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4Understanding the soil resistance along an embedded anchor chain is imperative for efficient 5 and economic design of an overall mooring system as it determines the magnitude and direction 6 of the load at the padeye of the anchor. The tensioning process of an embedded chain for 7 catenary moorings was modeled using a coupled Eulerian-Lagrangian (CEL) finite element 8 approach simulating the large deformations of the chain as it cuts through the soil to form an 9 inverse catenary. The analyses reveal that the configuration of the embedded chain and the 10 relationship between tension and chain angle at the padeye show excellent agreement with 11 previously published analytical predictions. However, the ratio of the tension at the padeye to 12 that at the mudline obtained from CEL is significantly higher than the theoretical values, mainly 13 due to partial mobilization of the frictional soil resistance along the length of the chain. The 14CEL results indicate that the partial mobilization is a result of the combined-loading effect 15 during failure of the soil around the embedded chain as it cuts through the seabed, in contrast 16 with the conventional assumption that the ultimate frictional and normal soil resistances are 17 mobilized simultaneously. A new design approach is proposed for calculating the local 18 equivalent coefficient of friction based on the yield locus for a deeply embedded chain and the 19 normality rule. 20

The kinematic behaviour of drag achors during embedment in sand is examined in this paper. A series of centrifuge model anchor tests has been performed in silica and calcareous sands in which both force and kinematic data were obtained during the course of anchor embedment. In this paper, the kinematic data have been examined to determine general rules for the kinematic behaviour of a drag anchor during embedment. These rules provide an essential step towards a theoretical simulation of a complete anchor embedment history and hence a predictive tool for the ultimate holding capacity of a drag anchor. Key words: drag anchor, kinematics, sand, limit equilibrium, ultimate holding capacity.

Mooring systems typically consist of an anchor and a mooring line and chain that connect the anchor to the floating infrastructure. When the anchor connection point (the 'padeye') is below the seabed surface, the interaction between the chain and the seabed will affect the amount of load transferred to the anchor and the load angle at the padeye. Reliable methods are needed therefore to assess these aspects in order to determine appropriate anchor design. Available solutions for the interaction between soil and chain generally ignore any reduction in the undrained shear strength of the soil as it is remoulded under the large strains associated with tensioning of the anchor chain. This is an unconservative assumption for anchor design, hence providing motivation for the study presented here. The system behaviour and the interaction of short chain segments with the seabed have been studied using a coupled Eulerian-Lagrangian (CEL) approach. The findings have led to two new design approaches that encapsulate how remoulding of the soil (which affects sliding resistance more than bearing resistance) affects the chain system response. Calculations using these methods captured the modelled chain system response well. Both the global chain analyses and the proposed design approaches suggest that approximately the entire chain load at the seabed surface (the 'mudline') is likely to be transferred to the anchor padeye, challenging conventional design practice.