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The Crucial Role of Track Ballast: Why Railroads Use Crushed Stone

Author: Science ABCTime: 2024-01-07 00:05:02

Table of Contents

What is Track Ballast? Crushed Stones Protecting Railway Tracks

On any train journey, you may have noticed the endless piles of stones lining the railway tracks. At first glance, they appear as regular pebbles. But frequent train travelers likely observed that regardless of country, the shape and texture of those stones look almost identical across the globe.

These crushed stones packed below, between and around the railroad ties collectively constitute the track ballast. More specifically, track ballast forms the trackbed on which sleepers or railroad ties lay. The thickness usually falls between 25-30 cm but can vary based on geographical factors affecting the railway track.

Key Characteristics of Track Ballast Stones

Track ballast typically comprises crushed rocks or stones. Less suitable materials like burnt clay occasionally substitute when needed. However, not just any rocks work. The stones have a specific shape, size, and jagged texture that interlocks them together to stay in place. Smooth, circular rocks would slide over each other, compromising the track ballast's strength and risking catastrophe.

6 Vital Functions Provided by Railway Track Ballast

Railway tracks contain steel and metallic components prone to corrosion and rust since they remain exposed to nature's elements. Track ballast mainly protects the railway track in the following ways:

  1. Holds the sleepers in place - Heavy trains exert constant stress and pressure daily. Track ballast keeps sleepers from moving longitudinally or laterally when rolling stock passes over them. Without it, the sleepers would likely buckle under the constant load.

  2. Distributes load - Trains weigh massively and put huge pressure on tracks and sleepers. The jagged edges of the crushed stones interlock and distribute the immense load evenly throughout the track ballast.

  3. Dampens vibrations - Track ballast absorbs vibrations from moving trains, adding to passenger comfort. Pay attention next time you ride a train and feel the difference when passing over sections without ballast.

  4. Enables drainage - Track ballast prevents water clogging or accumulation around the sleepers. Otherwise, water would pool on the tracks, rapidly rusting the steel.

  5. Prevents vegetation - Plant growth can severely undermine track strength, so vegetation must not encroach. Track ballast successfully keeps out grass, weeds and plants.

  6. Absorbs noise - The crushed stone's increased surface area substantially absorbs noise versus a flat plane. Trains on tracks without ballast sound much louder.

Regular Maintenance Needed for Railway Track Ballast

One might assume the stones just get deposited and remain undisturbed indefinitely after tracks open. But over time, ballast effectiveness suffers from dirt/mud accumulation among the stones, hampering drainage. Like the tracks, track ballast needs regular cleaning and maintenance. The stones occasionally get replaced entirely with fresh crushed stone. Specialized ballast cleaning machines reduce the manual labor for this task.

Cleaning Old and Dirty Track Ballast

If the track ballast collects too much dirt or mud, debris buildup prevents water from draining properly. So crews will bring in ballast cleaning machines every so often. These specialized devices scoop up the tired, dirty ballast, separate out the dried mud and soil, then redeposit the clean and reusable stones back around the ties.

Full Replacement of Railway Track Ballast

After many rounds of cleaning cycles, the ballast stones eventually wear too smooth and small to function properly. When that happens, railway maintenance crews must completely replace the old stones with a fresh batch of properly sized and jagged crushed rock to restore functionality.

Conclusion - Unassuming Pebbles Support Global Railways

It's remarkable that such an unassuming pile of stones constitutes the backbone enabling an industry impacting millions worldwide. Next time you see those gravelly mounds flanking some train tracks, you'll view them with new appreciation for the vital role they serve.


Q: What size and shape are track ballast stones?
A: Track ballast stones have a jagged, non-smooth surface with sharp edges. They are specifically shaped to interlock with each other and stay securely in place.

Q: Why can't you use just any type of crushed stone for track ballast?
A: The crushed stones used for track ballast need to have a specific size, texture and angularity to properly interlock, distribute load, absorb vibration, and serve other important functions.

Q: How does track ballast help with drainage?
A: Track ballast prevents water from pooling around the railway tracks. The spaces between the crushed stones allow water to drain efficiently.