Types of Ballast
The different types of ballast used on Indian Railways are described in the following.
Sand ballast
Sand ballast is used primarily for cast iron (CI)
. It is also used with wooden and steel trough sleepers in areas where traffic density is very low. Coarse sand is preferred in comparison to fine sand. It has good drainage properties, but has the drawback of blowing off because of being light. It also causes excessive wear of the rail top and the moving parts of the rolling stock.Moorum ballast
The decomposition of laterite results in the formation of moorum. It is red, and sometimes yellow, in colour. The moorum ballast is normally used as the initial ballast in new constructions and also as sub-ballast. As it prevents water from percolating into the formation, it is also used as a blanketing material for black cotton soil.
Coal ash or cinder
This type of ballast is normally used in yards and sidings or as the initial ballast in new constructions since it is very cheap and easily available. It is harmful for steel sleepers and fittings because of its corrosive action.
Broken stone ballast
This type of ballast is used the most on Indian Railways. A good stone ballast is generally procured from hard stones such as granite, quartzite, and hard trap. The quality of stone should be such that neither is it porous nor does it flake off due to the vagaries of weather. Good quality hard stone is normally used for high-speed tracks. This type of ballast works out to be economical in the long run.
Other types of ballast
There are other types of ballast also such as the brickbat ballast, gravel ballast, kankar stone ballast, and even earth ballast. These types of ballast are used only in special circumstances.
The comparative advantages, disadvantages, and suitability of different types of ballast are given in Table 8.1.
Table 8.1 Comparison of different types of ballast
|
Type of ballast |
|
Advantages |
|
Disadvantages |
|
Suitability |
|
Sand ballast |
> |
Good drainage |
> |
Causes excessive |
> |
Suitable for CI pot |
|
|
|
properties |
|
wear |
|
sleeper tracks |
|
|
> |
Cheap |
> |
Blows off easily |
> |
Not suitable for high-speed tracks |
|
|
> |
No noise produced |
> |
Poor retentivity |
|
|
|
|
|
on the track |
|
of packing |
|
|
|
|
> |
Good packing |
> |
Track cannot be |
|
|
|
|
|
material for CI |
|
maintained to high |
|
|
|
|
|
sleepers |
|
standards |
|
|
|
Moorum |
> |
Cheap, if locally |
> |
Very soft and turns |
> |
Used as a sub-ballast |
|
ballast |
|
available |
|
into dust |
|
|
|
|
> |
Prevents water |
> |
Maintenance of |
> |
Initial ballast for new |
|
|
|
from percolating |
|
track the difficult |
|
construction |
|
|
> |
Provides good |
> |
Quality of track |
|
|
|
|
|
aesthetics |
|
average |
|
|
(contd )
|
Type of ballast |
|
Advantages |
|
Disadvantages |
|
Suitability |
|
Coal ash or |
> |
Easy availability |
> |
Harmful for steel |
> |
Normally used in |
|
cinder |
|
on railways |
|
sleepers |
|
yards and sidings |
|
|
> |
Very cheap |
> |
Corrodes rail |
> |
Suitable for repairs |
|
|
|
|
|
bottom and steel |
|
of formations during |
|
|
|
|
|
sleepers |
|
floods and |
|
|
|
|
|
|
|
emergencies |
|
|
> |
Good drainage |
> |
Soft and easily |
> |
Not fit for high-speed |
|
|
|
|
|
pulverized |
|
tracks |
|
|
|
|
> |
Maintenance is difficult |
|
|
|
Broken stone |
> |
Hard and durable |
> |
Initial cost is high |
> |
Suitable for packing |
|
ballast |
|
when procured from hard rocks |
|
|
|
with track machines |
|
|
> |
Good drainage |
> |
Difficulties in |
> |
Suitable for high- |
|
|
|
properties |
|
procurement |
|
speed tracks |
|
|
> |
Is stable, and |
> |
Angular shape may |
|
|
|
|
|
resilient to the |
|
injure wooden |
|
|
|
|
|
track |
|
sleepers |
|
|
|
|
> |
Economical in the long run |
|
|
|
|
⇐Functions of Ballast | RAILWAY ENGINEERING - Contents | Sizes of Ballast⇒