Evaluation of Soil Dynamic Properties in Centrifuge Tests

This paper describes a method to compute the mobilized shear modulus, $G$, and damping ratio, $D$, using the nonlinear fit of experimental transfer functions obtained at different depths in centrifuge models, with the analytical expression of the amplification function for a viscoelastic soil layer on a rigid base. The corresponding shear strain, $\gamma$, is computed as a function of the particle velocity and shear wave velocity. The sources of potential error in the determination of $G$, $D$, and $\gamma$ embedded in the proposed method are identified and discussed in comparison with two other methods that have been proposed in the literature, based either on the determination of the time lag of accelerations between two accelerometers or on the evaluation of the shear stress-strain cycles from acceleration time histories recorded at different depths in the model. The performance of the three methods is evaluated using the experimental data obtained from nine centrifuge tests on dry sand. The values of $G$ obtained by the proposed method compare well with the results of laboratory and literature data; $D$ values are more dispersed and slightly higher than the literature data.