Dynamic behavior of large-diameter piles with considering liquefaction under clay layer

Marine structures are mostly constructed on deep foundations, namely large-diameter piles. Such support structures are driven into deposits of saturated granular soil, which is vulnerable to liquefaction under loadings of dynamic nature, e.g., earthquakes. Although numerous studies have been accomplished to obtain a comprehensive understanding of their performance during liquefaction, a conclusive study has not been presented for the specific case of large-diameter piles under a clay layer. This issue has great importance in case of offshore wind turbines, since they are very sensitive to dynamic loadings. In this study, a 3D FEM model was constructed by OpenSeesPL to explore soil and pile responses throughout liquefaction. To capture the precise behavior, a constitutive law based on a multi-surface plasticity was utilized for soil. The described model used in this study is capable of accurate prediction of sand behavior in undrained conditions. Different scenarios were tested: variations in pile dimensions, loading frequency and influence of clay layer. Sensitivity analyses show that loading frequency, presence of clay layer and pile diameter could significantly affect behavior of large-diameter piles in saturated soil conditions.