Albacora Leste Field Development-
            FPSO P-50 Mooring System Concept and Installation

a b s t r a c tTorpedo anchors (of diameter $ 1 m) are released from a height of 50-100 m from the seabed, achieving velocities up to 35 m/s at impacting the sediment. The strain rates induced in the surrounding soil by this dynamic installation is therefore significantly higher than those associated with installation of other offshore foundations and anchoring systems. The high strain rates enhance the mobilised undrained shear strength compared to that measured by in-situ penetrometer or laboratory tests. This paper reports the results from dynamic installation of a torpedo anchor in strain softening, rate dependent soft clays, quantifying the effects relative to results for ideal Tresca material. The three-dimensional dynamic large deformation finite element (LDFE) analyses were carried out using the coupled EulerianLagrangian approach. The simple elastic-perfectly plastic Tresca soil model was modified to allow strain softening and strain rate dependency of the shear strength. Parametric analyses were undertaken varying the strain rate parameter, the sensitivity and ductility of the soil, and the soil undrained shear strength. Overall, embedment depth for rate dependent, strain softening clays lay below that for ideal Tresca material. Increased strain rate dependency of the soil led to marked reduction in embedment depth, only partly compensated by brittleness. Key results have been presented in the form of design charts, fitted by simple expressions to estimate the embedment depth of a torpedo anchor.

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“…1; Brandão et al, 2006). They are released from a height of 50-100 m from the seabed, achieving velocities up to 35 m/s.…”

Section: Introductionmentioning

confidence: 99%

Effect of strain rate and strain softening on embedment depth of a torpedo anchor in clay

2015

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“…In recent years, broadly three DIA geometries have evolved including (a) dynamically penetrating anchor (Lieng et al 1999(Lieng et al , 2000(Lieng et al , 2010, (b) torpedo anchor (de Araujo et al 2004;Brandão et al 2006), (c) OMNI-max anchor (Zimmerman et al 2009;Shelton et al 2011). …”

Section: Geometry and Parametersmentioning

confidence: 99%

“…A distinguished strong or crust layer (either at the surface or underlaid by a soft mud layer) is prevalent in both shallow and deep ocean in the West coast of Africa, the Sunda Shelf, offshore Malaysia, Australia's Bass Strait and North-West Shelf (Castleberry II and Prebaharan, 1985;Ehlers et al 2005;Erbrich 2005;Colliat et al 2011;Kuo and Bolton 2013;Hossain et al 2014a). Layered deposits are also encountered at the Campos Basin, offshore Brazil and the Troll field in the North Sea, offshore Norway (Argiolas and Rosas 2003;Brandão et al 2006;Zimmerman et al 2009;Lieng et al 2010). Figure 1 shows examples of layered seabed with a surface and embedded strong layer.…”

Section: Introductionmentioning

confidence: 99%

Dynamic installation of a torpedo anchor in two-layered clays

Kim¹,

Hossain²,

Lee

2018

Can. Geotech. J.

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The behaviour of a torpedo anchor during dynamic installation in two-layered nonhomogeneous clay sediments was investigated through large-deformation finite-element (LDFE) analyses. Parametric analyses were undertaken varying the top layer thickness and strength ratio between two layers. Results show that the location of the demarcation point between the acceleration and deceleration phases of the anchor in the soil relative to the layer interface is the key factor directing the anchor behaviour in layered soils including the final embedment depth. Broadly speaking, the anchor behaviour in soft-over-stiff clay deposits is somewhat similar to that in single layer clay with strength increasing with depth. In stiff-over-soft clay deposits, the anchor penetrates deeper where the anchor deceleration phase (or the demarcation point) falls within the soft layer. Where the demarcation point lies within the top stiff layer, the anchor penetration depth decreases with increasing strength ratio, and the anchor penetration is terminated between the two layers for strength ratios ≥15. For assessing the anchor embedment depth in two-layered fine-grained ocean sediments in the field, an extended total energy–based method, along with a design expression, is proposed.

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“…It is chiefly based on Newtonian mechanics and assumes uniform clay. Several investigations have used similar approaches based on True's model for freefall anchor installation (de Araujo, 2004;Brandão, 2006;O'Loughlin, , 2013Hossain, 2014). A modified equation of motion is shown in Eq.…”

Section: Modified Bearing Resistance Approachmentioning

confidence: 99%

Damage Assessment of Free-fall Dropped Object on Sub-seabed in Offshore Operation

Won

Kim²,

Park

et al. 2015

Journal of Advanced Research in Ocean Engineering

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This paper presents the damage assessment of a free-fall dropped object on the seabed. The damage to a dropped object totally depends on the relationship between the impact energy and the soil strength at the mudline. In this study, unexpected dropping scenarios were first assumed by varying the relevant range of the impact velocity, structure geometry at the moment of impact, and soil strength profile along the penetration depth. Theoretical damage assessments were then undertaken for a free-fall dropping event with a fixed final embedment depth for the structure. This paper also describes the results of a three-dimensional large deformation finite element analysis undertaken for the purpose of validation. The analyses were carried out using the coupled Eulerian-Lagrangian approach, modifying the simple elastic-perfectly plastic Tresca soil model. The validation exercises for each dropping scenario showed good agreement, and the present numerical approach was capable of predicting the behavior of a free-fall dropped object.

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Albacora Leste Field Development- FPSO P-50 Mooring System Concept and Installation

Cited by 50 publications

References 3 publications

Effect of strain rate and strain softening on embedment depth of a torpedo anchor in clay

Effect of strain rate and strain softening on embedment depth of a torpedo anchor in clay

Dynamic installation of a torpedo anchor in two-layered clays

Damage Assessment of Free-fall Dropped Object on Sub-seabed in Offshore Operation

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