Railway
Ballast
Nikhil Saboo
IIT Roorkee
Menu
01 Background
02 Types
03 Ballast Design
04 Ballast Specification
05 Self Stabilizing Tracks
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01
Background
Ballast is the granular material, usually
broken stone or brick, shingle or
kankar, gravel or sand, packed
below and around the sleepers to
transmit load, and at the same time
allowing the drainage of track.
It provides suitable foundation for the
sleepers, hold them in correct position
and prevent their displacement by
lateral and longitudinal thrust.
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01
Background
Functions: Requirements:
▪Provide level and hard bed for sleepers ▪Tough
▪Hold sleepers in position ▪Hard enough
▪Transfer and distribute load to wide ▪Cubical, with sharp edges (angular)
area
▪Non-porous, non water absorbent
▪Provide elasticity or resilience to track
▪Resist attrition
▪Provide longitudinal and lateral stability
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02Types ▪ Blast Furnace Slag, Cinders
▪ Used in yards, sidings etc.
▪ Broken stone ▪ Used as initial ballast in new construction
▪ Mostly used on Indian Railways ▪ Cheap and easily available
▪ Procured from hard stones like granite, ▪ Corrosive, harmful for steel sleepers and
quartzite, hard trap, etc. fittings
▪ Economical in long run
▪ Moorum
▪ Sand ▪ Used as initial ballast in new constructions or
▪ Mostly used for CI Pot sleepers as sub-ballast.
▪ In low density areas with wooden and ▪ Also used as blanketing material on black
ST sleepers cotton soil.
▪ Coarse sand is preferred ▪ Others
▪ Causes excessive wear on rail top and ▪ Gravel, River Pebbles, Kankar, Brick Ballast,
moving parts of the rolling stock etc.
02
Ballast Design
▪ Minimum Depth of Ballast section = 1/2[Sleeper Spacing – Width
of Sleeper]
▪ A minimum cushion of 15-20 cm of ballast below the sleepers is
prescribed on IR.
▪ In LWR, it is 25 cm. For routes with speed more than 130 kmph, it
is 20-30 cm with 15 cm of sub-ballast.
03
Ballast Specification
▪ Quality ▪ Size and Gradation
▪ Hard, durable and angular ▪ 50 mm is the designated size
▪ Free from weathered and organic materials ▪ Retained on 65 mm: nil, 5% max
▪ Should be cubical in shape ▪ Retained on 40 mm: 40-60%
▪ Should be machine crushed ▪ Retained on 20 mm: not less than 98% for machine
crushed and not less than 95% for hand broken.
▪ Physical Properties
▪ Abrasion: 30% Max (BG), 35% Max (MG, NG) ▪ Compaction
▪ Impact Value: 20% Max (BG), 30% Max (MG, ▪ Packing: Compacted ballast cushion laid below
NG) sleepers as per the gradation
▪ Water Absorption: 1% Max ▪ Boxing: Relatively Loose ballast placed on the side of
the sleepers to provide them lateral stability
▪ Flakiness and Elongation Index: Max 50%
each
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https://pavementinteractive.org/reference-
desk/testing/aggregate-tests/los-angeles-
abrasion/
https://theconstructor.org/building/building- https://www.engineeringcivi
material/determination-of-aggregate-impact- l.com/flakiness-index-test-
value/1355/ for-aggregates.html
https://www.engineeringcivil.com/elongatio
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aggregates.html#:~:text=TEST%20DESCRIPTI
ON,size%20larger%20than%206.3%20mm.
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03
Ballast Specification
▪ Screening
▪ Procedure of renewing the ballast section
▪ Crushed material has clogged the voids causing
drainage problem
▪ Ballast has penetrated into formation
▪ Ballast has been blown away
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04
Self Stabilizing Track
• Running track creates conditions so that the
track gets stabilized with the help of ballast.
This is done by controlling the inertia of mass
ballast.
Ballastless Track??
• Predetermined quantity of ballast are pre- Geo Synthetic Reinforcements?
compacted and firmly constrained (through
State of the art??
special cages of different arrangements).
• Elastic medium in form of reinforced rubber or
PE layer is placed between sleeper bottom
and top of ballast block.
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THANK YOU
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