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Gravel holds train rails in place

Why are there small stones or gravel beside railroad tracks?

— Julian H., Medford

Believe it or not, Julian, those stones have a purpose. So much of a purpose, in fact, they have an official name. According to www.quora.com, the crushed stones (or gravel) are called ballast. The purpose of ballast is to hold the wooden cross ties in place, which keeps the rails from moving.

Even though they look, and are, heavy, the steel tracks on the ground face many challenges. They expand and contract because of the heat, experience ground vibrations, endure water buildup from rainstorms and weed growth from below. Train tracks are unburdened most of the time. But when a train passes through, the locomotives can carry loads as heavy as 1 million pounds.

To keep the tracks in place, workers start with a foundation on bare ground that is raised high enough to avoid flooding. The ballast is laid on top of the foundation; then come the beams and rails, which are surrounded by more crushed stone. Essentially, the sharp edges of the stones make it difficult for the beams to slide over each other, which locks them in place.

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