A Time-Domain Model for Embedded and On-Bottom Chains Incorporating Consolidation-Paper

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The paper presents a time-domain numerical model for predicting how an embedded mooring chain’s inverse-catenary shape and anchor loading evolve under staged operational loads. Unlike conventional methods, which assume equilibrium profiles and constant soil strength, the model accounts for the chain’s loading history and consolidation-related changes in seabed strength.<br /><br />The method uses a two-dimensional soil-strength map around the chain. At each load step, it updates local soil strength based on an assumed consolidation response and determines whether the chain profile breaks out or remains unchanged. It also accounts for increased friction beneath the on-bottom section of chain, which can reduce the load transmitted to the embedded section even when the inverse catenary does not move.<br /><br />Example calculations show that consolidation can limit further chain movement, leaving the inverse catenary less developed, with a steeper chain angle and lower tension at the anchor padeye. In the scenarios studied, consolidation substantially reduced padeye loads; in one case, the reduction approached 45%. Strength gains along the on-bottom chain also reduced tension reaching the dip-down point. The results further show that uncertainty in chain resistance parameters can have an effect comparable to consolidation.<br /><br />The authors conclude that consolidation may materially affect anchor design and should be considered in whole-life mooring analyses. However, the model’s consolidation assumptions—including the strength-gain magnitude, spatial distribution, and zone of influence—are simplified. Further research is needed to establish more realistic soil-strength changes and refine chain bearing and friction parameters.

Keywords

mooring chain

inverse catenary

anchor loading

time-domain model

seabed consolidation

soil strength

embedded chain

padeye tension

whole-life mooring

chain friction