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The LIQUITER program
determines the safety factors pertaining to the liquefaction of
incoherent saturated terrains subjected to earthquake phenomena.
 The
used calculation method, proposed by Seed and Idriss in 1982, is
the best known and most frequently used as it requires the
knowledge of only a few and commonly used geotechnical
parameters(volume weight, relative density and the mean particle
diameter).
Like all methods based on
the concept of resistance factors, it is necessary to evaluate
the resistance of the soil to the cyclic shear stresses: the
program uses the correlation between the resistance to
liquefaction and the number of blows of the SPT test. The last
input value required by the program is the definition of the
seismic parameters that are necessary to simulate the earthquake.
The used formula enables
one to take into account the sporadic character of the maximum
acceleration peaks through the ratio of cyclical stress induced
by the earthquake with reference to a mean value instead of the
maximum value.
For each SPT test that is
carried outs, the corrected number of blows is calculated in
such a way as to consider the lithostatic pressure, through the
use of a corrective coefficient that is a function of the depth
where the test is performed and the relative density.
It is also possible to
consider the presence of a load and take the layers of soil
above the aquifer, considered as loads acting on the underlying
terrain, into account.
The verification is based
on the determination of the resistance to liquefaction factor
witch is calculated as the ratio between the limit shear stress
that induces liquefaction and the maximum shear stress induced
by the earth quake, but leaving out the interstitial pressures
and deformations that develop during the earthquake.
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LIQUITER