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4.Prevention
of soil liquefaction during earthquakes
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| Soil liquefaction is the single largest factor
in building destruction during earthquakes. Soil liquefaction can take place
in subterranean layers of water-saturated sand. When the earth is vibrated such
as during an earthquake, the sand particles lose grain- to -grain contact and
are reoriented and densified to the point where the water pore pressures cause
the subsurface layer to act as a liquid. Since water has no shear strength,
the sand layer loses all stability causing existing surface structures to immediately
settle, tilt, fall on their sides, or collapse. |
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It is estimated that over 25 percent of the City of Tokyo
is built on soils that are subject to liquefaction. In-situ plasma arc processing
of a foundation can rapidly and selectively stabilize weak subterranean layers,
such as a saturated sand layer subject to liquefaction, even under existing
buildings and structures. This method still requires additional experimentation
and documentation.
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