Last edited 06 Mar 2020

Ballast

Contents

[edit] Introduction

Ballast is material like broken stone, gravel or any other granular material. It can, for example be spread and packed below and around sleepers. It provides good drainage for the track structure and holds sleepers in the correct position by preventing movements caused by lateral load.

Types of ballast include:

[edit] Broken stone

These are obtained from hard stones and should be strong, hard, tough, durable, angular and do not flake when broken.

Advantages:

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

Disadvantages:

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

[edit] Moorum

This is normally used as an initial ballast in new construction. It is red or sometimes yellow in colour. It is suitable for station yards.

Advantages:

Disadvantages:

  • It may turn into powder under heavy loads.
  • It may produce dusty track.
  • Maintenance of track with this type of ballast is difficult.

[edit] Sand

Coarse sand is generally used as ballast.

Advantages:

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

Disadvantages:

[edit] Kankar

Kankar are used as ballast where other materials are not easily available.

Advantages:

Disadvantages:

  • 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.

[edit] Brick ballast

It is generally in the form of broken over burnt brick.

Advantages:

  • It is cheap.
  • Its drainage is good.
  • It prevents growth of vegetation.
  • It is easily available.

Disadvantages:

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

[edit] Ashes

These are residue obtained from coal.

Advantages:

Disadvantages:

  • It has corrosive properties and hence affects the rails and metal sleepers.
  • It may make laid track dusty as it gets easily reduced to powder under heavy load.

[edit] Gravel

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

Advantages:

Disadvantages:

  • Due to its rounded shape, it can easily roll down due to vibrations and this 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.
  • Uniform grading of gravel is required.

[edit] Blast furnaces slag

A by product obtained from the manufacture of iron.

Advantages:

  • It is cheap.
  • It has good drainage properties.
  • It is strong and holds track in the correct gauge and alignment.

Disadvantages:

[edit] Selected earth

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

Advantages:

  • It prevents loss of good ballast on new formation.
  • It may be used on sidings and tracks.

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