Washout of a railway embankment.

(Versión en español aquí: http://ingjoseguerrero.blogspot.mx/2013/10/deslave-de-una-via-ferrea.html )

In the following video we can see the exact moment when a railway embankment wash out completely.

This phenomenon occurs when the embankment soil forming is completely saturated with water and it is subjected to a large external force, such as an earthquake or a thaw (the latter seems to be the cause of the fault shown in the video). The engineering name for this phenomenon is "soil liquefaction".

For those interested in engineering terms: below the video I expose a little more about this phenomenon.

Soil liquefaction describes the behavior of soils passing from a solid state to a liquid state or acquire the consistency of a heavy liquid, when they were subjected to the action of an external force, in certain circumstances.

This phenomenon produces violent instability of a slope. Is more likely that liquefaction occurs in loose granular soils saturated, or saturated moderately, with poor drainage; such as sediment sand or sands and gravels containing waterproof sediment grain.

 The conditions of a soil to be "liquefiable", according to the "Chinese Criteria", are:

A) In its particle size, the percentage by weight of particles less than 0.005 mm is less than 15%.

B) Their consistency limits: its liquid limit (LL) is less than 35%.

C) The relationship between its natural moisture and liquid limit (w / LL) is greater than 0.9.