Liquefaction

sand and water would be. Have a look at quick sand.

if you walk on the beach in wet sand where the wave just washed back you would notice your footprint filling up with sand/water from the bottom up.

Even dry sand in a desert will flow under wind, weight or vibration. Therefore special care need to be taken when building on sand.

A clear indication of this flow in dry sand is with a plastic pipe trenched into the sand and a reciprocating pump.

The slight variation of the diameter caused by the varying pressure pulse causes the sand particles to fall or flow deeper where it is compressed with the next pulse. This causes the pipe to slowly rise and within months the pipe is visible above the ground level.

I thought you had a good response considering the nature of the question. Vague questions are open to interpretation, sometimes we get it right, and other times we don't. I therefore assume you are referring to quick sand? so here is a link.

Regards JD.

liquefaction can occur in moist soils in response to shear. This can be caused by a tremor sequence or by a pile of moist soil changing its angle of repose as water is added to make the water table rise.

Think mud, the wetter it gets the lower it slumps.

As for buildings.

Think of a small building with a cellaras a boat. If you placed it in water it may well float as the empty cellar volume bouys it up. A building with no cellar will sin into the liquified soil. A tall one may well tilt sideways a little or a lot and fall down. With tremors added = big problems.

All soils in an earthquake are subject to liquefaction just depends on how violent the quake is .

I agree with the above, I should have done a bit more homework. Another Google search with the correct spelling come up with the following. Liquefaction

Regards JD.

Hello charma2633,

it is when the sandy soil becomes soaked and each grain begins to slide. You may not know it unless there is an Earth quake. When this happens the soil becomes a disastrous quick-sand. And anything standing on it stops being supported and begins to sink............

This site is: http://www.ce.washington.edu/~liquefaction/html/what/what1.html

example:

Description Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world. Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. Click on the picture to start animation. Schematic behavior of sand grains in a soil deposit during liquefaction. The blue column represents the pore water pressure. Here is an MPEG version (222 Kb)of the animation. Earthquake shaking often triggers this increase in water pressure, but construction related activities such as blasting can also cause an increase in water pressure. When liquefaction occurs, the strength of the soil decreases and, the ability of a soil deposit to support foundations for buildings and bridges is reduced as seen in the photo (SC) of the overturned apartment complex buildings in Niigata in 1964. The type of ground failure shown above can be simulated in the laboratory,as seen in the video. Click on the picture or on the play button to start video. Here is an MPEG version (298 Kb) of the video. Liquefied soil also exerts higher pressure on retaining walls,which can cause them to tilt or slide. This movement can cause settlement of the retained soil and destruction of structures on the ground surface (left, GH) Increased water pressure can also trigger landslides and cause the collapse of dams. Lower San Fernando dam (left, SC) suffered an underwater slide during the San Fernando earthquake, 1971. Fortunately, the dam barely avoided collapse, thereby preventing a potential disaster of flooding of the heavily populated areas below the dam.

Liquifaction occurs when the liquid (usually water) in the pore spaces between soil particles experiences an increase in pressure, as may occur in an earthquake. This increased pore pressure causes the soil particles to spread apart, until there is contact between particles, they are essentially floating in water. When this occurs the soil becomes essentially a viscous liquid.

Soils that are medium to fine grained and are poorly graded (all one grain size) are subject to liquifaction. Very fine grained soils are not as subject, as the pore spaces become so small that an increase in pore pressure is not able to be forced through the tiny pores very quickly. Very large grained soils (small gravels for example), are also not subject to liquifaction as the particles weigh more hence the pore pressures required to cause liquifaction are greater. Soils that are well graded (many grain sizes) have less chance of liquifaction as the small particles occupy the pores, resulting in small pore spaces, and the large particles take more pressure to suspend.

The buoyancy of an object in a liquified soil should be nearly equivalent to its buoyancy in water. A liquified soil should be considered to be just that, a liquid.

Hope this helps...