Reliability Analysis of Pile Running for Offshore Large-Diameter Monopiles Considering Soil Spatial Variability

The installation of large-diameter monopiles for offshore wind foundations faces growing risks from pile running, which refers to a sudden and uncontrolled penetration event causing substantial safety hazards and economic losses. This risk is amplified by the spatial variability of seabed soils, which is often oversimplified in deterministic design, leading to non-conservative predictions. This study proposes a probabilistic framework to quantify the influence of soil spatial variability on pile running risk. By combining the Coupled Eulerian-Lagrangian (CEL) method for large-deformation analysis with random field theory and Monte Carlo simulations, we model pile running in spatially variable clay, incorporating strain-softening and rate effects. Results show that soil randomness alters soil flow mechanisms, strongly controlling penetration velocity and resistance. Deterministic analysis underestimates the maximum running velocity, which follows a lognormal distribution. The framework establishes a direct link between failure probability and design safety factor, recommending FSdesign ≥ 1.5 to achieve a failure probability below 1%, in line with major offshore standards. Application to a Zhuhai offshore wind farm case study confirms the framework’s practicality and highlights the critical role of stratigraphic uncertainty. This work advances reliability-informed design by explicitly accounting for soil spatial variability to improve safety in monopile installation.