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Figure 10.8.
Variation of acceleration with normalized mean displacement
The seismic loading is represented by the cyclic stress ratio (CSR), which is the
ratio between the shear stress and the initial vertical effective stress. CSR is
calculated by the analytical expression of a shear wave propagating vertically to the
free horizontal surface of the site function of the seismic maximum acceleration.
The resistance is called the cyclic resistance ratio (CRR). It value is estimated
empirically. CRR is the minimal CSR value that has led to a liquefaction for a given
penetrometer resistance. The liquefaction criterion is then represented by all the
measured CRR, which give a limit curve in the plane (seismic stress,
in situ
resistance) separating the points representative of the liquefied and non-liquefied
sites (see Figure 10.9).
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