The Constructor

Ballast – Functions and Types

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Ballast is a granular material which is placed and packed below and around the railway sleepers. Different types of ballast materials used are broken stone, sand, gravel, moorum, brickbats etc. The main purpose of ballast is to transmit the load from sleepers to the formation(consolidated track bed) and to provide drainage facilities to the track.

Functions of Ballast

The functions of ballast are as follows :

Fig 1: Ballast Holding Sleepers

Types of Ballast

1. Broken stone Ballast

Broken stone is a widely used ballast in railways. It is obtained by crushing hard stones like granite, hard trap, quartzite etc. In lieu of broken stones, limestone and sandstone can also be used. It is suitable for high-speed railway tracks. The broken stone selected as ballast should be hard, tough and non-porous. It should stay strong against inclement weather conditions.

Fig 2: Broken Stone Ballast

Benefits of Broken Stone Ballast

Drawbacks of Broken Stone Ballast

2. Sand Ballast

Sand can also be used as a ballast material. It is well suitable under cast iron sleepers and can be seen in desert railway tracks where plenty of sand gets accrued on the track. Coarse sand is best suitable as ballast than fine sand.

Fig 3: Sand Ballast

Benefits of Sand Ballast

Drawbacks of Sand Ballast

3. Gravel Ballast

Gravel is a naturally occurring material formed by the erosion of rocks. They are suitable for all types of sleepers and are usually round and smooth and can be obtained from river beds, gravel pits etc.

Fig 4: Gravel as Ballast

Benefits of Gravel Ballast

Drawbacks of Gravel Ballast

4. Moorum Ballast

Moorum is formed by the decomposition of laterite. It is available mostly in red color and, sometimes, in yellow. If the track is to be laid on black cotton soil, moorum can be used as a blanketing material or sub-ballast since it prevents permeability of water into the subgrade or formation.

Fig 5: Moorum

Benefits of Moorum Ballast

Drawbacks of Moorum Ballast

5. Coal Ash or Cinder Ballast

Coal ash also called cinder is the by-product of coal-fired power plants and railway locomotives. It can be used as a ballast material since it is cheaply available and also possesses good drainage properties. It is used as a ballast especially for station yards and as initial ballast for newly constructed tracks.

Fig 6: Coal Ash or Cinder

Benefits of Coal Ash Ballast

Drawbacks of Coal Ash Ballast

6. Brickbat Ballast

Brickbats are nothing but crushed pieces of bricks which are generally over-burnt. Under-burnt brickbats are not suitable since they are not as porous as over-burnt brickbats.

Fig 7: Brickbats

Benefits of Brickbat Ballast

Drawbacks of Brickbat Ballast

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