Effect of Fine Content on Liquefaction Resistance of Saturated Marine Sandy Soils Subjected to Cyclic Loading

Offshore wind turbines are subjected to environmental loads such as wind and ocean waves throughout their entire service lives. Saturated sandy soils experience liquefaction under cyclic shear stresses induced by earthquakes or strong wave actions, which can result in the tilting, settlement, or even overturning of structures. This study investigates the effect of fine content (FC) on the liquefaction resistance (CRR) of saturated sandy soils with different density states. Sandy soils with varying FC values are examined under three scenarios: (1) constant relative density; (2) constant void ratio; and (3) constant skeleton void ratio. A series of undrained cyclic triaxial tests are conducted on sandy soils with different FC and density states (Dr, e, and esk). The results indicate that an increase in FC leads to a decrease in CRR at constant Dr or e, whereas CRR at constant esk increases with increasing FC. No clear correlation is observed between Dr, e, or esk and CRR for saturated sandy soils with varying FC. Since esk does not account for the effect of fine particles on the contact state of skeleton particles, the equivalent skeleton void ratio (esk*) is introduced to describe the particle contact state of sandy soils with different fine contents (FCs), considering the degree of fine particle participation. In addition, the test data reveal that the CRR of sandy soils with different FC and density states decreases with increasing esk*, and a power relationship between the reduction in CRR and the increase in esk* is established. This finding indicates that esk*, which considers the proportion of fines contributing to the load-sustaining framework, serves as a reliable index for evaluating the CRR of various sandy soils. We find that grain shape plays a significant role in influencing CRR, and the overall CRR of sandy soils increases as the grain shape changes from spherical to angular, compared to the published test results for other sandy soils.