Question: What is ballast? Why it is used in the railway track? Briefly describe the various types & advantages, disadvantages & suitability.
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Mumbai University > Civil Engineering > Sem 5 > Transportation Engineering 1

Marks: 10M

Year: Dec 2014

 modified 2.0 years ago  • written 2.0 years ago by Juilee ♦ 2.1k
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Ballast:

Ballast is material like broken stone, gravel or any other granular material spread and packed below and around sleeper.

It provides good drainage for the track structure, It provides weed of greed, It holds sleepers in correct position by preventing movements caused by lateral load therefore ballast is used in the railway track.

Types of ballast is as follows:-

1) Broken stone $\hspace{1cm}$ 4) Kankar $\hspace{2.1cm}$ 7) Gravel

2) Moorum $\hspace{1.8cm}$ 5) Brick ballast $\hspace{1.3cm}$ 8) Blast furnaces slag

3) Sand $\hspace{2.2cm}$ 6) Ashes/cinders $\hspace{1cm}$ 9) Selected earth

Broken sand:-

These are obtained from hard stones and it should be strong, hard, tough, durable, angular and does not flake when broken and hence Indian Railway adopt it very frequently.

• They are strong, durable and provide maximum stability to track.
• These are mostly used for high speed track in India.
• These types of ballast are cheaper in long run.

• The main disadvantages of this type of ballast is that its initial cost is more.

Moorum:-

It is normally used as an initial ballast in new construction. It is of red or sometimes yellow in color. It is Suitable for station yards.

• It is cheaper.
• It may serve as soiling when stone ballast is spread afterwards.
• Drainage property is good.

• It may turns into powder under heavy loads.
• It may produces dusty track.
• Maintenance of track with this type of ballast laid is difficult.

Sand:-

Coarse sand is generally used as ballast and is a moderate material to use as ballast.

• It is cheap material
• It is easily available
• It has good drainage property
• It produces less noisy track.
• It will not allow vegetation to grow on track
• It is used on temporary and unimportant track.

• Maintenance of tracks laid by these ballast is difficult
• Sand may blown by wind or may washed by rain
• It may spread due to vibrations and thus maintenance is difficult
• It may leads to wear if it gets into the moving part of train

Kankar:-

Kankar are also used as ballast where other chief material for ballast is not easily available.

• It is cheap
• It has got good drainage property
• Used for M.G. and N.G. tracks having light traffic

• It is soft and hence it may convert into powder under heavy load.
• It may have corrosive action on rails
• Maintenance of track is difficult

Brick ballast:

It is generally in form of broken over burnt brick

• It is cheap material for use as ballast
• It is drainage property is good
• It prevents growth of vegetation
• It is easily available

• It may have adverse effects on rails and metal sleepers as it may corrugate them
• Maintenance of track laid with this material as ballast is difficult
• It may produce dusty track as it turns into powder under heavy load

Ashes:

These are residue obtained from coal. It is also used as ballast.

• It is cheap and very economical as it is by product of every railway
• Available in abundant quantity
• It has very good drainage property

• It has got corrosive property and hence affect the rails and metal sleepers
• It may laid track dusty as it gets easily reduced to powder under heavy load

Gravel:-

It is one of the best material used as ballast next to broken stone consisting of smooth round shaped material obtained from riverbed.

• It is cheaper than broken stone
• It's drainage property is good
• It is useful for main line

• Due to rounded shape, it can easily rolls down due to vibrations and results in loosening of sleepers
• Washing is required if gravels are obtained from pits
• Screening is required as there is variation in size and quality
• In short, uniform grading of gravel is required

Blast furnaces slag:

A byproduct obtained from manufacture of iron can also be used as ballast.

• It is cheap
• It has good drainage property
• It is strong and holds track in correct gauge and alignment

• It is not available in large quantity

Selected earth:

These are indurate clay and decomposed rocks. These are used as ballast when tracks to be laid on new formation. After consolidation, the surface becomes hard then good type of ballast is laid.