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

Randolph, Mark

doi:10.1007/978-3-7091-1068-3_9

Cited by 18 publications

(7 citation statements)

References 13 publications

(13 reference statements)

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“…Under average compressive load, the foundation displaced downwards continously and the rate of displacement (Δw max/d)/ΔΝ remained constant and generally lower than 0.2% throughout the test. These results are consistent with other published findings that the direction of vertical displacement of a skirted foundation depends on the average vertical stress rather than the maximum vertical stress (Bye et al 1995, Byrne & Houlsby 2002, Kelly et al 2006, Randolph 2012.…”

Section: Comparison Of Foundation Response Under Cyclic Loading In Avsupporting

confidence: 93%

“…The contours of maximum shear strain, γmax, are presented as a function of maximum shear stress, τmax, normalised by the monotonic DSS strength, s u. The DSS tests used to develop the contour diagram are considered relevant here as DSS strength can be considered as an average strength between triaxial compression and triaxial extension (Mayne 1985, Randolph 2012. The DSS strength is considered representative of the range of stress paths in the soil surrounding and beneath a shallow foundation and therefore of the soil strength mobilised by a foundation at failure.…”

Section: Failure Criteria On a Shear Strain Contour Diagrammentioning

confidence: 99%

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Vertical cyclic loading response of shallow skirted foundation in soft normally consolidated clay

2019

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Skirted foundations are a potential foundation solution for a range of offshore structures, including hydrocarbon and renewable energy platforms and subsea structures. Offshore foundations can be subject to cyclic loading from environmental, installation, and operational events affecting the geotechnical response. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of vertical cyclic load sequences to investigate the effect of tensile or compressive average stress, the magnitude of the applied stress, and the effect of cyclic loading of low magnitude followed by consolidation on the foundation response. Results are presented as vertical foundation displacements normalized by the foundation geometry and interpreted within the traditional shear-strain contour approach. The findings indicate that the average, rather than maximum, vertical stress defines the foundation vertical displacement response and failure mode, a threshold stress exists below which a steady state is maintained even at a high number of cycles, and geotechnical resistance increases as a result of low-level cyclic loading followed by consolidation.

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Section: Comparison Of Foundation Response Under Cyclic Loading In Avsupporting

confidence: 93%

Section: Failure Criteria On a Shear Strain Contour Diagrammentioning

confidence: 99%

Vertical cyclic loading response of shallow skirted foundation in soft normally consolidated clay

2019

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“…DSS tests were chosen in this study as this type of tests is generally preferred in offshore geotechnical site investigation due to the efficiency of sample size and as shear strength from monotonic DSS tests, or simple shear tests, is considered approximately equal to the average soil strength in triaxial compression and extension (Mayne 1985, Randolph 2012 and therefore applicable to a range of stress paths encountered beneath a shallow foundation. It is noted that DSS tests (Bjerrum & Landva 1966) and simple shear tests (Joer et al 2011, Carraro 2017 are distinguished based on the boundary conditions on the specimen.…”

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confidence: 99%

Response of normally consolidated kaolin clay under irregular cyclic loading and comparison with predictions from the accumulation procedure

2019

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The accumulation procedure on contour diagrams of shear strain is used in geotechnical design to account for the effect of cyclic loading on offshore foundations. In this paper, contour diagrams of maximum shear strain are presented based on a series of stress-controlled, symmetrical and non-symmetrical, cyclic direct simple shear tests on normally consolidated kaolin clay that can be used to re-examine the extensive database of model testing in kaolin clay. It is shown that the failure under non-symmetrical cyclic loading can be defined at a higher maximum shear strain than under symmetrical loading, offering potential opportunities for reducing foundation sizes for structures that are less sensitive to displacement. Staged tests with parcels of uniform amplitudes have been also performed to compare the measured shear strains with the values predicted by the accumulation procedure. It is shown that the accumulation procedure predicts the strain measured in the symmetrical staged tests well but overpredicts shear strains measured in the non-symmetrical staged tests. KeywordsCyclic loading; normally consolidated clay; direct simple shear test List of notation a fitting parameter for contour diagram of γmax b fitting parameter for contour diagram of γmax c fitting parameter for contour diagram of γmax CSR cyclic stress ratio DSS direct simple shear e0 void ratio (as extruded) f frequency Gcyc cyclic shear modulus Gs specific gravity Published in Géotechnique https://doi.

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“…Low-amplitude repetitive drained loading may hinder the longterm performance of engineered and natural systems (Lekarp and Dawson 1998;Suiker et al 2005;Okamoto et al 2018;Maqsood et al 2020;Wang et al 2020;Zhao et al 2020;Postill et al 2021). The study of soil responses to repetitive mechanical loads has taken place in the context of highway design (Pell 1973;Sharp and Booker 1984;Brown 1996;Miller et al 2000;Nowamooz et al 2013), machine foundations (Anderson 2009), oil platforms (Bjerrum 1966), grain silos (Rahal and Vuez 1998), and wind turbine foundations (White and Lehane 2004;LeBlanc et al 2010;Cuéllar et al 2012;Randolph 2012;He et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Long-Term Response of Sand Subjected to Repetitive Simple Shear Loading: Shakedown, Ratcheting, and Terminal Void Ratio

Cha

Park

Santamarina

2023

J. Geotech. Geoenviron. Eng.

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Low-amplitude repetitive drained loading may hinder the long-term performance of engineered and natural systems. This study examines the volumetric and shear response of a uniform quarzitic sand subjected to repetitive drained simple shear loading under constant vertical stress while tracking the evolution of the secant stiffness and the small-strain shear modulus. We explore the effects of initial density, initial shear stress and cyclic shear stress amplitude to identify criteria that can be used to anticipate asymptotic volumetric and shear states. We analyze experimental results in reference to the sand response under monotonic simple shear loading. All specimens evolved toward some asymptotic terminal void ratio e T when subjected to simple shear cycles. Contractive specimens exhibited unceasing shear strain accumulation and ratcheting when the normalized shear stress exceeded τ Ã ¼ ðτ o þ Δτ Þ=τ ult > 0.85; on the other hand, dense-dilative specimens exhibited ratcheting only when the normalized shear stress exceeded τ Ã ¼ ðτ o þ Δτ Þ=τ ult > 1.25. The small-strain G max and the secant G pp shear moduli increased during repetitive shear cycles to reflect early fabric changes followed by abrasion/fretting among enduring contacts. Results obtained in this study allow us to propose simple guidelines to predict the asymptotic shear and volumetric response of uniform sands subjected to repetitive simple shear loading for first-order engineering analyses.

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

Cited by 18 publications

References 13 publications

Vertical cyclic loading response of shallow skirted foundation in soft normally consolidated clay

Vertical cyclic loading response of shallow skirted foundation in soft normally consolidated clay

Response of normally consolidated kaolin clay under irregular cyclic loading and comparison with predictions from the accumulation procedure

Long-Term Response of Sand Subjected to Repetitive Simple Shear Loading: Shakedown, Ratcheting, and Terminal Void Ratio

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