Railway track designers and engineers are faced with a number of challenges when laying hundreds of kilometres of track, not least of which is creating an even surface for the track to be laid. Benefits of track ballastĪs well as providing an extremely sturdy and stable base for the sleepers and track to be laid, track ballast also has a number of other benefits. The sharp edges of the stones make it very difficult for them to move – they essentially lock into place as the sharp edges cut into each other, helping to create an extremely stable base for the railway sleepers and track to be laid. If you were to use smooth-sided stones, like the ones you might find in a riverbed or in the ocean, there is a good chance these would roll or slide over each other when a train passes over. One thing you will notice about the stones used for track ballast is that they are extremely rough and sharp-edged. The main function of a railway sleeper is to provide a stable, even platform for the railway tracks and the ballast plays a key role in keeping the sleepers stable and level. The movement caused by heat expansion and contraction along the rail could cause the track to bruckle or break if it was fixed to the sleepers so they are instead attached using clips or anchors that allow for longitudinal movement.
Tracks are not, however, nailed onto the sleepers in a fixed position. Once the sleepers are laid, the railway track itself it attached to the sleepers. You will still see wooden sleepers in place on railway tracks throughout New Zealand, however, a lot of the new tracks that are being laid, as well as sleeper replacements are being carried out using pre-stressed concrete sleepers. Whilst they have traditionally been made from hardwood, heavily trafficked modern railway lines are increasingly turning to manmade alternatives including composite plastic, steel and more commonly pre-stressed concrete. They are extremely heavy, weighing up to 90kgs and you can fit around 2,000 of them for every kilometre of track. What is a railway sleeper?Ī railway sleeper, sometimes known as a “cross tie” in the USA or simply “railroad ties”, are beams that were traditionally made from hardwood that are laid perpendicular to the direction of the track at equal spacing apart. Once the ballast has been laid, the sleepers are put into position at equal distances apart and more track ballast is then packed between the sleepers and to the side, ready for the railway tracks themselves to be laid on top. The track ballast is initially laid on the bare ground, helping to raise the track level (more on this later). They basically form the track bed on which the sleepers are then laid. Track ballast is the name given to the rough, sharp-edged stones that are found underneath and alongside railway tracks. These crushed stones are known as ballast, and they serve a number of crucial roles in helping to maintain railway tracks and ensure the safety of the railway vehicles travelling along them.
It’s probably not something you have ever really thought about, however, the next time you are near a railway track, take a closer look at what sits beneath and alongside a railway track, no matter where you are in the world: crushed stones.
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