Efficient Gravity Installed Anchor for Deepwater Mooring

Zimmerman, Evan H.; Smith, Matt; Shelton, John T.

doi:10.4043/20117-ms

Cited by 58 publications

(31 citation statements)

References 3 publications

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“…Both those anchors have the mooring chain attached at the top of the anchor on the centreline. More recently a dynamically embedded anchor has been developed by Delmar for use in the Gulf of Mexico, with the mooring chain attached to a revolvable shank part way down the shaft of the anchor (Zimmerman et al, 2009) (see Fig. 38, bottom left).…”

Section: Dynamically Embedded Anchorsmentioning

confidence: 99%

Offshore Design Approaches and Model Tests for Sub-Failure Cyclic Loading of Foundations

Randolph

2012

Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads

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Section: Dynamically Embedded Anchorsmentioning

confidence: 99%

Offshore Design Approaches and Model Tests for Sub-Failure Cyclic Loading of Foundations

Randolph

2012

Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads

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“…It has also been used for temporary facilities in the Gulf of Mexico (Zimmerman et al 2009), although the design used in the Gulf of Mexico is quite different to that used offshore Brazil. The majority of performance data are from centrifuge studies (O'Loughlin et al 2004Richardson et al 2006Richardson et al , 2009Gaudin et al 2013;Hossain et al 2015) although a growing body of field experience is becoming available (Zimmerman et al 2009, O'Beirne et al 2015.…”

Section: Performance Data and Technology Maturity Of Each Anchor Typementioning

confidence: 99%

Novel Anchoring Solutions for FLNG - Opportunities Driven by Scale

O’Loughlin¹,

White²,

Stanier³

2015

All Days

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FLNG facilities present a more onerous anchoring requirement than existing floating structures. Optimisation of the anchoring technology through improved design or through novel anchor types offers potential cost and risk benefits. These benefits may also be applicable to smaller moorings for MODUs and FPSOs. This paper uses concept-level design calculations of anchor capacity to compare different anchor technologies in the context of FLNG and MODU/FPSO applications. Also, new observations from physical modelling of chain-soil interaction are presented. Opportunities are identified for significant cost and schedule savings by adopting the alternative plate anchor technologies that are either suction or dynamically installed. Considering fabrication alone, the estimated costs are reduced by 70% for FLNG and 80% for MODUs relative to the conventional suction caisson option. When installation vessel costs are considered, the absolute cost saving could be far higher than from fabrication alone because installation could be from an anchor-handling vessel rather than a construction barge with a heavy lift crane. Torpedo anchors have also been considered, but are less attractive. Centrifuge model data and calculations of the shape and capacity of the embedded anchor chain suggest that there may be over-looked capacity from the mooring chain both on and within the seabed. At the same time, upscaling of embedded plates to the scale required for FLNG applications increases the amount of chain slack that would be released into the mooring during in service loading, and this effect requires consideration in the overall mooring system design. Research and development activities aligned with the opportunities for reduced cost and risk in anchoring design are set out. 2

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“…A new hybrid anchoring system, referred to as the dynamically embedded plate anchor (DEPLA), combines the capacity advantages of vertically loaded anchors (Murff et al 2005;Gaudin et al 2006;Wong et al 2012) with the installation advantages of dynamically installed anchors (Medeiros 2001;Zimmerman et al 2009;Lieng et al 2010). The DEPLA comprises a removable central shaft or "follower" that may be fully or partially solid and a set of four flukes (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Installation of dynamically embedded plate anchors as assessed through field tests

Blake

O’Loughlin

2015

Can. Geotech. J.

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A dynamically embedded plate anchor (DEPLA) is a rocket-shaped anchor that comprises a removable central shaft and a set of four flukes. The DEPLA penetrates to a target depth in the seabed by the kinetic energy obtained through free-fall in water. After embedment the central shaft is retrieved leaving the anchor flukes vertically embedded in the seabed. The flukes constitute the load-bearing element as a plate anchor. This paper focuses on the dynamic installation of the DEPLA. Net resistance and velocity profiles are derived from acceleration data measured by an inertial measurement unit during DEPLA field tests, which are compared with corresponding theoretical profiles based on strain rate-enhanced shear resistance and fluid mechanics drag resistance. Comparison of the measured net resistance force profiles with the model predictions shows fair agreement at 1:12 scale and good agreement at 1:7.2 and 1:4.5 scales. For all scales the embedment model predicts the final anchor embedment depth to a high degree of accuracy.Résumé : Un système d'ancrage dynamique à ailerons (« dynamically embedded plate anchor » ou DEPLA) est une ancre en forme de fusée constituée d'un cylindre central et d'une empenne comportant quatre ailerons. Le DEPLA s'enfonce dans le lit de sable à une profondeur cible grâce à l'énergie cinétique acquise au cours de sa descente en chute libre dans l'eau. Après que le dispositif s'est enfoncé dans le sable, la partie cylindrique centrale est retirée, laissant l'empenne enfouie verticalement dans le lit de sable. Les ailerons constituent l'élément porteur de charge comme dans le cas d'un système d'ancrage à plaques. Le présent article décrit l'installation dynamique du DEPLA. Les profils de résistance nette et de vitesse sont obtenus à partir des valeurs d'accélération enregistrées par un appareil de mesure de l'inertie durant les essais du DEPLA sur place et comparés avec les profils théoriques correspondants, basés sur la résistance au cisaillement (qui augmente avec la vitesse de déformation) et la résistance de traînée propre à la mécanique des fluides. Une comparaison entre les profils des forces de résistance nette mesurés et les prédictions des modèles met en évidence une assez bonne concordance à l'échelle 1:12 et une bonne convergence aux échelles 1:7,2 et 1:4,5. Pour toutes les échelles, la modélisation de l'enfouissement de l'ancre permet de prédire la profondeur de pénétration du dispositif d'ancrage dans le sable avec un haut degré de précision. [Traduit par la Rédaction] Mots-clés : ancre, argile, dynamique, traînée dans un fluide, en mer, vitesses de déformation.

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Efficient Gravity Installed Anchor for Deepwater Mooring

Cited by 58 publications

References 3 publications

Offshore Design Approaches and Model Tests for Sub-Failure Cyclic Loading of Foundations

Offshore Design Approaches and Model Tests for Sub-Failure Cyclic Loading of Foundations

Novel Anchoring Solutions for FLNG - Opportunities Driven by Scale

Installation of dynamically embedded plate anchors as assessed through field tests

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