Centrifuge Modeling of Fines Content Influence on Liquefaction Behaviors of Loose Gravelly Soils

The effects of fines content on the liquefaction behavior and the dynamic response of gravelly soils were evaluated in this study. A total of six models of level-ground profiles of two saturated gravel-sand-fines mixtures were tested in a geotechnical centrifuge. The first soil mixture was composed of 50% gravel, 38% sand, and 12% fines, and the second soil mixture was composed of 50% gravel and 50% sand. Each soil mixture was subjected to three levels of uniform sinusoidal shaking amplitude: 0.19g, 0.27g, and 0.40g. Both models had comparable relative densities, void ratios, and shear-wave velocities, but the model with fines content had lower permeability by an order of magnitude. Acceleration time histories and pore-water pressure ratios were obtained and used to establish shear stress-strain behaviors during the shaking events. Shear modulus and damping are evaluated and analyzed in relation to the number of cycles and pore pressure development. Lateral displacement, surface settlement, and grain-size distribution of the model after each test were examined to understand the effects of fine particle migration and its influence on shaking amplitude. Based on the results of the two soil mixtures, the fines content had a relatively low impact on the cyclic shear strain, the rate of pore pressure development during shaking, the cyclic resistance ratio, and the reduction of shear modulus. However, the fines content has a noticeable impact on soil dilatancy, the rate of pore pressure dissipation during and after shaking, damping, volumetric strains, and soil fabric after shaking.