Almost everyone would have seen railway tracks. You must have noticed those small stones lying alongside the track on which your train races? Have you ever given any thought as to why there are almost always stones alongside a railway track?
Lets understand the basics
To start with, the stones that you see lying close to the railway tracks are collectively called track ballast. It basically forms the trackbed on which the railway sleepers are kept. Track ballast is packed between the sleepers, in the areas below, and on the sides of railway tracks.
what’s a sleeper?
A railway sleeper is a rectangular support that is usually kept perpendicular to the tracks. Sleepers are known by a few other names too, like a railroad tie or a crosstie. These are usually made of wood or pre-stressed concrete, although the latter is more widely used today. The function of railway sleepers is to hold the rails upright and properly spaced.
If you put smooth, round pebbles in the ballast, then they might roll or slide over each other when a train passes over the tracks; therefore, they would fail at their main job – providing solidarity to the tracks. Given that fact, you need stones of a specific type that won’t move around too much! In order to guarantee that the stones stay in place, they use sharp and edged stones in the ballast. Interesting, huh?
So can’t you just nail the tracks to sleeper?
The non-trivial movement caused by heat expansion and contraction along the length of the rail would cause it to break or buckle if any of it were fixed in place. So, instead, the rails are attached to the sleepers by clips or anchors, which hold them down but allow them to move longitudinally as they expand or contract.
So what are the uses of ballast?
In fact, the track ballast serves a number of purposes. First of all, it makes sure that tracks stay in place when super-heavy trains roll by on them. It also plays an instrumental role in keeping any vegetation in check that might grow around the tracks (and make the ground beneath the tracks weaker). Another important aspect of track ballast is that it seals out any water that may be around the tracks to actually reach the tracks on a regular basis. That doesn’t mean the ballast completely insulates the tracks from water, which would be impossible, but it does facilitate water drainage around and beneath the tracks so that water doesn’t stay near the tracks and compromise the solidarity of the ground.
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