Railway planning and construction - Railways, airports, docks and harbour engineering (RAHE)

SNS COLLEGE OF ENGINEERING
Kurumbapalayam (Po), Coimbatore – 641 107
An Autonomous Institution
Accredited by NBA – AICTE and Accredited by NAAC – UGC with ‘A’ Grade
Approved by AICTE, New Delhi & Affiliated to Anna University, Chennai
DEPARTMENT OF CIVIL ENGINEERING
COURSE NAME: CE8702 RAILWAYS, AIRPORTS AND HARBOUR ENGINEERING
IV YEAR / VII SEMESTER
Unit 1 – Railway planning & Construction
Topic 1 : Significance transport System

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SNSCE/ Civil Engg /VII sem / Shanmugasundaram N/ Ap/Civil
UNIT I
.
RAILWAY PLANNING AND CONSTRUCTION
Elements of permanent way – Rails, Sleepers, Ballast, rail fixtures
and fastenings, - Selection of gauges - Track Stress, coning of wheels,
creep in rails, defects in rails – Route alignment surveys, conventional
and modern methods - Geometric design of railways, gradient, super
elevation, widening of gauge on curves- Level Crossings.

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Significance of Road, Rail, Air and Water transports
(முக்கியத்துவம்)
Transportation is regarded as an index of economic, social
and commercial progress of a country.
An adequate transportation is indispensable for economic and
social progress of nation and the world as a whole.
Land, water and air have been used by mankind for developing
the transport modes like Railways, Highways, Waterways.

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Classification of transportation systems
.

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1. Road Transport
It is the oldest form of transport.
It includes various means such as bullock cart, tempo, auto rickshaw,
busses, car etc.

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Road Transport
The advantages of road transport are as follows:
It facilitates door-to-door service
Road transport is highly flexible. The route can be changed anytime.
It is economical for short distance.
There are less overheads and less cost in terms of maintenance.
It provides personalized service.

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Rail Transport
In India railways are owned and managed by the Central Government

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Rail Transport
The following are the features of rail transport:
It is suitable for bulky goods.
It is economical for long distance.
There is regularity in the operation of train.
There is less pollution, as the train operates on electricity.
There is uniformity in rates as the rates are fixed by the government.

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Water Transport
India is surrounded by the Bay of Bengal, the Arabian Sea and the
Indian Ocean. Therefore it has a long coastline.
Water transport refers to movement of goods and passengers on
waterways.
With the help of these means goods and passengers are carried to
different places, both within as well as outside the country.

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Water Transport
The following are the features of water transport:
Water transport plays an important role in international trade.
It possesses high load carrying capacity.
It is a relatively economical mode of transport for bulky and heavy goods.
Water transport does not require any special infrastructure like roads, and
airport.
Sea transport requires large investment on ships and their maintenance.

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Air Transport
Air transport is of recent origin in the development of
transport system of a country.
Air transport provides the fastest practical means of
transportation.
Indian air transport is one of the fastest developing aviation
sectors of the world.

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Air Transport
The following are the features of air transport:
Air transport is the most modern and the quickest mode of transport.
It’s very expensive, as the operating costs of aeroplanes are high.
Air transport provides comfortable, efficient and quick transport service
Air transport requires less investment on infrastructure.
Air transport is free from physical barriers.
It plays a significant role in the national defence of the country.
Air transport is the most risky form of transport because the chances of
accidents are greater in comparison to other modes of transport

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Significance & Coordination of all modes to achieve
sustainability
முக்கியத்துவம் & நிலைத்தன்லைலய
1. Industrial growth 2. Creates employment
3. Creates place utility 4. Bring countries closer
5. Serve several purposes 6. Stability in prices
7. Specialization and division of labour
8. Use of Economic resources 9. Standard of living
http://www.yourarticlelibrary.com/transport/transportations-system-
in-india-forms-significance-and-recent-developments/7552

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HAPPY LEARNING

Topic 2 : Elements of permanent way - 1

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Rails length
In general longer the rail, lesser the number of joints and fittings, lesser
the cost of construction and maintenance.
IR adopt standard rail length of 12.80m (42ft) for B.G and 11.89m (39ft)
for M.G.
However the length of a rail is restricted due to the following factors:
1) Longer rails are difficult to transport
2) Manufacture is difficult
3) Large internal stresses
4) Difficulties in handling wide expansion joints.

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Rails section
It is designated by weight per unit length.
1) Maximum axial load
2) Maximum permissible speed
3) Depth of ballast cushion
4) Type and spacing of sleepers
5) Gauge of the track
Two heavier rails sections 60 kg and 52 kg are recently introduced and
are designated in metric units.
Thus 60kg/m rail denotes that it has a weight of 60kg per meter length.

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Gauge
The clear horizontal distance between the inner (running) faces
of the two rails forming a track is known as Gauge.

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Types of Gauges
The different gauges prevalent in India are of the following three types :-
Types
Broad gauge
(BG) (1676mm
Metre gauge
(MG)
(1000mm),
Narrow gauge
(NG) (762 mm
& 610 mm).

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Elements of Railway or permanent way
.
Combination of rails, fitted on sleepers and resting on ballast
and sub-grade is called the railway track or permanent way.

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Component parts of a permanent way
 Rails
 Sleepers
 Ballast
 Fixture and Fastening
 Sub-grade

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.

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Track Formation
The purpose of track is to transfer train loads to the formation.
Requirements for Choosing a Track System:
1. Trains running on Track do not cause excessive environmental
pollution in the form of noise and ground vibration.
2.Costs of the total service life of the track must be as low as
possible.
3.Maintenance should be low and as inexpensive as possible

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Payment cross section

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Permanent way
In permanent way, the rails are joined in series by fish plates and bolts
& then they are fixed to sleepers by different types of fastenings.
On curved tracks, super elevation is maintained by ballast and the
formation is levelled.
Quantity of ballast is provided on the outer cess of each track for which
the base width of the ballast is kept more than for a straight track

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Rails
The rails on the track can be considered as steel girders for the
purpose of carrying axle loads.
They are made in high carbon steel to withstand wear and tear.
 Flat footed rails are mostly used in railways
Functions:
It provide hard, smooth & unchanging surface for heavy loads with
min friction b/w rails and wheels.
Rails bear stresses, lateral, thermal & braking forces.

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Types of Rails
 Double headed rails
 Bull headed rails
 Flat footed rails

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Types of Rails Sections

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Double headed rails
Foot and head are of same dimensions are called double headed
or dumb bell rails.
The head worn out due to rubbing action of wheels, the rails
could be inverted and reused.
 But by experience it was found that their foot could not ne used
as running surface get corrugated under impact wheel loads.

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Bull headed rails
The rails section whose head dimensions are more than that of their
foot are called bull headed rails.
Rail head is made little thicker and stronger than the lower part by
adding more metal to it.
Used more in points and crossings. Require chairs for holding them in
position

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Bull headed rails
.
Merits:
 B.H rails keep better alignment and provide more smoother
and stronger track.
These rails provide longer life to wooden sleepers and greater
stability to the track.
These rails are easily removed from sleepers and hence
renewal of track is easy.
Demerits:
B.H rails require additional cost of iron chairs.
These rails require heavy maintenance cost.
It has less strength and stiffness.

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Flat Footed Rail
The rails sections having their foot rolled to flat
are called flat footed or Vignole’s rails.
Initially thought that the flat footed rails could
fixed directly to wooden sleepers and would
eliminate chairs and keys required for the B.H
rails.
Heavy train loads caused the foot of the
 Rail to sink onto the sleepers and making the
spikes loose.
Steel bearing plates were used in between flat
footed rails.

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Flat Footed Rail
.
Merits:
Have more strength & stiffness
Require less no. of fastenings.
Maintenance cost is less.
Demerits:
These rails are not easily removed & renewal
of track becomes difficult.
Difficult to manufacture points and crossings.
Fittings get loosened easily.

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HAPPY LEARNING

Topic 3 : Elements of permanent way - 2

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Sleepers
These are the members generally laid transverse to the rails on
which rails are supported & fixed, to transfer the loads from
rails to the ballast & sub grade below.

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Functions of Sleepers
.
To hold the rails to correct gauge and hold the rails in proper
level.
To act an elastic medium in b/w ballast & rails to absorb the
blows & vibrations of moving loads.
It also add to longitudinal and lateral stability of the permanent
track on the whole.
To transfer the loads from rails to the ballast. To support and fix
the rails in proper position.
To keep the rails at a proper level in straight tracks and at
proper super elevation on curves.

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Requirement of Sleepers
The sleepers should be strong to act as a beam under loads.
It should be economical.
Maintain correct gauge.
Should provide sufficient bearing area for the rail.
Sleepers should have sufficient weight for stability.
It should facilitate easy fixing and taking out of rails without
disturbing them.
They posses easy removal and replacement of ballast.
Able to resist impact and vibrations of moving trains.

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Types of Sleepers
.
According to materials:
Wooden sleepers
Metal sleepers
cast iron sleepers
steel sleepers.
RCC sleepers
Pre-stressed concrete sleepers.

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Wooden Sleepers
Satisfy all the requirements and
suitable for track circuiting.
Life of wooden sleepers depends on
their ability to resist wear, attack by
white ants and quality of timber used.
Sal, teak, deodar & chair wood.
B.G - 2740 x 250 x 130 mm
M.G - 1830 x 203 x 114 mm
N.G - 1520 x 150 x 100 mm

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Wooden sleepers
Advantages
They are easy to manufacture
They are more useful for heavy loads and high speeds
They are easy to handle without damage
They are more suitable for soft formations
They absorb shocks and vibrations better than other types of sleepers.
Disadvantages
They are easily liable to attack by vermin (மண்புழு) and weather.
Hence their life is lesser than other type of sleepers
They are susceptible to fire.
Their maintenance cost is highest in comparison to other type of
sleepers
Their useful life is short about 12 to 15 years.

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Cast iron Sleepers
These are made of cast iron.
Types:
1. Pot or bowl sleepers
2. Plate sleepers
3. Box sleepers
4. CST-9 sleepers
5. Duplex sleepers

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Cast iron Sleepers
Advantages:
Life is more.
Maintenance cost is low
Durable
Disadvantages:
More ballast is required than any other
type
No. of fittings required is more
Liable to break
Not suitable for all type of ballast

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Steel Sleepers
Steel made of 6mm thick sheets.
At the time of pressing of sleepers, an inward slope of 1 in 20 on either
side is provided to achieve tilt of rails.
Standard size is 2680 mm
Types:
Key type steel sleepers
Clip and bolt type steel sleepers

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Steel sleepers
Advantages
It is more durable. Its life is about 35 years
Lesser damage during handling and transport.
Easy to manufacture.
It is not susceptible to vermin attack (wild animals or birds).
It is not susceptible to fire.
Its scrap value is very good.
Disadvantages
It is liable to corrosion.
Cracks at rail seats develop during the service.
Fittings required are greater in number.

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RCC Sleepers
Merits:
Have long life - 40 to 60 years.
Free from natural decay & attack of insects
require less fittings.
Provide more lateral and longitudinal rigidity
as compared to others
Maintenance cost is low.
Demerits:
It is brittle and cracks without warning
It cannot be repaired, and required
replacement.

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Pre – Stressed Sleepers
These sleepers are now-a-days extensively
used in Indian Railways.
These sleepers have high initial cost but are very
cheap in long run dueto their long life.
In these sleepers, high tension steel wires are
used.
These wires are stretched by hydraulic jack to
give necessary tension in thewires.
The concrete is then put under a very high
initial compression.
These sleepers are heavily damaged in
case of derailment or accidents oftrains.

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Sleeper Density
The space b/w two adjacent sleepers determine the effective
span of the rail over the sleepers.
The spacing of sleepers in a track depends on the axle load which the
track is expected to carry lateral thrust of locomotives to which it is
subjected.
It’s the no. of sleepers per rail length and it is specified as (M + x or N
+ x), where M - length of rail in m, x- is a number, varying acc to full
factors fixed by Railway board for various axle loads.
Methods of providing rail joints
Speed of trains
Max axle load expected on track

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Ballast
.
It is the granular material usually broken stone or brick, shingle
or kankar, gravel or sand placed & packed below & around the
sleepers to transmit the load from sleepers to formation and also
for drainage.

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Details of Ballast Sections
Dimensions BG MG NG
Width of ballast 3.35m 2.25m 1.83m
Depth of ballast 20 to 25cm 15 to 20cm 15cm
Quantity of stone
ballast/m length 1.036m3 0.71m3 0.53m3

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Functions of Ballast
.
Tohold the sleepers in position and preventing the lateral &
longitudinal movement.
Todistribute the axle load uniform from sleepers to a large area
of formation.
Toprovide elasticity to the track. Acts as elastic material b/w sub
grade and sleepers.
Todrainwaterfromthetrack
Topreventgrowthofweeds(களைகள்) insidethetrack.
Toprovideeasymaintenance.

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Characteristics of Good Ballast
It should have sufficient strength to resist crushing under heavy
loads of moving trains.
It should be durable enough to resist abrasion and weathering action.
Should have rough and angular surface to provide good lateral and
longitudinal stability to the sleepers.
Should have good workability, have easy spread of formation.
Should be cheaply available.
Should not have any chemical action on metal sleepers and
rails.

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Types of Ballast
.
1. Broken stone
2. Gravel
3. Sand
4. Ashes or cinders
5. Kankar
6. Moorum
7. Blast furnace slag
8. Brick ballast
9. Selected Earth

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Broken stone
This is the best type of ballast as it possesses all the characteristics
of a good ballast.
It holds the track to correct alignment and gradient due to its high
interlockingaction.

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Broken stone
.
The stones which are non porous, hard and do not flake on
breaking should be used.
Igneous rocks such as granite, quartzite and trap make excellent
ballast.
This type of ballast is used for high speed tracks.
Advantages
It is hard and resist crushing under heavy loads.
It has angular and rough surface and hence gives more stability to
thesleepers.
Its drainage property isexcellent.
Disadvantages
It is expensive.
It is not so easily available

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Gravel
Gravel is the second best material forballast.
This is obtained either from river beds or from
gravel pits and has smooth rounded fragments.
Gravel obtained from pits usually contains earth
which should be removed by washing.
Gravel obtained from river beds is screened and
required size gravel is used.
Larger size gravels are broken into required size.
Round edges gravels are broken to increase
their interlocking action.

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Gravel
Advantages
Gravel is cheaper than stoneballast.
The drainage propertyof gravel excellent.
It holds the track to correct alignment and gradient.
It is easy to use gravel ballast than stone ballast at certain places where
formation isunstable.
Disadvantage
It requires screening before use due to large variation in size.
Gravel obtained from pits requireswashing.
Due to round faces the packing under sleepers is loose.
Gravel easily roll down due tovibrations.

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Cinders or Ashes Sand
Cinders or Ashes
 The residue obtained from the coal used in
locomotives is known as Cinder or Ash.
 They are cheap and easy available.
 They are harmful for steel sleepers.
Sand
 It stands fourth in merits as ballast material.
 Coarse sand is better than fine sand.
 It has good drainage property but blown
(சேதமளைந்தது) off due to light weight.

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Brick ballast and Kankar
Brick ballast
 Where stone or other suitable ballast
is not available, over burnt brick
ballast can be used.
 Use in light traffic areas.
Kankar
 It is found in the form of particles of
varying sizes.
 Where stone is not easily and at
reasonable price available, kankar can
be used as road metal and ballast for
railway tracks.

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Moorum
Decomposed late-rite rocks
Red in colour
Under heavy loads crumbles to
powder
Used in sidings and embankments

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HAPPY LEARNING

Topic 4 : Rail Fixtures and Fastenings

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Rail Fixtures and Fastenings

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.

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The important fittings commonly used in a permanent way are
1. Fish plates
2. Spikes
3.Bolts
4. Bearing plates
5. Chairs
6.keys
7.Anti-creepers or anchors
8.Blocks

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Functions of Fixtures and Fastenings
To join the rails end to end to form full length of track.
To fix the rails tosleepers.
To maintain the correct alignment of the track.
To provide properexpansion gap between rails.
To maintain the required tilt ofrails.
 To set the points and crossings in proper position.

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1.Fish plates
Fish plates are used in rail joints to maintain the continuity of the
rails & to allow for any expansion or contraction of the rail caused by
temperature variations.

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2. Spikes
For holding the rails to the wooden sleepers (also known
as a cut spike or crampon) is a large nail with an offset head
that is used to secure rails and base plates to railroad ties in
the track.
Types of Spikes.
Dog spikes
Screw spikes
Round spikes
Standard Spikes

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3.Bolts
Bolts are used for connecting fish plates to the rails at rail
joint, bearing plates and chairs to wooden sleepers etc.

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4. Bearing plates
These are the plates which are provided in between the flat
footed rails and wooden sleepers.

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5.Chairs
For keeping the bull headed rail in proper
position, special devices are provided in between
the sleepers and the rails which is known as the
Chairs.

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6.Key
They are generally wedge shaped wooden pieces or metal pieces.
 They keep the rail in proper position.
Wooden keys are cheaper, but liable to be attacked by vermin.
Hence a number of metal keys have been devised.

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7. Anti creepers
A clamp that is attached to the flange of
a railroad rail and rests on a tie; it is part of
the track superstructure when spikes
are used for fastening the rail and tie.
Anti-creepers inhibit the lateral
displacement of the rails caused by the
action of the wheels of the rolling stock.

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8.Blocks
They are inserted in between the
two rails running close to each other and
bolted to maintain the required distance
They may touch either the webs or the
finishing faces or both.

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HAPPY LEARNING
.

Topic 5 : Track stress, Wheel load and Coning of wheels

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Requirements of an Ideal Permanent way
.
Permanent track is regarded to be semi elastic in nature.
The gauge should be correct and uniform.
The rails should be in proper level. Two rails must be at same
level.
The alignment should be correct. (i,e) it should be free from
irregularities.
The gradient should be resilient and elastic in order to absorb
shocks and vibrations of running track.
The radius and super elevation on curves should be properly
designed and maintained.

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Drainage system must be perfect for enhancing safety and durability
of track.
 Joints, including points and crossings which are regarded to be
weakest points of the railway track, should be properly designed and
maintained.
 If there is trouble from the creep, the preventionary measures should
be to prevent it.
There should be adequate provision for easy renewals and
replacements.
The track structure should be strong, low in initial cost as well as
maintenance cost

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.
The permanent way should be properly designed so that the load
of the train is uniformly distributed over the tworails.
 The track should have enough lateral strength so that it can
maintain its stability even with variation in temperature and other
factors.
All the components of permanent way should satisfy the design
requirements.
On curves proper super elevation should be provided to the outer
rail.

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Track stress
Stresses on railway tracks are caused due to various reasons
Wheel loads
Dynamic effect of wheel loads
Over balance of driving wheels of locomotive
Horizontal thrust
Pressure exerted by flanges of wheels
Irregularities in the track
Additional stresses on curves.

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Wheel Load
.
This is the static load which is continuously acting on the rail when
the wheels are in stationary position .
Dynamic Augment of vertical loads
On account of vertical impact due to speed and rail vibrations, etc.,
the dynamic load is much more than the static load.
The dynamic wheel load is obtained by increasing the static wheel
load by an incremental amount given by the speed factor.
Impact factor = V2/30000(speeds upto 100kmph)

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Hammer blow effect
The centrifugal forces due to revolving masses in the driving and
coupled wheels of a locomotive, such as crank pins, coupling rods, and
parts of the connecting rod, are completely balanced by placing
counterweights near the rim of the wheel, diametrically opposite to
the revolving masses.
The vertical component of the centrifugal force of the weight
introduced to balance the reciprocating masses causes variation in the
wheel pressure on the rail, and is called the hammer blow.
The heavier the weight added to balance the reciprocating masses,
the greater the hammer blow.
This create overbalance of driving wheels.

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Hammer blow effect

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Steam effect
 A steam locomotive works by converting coal energy into steam energy
(நீராவி அழுத்தம்).
 Steam pressure acts on the piston and is transmitted to the driving wheels
through the crank pins and connecting rod.
 The vertical component of the crank pins and connecting rod is at an
angle to the piston rod.
 It creates horizontal thrust on the track.

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Pressure by wheel flanges
 Trains not always move in a straight direction. But moves in a zig-zag
manner.
 Because of such movements lateral pressure is exerted by the flanges
on the rails.
 Although coning is provided in the wheels, this pressure cannot be
completely avoided
Irregularities of track
Non-uniformity gauge may cause hammer blow, lateral thrust

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Coning of wheels

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Coning of wheels

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Coning of wheels

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Coning of wheels
"Coning of wheels" is what allows a train to take a turn without slipping
off its tracks.
Tilting is achieved by using inclined base plates.
The flanges are never made flat. But, they are in the shape of a cone
with a slope of about 1 in 20.
As the wheels are set on the axle, there is some chance for lateral
movement b/w the flanges of the wheels and the rails.
Without coning, the flanges would cause, a slight but sudden stock to
the sides of the rails.
It is done mainly to maintain the vehicle in the central position with
respect to the track.

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Coning of wheels
The wheels generally, remain central on a straight and level surface
and the circumference of the threads of both the vehicle areequal.
However on a curve , the outer wheel has to negotiate more distance as
compared to the inner wheel.
Due to centrifugal force on a curve, the circumference of the thread of
the outer wheel thus becomes greater than that of the innerwheel.
This helps the outer wheel to travel longer distance than the inner
wheel.

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Coning of wheels
.
Advantages
It helps the vehicle to negotiate a curve smoothly.
It provides a smooth ride
It reduces the wear and tear of the wheel flanges.
Disadvantages
The outer rail will have more pressure while the inner rail will
have lesserpressure.
Owing to the centrifugal strength, the parallel components incline
to turn the rail out and gauge has broadening tendency.
Due to this condition if the voids sleepers have no base plate
beneath the edge of the rail they will be damaged.

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HAPPY LEARNING

Topic 6 : Creep, Wear and Defects in Rails

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Creep in Rails (த ொய்வு)
It is defined as the longitudinal movement of rails with respect to
sleepers in a track.
Indication ofcreep:
Closing of successive expansion spaces at rail joints in the direction of
creep and opening out of joints at the point from where the creep
starts.
Marks on flanges and webs of rails made by spike heads by scraping or
scratching as the rails slide.

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.
There are three main causes of Creep
1. Wave motion of trains.
2. Expansion and contraction of rails
due to variation in temperature.
3. Due to starting, accelerating, slowing
down (decelerating) and stopping of
trains.
Wave Motion
When train passes on a track, the portion of rail length under the
wheel of train will under more stresses and little depression will exist.

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Wave Motion
As a result, this depression will cause (set) a wave motion in the rail or
track
Direction Of Creep
Alignment Of Track:
Creep is more on curve track than on a tangent portion (straight
track).
Grades:
In upgrades tracks, creep will be less and in down grades track creep
will be more.
Direction of movement of trains:
Creep will be more in the direction to which the loaded train moves
more.

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.
Extent Of Creep
 Creep does not vary at some constant rate. (it is not constant)
 Creep does not continue in one direction only.
 Creep for two rails of the track will not be in equal amount.
Result Of Creep
 Expansion gap is reduced, buckling of track take place.
 Sleepers are moved out of a square.
 Crossing points get disturbed.

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Classification of Wear
A) Based on location:
On sharp curves
On gradients
On approaches to stations and brakes are frequently applied.
In tunnels
• Where sand is used on rails to produce more friction on damp rails
but on the contrary it gives more wear.
• The gases emitting from the engine being confined attack the metal
and result in wear.
In coastal area, due to action of sea breeze, the corrosion of metal
takes place.
On weak foundations sinking of rails due to heavy loads gives
uneven surface which results in wear

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Classification of Wear
B) basis of position of wear:
Wear on top or head of rail.
Wear at the ends of rails
Wear on the sides of the head.

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Wear in Rail

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Defects in Rails
Corrugation of rails (நநைிவு)
 Corrugation consists of minute depressions on the surface of rails,
varying in shape and size and occurring at irregular intervals.
The factors which help in the formation of rail corrugation, however,
are briefly enumerated here.
(a) Metallurgy and age of rails
(i) High nitrogen content of the rails.
(ii) Effect of oscillation at the time of rolling and straightening of rails.
(b) Physical and environment conditions of track
(i) Steep gradients (ii) Yielding formation
(iii) Long tunnels (iv) Electrified sections

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Defects in Rails
(c) Train operations
High speeds and high axle loads.
 Starting locations of trains.
 (iii) Locations where brakes are applied to stop the train.
(d) Atmospheric effects
High moisture content in the air particularly in coastal areas.
(ii) Presence of sand.

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Route Alignment Survey
Alignment may be defined as the layout of the centre line of a railway
track.
 Basic requirement of an ideal alignment are economic, easy for
construction, operation and maintenance, safe.
1. Traffic survey
2. Reconnaissance survey
3. Preliminary survey
4. Location survey

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1. Traffic survey
The main aim of traffic survey is to submit the field data to the
authority judge the suitability of the project.
Particulars of villages and towns within about 20km from the
proposed track along with the population.
Location of existing industries and the potential growth of them.
Volume of traffic in terms of passengers and goods wagons.
Availability of export based natural resources like, iron, coal, etc.

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2. Reconnaissance survey
Reconnaissance survey should furnish the following details:
Topographical features of the area.
Existing water resources along with their discharge details .
Natural features like ridges, valley, forest, etc.
Geographical and soil classification.
3. Preliminary survey:
Construction pillar is erected to mark the starting point.
A fly leveling is done to connect the starting point and a nearby GTS
bench mark.

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3. Preliminary survey:
A compass survey is conducted along the alignment to prepare a
route survey map covering about 100m on either side of the
alignment.
A cross sectional leveling is done at regular intervals say 100m.
4. Location survey
The transfer is done by adopting the following steps:
15cm pegs at 30m intervals are driven .
Every tenth peg is marked by 60cm pegs.
Pegs are also driven to demarcate the center line of the track.
At every km length masonry pillars are constructed which serve as
bench marks.

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Factors controlling alignments
.
Obligatory points
Traffic potential
 Geometric design standards
Topography
Economic viability
Techno economic characteristics
Other considerations

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Obligatory points
It is the controlling points
which govern the alignment of
railway tracks. Alignment has
to pass through are,
Important towns and cities
Shortest width and permanent
path of rivers
Hill passes

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Conventional and modern methods
.
Some of these survey aids and techniques are the following:
Remote sensing data
Aerial photographs
Electro - magnetic distance measurement
Digital terrain modeling
Geographic information system
Remote sensing data
Remote sensing data or satellite imaginary provides a bird’s
eye view of large areas.
Indian space research organization(ISRO) provides such maps
which are up dated once a month.
Ground conditioned can be well defined with a combination of
satellite images and topographical maps.

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Aerial photographs
Aerial photogrammetric is that type of photography wherein the
photographs are taken by cameras mounted on an aircraft lying over the
area.
Stereo photographs are taken is another system which is a recent
development.
 In this system photographs are taken in pairs at the ends of a base line
of known length and direction.

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Electro magnetic distance measurements (EDM)
.
Electro magnetic distance measurements is a general term used
collectively in the measurements of distance applying electronic
methods.
Depending on the type of carrier wave used, EDM instruments
may be classified as
(1)microwave instruments
(2)visible light instruments and
(3)infrared instruments.
These instruments are very light and compact and can mounted
with theodolite.
Thus these instruments enable to measure angles and distances
simultaneously.

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DTM & GIS
Digital terrain modeling(DTM)
It’s a computer aided design and most economical alignment may be
obtained.
After the alignment decision, ground stations are fixed in the form of
mutually visible points.
Geographical information system (GIS)
GIS is new technology which covers a number of fields such as remote
sensing, cartography, surveying and photography.

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Soil Suitability Analysis
Railway formation of soil for embankment No 1 barrow pits shall be
allowed with in right of way and contractor shall bring to embankment
materials from his own resource outside the right of the way

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Soil Suitability Analysis
(a) Soil having following characteristics should be used.
 Soil with fine particles (finer then 75 microns) not more then 50%
 Soil with liquid limit less then 35% and plasticity index less then 15%
 Soil having uniformity co-efficient preferably above 7
(b) Following soils should not be used.
 Soil having 10 to 15% clay and silt grater then 50% exhibiting
distractive nature.
 Maximum dry density less 1.5gm/cc by light compaction
 Peat and organic soils
 Poorly graded sand with co-efficient of uniformity less then 2.

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Geometric design of railways
Necessity of geometric design of a railway track
The need for proper geometric design of a track arises because of the
following considerations
(a) To ensure the smooth and safe running of trains
(b) To achieve maximum speeds
(c) To carry heavy axle loads
(d) To avoid accidents and derailments
due to a defective permanent way
(e) To ensure that the track requires least
maintenance.
(f) For good aesthetics

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HAPPY LEARNING

Topic 7 : Gradient and Super Elevation

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Gradient

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Gradient
Gradient is the rate of rise or fall of the track.
 It is expressed as the ratio of vertical distance to horizontal distance
or as percentage of rise or fall.
 If any track rises 1 m in 100 m horizontal length, its gradient is
expressed as 1 in 100 or 1 percent.
If another track falls by 1 m in 50 m length, its gradient is 1 in 50 or 2
percent.
Gradients are provided to the formation of rail track to serve the
following purpose:
(i) To reduce the cost of earthwork.
(ii) To provide uniform rise or fall as far as practicable.
(iii) To reach the stations situated at different elevations.
(iv) To drain off rain water

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Types of Gradient
(i) Ruling gradient (ii) Momentum gradient
(iii) Pusher gradient (iv) Station yard gradient
(i) Ruling gradient
Ruling gradient is the maximum gradient to which the track may
be laid in a particular section.
It depends on the load of the train and additional power of the
locomotive.
In plains - 1 in 150 to 1 in 200
In Hilly tracks - 1 in 100 to 1 in 150

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Types of Gradient
(ii) Momentum gradient
Gradient which is steeper than ruling gradient and where the
advantage of momentum is utilized, is known as momentum gradient.
A train gets momentum when moving in down gradient and this
momentum can be utilized for up
gradient.
This rising gradient is called momentum
gradient. In such gradients no signals
are provided to stop the train.

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Types of Gradient
(iii) Pusher gradient
Pusher gradient is the gradient where extra engine is required to push
the train.
These are steeper gradient than ruling gradient and are provided at
certain places of mountains to avoid heavy cutting or to reduce the
length of track.
 A pusher gradient of 1 in 37 on
western Ghats with B.G.track is provided.
 On Darjeeling Railway with
N.G. track, a ruling gradient of
1 in 25 is provided.]

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Types of Gradient
.
(iv) Station yard gradient
Station yard gradient is the minimum gradient provided in
station yard for easy draining of rain water.

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Types of Gradient
(iv) Station yard gradient
Gradients are avoided as far as possible in station yard due to
following reasons
(a) In station yard, Bogies standing on gradients may start moving
due to heavy wind and may cause accident.
(b) The locomotives will require extra force of pull the train on
gradients at the time of starting the trains.
In station yards, maximum limit of gradient is fixed as 1 in 400 and
minimum gradient recommended is 1 in 1000 for easy drainage of
rain water.

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Grade Compensation on Curves
.
Grade compensation on curves is the reduction in gradient on
curved portion of a track.
On curves extra pull is required to pull the train due to more
tractive (இழுளவ) resistance.
Therefore, if gradients are to be provided on curves some
compensation should be given in ruling gradients to overcome the
increased tractive resistance to a certain limit and to pull the trains
with same speed.
It is expressed as percentage per degree of curve.
(i) On B.G. curves – 0.04 percent / degree
(ii) On M.G. curves – 0.03 percent / degree
(iii) On N.G. curves – 0.02 percent / degree

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Degree of curve.
A curve is defined by its degree or radius. The degree of a curve is the
angle subtended at the center by a chord of 100 feet or 30.48m.
If R is the radius ofcurve,
Circumference of the curve= 2 ∏ R
Angle subtended at the center by the circle = 360 degree
Angle subtended by the arc of 30.48m = 1750/R Thus, a 1 degree
curve has a radius of 1750 m.
D = 1750 / R, D= degree, R = radius.

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Degree of curve
.
Maximum degree of curvature for B.G = 10 deg (min. R = 175m)
Maximum degree of curvature for M.G = 16 deg (min. R = 109m)
Maximum degree of curvature for N.G = 40 deg (min. R = 44m)
V = 4.4 √(R – 70) - B.G
V = 4.35 √(R – 67) - M.G
V = 3.6 √(R – 6.1) - N.G ,
V in kmph.

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Super elevation on Curves (Cant)

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Cant is defined as the difference in height between the inner and outer
rails on the curve.
It is provided by gradually raising the outer rail above the inner rail
level.
The inner rail is considered as the reference rail and normally is
maintained at its original level.
The inner rail is known as the gradient rail.

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Function of super elevation:
Neutralizes the effect of lateral force.
It provides better load distribution on the two rails.
It reduces wear and tear of rails and rolling stock.
It provides smooth running of trains and comforts to the passengers.
Equilibrium speed:
It is the speed at which the effect of centrifugal force is exactly
balanced by the super elevation provided.
When the speed of a vehicle running on a curved track is such that the
resultant weight of the vehicle and the effect of radial acceleration is
perpendicular to the plane of rails and the vehicle is not subjected to
an unbalanced radial acceleration, is in equilibrium then its
particular speed is called equilibrium speed.

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Speed
Maximum permissible speed:
This is the highest speed which may be allowed or permitted on a
curved track taking into consideration of the radius of curvature,
actual cant, cant deficiency, cant excess and the length of the
transition curve.
When, the maximum permissible speed on the curve is less than
the maximum sanctioned speed of the section of a line,
permanent speed restriction become necessary on such curves.

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Cant Deficiency
The equilibrium cant is provided on the basis of equilibrium speed
(average speed or weighted average speed) of different trains.
But this equilibrium cant or super elevation falls short of that required
for the high speed trains.
This shortage of cant is called “Cant Deficiency”
In other words, cant deficiency is the difference between the equilibrium
cant necessary for the maximum permissible speed on a curve and the
actual cant provided (on the basis of average speed on the train)

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Limits of cant Deficiency
Gauge
Cant deficiency for speeds
upto 100 Km.p.h
Cant deficiency of speed
higher then 100 Km.p.h
B.G 7.5 cm (75mm) 10.0 cm (100mm)
M.G 5.0 cm (50mm) Not specified
N.G 4.0 cm (40mm) Not specified

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Negative Super Elevation
When a main line is on a curve & has a turn out leading to a branch
line, the super elevation necessary for the average speed of trains over the
main line cannot be provided.

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Types of Gradient
(iii) Pusher gradient
Pusher gradient is the gradient where extra engine is required to push
the train.
These are steeper gradient than ruling gradient and are provided at
certain places of mountains to avoid heavy cutting or to reduce the
length of track.
 A pusher gradient of 1 in 37 on
western Ghats with B.G.track is provided.
 On Darjeeling Railway with
N.G. track, a ruling gradient of
1 in 25 is provided.]

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Widening of Gauge on Curves
.
Due to rigidity of the wheel base, when the outer wheel of the front
axle strikes against the outer rail, the outer wheel of the rear axle
cheers a gap with the outer rail.
This can be accounted by widening the gauge failing which there is
every possibility of tilting of rail outwards on curves.
Extra width of gauge d, in cm,
d = 13(B+L)2 / R
B = rigid wheel base in m
B= 6 - B.G, B=4.88 m - M.G
R = radius of the curve in m
L = lap flange, L = 0.02 √(h2 + Dh)

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Widening of Gauge on Curves
Due to impounding action of wheels on curves , the gauge of the track
gets widened and the rails get tilted outwards.
To prevent the tendency of tilting the rail outward, the gauge of the
track on curves is suitably widened.
The amount of widening of gauges depends on the radius of curve ,
gauge and rigid wheel base of the vehicles.
The widening
13(B+L)2
d = -------------
R
Where , d is the extra width of gauge in cm
B is rigid wheel base in metres.

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HAPPY LEARNING
.

Topic 8 : Points and Crossing

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Points and Crossings
.
Outline
Turnout
Types
 Left hand
 Right Hand
 Components
Points and Switches
 Crossings

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Turnout
Turnout is an arrangement of points and crossings with lead rails by
which trains may be diverted from one track to another moving in the
facing direction.
A turnout is left handed or right handed as the train taking the turnout
in the facing direction is diverted to the left or right of the main line.
Component parts of a Turnout
(i) A pair of tonguerails (ii) A pair of stockrails
(iii) Two check rails (iv) Four lead rails
(v) A veecrossing (vi) Slide chairs
(vii) Stretcher bar (viii) A pair of heel blocks
(ix) Switch tie plate or gauge tie chair
(x) Parts for operating points – Rods, cranks, levers etc.
(xi) Locking system which includes locking box, lock bar, plunger bar etc.

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(i) A pair of tongue rails
.
The tongue rails along the stock rails in a turnout form a pair of
points or switches.
The tongue rails facilitate the diversion of a train from the main
track to a branch track.

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(ii) A Pair of Stock Rails:
They are the main rails to which the tongue rails fit closely.
The stock rails help in smooth working of tongue rails.

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Rails
(iv) Four Lead Rails:
Outer straight lead rail, outer curve lead rail, inner straight lead rail
and inner curve lead rail are the four lead rails provided in a turnout.
The function of these rails is to lead the track from heel of switches to
the toe of crossing.
(v) A Vee Crossing:
A Vee crossing is formed by two wing rails, a point rail and a splice rail.
It provides gaps between the rails so that wheel flanges pass through
them without anyobstruction.
(vi) Slide Chairs:
Slide chairs are provided to support the tongue rail throughout their
length and to allow lateral movement for changing ofpoints

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Turnout Components

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Switches / Points

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Switches / Points
CHECK RAIL

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Crossing
Requirements of ideal crossing
(i) Crossing assembly should be rigid enoughto withstand severe
vibrations.
(ii) Wing rails and nose of crossing should be able to resist heavy wear
due to movement of wheels, hence should be manufactured of special
steel (alloysteel).
(iii) The nose of crossing should have adequate thickness to take all
stresses acting on the crossing.

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Types of Crossing
Crossings can be classified asfollows:
1. Square crossing
2.Diamond Crossing
3.Cross Over
4.cissor Crossing
5.Symmetrical Split
6.Acute angle or V-crossing or Frog
7.Obtuse angle or Diamond crossing

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1.Square Crossing
Square crossing is formed when two straight tracks of same or different
gauge, cross each other at right angles.
This type of crossing should be avoided on main lines because of heavy
wear ofrails.

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2.Diamond Crossing
Angle of intersection (crossing angle) of two tracks is when not 900 ,
then crossing is called diamond crossing

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2.Diamond Crossing
.

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2.Diamond Crossing (Double Cross)

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Cross Over
.
A cross over is introduced to transfer a train from one track to
another track which may or may not be parallel to each other

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4.Cissor Crossing
If two cross over's are required between two parallel tracks and there is
no sufficient space for crossing to be kept separate, then they are made
to over-lap each other and result is a scissor crossing.

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5.Symmetrical Split
.
If radius of main track is equal to the radius of turn out curve, then
the turn out is known as symmetrical split.

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6.Acute Angle Crossing
Acute angle crossing is formed when left hand rail of one track
crosses right hand rail of another track at an acute angle or vice
versa.
This type of crossing consists of a pair of wing rails, a pair of
check rails, a point rail and a splice rail.
This crossing is widely used.

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7.Obtuse Angle Crossing
Obtuse angle crossing is formed when left hand rail of one track crosses
right hand rail of another track at an obtuse angle or vice versa.
This type of crossing consists mainly of two acute angle and two obtuse
angle crossings.
This is also called Diamond crossing.

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Unit 1 Completed

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H H
A A
P P
P P
Y Y
LEARNING

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