Components, systems and materials › Railway track components › Ballast
Ballast
What it is
Ballast is the bed of hard, angular crushed stone on which railway sleepers rest.
Where it is used
Ballasted railway track on embankments, cuttings and bridges with ballast decks.
How it works
Angular stones lock together to hold sleepers firmly against vertical, lateral and longitudinal movement, which is vital for long welded rails. The ballast layer spreads loads to the formation, allows quick drainage through its voids and can be re-packed by tamping machines to restore track geometry.
Types
- Standard track ballast of specified grading
- sub-ballast or blanket layers beneath it
Materials
Hard, durable crushed igneous or similar rock with low abrasion and impact values and few flaky or elongated pieces.
Depth below the sleeper and shoulder width follow track standards for the traffic and speed. Properties such as abrasion value, impact value, flakiness and grading are specified and tested. Formation and blanket layers below protect the subgrade.
Installation and QA steps
- Test the source quarry and supplied stone.
- Spread ballast in layers.
- Lift and tamp the track to design level and alignment.
- Regulate the profile and shoulders.
- Stabilise and monitor geometry; clean or renew fouled ballast.
- Fouling with fines from wear and subgrade pumping
- loss of shoulder reducing lateral resistance
- crushing of weak stone
- poor drainage causing mud spots
Codes cited
- Indian Railways Permanent Way Manual (India): Standards and practice for track laying and maintenance.
Cited by number only. We do not reproduce code text, tables or figures.
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