Ultimate lateral bearing capacity of rigid pile in clay considering soil stress history and scour-hole dimension

Rigid monopiles in a marine environment are frequently subjected to severe lateral loads and scour effects, which complicates the stability assessment of monopiles. This paper proposes a 'double failure mechanism' that integrates the meniscus-conical failure wedge and rotational failure model to evaluate the ultimate lateral bearing capacity of a rigid pile in clay under scour conditions. Considering the influence of scour-hole, three distinct failure modes are introduced based on the possible ranges of failure. The critical 'double failure mechanism' can satisfy both the force balance and the moment balance of the pile-soil system. Based on this framework, an analytical solution for the ultimate lateral bearing capacity of a rigid monopile with considerations of these three failure modes is derived using the limit equilibrium method. Additionally, the combined effects of additional stress and stress history on soil properties are accurately analyzed. The FEM results and existing theoretical solutions are employed to validate the derived limit equilibrium solution. Finally, the effects of scour-hole dimensions and load eccentricity on the ultimate lateral bearing capacity of a rigid monopile, wedge failure and rotational failure are investigated.