Envelope of bearing capacity for gravity anchors in strain-softening soils under VHM loading: A Cosserat continuum FEM study

In offshore foundation bearing capacity analysis, the failure envelope method is widely used because it clearly separates load components. However, previous studies on the bearing capacity of gravity anchors under combined loads have not effectively accounted for soil strain-softening behavior. To address this limitation, a Mohr-Coulomb-matched Drucker-Prager model is adopted within the Cosserat continuum framework (MC-matched DP model). Numerical simulations were conducted using Abaqus’s user-defined element (UEL) functionality. Validation against existing literature confirms the accuracy and applicability of the Cosserat continuum model for analyzing the bearing capacity of gravity anchors under VHM combined loading conditions. This approach successfully resolves numerical convergence difficulties and pathological mesh dependency issues commonly observed in finite element analyses of strain-softening soils. The model was then applied to conduct a comprehensive analysis of the bearing capacity envelopes of gravity anchors. Through parametric studies, the influences of anchor embedment depth, vertical load magnitude, and strain-softening degree on the bearing capacity envelope were systematically investigated. Normalized bearing capacity envelope formulas were derived for various scenarios, providing a robust framework for evaluating the performance of gravity anchors under different conditions.