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Abstract To investigate the distribution features of rd under different types of excitations，firstly FLAC3D is used to calibrate the results of dynamic centrifuge tests on saturated sand；and then the validated numerical model is used to study the variation of rd curves with soil depth under seismic and harmonic excitations. The results show that the proposed empirical equation of rd is fairly accurate in non-liquefied cases；whereas larger differences exist between the distribution of shear stresses and the predicted values by empirical equation in liquefied cases. Besides，the duration of seismic excitation also influences rd，where the generation level of pore water pressure and the softening degree of soil are major factors. As for the effect of seismic input frequency，it is closely related to the predominant frequency of the site；i.e. the closer the two frequencies become，the more drastic the variation of rd curve is. Therefore，the effects of seismic motion and site conditions should be considered when the Seed-Idriss equation is used to calculate CSR in liquefaction evaluation.
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Received: 28 February 2010
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