Behaviour of Embedded Mooring Chains in Clay During Chain Tensioning

Dutta, Anindya; Degenkamp, Gijs

doi:10.4043/6031-ms

Cited by 9 publications

(4 citation statements)

References 6 publications

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“…Degenkamp and Dutta (1989) quantified 148 average values of En and Et as 2.5 and 8.0 by investigating 6db stud-link and 5db studless chains 149 with both orthogonal and diagonal configurations. The bearing factor Nc was assumed 150 equivalent to that of a strip foundation, increasing with depth from 5.14 at mudline to a 151 maximum of 7.6 (Degenkamp and Dutta 1989; Dutta and Degenkamp 1989;Neubecker and 152 Randolph 1995a;Neubecker and Randolph 1995b;Neubecker and Randolph 1996). These 153 result in values of μ between 0.4 and 0.6.…”

Section: Chain-soil Forces: 125mentioning

confidence: 99%

Numerical Study of Mobilized Friction along Embedded Catenary Mooring Chains

Sun

Feng

Neubecker

et al. 2019

J. Geotech. Geoenviron. Eng.

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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

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Section: Chain-soil Forces: 125mentioning

confidence: 99%

Numerical Study of Mobilized Friction along Embedded Catenary Mooring Chains

Sun

Feng

Neubecker

et al. 2019

J. Geotech. Geoenviron. Eng.

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“…Behaviour of the embedded chain may be obtained by integrating the governing equilibrium from one end of the chain to the other [13,[16][17][18][19]. Here T is the tension in the chain acting over the incremental chain length ds, θ the chain angle to the horizontal, wc the submerged weight of chain per unit length, and Q and F respectively the normal and frictional soil resistances per unit length in the directions perpendicular and parallel to the chain axis.…”

Section: Appendix -Existing Design Relationshipsmentioning

confidence: 99%

Numerical investigations of the effect of strain softening on the behaviour of embedded mooring chains

Sun

Feng

Bransby

et al. 2019

Applied Ocean Research

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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.

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“…Effect of the mooring line profile below mudline should be taken into account in evaluating the adequacy of the anchor to safely transmit the mooring loads 11 . That is since the line profile (inverse catenary) usually increases the vertical component of the load at the pile padeye, which is usually the controlling component.…”

Section: Figure 3: Types Of Slender Anchor Pilesmentioning

confidence: 99%

Industry Trends for Design of Anchoring Systems for Deepwater Offshore Structures

Eltaher¹,

Rajapaksa²,

Chang³

2003

All Days

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This paper was selected for presentation by an OTC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Offshore Technology Conference or its officers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Offshore Technology Conference is prohibited.

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Behaviour of Embedded Mooring Chains in Clay During Chain Tensioning

Cited by 9 publications

References 6 publications

Numerical Study of Mobilized Friction along Embedded Catenary Mooring Chains

Numerical Study of Mobilized Friction along Embedded Catenary Mooring Chains

Numerical investigations of the effect of strain softening on the behaviour of embedded mooring chains

Industry Trends for Design of Anchoring Systems for Deepwater Offshore Structures

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