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