This document discusses various topics related to railway tracks, including reasons for rail failures, types of rail failures, causes and measurement of creep in rails, methods to correct creep, types of rail joints, requirements of an ideal rail joint, types of rail fastenings, and requirements of sleepers. It provides details on factors that influence rail failure, different types of rail failures such as crushed head, transverse fissure, etc. It also discusses various causes of creep in rails and methods to measure and correct creep, including pulling back rails and using creep anchors.
1. TOPIC-
NAME ENROLL NO.
PATEL JIMI 131100106029
PATEL MILIND 131100106035
PATEL VIRAJ 131100106040
PATEL YASH 131100106042
SHAH ASHIT 131100106051
GUIDED BY: Prof. Rajan
lad
2. Rail failures - Reasons
Sometimes rails fail suddenly without any notice.
Factors that influence the failure are as follows.
Axle load of locomotive
Constant reversal of stresses
Defects in manufacture
Design of rail joints
Fatigue caused by shearing stresses
Frequency of rail renewal
Maintenance of rail joints
3. Rail length
Rail quality
Rail section
Rail welding
Speed of trains etc.,
The above are some of the main reasons of the
rail failure
4. Rail failures - Types
1. Crushed head
2. Transverse fissure
3. Split head
4. Horizontal fissure
5. Square of angular breaks
5. Crushed head
Head gets crushed, metal flows on the head of rail
Defects in manufacture, flat spots on wheels, slipping of
wheels, week support at the rail end etc.,
Skidding causes flat spots, loose fish bolts cause week
support at ends
Transverse fissure
Fissure or hole in the head
In the form of a cross wire crack starts inside head and
spreads gradually
Poor manufacture, excessive straining
Very dangerous, rail breaks with out any sign often
6. Split head
Head is split into 2 parts
If the surface of crack appears smooth and dark, it is
called as piped rail
Formed due to cavity during manufacture, or shrinkage
of metal
Horizontal fissure
A fissure developed keeps on increasing
Outcome of worn fish plates or insufficient ballast
Square or angular breaks
Rail breaks either in vertical plane or angular plane
7. Creep of rails
Longitudinal movement of rails in a track is
termed as creep
Common to all railway tracks
Value changes from 0 to 130mm per month
8. Creep - causes
Brakes
Due to forces while starting or stopping
Starting – rails pushed backward
Stopping – rails pushed forward
Wave motion of wheels
Due to wheel loads rails deflect as continuous beam
Crests at supports (i.e., sleepers)
Changes in temperature
Unequal expansion and contraction
Happens more during hot weather
10. Creep - causes
Following are some of the minor causes
rails not tightly fixed
Bad quality sleepers
Bad drainage
No proper consolidation of the bed of track
Gauge maintained tight
Improper super elevation at curves
Over capacity of traffic on rails
Bad joints due to poor maintenance
11. Allowance of rail expansion joints
Decaying sleepers
Uneven spacing of sleepers
Defective packing
Insufficient ballast
Improper usage of brakes
12. Factors determining the magnitude of
creep
Alignment of track
Greater on the curves
Gradient of track
More on down gradient
Direction of motion of trains
One way or 2 way, no of lanes, load of trains
Embankments
Creep more on newly constructed embankments
Weight and type of rail
Light weight rails creep more than heavy weight
rails
13. Results of creep
Sleepers move out of
position
Gauge disturbance
Gap variation at joints and
other parts, results in
uneven stresses
Points and crossings will be
disturbed
Difficult to refix rail with
creep
Interlocking mechanism
also gets disturbed
14. Measurement of creep
Measured using creep indicator
On the side of bottom flange of rail on either sides,
a mark is made by chisel
Two posts of rail are driven in the formation and
their tops are in level with top of sleeper
String fastened to the post and passed through
markings towards rail
Distance between string and the marks on the
bottom of rails will indicate creep during a course of
time
16. Methods for correcting creep
Pulling back of rails method
Rails are pulled back equal to the amount of creep
Manually or using jacks
Sleeper fittings are made loose, fish bolts are removed
at one end while at the other end are made loose
At the other end a liner is placed and the rail is pushed
or pulled as required
Following points should be noted
Track should be packed properly after pushing/pulling
Facility should be there to avoid restrictions to existing traffic
Labour should be procured
All fish plates, bolts should be cleaned, oiled and refixed
Good to adjust creep before summer
17. Usage of Creep anchors
Pulling back method is tedious, costly
75% decreased using creep anchor
Creep anchor is a cast iron piece which is made to
grip the rail
The arrangement of anchors prevent the movement
of rails there by creep, because the sleepers which
are embedded in the ballast should move for
movement to take place
18. Methods for correcting creep
Different types of anchors are available
Following points should be kept in mind while using
creep anchors
Creep anchor should be strong enough to resist stresses
No of anchors are determined by the intensity of creep. 4
anchors per rail are provided for a creep of 7.5 to 15cm
Creep anchors should be placed at points where the creep
originates
Should be avoided on railway bridges
19. Methods for correcting creep
Additional creep anchors should be provided on
level crossings, at places where heavy brake
applications are made
Defective creep anchors should be replaced
Anchors fixed to rails by using clamping, wedging
and other methods
Creep anchors should be fixed to good and sound
sleepers
20. Methods for correcting creep
Use of steel sleepers
Use of steel sleepers on a track minimizes creep
Sleepers are provided with fittings which do not
easily allow the creep to occur
They will also have a good grip with ballast to resist
their movement in ballast
Increase in number of sleepers will also help in
prevention of sleep.
21. Rail joints
Rail joint are necessary to hold together the
adjoining ends of rails in the correct position to
ensure continuity. Joint form the weakest part of
the track.
It is observed that strength of a rail joints is only
50%of the strength of a rail.
22. Requirements of Ideal Joint
Rail joint should hold the two ends of the rails as
nearly as possible. The two ends should be at the
same level and in the same straight line.
Rail joint should have same strength and stiffness
as rails which it joins
Joint should provide space for the expansion and
contraction of rails
Joint should be such that any rail can be taken
out easily or disconnected without disconnecting
entire track
Fishplates, rail contact surfaces wear gradually.
Joints should be able to cope up with this
adjustment.
23. Ideal joint should be cheap and economical for
setting up and maintenance.
It should be durable
Should provide sufficient elasticity so that
vibrations and shocks can be absorbed.
It should provide resistance to longitudinal forces
developed due to acceleration, deceleration to
reduce creeping effect.
Joints should be universal type so that they can
be used for all type of sleepers.
24. Avoidance of joints
In order to obtain better and smooth running of
trains joints are avoided at the following
situations.
Bridge spans of 6m and below
Level crossings
Within 3m of approach of the bridge abutment
25. Types of Rail Joints
Types according to position of joints
Square joints
Staggered joints
Types according to position of sleepers
Suspended joints
Supported joints
Bridge joints
26. Square joints
When a joint in one rail is exactly opposite to the
joint in the parallel rail it is called as square joint.
Very common type of joint in straight track.
Also most preferred.
Staggered joints
When a joint in one rail is exactly opposite to the
center of the parallel rail length it is called as
staggered joint.
27. Advantages of staggered joints
Centrifugal force has a tendency to push the track
out of line. Since the joints are weakest points they
are more vulnerable. But staggered joints resist
them to a great extent.
More uniform vertical continuity of the track is
formed
Produce more smooth running than square joints
Possibility of forming kinks will be decreases
28. Decreases the vertical disturbance of wheels
Number of impacts at joints are doubled but
intensity is halved
Number sleepers per rail length will be increased by
one.
Staggered joints are more adopted on sharp
curves and not favoured on straight track.
It is not a rigid rule to fix the rail exactly at the
center.
29. Suspended Joints
The rail joint when placed at the center of 2
consecutive sleepers is known as suspended
joint.
Load is equally distributed on sleepers
When the joint is pressed down both the rail ends
are pressed down evenly.
More commonly adopted
Provide greater elasticity to the track
Cause less disturbance to the wave motion of track
Require more maintenance
30. Supported Joints
Sleeper is placed exactly below the joint
It appears like rails are supported at weakest part.
These are not used at present
Supported joint did not give sufficient support to the
heavy axle loads
If the joint is packed too hard it prevents it from
settling at times
It leads to the battering of rails as wave motion is
not carried uniformly.
31. Bridge joints
It is similar to suspended joint.
Difference is here, a sufficient length of metal is
used to connect the ends of 2 rails, so that there
is no bending stress in the rail.
Bridge is placed at bottom of rails and rests on
sleepers
Sleepers at the end will have to be notched out at
the sides or will have to be placed at a lower level
than other sleepers to accommodate bridge.
32. Bridge joints
The end sleepers are supposed to work as
unyielding fixed supports.
But practically they are not working as fixed
unyielding supports.
As a compromise between supported and bridge
joints Indian railways provide semi-supported joints.
Sleepers at rail joints are bought close here in this
case.
33. Rail fastenings:
A rail fastening system is a means of fixing rails to
railroad ties.
The terms rail anchors, tie plates, chairs and track
fasteners are used to refer to parts or all of a rail
fastening system.
Various types of fastening have been used over the
years.
34. Requirements of ideal fastening
Good fastening connecting rail and sleeper plays
a vital role in improving the efficiency of railway
track.
Following are some of the requirements of ideal
fastenings.
Capable of absorbing shocks and vibrations
Capable of giving protection to the sleeper against
different forces
Provide insulation in case of electrified tracks
35. Requirements of ideal fastening
Capable of resisting the creep
Capable of securing the correct gauge
Should be economical
Consist minimum equipment
Should be durable
Should be easy to fix and adjust
Should be non corrosive
Should have sufficient strength to resist damage
due to derailment
36. Requirements of ideal fastening
Should be possible to remove only using special
tools
Should safe guard the alignment in all aspects
Should not adversely affect the rail and sleepers
Should not be too rigid
Adequate strength to resist lateral forces
Should possess high torque resistance
37. Fastening for rails
Following are the fastenings which are used to
keep the rails in their correct position.
Fish plates
Spikes, fang-bolts and hook-bolts
Chairs and keys
Bearing plates
38. Fish plates
Purpose: connecting the rails at the ends
Holes are drilled through web and rails and fish
bolts, nuts are provided in these holes.
When bolts, nuts are tightened it forms a
continuous track
Design: The pair of fish plates should have the
same strength in bending as the original rail. This
can be achieved by improving section of fish plate
or by using high tension steels.
For details, types and failures: refer text book
39. Spikes, fang-bolts, hook-bolts
Purpose: Spikes are required to hold the rails to
the wooden sleepers.
Dog spikes
Screw spikes
Round spikes
Elastic spikes
40. Chairs and keys
For double headed and bull headed rails chairs
are required to hold them in position.
These are made of cast iron and help in
distributing the load from rails to sleepers.
Chairs are fixed with sleepers by means of
spikes.
Keys are required to keep the rail in proper
position.
41. Welding of rails
To join two rails and thus increase the length of
rail
To repair the worn out or damaged rails and thus
increase their life
To built up the damaged components of points
and crossings
42. Advantages of Welding
Increases the life of rails due to decrease in wear
at ends
Decrease in maintenance cost to 25%
Smooth functioning of track
Decrease in creep
Welded rails better for electrified tracks
Better for large bridges as rails of length equal to
each span give better performance and reduce
the effect of impact
43. Welding of rails result in decrease in construction
cost due to less number of joints
Fast and heavy traffic can be permitted on the
track
Tractive effort is reduced due to elimination of
energy losses at joints
Risks of sabotages and accidents are reduced
More stability in lateral, longitudinal, vertical
directions of track
44. Welding of Rails
Welding methods
Gas pressure welding
Electric arc welding/Metal arc welding
Flash butt welding
Thermit welding
Looking at the advantages, requirements and
facilities available one of the methods is chosen.
45. Gas Pressure Welding
2 different types of gases – oxygen, acetylene
Kept in 2 different cylinders
Burned at 1200C temperature
Metal rails butted together and welding done.
Metal flows from rails to form a single section
Cheaper, good quality but limited outputs
46. Electric Arc Welding
2 rails are treated as 2 different terminals.
Electric current is passed across the gap of
butted rails using different techniques.
Insert plate technique
Scheron process
Enclosed space technique
Current produces heat to melt the electrode kept
in the gap
Electrode will have same metal composition as
rail
This method can also be used for repair works
47. Sleepers
Functions : in a railway track sleepers add to the
stability of the pavement. Following are the
functions.
Supports the rails firmly
Maintains the uniform gauge on track
Distributes the weight coming on the rails over a
sufficiently large area of ballast
Acts as an elastic medium between rails and ballast
to absorb vibrations of trains
Provides for easy replacement of rail fastenings
without disturbing traffic
48. Sleepers
Functions…contd.
Permits insulation of track for electrified sections
Maintain the track at proper grade by allowing
raising of the rails and tamping the required quantity
of ballast
To maintain the alignment of track
Transfers the load from rails to ballast
49. Requirement of sleepers
Following are the requirement of good sleepers
They should maintain correct gauge
Rails should be easily fixed and taken out from the
sleepers without moving them
Sleepers should provide sufficient bearing area for
the rail
Sleepers should provide sufficient weight for the
stability
They should be sufficiently strong to act as a beam
under loads
They should provide sufficient effective bearing
area on the ballast
They should not be pushed out easily of their
50. Requirement of sleepers…contd..
Design should be such that packing and tamping
should not damage them
Should be economical in initial as well as in
maintenance cost
Fittings of the sleepers should be such that rails can
be easily adjusted during maintenance operations
If track circuiting is required, it should be possible to
insulate them from rails
They should be able to bear the stresses
Should not be too heavy, nor too light
Design and spacing should be such that ballast
packing can be done easily and effectively in less
time.
51. Types of Sleepers
Depending upon the position in a railway
track, the sleepers may be classified as
follows
Longitudinal sleepers
Transverse sleepers
Timber or Wooden sleepers
Steel sleepers
Cast iron sleepers
Concrete sleepers
52. Longitudinal sleepers
Early form of sleepers
Consisted of slabs of stones or pieces of timber placed
parallel to rails
Cross pieces were provided at intervals to maintain the
correct gauge of track
At present these sleepers are not in use because,
Running of train not smooth
Cost is more
More noise is created
Etc.,
53. Transverse sleepers
Also called as cross-sleepers
First introduced in UK in year 1835
Highly popular, and most used in railways at present
Most of the disadvantages of longitudinal sleepers are
taken care
Depending on the type of material used for
manufacturing these sleepers, classified into different
types:
Timber sleepers
Steel sleepers
Cast iron sleepers
Concrete sleepers
54. Timber sleepers
Also called as wooden sleepers
Fulfils most of the requirements of ideal sleeper
Used universally
But due to high cost, mainly used as sleepers for
girder bridges
Salwood, Deodar, fir and chirwood are used as
alternatives where those are easily available
At present usage and manufacturing decreased
because of the advent of new type of sleepers
55. Timber Sleepers - Features
Utility:
Very much useful for heavy loads and high speeds
Life:
Depends on various factors such as climatic
conditions, intensity and nature of traffic, quality of
wood, method of packing, type of fastening,
protection against mechanical wear etc.,
Treatment:
Liable to be attacked by vermins hence treatment
required to have more resistance.
Preservatives are used for this purpose.
Solutions used for timber sleepers are zinc chloride,
creosote solution, salt solution or bi chloride of
mercury salt.
56. Timber sleepers - Features
The methods of zinc chloride solution and mercury
salt solutions are known as burnettising and
kyanizing respectively.
Some times sleepers are just painted.
Corrosion:
Not corroded
Insulation:
Ideal for track circuited section as they are good
insulators
Size:
Depends on the load coming and quality of wood.
Depending on the treatment i.e., treated or not, size
of wooden sleepers are standardized by Indian
railways.
57. However, longer sleepers upto length 488cm are
used for bridges with open flooring, points and
crossings.
Section of sleepers is also increased by
300x160mm.
58. Timber sleepers - Features
Driving of spikes:
spikes should be driven carefully through the
sleeper
Else damaged, gauge will be disturbed
Name and year:
Name of wood used and year of laying the sleepers
is normally marked on the top surface of sleeper.
Normally nails with letters and markings were used
before but not used these days
Adzing:
Wooden sleepers are adzed or cut at rail seat to get
a slope of 1 in 20 when un canted bearing plates
are used.
59. Timber sleepers - Features
Adzed surface will be treated normally with tar or
creosote
Improper adzing leads to uneven surface for the
rails.
Further creeping and other types of damage will
occur
Storage:
Large area exposed to air and ventilation is
normally used
Care will be taken so that sun do not fall directly on
the sleepers
Stack is some times covered with earth to prevent
fire accidents
60. Timber Sleepers as Bridge
sleepers
Thicker than standard sleepers. Minimum depth
of sleepers without fastenings should be 150, 125
and 125 mm for BG, MG and NG respectively
Length of sleepers is D+30 cm. D is out side
distance between edges of parallel girders
Should not be adzed
Necessary to provide bearing plates
Should be placed sufficiently close to prevent the
wheels of derailed train falling through the space
between the adjacent sleepers. Max space is 50,
30, 25 cm for BG, MG and NG respectively.
61. Composite Sleeper Index (CSI)
Forest research institute, Dehradun arrived at a
formula taking different strength parameters into
account for the use of timber for sleepers
An index number is worked out using this formula
with which we can identify whether a timber can
be used or not for sleeper
Chir – 54
Deodar – 63
Fir – 58
Sal – 112
Teak - 82
62. Composite Sleeper Index (CSI)
Minimum CSI values for different sleepers are as
follows
Bridge sleepers – 1455
Crossing sleepers – 1352
Track sleepers –783
Bearing plates are used in case timber has a CSI
value less than 82.
CSI = (S+10H)/20
S = strength index of timber at 12% moisture
H = Hardness index of timber at 12% moisture
63. Timber Sleepers - Advantages
Less no of fittings
Simplistic design
Suitable for all types of ballast
Easy to lay, relay, pack, lift and maintain
Less noisy track
Economical overall
Obtained in different sized and lengths for easy
adoptability at certain locations viz., bridges,
crossings etc
64. Permits track circuiting
Damage during derailments is less
Can be placed on yielding formations because of
more bearing area
Possible to widen the gauge easily with wooden
sleepers
65. Timber Sleepers - Disadvantages
Difficult to maintain gauge
High maintenance cost
Less useful period
Easily disturbed from their positions
Easily subjected to wear and decay due to
various forces and causes
Require special treatment for protection
Possess less scrap value
66. Steel Sleepers
Extensively used in Indian railways
Consist of steel troughs made of 6mm thick steel
sheets
Both ends bent down to check the running out of
ballast
2 types
1. Jaws or lugs pressed out of metal and keys are
used for holding the rail. At the time of pressing cant
of 1 in 20 is also provided for the rails
2. holes are made in the sleepers and clips, bolts are
used for fixing the rail.
For fixing the rails, first rails are inserted into the
lugs and wedges/keys are fixed on both sides of
rails. Gauge can be adjusted with the help of keys.
68. Steel Sleepers - Characteristics
Life:
Useful life of steel sleepers is taken as 30 to 40
years on a normal route
On high density traffic routes it can be taken as
about 20 years
Track provide with steel sleepers doesn’t require
much attention as renewal is not frequent.
Corrosion:
Steel sleepers not liable to be attacked by vermins
But easily corroded due to moisture. Hence,
treatment is done to protect against corrosion.
69. Steel Sleepers - Characteristics
Insulation:
Cannot be used in electrification of track. As they
are not good insulators.
Details:
Consist of a trough or channel made of steel plate
about 6mm thick.
Ends bent down to prevent running of ballast
Rails are fixed with steel sleepers by the help of
keys to the pressed up lugs.
70. Steel Sleepers - Requirements
Should be possible to fix the rails easily in
sleepers with out disturbing the sleepers
Should be possible to insulate them easily incase
at place where track circuiting exists.
Rail should have enough bearing area
Thickness and shape should be such that they
will be strong as beams
Capable of maintaining correct gauge
Should be designed in such a way that tamping
or packing should not damage the edges
71. Steel Sleepers - Requirements
Should be sufficiently heavy for the purpose of
stability
Should have effective bearing area on the ballast
Should not be capable of being easily pushed out
of position.
Etc.,
72. Steel Sleepers - Advantages
Less fastenings, simple in nature
Maintenance and adjustment of gauge are easy with
steel sleepers
Manufacturing process of steel sleepers is simple in
design and operation
Are available in one piece
Possess good scrap value
Light in weight, easy handling
Meets requirement of long welded track in cases
Good anti creep sleeper
Behaves better in the case of yielding formation.
73. Steel Sleepers - Disadvantages
Cost of steel sleepers is high
Cracks develop at rail seat
Rounded ends of sleepers prevent lateral shift
Liable to corrosion
Are not good insulators
Excess damage during derailment
Steel sleepers are difficult to pack at the rail joints
because of their close spacing.
Leads to battering of rails
74. Cast-iron sleepers
Were adopted on indian railways since 1870
More than 50 % of the sleepers are made of cast
iron as of 2000
They are generally of the following types
Pot sleepers
Plate sleepers
Box sleepers
C.S.T.- 9 sleepers
Duplex sleepers
75. Pot sleepers are in the form of two bowls placed
under each rail and connected together by a tie-
bar
Total effective area of the both pot sleepers is
kept 0.46sq.m which is equal to effective bearing
area of a wooden sleeper.
Two holes are provided under each sleeper for
inspection and packing ballast
And the rail seat is given a slope of 1 in 20.
Both the pots are connected together with a tie
bar with necessary fittings such as keys, gibs and
cotters.
76. Plate sleepers consist of a plate of 851x254mm in
dimensions, with 254mm side parallel to the rails.
Both sleepers provide an effective bearing area of
0.46sq.m under each rail.
Plate is provided with projecting rib in the bottom
to provide a grip in the ballast to check the lateral
movement of sleeper.
At the top plate stiffeners are provided to increase
the strength.
Sleeper plates are connected by means of a tie
rod.
77. C.S.T. – 9 Sleepers: These are more satisfactory
than other type of CI sleepers.
It is actually a combination of plate, pot and box
sleeper.
It essentially consists of a triangular inverted pot
on either side of the rail seat.
Suitable rail seat or rail chair is provided at the
top to hold rails at 1 in 20 cant.
Two pieces of sleeper are connected by means of
a tie rod.
78. Cast-iron sleepers -
characteristics
Details:
C.I sleepers consists of 2 pots or plates with ribs
below and connected by a wrought iron tie bar of
section of about 51x13mm.
Each pot or plate is placed below each rail.
Shape of pot or plate is used to be circular prior. But
present, oval shape with larger diameter 610mm
and smaller diameter 508mm is preferred.
Each pot is provided with holes for packing ballast
and inspection.
Plate sleepers consist of rectangular plates of size
about 864x305mm.
The projecting ribs are kept below for their lateral
stability.
Tie bars can be fixed by keys, gibs, cotters and
79. Cast-iron sleepers -
characteristics
Scrap value:
Possess considerable scrap value. Broken pots and
plates can be melted and reused for preparing new
pots and plates.
Maintenance of gauge:
In case of CI sleepers there is no rigid connection
between 2 separate supports. Hence difficult to
maintain the correct gauge.
Fittings:
The cast iron sleepers require a large number of
fittings than any other type of sleepers.
80. Cast-iron sleepers -
characteristics
Handling:
The C.I. Sleepers are liable to be broken and
seriously damaged, if roughly handled.
Life:
The usual life of C.I. Sleepers may be taken as 35
to 50 years in normal routes.
15 to 20 years in heavy traffic routes.
The service life can be increased by proper packing
, clean ballast, providing coal tar to tie-bar etc.
81. Cast-iron sleepers - Advantages
It can be easily dismantled and assembled.
Hence, transport is easy even though it is heavy.
Can tolerate certain amount of rough handling.
Possess high scrap value
Good longitudinal and lateral resistance
Shape is well suited for ballast packing and skill
required for its maintenance is minimum
Adjustment in gauge can be done ( about 5mm)
with help of cotters in case if it is needed.
Sleeper is not affected by the random or irregular
dropping of fire by the steam engines.
82. Cast-iron sleepers -
Disadvantages
During derailment damage is excessive and it
requires more time for restoration.
Not suitable for circuiting of track.
Leads to early wear of sleeper because of small
bearing area at the rail seat.
Not suitable for modern methods of maintenance
Possess poor ability to retain the packing due to its
rigid fastenings.
It takes about 6 months for proper consolidation after
complete track renewal and sleeper renewal.
When these sleepers are used, rails have longer
unsupported length and may therefore lead to
battering of rails.
83. Concrete Sleepers -
characteristics
Type:
Can be made of R.C.C or pre-stressed concrete.
Weight:
Weight of concrete sleepers varies from 150 to 300kg
which is more than wooden or metal sleepers.
This provides more stability to track.
Life:
Good durability
Useful life of about 30 to 25 years on high density routes
84. Concrete sleepers -
characteristics
Suitability:
Most suitable for welded tracks
Dead weight of entire track assembly including
sleepers play an important role in the design of
welded rail track.
Since, weight is more they perform better under
welded rails
Fastenings:
Should firmly hold the rail to resist creep
Should be easily dis-engaged and re-engaged
Different types of fastening equipment is available
for concrete sleepers.
Ideal fastenings for sleepers and rails will differ
according to the type of track, type of traffic and the
climatic conditions.
85. Concrete sleepers -
characteristics
Special PSC sleepers have been developed to
meet with the special requirement of different
locations such as sharp curves, level crossings
with facilities for providing check rails, guard rails
etc.,
Mass production:
Mass production techniques are to be adopted for
the design and manufacture of sleepers.
Economical production of concrete of high strength,
handling of sleepers, good plant design, accelerated
hardening of sleepers etc., have to be taken care
off.
Initial cost of concrete sleepers will be very high, but
maintenance and other things will be economical
because of long life.
86. Concrete sleepers -
characteristics
Environmental protection:
These PSC sleepers are environmental friendly.
Conserves forest.
Structural advantages:
Have lot of structural advantages
Center to center distance can be increased by 20%
compared to timber sleepers
Deflection under loading is much less
Improves lateral, longitudinal and vertical stability
Reduced bending stresses, reduced wear of rolling
track, less chance of derailment, reduction in tractive
effort etc.
87. Concrete sleepers - Advantages
High electrical resistance
Good resistance to abrasion
Increased bond resulting in shorter transmission
length.
Increased impermeability
Reduction in loss of pre-stress due to reduction in
shrinkage, creep and elastic shortening
Very high fatigue strength.
88. Concrete sleepers - Drawbacks
The damage during derailment is excessive
Possess no scrap value
Require complete mechanization in handling
Requires use of superior and costly technology
for manufacture.
89. Sleeper Density
No of sleepers present in a given length of rail
Spacing of sleepers is indicated by formula n+x
n = length of rail
x = no of sleepers more than n.
Sleepers density depends on several factors:
Lateral thrust of locomotives to which the track is
subjected
Axle –load which the track is expected to carry
Sleepers density cannot be increased indefinitely
– minimum spacing is required for packing ballast
and maintenance.
Wooden sleepers 300mm (for BG), 250mm (for
MG)
Metal sleepers 380mm (for BG), 330mm (for MG)
90. Sleeper density
In case of staggered joints an extra sleeper is
required
Sleepers are placed nearer at rail joints
compared to other locations.
In n+x expression, x value is fixed by indian
railway considering the following:
Axle load and speed
Type of ballast and ballast cushion
Type and section of rails
Type of sleeper and its bearing area on the ballast.
91. Ballast
Material placed between the sleeper and top of
the formation is known as ballast.
Load from the wheels will be taken up by the
ballast through rails and sleepers.
Ballast serves as foundation of railway track and
is present just below the sleepers.
92. Ballast - Functions
To provide a hard and smooth surface for the
ballast to rest on
Hold the sleepers in place during the passage of
trains
To transmit and distribute the load from sleepers
to formation
Allow for maintaining correct track levels without
disturbing the rail road bed.
Protect the surface of formation from direct
exposure to sun, frost or rain.
To form an elastic bed
93. Ballast - Functions
To drain the water immediately and keep the
sleepers in dry condition
To discourage the growth of vegetation
To resist lateral, longitudinal and vertical
displacement of track.
94. Requirements of ideal material for
ballast
Should be possible to main uniform depth of material
for uniformly distributing the load to formation
Should provide sufficient grip over the sleepers to
prevent their movement
Ballast should not be too rigid, it should be elastic in
nature.
Material of ballast should not be brittle, should
possess required compressive strength.
Should provide good drainage facility.
Should be cheap and easily available.
Should not have any chemical action on rail and metal
sleepers
Should be durable and abrasion resistant
96. Broken stone
One of the best material, but expensive.
Many important tracks are having stone ballast
It has good interlocking characteristics, due to
that it holds track in correct alignment and
gradient
It is resistant to abrasion, provides good
drainage.
Stones which are non-porous, hard and tough
should be used as ballast
97. Gravel
It is next best material after broken stone. It consists of
smooth rounded fragments obtained from river beds
and other natural deposits.
Washing should be done for the material obtained from
pits
Uniform and required size of aggregates should be
used.
Rounded pieces are sometimes broken to improve
interlocking properties.
Advantages:
Cheaper than stone ballast
Good drainage property
Disadvantages:
Easily rolls down due to vibration
98. Ashes or Cinders
The residue from the coal used in locomotives and
other furnaces is known as the ashes or cinders.
It is by product of railway systems which are run by
coal fuel
99. Sand
Coarse sand is preferred to fine sand
Not used in main and branch lines. Used only in
some unimportant lines, sidings, yards.
100. Kankar
Found in many places
Suitable only if other types of material is not
available and if the traffic is less on metre gauge
and narrow gauge
It becomes powder very easily and hence not
prefered
More maintenance is required if used
101. Moorum
Decomposition of laterite results in the formation of
moorum
Present in red/yellow colour
Used for unimportant lines and sidings
102. Brick bats
Over burnt bricks are broken into suitable sizes and
used as ballast
Advantages:
Useful at places where suitable material is not
available
Good drainage properties
Disadvantages:
Turns into powder form very easily
Track becomes dusty and high maintenance is
required.
103. Selected earth
For sidings and newly constructed tracks,
selected earth of suitable quantity is sometimes
used as ballast
The main purpose of using earth on new
formation is to prevent the loss of valuable and
expensive ballast sinking into the soft formation.
104. Specifications of Stone ballast
Quality:
Should be durable, hard, resilient to impact and free
from adherent coatings.
Should not contain more than 10% by weight of quarry
dust, rubbish or any other matter which passes
through 5mm sieve
Faces of ballast should result from crushing, only one
smooth surface is allowed
Size:
20 to 50mm size with reasonable proportion of
intermediate sizes.
50mm – wooden and CI spot sleepers
40mm – CST -9 sleepers
105. Specifications of
stone ballast
grading:
Ballast should be well graded
Sampling:
Sample of ballast is collected
at the rate of 1cu.m per 2000cu.m.
Over sized ballast:
When more than 10% of ballast retains on nominal
size sieve it is called over sized ballast
Stacking:
Ballast should be stacked along the quarry siding.
Height of stack should not be less than 120cm.
106. Depth of Ballast Section
Depth of ballast section can be calculated by
using the below formula
D = (S-b)/2
Where D – depth of ballast section
S – sleeper spacing
b – width of sleeper
Normally the value ranges in between 20 to 25cm
from the above formula.