Evaluation of the long-term behaviour of monopile foundations under cyclic lateral loading using 1g physical modelling
Evaluation of the long-term behaviour of monopile foundations under cyclic lateral loading using 1g physical modelling
Monopiles are the predominant foundation type for Offshore Wind Turbines (OWTs), which experience intense cyclic lateral loading throughout their service life. However, predicting their long-term serviceability remains challenging due to limitations in existing design models that often neglect high-cycle soil-structure interaction effects. This study investigates the long-term behaviour of rigid monopiles in saturated sand using 1g physical modelling, addressing key knowledge gaps in predicting high-cycle performance. Two laboratory-scale tests, designed to replicate extended operational conditions, were subjected to 10,000 cycles of one-way lateral loading. The results consistently show that most of the accumulated lateral displacement occurs during the initial loading cycles (e.g., about 50% within the first 600 cycles), after which the accumulation rate decreases markedly and eventually approaches a stable value. Analysis of hysteresis loops revealed that the soilpile resilient stiffness initially decreases (up to 1,500 cycles) due to sand fabric rearrangement, but later increases and stabilizes as soil densification develops under prolonged cyclic loading. Moreover, doubling the cyclic load amplitude produced more than twice the accumulated displacement, underscoring the non-linear nature of the foundation response. These findings provide valuable insights for improving Serviceability Limit State (SLS) assessments of OWT monopiles.
M. Hajialilue-Bonab; Amin Pazhouhandeh; Emad Maleki Tabrizi; Salar Rahnema
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Session 6: Onshore and offshore foundation systems
https://doi.org/10.53243/ICPMG2026-389