A simplified procedure for the prediction of liquefaction-induced settlement of offshore wind turbines supported by suction caisson foundation based on effective stress analyses and an ML-based group method of data handling

Abstract In this research, a series of non-linear dynamic finite element (FE) effective stress analyses were conducted to analyze the influence of the suction caisson geometry, ground motion intensity and contact pressure caused by the offshore wind turbine (OWT) on the settlement pattern and seismic demand of the OWT's structure on saturated dense sand. The baseline model and the FE procedure were validated using a database of well-documented centrifuge tests. However, particular attention was given to the calibration campaign based on the measured system response quantities, such as the settlement, acceleration and pore-pressure time histories. The FE results identified the contact pressure as an important state parameter caused by the OWT's mass; the governing ground-shaking intensity measures that play a significant role in the derivation of an analytical framework for predicting liquefaction-induced OWT settlements during major events are the shaking intensity rate (SIR), Arias Intensity (Ia)${I}_a)$ and spectral acceleration at a period equal to 1 s (T = 1 s). The results revealed that approximating expressions derived using the modified least-squares method (MLSM) reasonably capture the complex phenomenon of liquefaction-induced settlement, with some exceptions at lower SIR values. Finally, to obtain the approximating expressions, the database was combined with a machine learning (ML)-based group method of data handling (GMDH) that appropriately describes the interplay of multiple properties of the foundation soil, structure and seismic events while incorporating the effect of the interaction between the suction caisson, foundation soil, excess pore-pressure generation and cyclic shear stresses.