Liquefaction Resistance of Sands Containing Varying Amounts of Fines

Results of undrained cyclic triaxial tests on sand-(nonplastic) silt mixtures (under conditions of constant global void ratio) reported by Xenaki and Athanasopoulos (2003) are further analyzed in the framework of recent advances on the subject of liquefaction behavior of fine-grained soils. The observed behavior, for all values of fines content (0% to 100%), is found to have the characteristics of the "sand-like" behavior described in the literature. The same characteristics are also exhibited by plastic sand-clay mixtures with plasticity index ranging from 2 to 11. The undrained initial modulus of the specimens and the amplitude of pre-liquefaction strains were found to decrease and increase, respectively, with increasing fines content, thus negating the beneficial effects of dilatancy in this type of soils. The existence of a critical value of fines content, FC_cr, at which liquefaction resistance is minimized, is confirmed and shown to be useful in describing the behavior of the mixtures in terms of their relative density.