New observations on the coupling effect between factors influencing the capacity of plate anchors in clay

This paper presents systematic three-dimensional (3D) finite element analysis of the bearing capacity factor ( N c ) and failure mechanisms of plate anchors under the coupled influence of embedment ratios, aspect ratios, inclinations, and soil undrained shear strength profiles. Existing design equations are evaluated against the new dataset and have proven insufficient to capture the complex interplay of these factors. The anchor capacity variations are interpreted along with changes in failure mechanisms, revealing several new insights: (i) the embedment ratio required to trigger deep failure mechanisms depends on the coupled influence of multiple factors; (ii) deep failure mechanisms’ configurations can continuously evolve with embedment in non-uniform soil, producing further N c variation, while the widely held view regarding their embedment-independence applies only in uniform soil; and (iii) the threshold aspect ratio for 3D anchors to act strip-like is not fixed but depends on the coupled influence of multiple factors. Collectively, these findings also highlight a critical but widely overlooked pitfall: the widespread practice of simplifying 3D anchors as strip anchors may fundamentally alter the failure mechanism and lead to misleading conclusions. Existing knowledge based on strip anchors must therefore be applied with caution. • Systematic three-dimensional finite element investigations into plate anchor capacities in real-world conditions. • Embedment ratio required to trigger deep failure mechanisms depends on the coupled influence of various factors. • Deep failure mechanisms' configurations in non-uniform soil can continuously evolve with embedment, producing further N c increase. • The influences of aspect ratio, inclination, embedment ratio, and soil strength profile are highly coupled. • Simplifying 3D anchors as strip anchors may fundamentally alter the failure mechanism.