Why do railroad tracks have gravel and rocks in between the railroad ties? can it be bare?

Question

Why do railroad tracks have gravel and rocks in between the railroad ties? can it be bare?

Answer 1

In the simplest terms, The gravel "ballast" acts both as a shock absorber to cushion the weight of the train, and also to allow for drainage of rain

Answer 2

I'm sure that it could. But I know when they grade it, gravel is used. Just like a regular road. I am just assuming that it serves a double purpose in stopping things from growing there as well. But I know enough about that to be...well stupid.

Answer 3

The tracks are actually sitting on top of a bed of gravel, which is an excellent, stable and non-eroding base.  The technique of laying gravel over dirt before road stones are laid dates back to the Roman times.

Answer 4

Track can be fitted to naked bedrock.  This is hardly ever widely available.  Engineers utilize crushed stone atop an elevated bed of selected material both to keep road secure from surface drainage and provide sound footing for rail traffic.  Trains are heavy and their passage vibrates.  Vibrated earth with water content turns to mud.  Shifting ground warps tracks.  Crushed rock seperates the vibration and weight from soil transfer.

Answer 5

For drainage.  Otherwise ties will be sitting in water, which will rot them... and during winter, ice will freeze-thaw, causing heave.

Yes, they have "bare" track, that's called slab track.  The track bolts directly to a concrete slab which is made with provision to support the weight and hold gage. Used in transit and high speed passenger, often.

Also, in temporary trackwork, it's common to just throw track on top of the ground without ballasting.

Answer 6

This is called ballast. And no, it cannot be bare. The ballast is needed to and provides track stability, drainage, and support of significant loads carried by railcars. In addition, it deters the growth of vegetation and allows for track maintenance to be performed more easily. It also provides a smooth running surface - without ballast your journey would be bone breaking to say the least.

Answer 7

Its part of holding the ties for support  together and  draining . As well it reduce expansion fom the weather .

Answer 8

Railroad tracks cannot be bare, or without the ballast and gravel.

Like highways and roads, railroad tracks need to be graded and constructed in a certain way.  Roads have gravel beds that are usually paved or concreted, which forms the actual road surface.  Railroad tracks rest on a gravel (ballast) bed, which holds the ties in place, keeps the track stable and level, and provides drainage.

Answer 9

Fist of all, be assured, if they didn't need to be there, the railroad would not be paying money to buy them and put them there.

The ballast is usually crushed, angular stone, 2" to 4".

Since ties cannot sit on bare dirt, the successive load and release would cause the dirt to flow, and the track would not stay in allignment.

Therefore there is a layer of ballast between the bottom of he ties and the dirt.  This distributes the load under each tie and spreds it out.  The ballast is compacted and the dirt and ballast conform to each other at the interface.

The interlocking features of the angular edges of the crushed stone interlock to spread the load. (round rock would not work, each stone would slide past each other)

Over a period of time the ballast migrates into the subgrade, and the subgrade migrates into the ballast and the track gets out of level and line.  Then it's time to either dig it out and clean it, or raise the track with more ballast between the ties and fouled ballast (which acts just like dirt.).

The ballast between the ties (the space between them is called the "crib") also has a purpose.  When a train brakes, the track tries to move the direction the train is braking.  The ties push against the ballast in the cribs, which is interlocked with the ballast below the cribs and creates the force that resists longitudinal movement of the track.

There is one significant change that has occured.  If you look at old photos, you may notice that they didn't put ballast at the end of the ties.

With continous welded rail, in hot times as the rail expands it needs lateral force to keep the track from buckling out of line.  thus railorads started to ballast shoulders, up to 2 ft.  This is to keep the track in line.  The interlocking angles of the compaced ballast resist the forces trying to buckle the track out of line.