Question: How is it going to be safe the train could fall of?

Natalie Wride answered on 17 Jun 2016:

Hi 728envf43 🙂

This is a great question. I’m looking at how the ground responds to vibrations. The trains cause the ground to vibrate and it ‘compacts’ the soil, this mean the soil squishes under the vibrations – it’s a bit like repeatedly hitting playdough with the palm of your hand, it’ll eventually form a ‘dip’ where your hand has been.

This is a common problem but becomes more important for high speed trains because they travel so quick – as fast as an aeroplane taking off! You might have noticed when you’ve been in the car that the journey can feel more bumpy when you’re driving over it faster? The same thing happens on the rail lines, so if we have areas of ground along the trainline that have squashed because of vibrations the passengers might start to feel a bit travel sick!! In the ultimate worst case, which is extremely unlikely, the trains travel at such fast speeds that a large bump could case the train to derail like you said 🙂

As Engineers, there’s lots of things we can do, firstly to either stop or slow the development of bumps beneath the train lines – we can built parts of the track and leave them so that the ground gets used to the weight of what’s been put on it before we use them. We can also put special plastic or fabric meshes in the ground which reinforce the soil – a bit like the pasta sheets in your lasagna!! We can also use fabric drains which drain water in the soil as this can contribute towards the bumps.

If there are still bumps on the track it’s important we notice these and examine them to make sure the trainline is still safe. We might repair them if they’re bad or we might slow down the speed of the train until we are able to repair them.

I hope this answers your question 🙂 much of the risk of trains derailing is removed by good engineering design and the remaining risk can be limited by good maintenance 🙂