Effect of coefficient of uniformity on cyclic liquefaction resistance of granular materials

Using three-dimensional discrete element method, we analyze the particle size distribution (PSD) effect on the cyclic liquefaction resistance of spherical particle assemblies. For the same mean particle size and log-linear type PSD, the coefficient of uniformity (Cu) is chosen as a descriptor of the PSD. Samples with five levels of Cu are isotropically compressed to the same pressure and two relative densities (Dr) informed by the maximum and minimum achieved void ratios determined for each Cu. The ten samples are subjected to constant volume cyclic simple shearing at different cyclic stress ratios until reaching initial liquefaction, in 56 simulations. The simulations suggest that at each Dr the evolution pattern of excess pore pressure ratio against the number of loading cycles normalized by the number of cycles to liquefaction is minimally affected by the Cu. For the samples with lower Dr, increasing the Cu in the range 1-3 first increases and then decreases the liquefaction resistance; this trend reverses at the higher Dr. Two critical state parameters based on the void ratio and the coordination number at the pre-shearing state of the samples correlate well with the cyclic liquefaction resistance for the ranges of Cu and Dr considered in this study.