Why are there crushed stones alongside rail tracks? - Quora
Answer (1 of 160): The technical term for these crushed stones is "Ballast". Tamping machine (or ballast tamper) is a machine used to pack the track ballast under railway tracks to make the tracks more durable. Usually, a 25–30 cm thick ballast layer (crushed stone 30/60) below the bottom face of...
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