Railroad Track Post-Earthquake

[FlashSet]

This is old(er), but I can't find a thread about it here...

Canterbury earthquake caused distortions in rail: here

Assuming this is from an earthquake, what kind of waves would cause this? Parallel to the rails causing compression and buckling? Perpendicular to the rails?

Are thermal stresses ever big enough to cause something this major?

 

[MikeHalloran]

No real expertise claimed here.

The text with the photos suggests that the ground under the straight rails foreground and background acted like tectonic plates on a smaller scale, moving toward each other, compressing the rails in a localized area, causing them to buckle.

Passages in "Shogun" (yes, nominally fiction) describe islands of relatively undisturbed ground moving laterally, away from each other, producing crevasses of considerable depth, then closing up and trapping any objects or persons unlucky enough to fall in the transient crevasses.

So maybe the rails could be pulled straight, and _then_ compressed. The gravel/grass interface certainly suggests some funky stuff happened.

It's not strictly a thermal phenomenon, but I have seen frost heaves of similar frequency in highways.





Mike Halloran
Pembroke Pines, FL, USA

 

[msquared48]

I do not question this, but it could be due to two or three different horizontal shear waves in the ground that came through at the ground surface above the fault line.

What I would like to know is where the extra length of track came from to make these horizontal waves - has to be a good 20 feet or more needed here to make these ciurves.

From experience, I believe that all things are possible with earthquakes. Just look at the twisted shapes in the folds of gneisses and schists from metamorphosis and seismic action and you will see what I mean, just on a much larger scale.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[GeoPaveTraffic]

I've seen rail lines move significnat distances from thermal stresses,so the "extra" track could have come from thermal expansion if it was a hot day and the track segment was long. I've seen curves jump completely off the road bed when disturbed by constrction equipement on a hot day.

My best guess as to what happened is that there was some localized fault rupure at this location causing the track on one side to move horizontally slightly relative to the other side. This allowed the thermal stress in the rail to release which caused the track to buckle.

I'm sure there are other possibilities. All in all an interesting photo.



Mike Lambert

 

[msquared48]

Now that makes sense - high thermal stresses causing compression and the earthquake indcing lateral instability causing lateral buckling in a column. Never thought of it that way.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[fcu45]

That would be due to the surface waves (P-waves) which has compressive longitudinal action parallel to earth surface.

Point of view: It might not be the same concept; but looks similar to the reaction of (Say long thick rope and strand cable) if you have shaken it left and right from one end while the remaining is laying on ground.

 

[fcu45]

Just thinking

http://www.youtube.com/watch_popup?v=-uIVkb256R0&feature=player_embedded