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Amazing Facts

Amazing facts about Quicksand





  1. Quicksand is a a condition which occurs when an otherwise
    static body of sand is "aggitated" in such a way that the grains
    lift away from one another. As friction is transferred through
    the sand body via grain-to-grain contacts the separation of
    grainscauses a dramatic reduction in the shear strength of the
    material and it starts to behave in a liquid-like manner, i.e.
    the sediment liquifies.There are a number of "aggitation"
    processes:

  2. The upward passage of pore fluid exerts a drag force on the
    individual grains. If the drag force is great enough it will
    balance the weight of the grains and they will no longer rest on
    their neighbours. This processes is often called "fluidisation".

  3. Vibrations cause grains to move laterally, colliding with
    their neighbours as they do so. If the vibration energy is great
    enough the collision rate and grain velocities increase such
    that the majority of grains are moving and colliding rather than
    resting statically on their neighbours. The sediment then
    becomes liquified.

  4.  During earthquakes and other large vibration activity (e.g.
    storm waves, impact of dense flows, etc.) vibration can causes
    an initial movement of grains,compaction and pore waters are
    expelled. The action of the expelled water is combined with the
    vibration behaviour to produce a complicated liquification
    process which is often called "liquefaction".

  5. Shear across a granular body of sediment can cause a similar
    collision process to that occurring during vibration. Therefore
    unidirectional shear across a body of sand can also cause
    liquification. "Granular temperature" models have been used to
    investigate this process in granular flows.



   
Related Tags: Earthquakes  Vibrations  Amazing  
 
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