Closure to “Liquefaction Potential at Ekofisk Tank in North Sea”

Lee, Kenneth L.; Focht, John A.

doi:10.1061/ajgeb6.0000226

Cited by 6 publications

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“…A more realistic approach in evaluating the stability of offshore foundations during an ocean storm should take into account the generation as well as the dissipation of pore pressures in the sand during the storm period. Lee and Focht (1975) also evaluated the liquefaction potential of the Ekofisk tank considering all possible configuration of waves for the 100 year storm. A design curve for the 100 year storm, which represents the equivalent uniform cyclic stresses induced by the storm, was produced.…”

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

“…By comparison of these two sets of curves, it was concluded that the sand with 100% relative density would be safe against the 100 year storm whereas sands with either of the lower densities would not. Lee and Focht (1975) then extended their studies to consider the effects of pore pressure dissipation during storm loading. Using knowledge of the coefficient of permeability and the modulus of compressibility of the sand, the time period for 10% consolidation was estimated.…”

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

“…While the approach introduced by Lee and Focht (1975) provides an excellent example of a practical method of studying the development of pore water pressures beneath an offshore tank, the method used to include the effect of pore pressure dissipation during a storm incorporates approximations that introduces additional uncertainty.…”

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

“…For the purposes of economy and convenience, the actual time history of the storm was replaced by that of an equivalent storm producing the same overall effects. This equivalent storm was determined using the weighting procedure for wave effects described by Lee and Focht (1975) and Seed et al (1975b). Two zones, one just beneath the centre of the tank and another beyond the edge of the tank, were considered to be the zones where significant pore pressure ratios are likely to develop.…”

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

“…The first and simplest form of study was performed by Bjerrum (1973), in which the effects of drainage and stress distributions in the soil under the foundation were completely ignored. Lee and Focht (1975) extended the method presented by Bjerrum and considered the effects of pore pressure dissipation during storm loading using results from experimental studies. In their work, the results of a series of cyclic load tests on samples of sand, obtained under partially drained conditions, were used.…”

Section: 61: Historical Backgroundmentioning

confidence: 99%

See 4 more Smart Citations

A semi‐empirical method for the liquefaction analysis of offshore foundations

Taiebat

Carter

2000

Int. J. Numer. Anal. Meth. Geomech.

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SUMMARYThis paper presents a relatively simple method for three-dimensional liquefaction analysis of granular soil under o!shore foundations. In this method, the Mohr}Coulomb model, which de"nes the elasto}plastic stress}strain relationship under monotonic loading, is modi"ed to accommodate the plastic strains generated by cyclic loading. The e!ects of cyclic loading, evaluated from the results of laboratory tests on saturated samples of soil, are incorporated into the model. The method is implemented in an e$cient "nite element program for analyses of three-dimensional consolidating soil. The practicability of the model is demonstrated by analysis of a typical o!shore foundation, and the predictions of the numerical analysis are compared with the observed behaviour of the foundation.

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Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

Section: 6: Liquefaction Analyses Of Foundations Under Storm Loadingmentioning

confidence: 99%

Section: 61: Historical Backgroundmentioning

confidence: 99%

See 3 more Smart Citations

A semi‐empirical method for the liquefaction analysis of offshore foundations

Taiebat

Carter

2000

Int. J. Numer. Anal. Meth. Geomech.

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Structural safety of an ocean outfall against hurricane damage

1990

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Travelling wave-induced liquefaction of sand deposits

Yang¹,

Poorooshasb²,

Cheung³

1994

Can. J. Civ. Eng.

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The sea-floor deposit is assumed to be a saturated porous medium modelled by a two-phase system for which the coupled governing equations are derived from the theory of mixture. A constitutive model based on the generalized plasticity-bounding surface formulation is proposed to describe the soil behavior. An artificial boundary is suggested to deal with the unbounded domain problem. Thc coupled governing equations and the material model have been implemented into a nonlinear finite element program to analyze the travelling wave-induced liquefaction of seabed deposits. The rcsults of two case studies are presented. The first case examines the response of sand deposit to the wave train at a site of underwater pipelines for nuclear power plants in Lake Ontario where the deposit was found to vary from loose to medium dense. The second case investigates the sea-floor behavior under a storm wave at the Ekofisk oil tank site in the North Sca where the deposit was reported to be dense. The results agree with the field observations.Ke? ~vorc1.s: seabed instability, liquefaction, finite element, plasticity, sand, cyclic loading, travelling wave, unbounded domain.On a Cmis I'hypothkse que les dCpBts de fond ocCaniq~~e constituent un milieu poreux sature, niodellisC par un systkme a deux phases pour lequel les Cquations principales co~~plCes sont obtenues a partir de la thiorie du melange. Un modkle constitutif base sur la formule gCnCralis6e plasticit&-surface de delimitation est suggCrC pour dCcrire le comportement du sol. Une frontikre artificielle est proposee afin de tenir compte du problkme du domaine illimitC. Les Cquations principales co~~pldes et le modele de materiau ont ete mis en oeuvre sous forme de programme non IinCaire d'CICments finis afin d'analyser la liquefaction des depbts de fond marin provoquee par I'onde progressive. Les rksultats de deux Ctudes de cas sont prCsentCs. Le premier cas examine la rCaction des dCp6ts de sable au train d'ondes sous les pipelines submerges de centrales nuclCaires du lac Ontario oil les dCpBts varient de meubles 2 moyennement denses. Le second cas analyse le co~nportement du fond ocCanique soumis a une onde de temp&te aux installations de stockage dc petrole de Ekofisk, dans la mer du Nord, oh les dCpBts sont denses. Les rCsultats obtenus correspondent ;tux observations in situ.Mots clks : instabilitk du fond ocCanique, IiquCfaction, ClCment fini, plasticite, sable, chargement cyclique, onde progressive. domaine illimitk.[Traduit par la redaction]Can.

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Closure to “Liquefaction Potential at Ekofisk Tank in North Sea”

Cited by 6 publications

References 0 publications

A semi‐empirical method for the liquefaction analysis of offshore foundations

A semi‐empirical method for the liquefaction analysis of offshore foundations

Structural safety of an ocean outfall against hurricane damage

Travelling wave-induced liquefaction of sand deposits

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