Understanding the dynamic behaviour of soil is crucial for the design of geotechnical structures, particularly for offshore wind turbine foundations. This study evaluates the performance of a nonlinear numerical model in accurately capturing soil response under dynamic shear loading, comparing its simulated response to experimental data obtained from Resonant Column Tests (RCT). The research systematically investigates the role of higher-order odd harmonics in the numerical solution, assesses the differences between linear and nonlinear models, and validates the nonlinear model against experimental results.

The findings reveal that higher-order harmonics contribute negligibly to the numerical response, simplifying the model's implementation. Furthermore, the nonlinear model effectively captures the resonance shift observed in experimental data, outperforming the linear model, particularly at higher strain levels where soil softening effects become significant. While the model demonstrates a strong correlation with experimental results, discrepancies arise in high-strain scenarios, primarily due to limitations in damping representation. To address this, corrective approaches such as a damping correction factor and strain radius adjustments were explored, improving model accuracy but failing to eliminate errors entirely. The study highlights the necessity of incorporating a strain-dependent damping formulation to enhance predictive capabilities for high-strain soil behaviour.

The results confirm that nonlinear numerical modelling is a valuable tool for capturing essential soil dynamics, but further refinements in damping representation are required to improve alignment with experimental data. Future research should focus on advanced damping models to ensure greater accuracy in high-strain dynamic soil simulations.