To take into account the magnitude of the earthquake, the method proposed by Yoshimi and Tokimatsu calculates the Cyclic Stress Ratio with the following equation:
where is introduced a correction factor rn function of the magnitude M:
The liquefaction resistance is obtained by the following expression:
where:
a = 0,45.
Cr = 0,57.
n = 14.
ΔNf = 0 for clean sands and ΔNf = 5 for silty sands
N1,60 = [1,7 / (σ'v0 + 0,7)] Nm
Cs is an empirical constant which depends on the amplitude of the shear deformation.
The previous relationship was obtained by the authors by correlating the results obtained from cyclic triaxial tests with the results of standard penetration tests SPT.
The authors, for design purposes, suggest to adopt a value of FS > 1.5 for loose and medium sands and FS > 1.3 for medium-dense sands.
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