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 (C_u) is chosen as a descriptor of the PSD. Samples with five levels of C_u are isotropically compressed to the same pressure and two relative densities (D_r) informed by the maximum and minimum achieved void ratios determined for each C_u. 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 D_r 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 C_u. For the samples with lower D_r, increasing the C_u in the range 1–3 first increases and then decreases the liquefaction resistance; this trend reverses at the higher D_r. 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 C_u and D_r considered in this study.