A simple sand model for p–y analysis of OWT foundations under low-to-moderate-cycle loading

Offshore wind turbine (OWT) structures commonly undergo many environmental loadings, potentially leading to instability in the underlying foundation soil. Therefore, this study introduces a simple model aimed at predicting the response of sand under low-to-moderate-cycle loading. The model is constructed based on an extensive database, encompassing a series of cyclic triaxial tests performed on reconstituted fine sand. Various influencing factors, such as the initial stress ratio, initial confining stress, and relative density, are considered in the prediction model. A key feature of the proposed model is its ability to simultaneously predict stiffness degradation and strain accumulation, both of which are determined by the initial stress ratio. The estimated stiffness degradation and strain accumulation function as p -multipliers and y -multipliers, respectively, enabling the adjustment of the preselected p – y curve to predict the response of an OWT pile foundation subjected to prolonged cyclic loading. To validate and demonstrate the proposed model and approach, three centrifuge tests conducted on a monopile in loose to dense sand are adopted. The simulation results demonstrate favorable agreement with measurements as a function of the applied cycle count.