I have a question about train derailments... How much can the groundshift before it causes problems?

Question

I am doing a research project on it and cant find anything about it.

Answer 1

Roadbed caused derailments can occur in different ways.

The rails can spread, exceeding the 4'81/2' gage and the equipment will drop off of the tracks.

A rail can break under the train, and cause a derailment with no shift at all.

Defective switch components can fail and cause a derailment with no shift.

Shifted track is not unusual in areas where there is a lot of curvature and high daytime ambient temperatures. Usually minor, these are commonly referred to as a "sun kink," most often still able to be ran on, at reduced speed. When excessive, these can kick the entire tie/rail structure out of the ballast and the next train coming along is going to wind up in the ditch.

Sections of railroad where the speed limit is 40 mph or higher must be inspected daily by maintenance of way personnel. Most carriers will put out a "heat order," in the form of a track bulletin given to train crews when assuming duty, advising of conditions and ordering a train to operate at a slower speed due to high temperatures. These measures are quite necessary where there is CWR, continuous welded rail, in use, which has problems with temperature extremes and the resultant expansion and contraction.

Answer 2

It's a question of how much it distorts the geometry of the track, versus how fast the train is going.

The law gives numbers, in inches, of legally allowable deviation for different train speeds.
http://edocket.access.gpo.gov/cfr_2003/octqtr/49cfr213.55.htm
http://edocket.access.gpo.gov/cfr_2003/octqtr/49cfr213.63.htm

They mention 5 classes of track; those are
Class 1 = 10 mph max speed for freight
Class 2 = 25 mph
Class 3 = 40 mph
Class 4 = 60 mph
Class 5 = 80 mph

Answer 3

are you talking in the case of a earthquake will the rail bed shift