Design and Testing Out of Deepwater Seabed Sampler

Lunne, Tom; Tjelta, Tor Inge; Walta, Axel; Barwise, Andy

doi:10.4043/19290-ms

Cited by 5 publications

(3 citation statements)

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“…Another process that is well known to affect the stiffness and undrained cohesion of clayey sediments is the persistent input of gassy fluids into the porous medium. Several authors have already shown how a few percent of gas saturation is enough to damage the sediment structure and highly affect its shear strength with little effect on its density (Hight & Leroueil, 2003; Lunne et al., 2001; Sultan et al., 2012; Wheeler, 1988; Zhu et al., 2021). Sultan et al.…”

Section: Discussionmentioning

confidence: 99%

“…Sediment strength and free‐gas dynamics have a coupled relationship. While sediment properties control gas nucleation and migration (Boudreau et al., 2005; Johnson et al., 2002; Sills et al., 1991; Terzariol et al., 2021; Zhou & Katsman, 2022), gas exsolution/dissolution and expansion/compression (Sobkowicz & Morgenstern, 1984) may alter the properties of the host sediments (e.g., elastic and mechanical properties (Barry et al., 2010; Boudreau, 2012)), its compressibility (Blouin et al., 2019; Puzrin et al., 2011; Thomas, 1987) and its shear strength (Hight & Leroueil, 2003; Lunne et al., 2001; Sultan et al., 2012; Wheeler, 1988).…”

Section: Introductionmentioning

confidence: 99%

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Spatial Changes in Gas Transport and Sediment Stiffness Influenced by Regional Stress: Observations From Piezometer Data Along Vestnesa Ridge, Eastern Fram Strait

et al. 2023

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatial Changes in Gas Transport and Sediment Stiffness Influenced by Regional Stress: Observations From Piezometer Data Along Vestnesa Ridge, Eastern Fram Strait

et al. 2023

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“…4, where results from large deformation finite element (LDFE) analyses [23] are compared with resistance curves obtained using Eq. This feature alone would lead to a significant increase in predicted penetration, essentially computing the penetration by taking a = 3 (rather than 6) in the N c term in Eq. A buoyancy factor of f b = 1.5 is needed to match the LDFE results (corresponding to a value of N b ∼ 1 at w/D = 0.5), with the buoyancy resistance then representing up to 16 % (at an embedment of 0.5D) of the total resistance.…”

Section: Static Penetration Resistancementioning

confidence: 99%

Pipeline Embedment in Deep Water: Processes and Quantitative Assessment

Randolph

White²

2008

All Days

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The paper outlines the processes that determine pipeline embedment in soft sediments typical of deep water, and describes quantitative methods for assessing the contribution to pipeline embedment from each process. The main processes considered are: self-weight, force concentration during installation, and cyclic lateral and vertical motion during pipe-laying. For each process, non-dimensionalized solutions are provided to evaluate embedment for given pipeline and soil properties, and different conditions operative during pipe-laying. Methods to establish a penetration resistance profile using modern penetration testing techniques are described, and the up-scaling of these measurements to pipeline behavior is discussed. The important effects of heave and soil self-weight are also quantified, and the effects of remolding and subsequent reconsolidation following a cyclic event are also demonstrated. Finally, the influence of cyclic motion within the touchdown zone during pipe-laying is explored. Examples of numerical and physical modeling of the lay process show that these dynamic effects can have a dominant influence on the as-laid embedment. Approaches for quantifying this aspect of behavior in design are discussed. OTC 19128and is the parameter that most significantly affects the feasibility of a design [1]. Empirical and theoretical solutions for predicting pipeline embedment are available, but are consistently found to under-estimate the embedment when compared with field survey data, primarily due to additional penetration caused by the static load concentration at the touchdown point, and dynamic oscillations of the pipeline as it is laid [2]. This paper examines recent developments in estimating pipeline penetration, including theoretical studies based on large deformation finite element analysis, and physical model tests to evaluate the effect of cyclic deformations on pipeline penetration. Seabed CharacterizationImproved reliability in estimating pipeline penetration hinges on accurate measurement of the shear strength profile, particularly in the upper 0.5 m of the seabed. Techniques to achieve this include: (a) in situ testing; (b) ship-based vane or penetrometer tests in box-cores recovered from the seabed; (c) laboratory tests on samples obtained from the seabed. All such measurements become more challenging in very soft sediments, either because of disturbance to the recovered samples or, for the in situ testing, due to minor errors in the depth datum or load cell zero readings, both of which become much more significant at shallow depths and low strength material.Modern techniques for obtaining large diameter piston cores have led to improvement in sample quality over most of the sample length [3,4], but any slight delay in triggering the piston of gravity corers will lead to gross disturbance of the very shallow soils, and also to uncertainty in the depth datum [5]. The development of a static sampler activated from a fixed frame [6] should lead to further improvement, provided the shallow material...

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In Situ Geotechnical Investigations

Fernandes

Chaminé

2022

Springer Tracts in Civil Engineering

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Design and Testing Out of Deepwater Seabed Sampler

Cited by 5 publications

References 0 publications

Spatial Changes in Gas Transport and Sediment Stiffness Influenced by Regional Stress: Observations From Piezometer Data Along Vestnesa Ridge, Eastern Fram Strait

Spatial Changes in Gas Transport and Sediment Stiffness Influenced by Regional Stress: Observations From Piezometer Data Along Vestnesa Ridge, Eastern Fram Strait

Pipeline Embedment in Deep Water: Processes and Quantitative Assessment

In Situ Geotechnical Investigations

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