Liquefaction Evaluation of a Gravel-Sand Mixture Using Centrifuge Tests

Two centrifuge modeling tests were performed in this study to evaluate liquefaction behaviors of a gravel-sand mixture comprised of 50% gravel and 50% sand by weight. The tests were conducted under the centrifugal acceleration of 50 g to simulate a prototype soil profile height of 7.6 m. The models were shaken using 1-Hz shaking motions with the amplitude of about 0.19 g and 0.40 g. The paper analyzed the dynamic response and liquefaction behavior of these models based on observations of pore pressure development, stress-strain behaviors, and acceleration response spectra. For the high-amplitude shaking test, liquefaction occurred in most soil layers in the model but for the low-amplitude shaking test, only the surface layer was liquefied. Dilation behavior was observed at different stages of liquefaction depending on the amplitude of shaking and effective stress. Pore water dissipation occurred rapidly during the lower amplitude shaking event caused an increase in the soil stiffness. Liquefaction was also assessed from the amplification of acceleration response compared with the base shaking acceleration. Amplification of the accelerations was found for the non-liquefied soil layers while de-amplification of the accelerations was observed for the liquefied soil layers due to a reduction in soil stiffness.