizontal position and calling on signal is in inclined

position, it indicates that the train is permitted to proceed cautiously on the line till it comes

across the next stop signal.



Co-acting signals -

Co-acting signals are duplicate signals fixed below ordinary signals and are provided where, in

consequence of the height of the signal post, or of their being an over-bridge or other obstacle,

the main arm or light is not in view of the Driver during the whole time that he is approaching

it. Co-acting signals shall be fitted at such height that either the main arm or light or the Co-

acting arm or light is always visible.

Repeater signals -

A signal placed in rear of a fixed signal for the purpose of repeating to the Driver of an

approaching train the aspect of the fixed signal in advance is called a Repeater signal. A

Repeating shall be provided with an ‘R’ marker and shall be of banner type, or a square ended

semaphore arm, or a color light signal.

Shunt signals:

Signals used for shunting purposes are distinct from stop signals as their function is different.

They do not indicate that the line ahead is clear, but that movements may proceed as far as the

line is clear. Shunting signals are in the form of a miniature semaphore arm, mounted at ground

level or on a signal post. Many of those at ground level have the arm superimposed on a white

or black disc to aid visibility. This type is generally called a disc signal.

Signals based on their location

Outer Signal, Home Signal, Routing Signal, Starter Signal and Advanced Starter Signal

Signalling systems

Mechanical signaling system and Electrical signaling system

Component Mechanical Electrical Signals Mechanically operated – lower

quadrant or Upper quadrant Coloured light signals with 2, 3 and 4 aspect signaling

Points Mechanically operated Electrically operated Level crossing gates

Manually operated swing leaf gate or mechanically operated

Electrically operated lifting barriers

Transmission systems

Single or double wire transmission systems to the requisite points

Electrical transmission through over head wire or under ground cable

Operating units

Mechanical interlocking with tappets

Interlocking through relays

Monitoring units

With the help of detectors With the help of DC or AC track circuits, axle counters etc.



Systems for controlling train movement:

Time interval system (There is time interval between two successive trains in this system) and

space interval system (There is time interval between two successive trains in this system)

Methods of controlling train movement:

One engine only system: This system permit only one train to remain in a section at one time.

The movement is controlled with the help of a wooden staff or token with suitable

identification marks. This system is suitable only for short branch line.

Following train system: In this system train follow one another after a time interval that is

generally less than 15 min. Trains scheduled after the first train can run at a maximum speed of

25 km/h. Since adequate time interval is kept between two successive trains safety is ensured to

a limited extent.

Pilot guard system: In this system a person known as pilot guard accompanies a train by

riding on the foot plate of the engine and returns to the same station with another train. The

pilot guard normally identified by his/her uniform.

Absolute block system: In this system entire length of track is divided into a number of

sections called block sections. A section is usually the distance between two stations. Two

adjacent block sections are separated by block station, where block instruments are installed in

pair. The block instruments are used to show whether the block section is occupied by train or

clear. Each block instruments are electrically connected in series, telegraphically operated and

verbal exchange is done telephonically. Each block station is under the control of a station

master where as each block section is under the charge of two block stations situated at the

either end of block section.

Automatic block system: the signals are actuated by the movement of trains and therefore the

trains can follow each other between two stations. It is controlled by track relays, and when a

train enters a particular block, the signal is at danger position until the train leaves the block.

Centralized Train Control (CTC):

The operation of all points and signals of the various stations of a section in centralized at one

place in such a system and controlled by a single official called CTC operator. CTC operator

virtually takes the responsibility of various station masters of individual stations and operates

all the points and signals through remote control. The coverage will be upto a distance of 120

km on either side. In CTC panel interlocking is provided which ensures highest level of safety.



Interlocking: Interlocking is an arrangement of signals, points and other apparatus so interconnected by

means of mechanical or electrical locking that can be operated in a predetermined sequence to

ensure that there is no conflicting movement of signals and points and trains run safely.

Essentials:

- it should not be possible to turn a signal off unless all points for the line on

which the train is to be received are correctly set

- the line is fully isolated before the signal is turned off

- after the signals turned off, it should not be possible to do any adjustments

- it should not be possible to turn off any two signals at the same time

- wherever possible, the points should be so interlocked as to avoid any

conflicting movement

Methods

Key Interlocking

It is the simplest method of interlocking and still exists on branch lines of small stations on

Indian Railways. There are two systems under this;

(i) Single lock and Key system

(ii) Double lock and Key system

Single lock and Key system: This system is based on the principle of providing two locks with

a single key. Let ‘A’ be the lock of the signal and ‘B’ be the lock of the point. The normal

setting of the point is for the main line with signal in ‘ON’ position.

To lower the signal for the main line, insert the key in lock A and turn it, the signal is now

released. After lowering the signal, it is not possible to withdraw the key from the lock A. Thus

the points are correctly set for the main line.

For setting points for the siding, first place the signal to normal position and remove the key

from lock A. Insert the key in lock B and turn it to release the points for the siding. While

setting the points for siding, the signal for the main line remains locked and hence cannot be

lowered.

Double lock and key system: There will be two locks in this system.



Route Relay Interlocking (RRI) is the system used in large and busy stations that have to

handle high volumes of train movements. In this, an entire route through the station can be

selected and all the associated points and signals along the route can be set at once by a switch

for receiving, holding, blocking, or dispatching trains. Regardless of whether the mechanisms

are controlled manually or by electronic circuits, and whether they are operated mechanically

or electrically, all interlocking schemes usually enforce several or all of the following rules:

• No signal can be pulled off unless corresponding points are set correctly.

• Facing points are locked to the corresponding route when a signal is pulled off.

• Signals for conflicting movements cannot be pulled off simultaneously.

• Points for conflicting routes cannot be set simultaneously.

• Trailing points are locked to the rear when a signal is pulled off.

• Distants, warners, repeaters, etc. cannot be pulled off unless the corresponding stop

signals are pulled off.

• Gate stop signals cannot be pulled off unless level-crossing gates are blocked to road

traffic.

Tappets and lock system

Tappet Locking is a system used to prevent signals being pulled off for conflicting routes. Each

signal lever (or point lever, slot lever, etc, in the frame) moves a plunger (also known as driving

iron) either directly attached to it or through a connecting mechanism. The plungers move

lengthwise. Attached perpendicularly to them are tappet bridles (also known as locking bars).

Tappets are small flat bars or wedges that are attached to the bridles with cams, so that they can

move slightly sideways (along the bridle). A tappet on the locking bar of one plunger presses

against a different plunger. Each plunger has notches that correspond to the wedge shape of the

tappets. The notches are placed in such a way that at specified configurations of the signal

levers, tappets can fit into the notches. When a signal lever is moved, tappets attached to it can

slide in or out of notches on other signal levers' plungers because of their cams. However, a

plunger that has a tappet from another signal lever wedged in its notch cannot move - or vice

versa.



Mechanical devices for Interlocking

Detector: A Detector is a very basic mechanical interlocking device that ensures that a signal

can be pulled off for a route only after the points have been set correctly for it. It also ensures

that the tongue rails for the points are positioned correctly. The detector consists of a set of

signal slides that operate perpendicular to the a blade connected to the points which determine

the route. The blade connected to the points has a number of notches, matching the number of

signals. Each signal slide has just one notch. The notch on the signal slide fits into the notch of

the point blade only when the points are correctly set for the route of the corresponding signal.

When the signal slide is positioned in this way, it frees the signal to be pulled off. Then when

the signal is pulled off, it moves the signal slide such that the points cannot be changed because

the notch of the point blade fouls the signal slide.

Stretchers and Lock Stretcher Bars: A pair of tongue rails for a switch is often provided with

two stretchers, which connect the two tongue rails together. The front stretcher extends under

the stock rail to prevent the phenomenon of 'jumping' or 'dancing' switches. If one or the other

tongue rail gets bent out of shape, one or both stretchers will break.

A Lock Stretcher Bar consists of an additional stretcher connected separately to the tongue rails

such that if either the tongue rails bend or the front or rear stretchers break, the notches on the

front or rear stretchers will foul the blade for the detector mechanism and prevent the signal

from being taken off for the route.

Plunger Lock: Additionally, the lock stretcher has two notches, and a Plunger Lock, which is a

bar perpendicular to the lock stretcher (and therefore parallel to the rails) fits in one or another

of them, when the points are set for the corresponding route. When the lock plunger is set in

one or the other notch, it prevents the points from moving. This is an additional locking

mechanism beyond that provided by the detector. Often the locking is accomplished by a

separate locking lever after the main lever to set the points is operated. Sometimes the locking

is done in the same action as setting the points, but this is less reliable and harder to work.

Lock Bar: A Lock Bar is a long bar, corresponding to the longest wheel base of vehicles

operating on the line (14m - 42' as a minimum for BG, or 13m - 40' for MG), provided parallel

to and close by the inside of one of the stock rails, and connected to the mechanism locking the

points. It is set up in such a way that when the points are set and locked, the lock bar moves

vertically up until it reaches the level of the wheels riding on the rails. As long as the train is



moving over the points, one or another wheel presses down on the lock bar, forcing it to be

locked in position so that the points cannot be changed.

Slotting of signals: Inter cabin control of signals for the purpose of bringing them to ‘OFF’

position is called slotting of signals. By these arrangements, the cabin man of a recovering

signal cabin can not operate the signals unless the cabin man of the dispatching signal cabin

releases the control lever of the signal. On the other hand, by slotting of signals, it is possible to

put back the signal to danger position.

Construction of New railway lines: New railway line is required for any one of the following reasons:

- Strategic and political considerations

- Development of backward area

- Connecting new trade centers

- Shortening existing rail lines

The main tasks involved in new construction of new lines are as follows:

Land acquisition, earth work formation, plate laying and packing of track.

Earth work for formation:

Depending upon the rail level and general contour of the area, the formation may be laid in an

embankment or cutting. Formation laid in an embankment is generally preferred because it

affords good drainage. Some of the points to be kept in mind with regard to earth work:

- Earth work is normally done 30 cm layers so that the soil is well compacted

- Mechanical compaction is generally done to obtain 90%MDD at OMC

- Blanket of thickness 30 cm is provided when soil is not of good quality

- Cost of cutting vs cost of filling to be counter balanced

- Entire section may be divide to convenient zones for early execution of work

Plate laying:

The assemblage of railway track components on a prepared formation is called plate laying or

track linking.

Method of plate laying:

1. Side method or tramline method

2. Telescopic method

3. American method



1. Side Method or Tramline method:

The materials will be dumped adjacent to the proposed line and will be made use of. This

method is very much suitable where double track is required. Existing track can be used for the

additional track construction. If there is no track is available for transporting materials, road is

to be constructed and then track can be constructed and this method is suitable for flat terrain.

2. Telescopic method:

In this method, the material is transported through wagons from the material depot to the work

site by using newly laid track. The laying of new track is advanced telescopically till

destination is reached. All the required materials are stored in a material depot before

construction. Materials can be shifted to some other point when distance of construction

becomes more from the rail head.

3. American method:

Special track laying machines are employed for plate laying work. The procedure in this

method is:

- Required number of sleepers as per sleeper density and two rails are first

prepared in the workshop and assembled.

- The assembled panels and track laying machines are delivered at the end of

rail head by the material train.

- With the help of special machine, the assembled panel is downloaded and is

linked with rail head

- The material rail is moved ahead of rail head by one rail length

- These steps are followed till the entire length of the track is laid.

Methods of packing of track:

1. Beater packing

2. Measured Shovel Packing

3. Packing by track tamping machines

1. Beater packing:

A beater is basically a pickaxe with one of its end blunted into T-shape. The pick end is used

for loosening the ballast core and the blunt end is used for forcing the ballast under the sleeper.



2. Measured Shovel Packing:

This method of maintenance of track without use of any sophisticated mechanical aid is an

improved form of manual method. It is generally employed only when ballast has already been

consolidated by passage of trains and only minor depressions in cross and longitudinal levels

need to be made up.

3. Packing by track tamping machines

Off-Track tampers:

They are portable and can be quickly taken off of the track just two people. These tampers

work during the interval between passage of trains and do not require any traffic blockage.

They consist of tools driven by compressed air, electricity or petrol. There are basically two

types of off track tampers namely, self contained tampers and those that are worked from a

common unit. They may be vibratory (by means of vibration) or of the percussion type (by

means of blows) or a combination of both.

On-track tampers:

They are self propelled vehicle which facilitate automatic tamping of sleepers through the

controls provided in the operator’s cabin. The weight of these tampers varies from 20 to 30 t

and cannot be easily removed from the track. Hence traffic is to be blocked during its

operation. These tampers can simultaneously do tasks like lifting, aligning, leveling and

tamping.

Maintenance of track alignment:

Tracks can be conveniently maintained either manually or with modern methods.

Essentials of track maintenance:

- gauge should be correct

- no difference in cross levels in straight reach

- longitudinal level should be uniform

- alignment should be straight and kink free

- ballast should be adequate and sleepers to be well packed

- no excessive wear and tear of track

- track drainage should be good and the formation should be well maintained

Through packing:

Opening of road



Examining of rails, sleepers and fastenings

Squaring of sleepers

Aligning the track

Gauging

Packing of sleepers

Repacking of joint sleepers

Boxing ballast section and dressing

Systematic Overhauling:

Shallow screening and making up of ballast section

Replacement of damaged or broken fittings

All items included in through packing

Lubrication of rail joints

Picking up slacks:

Slacks are those points in the track where the trains are running faulty or sub standard. It may

be due to

- Stretches of yielding formation

- Poorly maintained sections

- Improperly aligned curves

- Approaches to level crossings, girder bridges particularly in sag

- Portions of track with poor drainage

Maintenance of Rail Surface

The surface of rail susceptible to certain defects in the absence of proper care and maintenance.

Each defect should be dealt with carefully at the proper time.

Hogged joints

High joints

Blowing and pumping joints

Track Renewal

The process of replacement of existing rails and sleepers either separately or together by new or

old serviceable material is called track renewal. They can be broadly classified as under:

Complete track renewal: This implies the renewal of all the components. Necessary

recoupment of ballast and the provision of ballast cushion will also be done.



Through rail renewal: It involves the renewal of the rails between one point and the next.

Through sleeper renewals: This entails the renewal of the entire lot of sleepers from one

point to another.

Casual renewal: This entails the replacement of some of the unserviceable rails or sleepers or

both with serviceable, released rails and sleepers of a similar type and age.

Primary renewal: This refers to renewals that are done using new permanent way materials.

Secondary renewal: This refers to renewals that are done using released, serviceable

permanent way materials.

Factors responsible for track renewal:

Criteria for rail renewal:

Incidence of rail fractures failures

Wear on rail (loss of section, corrosion in web and foot, vertical wear, lateral wear)

Difficulty in track maintenance

Criteria for sleeper renewal:

When the sleeper does not fulfill the requirements of maintaining gauge, seating and tight grip,

then renewal of sleepers required.

Track Drainage:

Need for proper drainage:

Settlement of embankment

Reduction in bearing capacity

Failure of embankment

Formation of ballast pockets

Shrinkage and cracking of banks

Adverse effects of black cotton soil

Formation of slush

Requirements of good drainage system:

Surface water should not percolate to track

Effective side drains

Longitudinal drains to be saucer shaped

Provision for clearing and inspection

Drain top to be below cess level



No erosion of banks

Formation to be of good soil

Proper sub-surface drainage

Proper outfall

Special arrangements for waterlogged areas and other difficult situations

Practical tips for good drainage

Maintain proper cess level, No vegetation, area below rail foot to be clear, cleaning and repair

of drains.

Track drainage systems

Surface drainage:

Drainage of mid sections:

Side drain

Lining of drains

Adequate opening under level crossing

Catch water drain

No surplus ballast

Drainage in station yards:

Open surface drains

Saucer shaped drains

Drain top to be below cess level

Outflow and slope

Position of ballast sections

Network of cross and longitudinal drains

Drainage of station platforms:

Slope away from track

Discharge on non-track side

Discharge not towards run through lines

Sub-surface drainage

Provision of inverted filter

Paving of catch water drains

Provision of sand piling



Drainage of water pockets by perforated pipe

Cement grouting

Drainage of water pockets by puncturing holes

Modern methods of track maintenance: 1. Mechanized maintenance of track with the help of track machines (refer page 90)

2. Measured Shovel Packing

3. Directed Track maintenance

Measured Shovel Packing (MSP):

This method of maintenance of track without use of any sophisticated mechanical aid is an

improved form of manual method. It is generally employed only when ballast has already been

consolidated by passage of trains and only minor depressions in cross and longitudinal levels

need to be made up.

Scope of MSP:

The process of MSP is suitable for the following types of work:

- Through packing of the flat bottomed sleepers

- Packing of joint wooden sleepers in metal sleepers track

- Through packing of points and crossings with wooden and steel sleepers

- Dehogging of rail ends

Advantages of MSP:

- Work carried out is precise and finer adjustments that are permissible in

MSP

- Retentivity of packing especially in joint sleepers is more compared to other

types

- MSP gives an increased output per gangman and is therefore economical

- Minimum clean ballast cushion is not need when work is done through MSP

Disadvantages of MSP:

- MSP is suitable only for flat bottomed sleeper and hence its scope is limited

- This procedure requires special size stone chips, which may not be easily

available

- MSP is not effective for newly screened tracks

- Skilled labourers required



Through MSP of flat bottomed sleeper tracks:

- Measurement of voids

- Fixation of high points

- Converting high points to good points

- Longitudinal leveling

- Total lift

- Opening out of ballast

- Lifting and packing of tracks

- Provision of ramps

- Alignment

- Boxing and dressing of ballast

- Majoration of Joints

- Checking of work done

Directed track Maintenance (DTM):

As the name suggests, the maintenance is to be done as per the directions given every day and

not as routine one. In other words, it is a need based maintenance and not a routine

maintenance. In this s\system, track will be maintained at predetermined standards.

Objectives: Maintaining a track at predetermined standards and reduction in the cost of

maintenance by avoiding unnecessary work.

Work done under DTM:

Systematic overhauling: It will be done depending on the local factors such as condition of

track and formation, traffic density, permissible speed and rainfall.

Periodic maintenance work: Lubrication of joints, cleaning of side drains, catch water drains

and repairs of the formation.

Occasional maintenance work: Scattered renewal of rails, sleepers and other track

components, adjusting creep, restoring correct spacing between sleepers, over hauling at level

crossings, points and crossings.

Need based maintenance: Locating defects with some devices, by systematic inspection, by

recording observations and rectifying the above based on the need.

Highway 3rd Sem Lecture Note

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Transcript of Highway 3rd Sem Lecture Note