Liquefaction resistance of sands containing plastic fines with different plasticity

Soils in the field or at reclaimed sites commonly contain some amount of silt or clay rather than clean sand only. The effect of a low fraction of plastic fines within sand matrix on liquefaction resistance is not clearly understood. In this study, clean sand was mixed with 10% plastic fines having different plasticity indexes (PIs), and the effect on liquefaction resistance was evaluated in terms of cyclic stress ratio. A series of undrained cyclic triaxial tests were carried out on loose, medium, and dense specimens that were reconstituted in the laboratory by the undercompaction method. The results showed that liquefaction resistance tended to decrease as the PI of 10% fines in the specimens increased. Liquefaction resistance of loose specimens was marginally influenced by the plasticity of fines. However, in the case of dense specimens, liquefaction resistance decreased up to 40% as the PI of 10% fines increased. It was shown that even though a low fraction of plastic fines was included within sand matrix, it still had a significant effect on the liquefaction resistance of sandy soils.