Consolidated undrained load-carrying capacity of subsea mudmats under combined loading in six degrees of freedom

Feng, Xueyang; Gourvenec, Susan

doi:10.1680/geot.14.p.090

Cited by 42 publications

(22 citation statements)

References 20 publications

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“…The steady state coefficient of sliding friction derived from the test observation agrees well with analytical and numerical predictions based on critical state soil mechanics (Cocjin et al 2016;Feng & Gourvenec 2015). shows that a long term sliding resistance given by tanϕ′ where ϕ′ = 23.5° is the internal angle of soil friction, is eventually achieved when the soil has undergone sufficient cycles of sliding (and hence shearing), pore pressure generation and reconsolidation to reach critical state conditions, resulting in no further contraction and excess pore pressure generation (Cocjin et al 2015, Cocjin et al 2016, Feng & Gourvenec 2016.…”

Section: Example Application Of the Multi-dof Loading Systemsupporting

confidence: 72%

A Simple Approach to Multi-Degree-of-Freedom Loading in a Geotechnical Centrifuge

O’Loughlin

Cocjin²,

Gourvenec

et al. 2018

Geotechnical Testing Journal

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This paper considers an alternative approach for multi-planar loading and multi degree-of-freedom movement in geotechnical centrifuge model tests. The multi degree-of-freedom loading system allows for vertical load control on the vertical axis, and either displacement or load control on the two horizontal axes, whilst allowing rotation about these axes. The system is described in detail and the system performance is validated through results from a centrifuge test comparing observed results with analytical and numerical solutions. The validation of the system considers a mudmat foundation under large amplitude lateral displacement, where two displacement degrees-of-freedom and two rotational degrees-of-freedom were of interest. However, the apparatus is versatile and can be used for testing other foundation types or pipelines, with up to six degrees-offreedom. 1. INTRODUCTION Offshore structures are typically subjected to multi-directional loading and respond with displacement in multiple degrees of freedom. Foundations of fixed-base structures, oil and gas platforms or wind turbines, experience a combination of vertical load from the self-weight of the structure, horizontal loads from the action of wind, waves and currents, and moment loading from the height offset between the action of the horizontal loads and the foundation; foundations of subsea structures can experience complex multi-directional loading from multiple pipeline and spool expansion loads acting at vertical and horizontal eccentricities to the centroid of the foundation (Randolph 2012, Feng et al. 2014); offshore pipelines are subject to vertical self-weight loads, multi-directional installation loads and thermally induced axial and lateral loads during operation and respond with settlement/burial, axial walking and lateral buckling. Independent control of loading and acquisition of displacement, or vice versa, in all six degrees of freedom poses quite an experimental challenge for actuation systems. This is more achievable at 1g than in a centrifuge as the space requirements for the actuation and position measurement systems can be more easily accommodated on the laboratory floor than within the constrained space available on a centrifuge package (Byrne 2014). Centrifuge actuators typically have two or three displacement degrees of freedom (DoF) along the horizontal and vertical planes, although actuation systems that add a rotational DoF have also been developed

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Section: Example Application Of the Multi-dof Loading Systemsupporting

confidence: 72%

A Simple Approach to Multi-Degree-of-Freedom Loading in a Geotechnical Centrifuge

O’Loughlin

Cocjin²,

Gourvenec

et al. 2018

Geotechnical Testing Journal

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“…where the increase in operative soil strength is linked to the pipe weight. The observed increase in 388 lateral breakout capacity, Hult, due to consolidation is higher than the predicted gain in vertical 389 pipe capacity, Vult, consistent with analysis of mudmat foundations (Feng and Gourvenec (2015)). 390…”

Section: Comparison With Theoretical Solutions For the Consolidated supporting

confidence: 60%

“…The increase in the vertical and lateral breakout capacities through consolidation as 382 observed in the present set of centrifuge test results is predicted well through Equations 15 -16 383 using the scaling parameters f fsu(V) = 0.439 derived in FEA studies carried out by Chatterjee et 384 al. (2014) for pipe, and f fsu(H) = 0.919 derived by Feng and Gourvenec (2015) as shown in 385 Figure 11. The results demonstrate that the expansion of the failure envelopes through 386 consolidation is captured well by the theoretical framework outlined by Gourvenec et al (2014), 387…”

Section: Comparison With Theoretical Solutions For the Consolidated mentioning

confidence: 95%

Softening and consolidation around seabed pipelines: centrifuge modelling

2018

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Solutions for lateral breakout and axial response of submarine pipelines are well established if the 20 undrained shear strength conditions of the soil are known and defined simply (such as uniform or increasing proportionally with depth). In reality, the geometry of the free surface and the 22 distribution of undrained shear strength around a submarine pipeline post-lay are affected by the 23 lay process. This is because of soil berms that form adjacent to the pipe, and remoulding and 24 subsequent reconsolidation of the seabed. The effect of post-lay consolidation on the subsequent 25 lateral and axial response of submarine pipelines has not been previously investigated through 26 physical model testing. 27 This paper presents results from centrifuge model tests describing lateral breakout behaviour of a 28 pipe on soft clay as a function of (i) pipe installation conditions, (ii) post-lay pipe weight and (iii) 29 consolidation prior to break out. In addition, the effect of post-lay consolidation on axial pipe 30 response is studied. The experimental results are compared with available numerical and 31 analytical predictions. 32 The results quantify the influence of the installation process, pipe weight and post-installation 33 consolidation on the lateral break out resistance and trajectory of the pipe and also the axial pipe 34 response, and show how existing prediction methods can capture these effects.

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“…Undrained capacity is considered, given that the operational loading rates for subsea mudmats are determined by the rate of the heating and cooling processes of the attached pipelines, which typically take place over a few hours (Jayson et al 2008), a time frame to ensure an undrained response around the foundation of a subsea structure in most fine grained materials (Feng & Gourvenec 2015). …”

Section: Effect Of Interface Condition On the Undrained Capacity Of Smentioning

confidence: 99%

Effect of interface condition on the undrained capacity of subsea mudmats under six-degree-of-freedom loading

2017

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Consolidated undrained load-carrying capacity of subsea mudmats under combined loading in six degrees of freedom

Abstract: Published in

Cited by 42 publications

References 20 publications

A Simple Approach to Multi-Degree-of-Freedom Loading in a Geotechnical Centrifuge

A Simple Approach to Multi-Degree-of-Freedom Loading in a Geotechnical Centrifuge

Softening and consolidation around seabed pipelines: centrifuge modelling

Effect of interface condition on the undrained capacity of subsea mudmats under six-degree-of-freedom loading

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