Upper‐Bound Solution for Ultimate Bearing Capacity of Laterally Loaded Rigid Monopile in Clay Under Scour Condition

ABSTRACT Scour has long been recognized as a crucial factor in assessing the stability of monopiles in the marine environment. Assessing the stability of pile foundations from the perspective of bearing capacity is a widely adopted approach. The upper‐bound analysis can offer a valuable way to evaluate the bearing capacity of scoured rigid monopiles in clay. Therefore, this study introduces three potential three‐dimensional collapse mechanisms to assess the ultimate lateral bearing capacity of rigid monopiles under scouring conditions. The failure mechanisms include an enhanced meniscus‐conical wedge and a rotational spherical mechanism. Using plasticity theory, rigorous upper‐bound solutions specific to these failure mechanisms are derived, incorporating the soil's stress history. These solutions were also found to match results from finite element (FE) analyses. The study further investigates the influence of pile size, soil properties and adhesion factors on the reduction of pile bearing capacity due to scour, using parameterization. An empirical formula is proposed to quantify this reduction, and its predictions are validated with FE‐based results.