Railway & Airport Engineering (CV704) Sleepers & Ballast
SLEEPERS
Sleepers are the members generally laid transverse to the rails on which the rails
are supported and fixed, to transfer the loads from rails to the ballast and sub grade
below
FUNCTIONS OF SLEEPERS
1. To hold the rails in correct gauge and alignment
2. To act as an elastic medium between the ballast and rail to absorb the blows
and vibrations of moving loads.
3. To provide longitudinal and lateral stability of the permanent track on the
whole.
4. Providing means to rectify track geometry during service life.
5. To support the rails at proper level in straight tracks and at proper super
elevation on curves.
6. To distribute the load from the rails to the index area of ballast under laying it
or to the girders in the case of bridges.
7. To hold the rails in proper level.
REQUIRMENT OF AN IDEAL SLEEPER
1. The initial as well as maintenance cost should be minimum.
2. The weight of the sleeper should be moderate so that it is convenient to handle.
3. The designs of the sleeper and the fastenings should be such that it is possible
to fix and remove the rails easily.
4. The sleeper should have sufficient bearing area so that the ballast under it is
not crushed.
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
5. The sleeper should be such that it is possible to maintain and adjust the gauge
properly.
6. The material of the sleeper and its design should be such that it does not break
or get damaged during packing.
7. The design of the sleeper should be such that it is possible to have track
circuiting.
8. The sleeper should be capable of resisting vibrations and shocks caused by the
passage of fast moving trains.
9. The sleeper should have anti-sabotage and anti-theft features.
DIFFERENT TYPES OF SLEEPERS
The sleepers mostly in use in Indian railways are:
i. Wooden sleepers
ii. Cast iron sleepers
iii. Steel sleepers
iv. Concrete sleepers
COMPARISON OF CHARECTERISTICS OF DIFFERENT TYPES OF
SLEEPERS
WOODEN STEEL C.I CONCRETE
CHARACTERISTICS
SLEEPERS SLEEPERS SLEEPERS SLEEPERS
40 to 50 40 to 50
Service life 12 to 15 years 50 to 60 years
years years
Weight of sleeper for
83kg 79kg 87kg 267kg
B.G
Cost of maintenance high medium medium low
No gauge
Gauge adjustment difficult easy easy adjustment
possible
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
Damage By white ants corrosion corrosion No damage
Conventional
Suitability for fastening & elastic CF & EF EF EF
fastening
Not suitable Suitable for
Suitability to track For all routes All routes for high high speed
speed routes routes
Creep excessive less less minimum
Higher than
No scrap
Scrap value low wooden High
value
sleeper
STANDARD DIMENSION FOR WOODEN SLEEPER
Bearing Area
LENGTH WIDTH DEPTH
GAUGE per Sleeper
(cm) (cm) (cm)
(m2)
B.G 275 25 12.5 0.465
M.G 180 20 11.5 0.31
N.G 150 18 11.5 0.209
For bridges and points and crossings, longer sleeper of thicker sections
25cmx15cmx or 25cmx18cm are used
Bearing area under each rail = bearing length under each rail x width of sleeper
= 0.9m x 0.25m
= 0.225m2
Thus bearing area per sleeper = 2 x 0.225 = 0.450m2
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
BALLAST
The ballast is a layer of broken stones, gravel, moorum, or any other granular material
placed and packed below and around sleepers for distributing load of rail from the
sleepers to the formation.
Functions of Ballast
Provides a level and hard bed for the sleepers to rest on.
Holds the sleepers in position during the passage of trains.
Transfers and distributes load from the sleepers to a large area of the formation.
Provides elasticity and resilience to the track for proper riding comfort.
Provides the necessary resistance to the track for longitudinal and lateral stability.
Provides effective drainage to the track.
Provides an effective means of maintaining the level and alignment of the track.
Discourage the growth of vegetation
Requirements of a Good Ballast
Ballast material should possess the following properties.
(a) It should be tough and wear resistant.
(b) It should be hard so that it does not get crushed under the moving loads.
(c) It should be generally cubical with sharp edges.
(d) It should be non-porous and should not absorb water.
(e) It should resist both attrition and abrasion.
(f) It should be durable and should not get pulverized or disintegrated under
adverse weather conditions.
(g) It should allow for good drainage of water.
(h) It should be cheap and economical.
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
Types of Ballast
The different types of ballast used on Indian Railways are:
Sand ballast
Sand ballast is used primarily for cast iron (CI) pots. It is also used with wooden
and steel trough sleepers in areas where traffic density is very low. Coarse sand is
preferred in comparison to fine sand. It has good drainage properties, but has the
drawback of blowing off because of being light. It also causes excessive wear of
the rail top and the moving parts of the rolling stock.
Moorum ballast
The decomposition of laterite results in the formation of moorum. It is red, and
sometimes yellow, in colour. The moorum ballast is normally used as the initial
ballast in new constructions and also as sub-ballast. As it prevents water from
percolating into the formation, it is also used as a blanketing material for black
cotton soil.
Coal ash or cinder
This type of ballast is normally used in yards and sidings or as the initial ballast in
new constructions since it is very cheap and easily available. It is harmful for steel
sleepers and fittings because of its corrosive action.
Broken stone ballast
This type of ballast is used the most on Indian Railways. A good stone ballast is
generally procured from hard stones such as granite, quartzite, and hard trap. The
quality of stone should be such that neither is it porous nor does it flake off due to
the vagaries of weather. Good quality hard stone is normally used for high-speed
tracks. This type of ballast works out to be economical in the long run.
Other types of ballast
There are other types of ballast also such as the brickbat ballast, gravel ballast,
kankar stone ballast, and even earth ballast. These types of ballast are used only in
special circumstances.
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
SIZE AND SECTION OF BALLAST
Ballast size for wooden sleeper tracks = 5.1cm
Ballast size for steel sleeper tracks = 3.8cm
Switches & crossings = 2.54cm
DIMENSION B.G M.G N.G
Width of ballast 3.35m 2.25m 1.83m
Depth of ballast 20 to 25cm 15 to 20cm 15cm
Quantity of stone ballast
1.036m3 0.17m3 0.53m3
per meter length
Minimum Depth of Ballast Cushion
The load on the sleeper is transferred through the medium of the ballast to the
formation. The pressure distribution in the ballast section depends upon the size
and shape of the ballast and the degree of consolidation. Though the lines of equal
pressure are in the shape of a bulb, yet for simplicity, the dispersion of load can be
assumed to be roughly 45° to the vertical. In order to ensure that the load is
transferred evenly on the formation, the depth of the ballast should be such that the
dispersion lines do not overlap each other.
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
For the even distribution of load on the formation, the depth of the ballast is
determined by the following formula
Sleeper spacing (S) = width of the sleeper (W) + 2 × depth of ballast (Db)
S = w + 2 x Db
Db =
If a BG track is laid with wooden sleepers with a sleeper density of N + 6, then the
sleeper spacing would be 68.4 cm. If the width of the sleeper is 25.4 cm, then the
depth of the ballast cushion would be
d=
A minimum cushion of 15–20 cm of ballast below the sleeper bed is normally
prescribed on Indian Railways.
Guidelines for Provision of Sub-ballast
The sub-ballast is normally made of granular material and is provided between the
formation and the ballast in order to distribute the load evenly over the formation.
The following points should be kept in mind while selecting a material for
sub-ballasts.
(a) The material should consist of coarse granular substance such as river gravel,
stone chips, quarry grit, and predominantly coarse sand. Ash, cinder, and
slag containing predominantly fine and medium sand should not be used.
(b) The material should be non-cohesive and graded. The uniformity coefficient
should be more than 4 to ensure that the sub-ballast is well graded.
(c) The material should not contain more than 15% of fines that measure less
than 75 microns.
(d) The thickness of the sub-ballast should not be less than 150 mm.
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
RAILS
Rails are the members of the track laid in two parallel lines to provide an
unchanging, continuous, and level surface for the movement of trains. To be able
to withstand stresses, they are made of high-carbon steel.
Function of Rails
Rails provide a continuous and level surface for the movement of trains.
Rails provide a pathway which is smooth and has very little friction. The
friction between the steel wheel and the steel rail is about one-fifth of the
friction between the pneumatic tyre and a metalled road.
Rails serve as a lateral guide for the wheels.
Rails bear the stresses developed due to vertical loads transmitted to them
through axles and wheels of rolling stock as well as due to braking and thermal
forces.
Rails carry out the function of transmitting the load to a large area of the
formation through sleepers and the ballast.
TYPES OF RAIL
1. Double Headed Rail
2. Bull Headed Rail
3. Flat Footed Rail
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
Double Headed Rail Bull headed rail Flat Footed Rail
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
DOUBLE HEADED RAILS
The rail sections, whose foot and head are of same dimensions, are called Double
headed or Dumb-bell rails. In the beginning, these rails were widely used in the
railway track. The idea behind using these rails was that when the head had 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 be used as running surface
because it also got corrugated under the impact of wheel loads. However, this
section was abandoned
BULL HEADED RAILS
The rail section whose head dimensions are more than that of their foot are called
bull headed rails. In this type of rail the head is made little thicker and stronger
than the lower part by adding more metal to withstand better wear and tear. These
rails also require chairs for holding them in position. Bull headed rails are
especially used for making points and crossings.
MERITS
1. B.H. Rails keep better alignment and provide more smoother and stronger
track.
2. These rails provide longer life to wooden sleepers and greater stability to the
track.
3. These rails are easily removed from sleepers and hence renewal of track is
easy.
DEMERITS
1. B.H. rails require additional cost of iron chairs.
2. These rails require heavy maintenance cost.
3. B.H. rails are of less strength and stiffness.
Kishor Kumar S Dept. of Civil Engg., MCE
Railway & Airport Engineering (CV704) Sleepers & Ballast
FLAT FOOTED RAILS
The rail sections having their foot rolled to flat are called flat footed or vignole`s
rails. This type of rail was invented by Charles Vignole in 1836. It was initially
thought that the flat footed rails could be fixed directly to wooden sleepers and
would eliminate chairs and keys required for the B.H. rails. But later on, it was
observed that heavy train loads caused the foot of the rail to sink into the sleepers
and making the spikes loose. To remove this defect, steel bearing plates were used
in between flat footed rails and the wooden sleeper. These rails are most
commonly used in India.
MERITS
1. F.F. rails have more strength and stiffness.
2. No chairs are required for holding them in position.
3. These rails require less number of fastenings.
4. The maintenance cost of track formed with F.F. rails is less.
DEMERITS
1. The fittings get loosened more frequently.
2. These rails are not easily removed and hence renewal of track becomes
difficult.
3. It is difficult to manufacture points and crossings by using these rails.
Kishor Kumar S Dept. of Civil Engg., MCE
