Shallow penetrometer tests: theoretical and experimental modelling of the rotation stage

Schneider, Mark; Stanier, Sam; White, David; Randolph, Mark

doi:10.1139/cgj-2018-0657

Cited by 3 publications

(3 citation statements)

References 27 publications

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“…This value is similar to the spacing ratio 231 between the intact and remoulded or critical state lines, which controls the gain in strength 232 predicted from these critical state-type frameworks. Parallel work for the axial friction on 233 pipelines and shallow penetrometers shows that the undrained strength of normally-234 consolidated soil can rise by this ratio under episodes of sliding failure and reconsolidation 235 (White et al 2015, Schneider et al 2019). The present study suggests that the same ratio may 236 be generally applicable for bearing-type loading.…”

Section:  Consolidation Immediately Following the Initial Penetration (Ie Without Load Cycles 189mentioning

confidence: 99%

Load-controlled cyclic T-bar tests: a new method to assess effects of cyclic loading and consolidation

O’Loughlin

Zhou

Stanier

et al. 2020

Géotechnique Letters

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Full-flow T-bar and ball penetrometer tests are often used to measure intact and remoulded soil 46 strengths, with the latter determined after several large amplitude displacement cycles. In 47 offshore design the remoulded soil strength is often the governing design parameter during 48 installation of subsea infrastructure, whilst a 'cyclic strength' applies for the less severe 49 operational cyclic loading. This paper utilises T-bar penetrometer tests to measure both 50 remoulded and cyclic strengths, where the latter is determined via a new test protocol involving 51 cycles between load rather than displacement limits. The tests use kaolin clay and a 52 reconstituted carbonate silt and involve three cyclic phases with intervening consolidation 53 periods. The results demonstrate the important and beneficial role of consolidation, with the 54 loss in strength due to remoulding sometimes surpassed by the strength recovery from 55 consolidation. The most significant gains in strength, to 2.5 times the initial value, were 56 measured in the load-controlled cyclic tests. These data demonstrate a novel way to characterise 57 undrained cyclic strength, taking advantage of consolidation to reduce conservatism.

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Section:  Consolidation Immediately Following the Initial Penetration (Ie Without Load Cycles 189mentioning

confidence: 99%

Load-controlled cyclic T-bar tests: a new method to assess effects of cyclic loading and consolidation

O’Loughlin

Zhou

Stanier

et al. 2020

Géotechnique Letters

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“…This paper and the accompanying companion paper (Schneider et al 2020b) describe new interpretation methodologies for these box-core scale penetrometers and validate their operation in laboratory conditions. This paper illustrates the fundamentals of the penetration and dissipation phase, while the rotation stage is outlined in the companion paper.…”

Section: Introductionmentioning

confidence: 93%

Shallow penetrometer tests: theoretical and experimental modelling of penetration and dissipation stages

et al. 2020

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Shallow penetrometers are devices that penetrate into and measure the properties of surficial offshore sediments via multi-phase tests involving penetration, dissipation, and rotation stages. In fine-grained soils such as silts and clays, these testing stages yield undrained strength, consolidation, and friction properties relevant to subsea pipeline and shallow foundation design. This paper describes toroid and hemiball devices of the scale for use in box-core samples and associated interpretation methods for the penetration and dissipation stages. The aim of the paper is to provide all tools needed to design and interpret these tests. New large-deformation finite element (LDFE) dissipation solutions are presented, which can be used for back-analysis of the dissipation stage. Results of an extensive laboratory proof testing exercise in kaolin clay, for both the hemiball and toroid penetrometers, are also reported. These results highlight the potential of the two devices to quickly and economically assess strength and consolidation characteristics of fine-grained sediments in box-core samples recovered to the deck of a site investigation vessel.

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“…Shallow penetrometers have been inspired by the needs of surfacelaid pipeline design, for which episodic hardening can be a key parameter. Versions of these penetrometers scaled for use in box cores have been successfully trialled within the RIGSS JIP (www.rigssjip.com) [66,67].…”

Section: In Situ or Model Test Determinationmentioning

confidence: 99%

Whole Life Design: Theory and Applications of This New Approach to Offshore Geotechnics

Gourvenec

2022

Indian Geotech J

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Geotechnical properties can evolve throughout the design life of a structure due to actions imposed during installation, the operational life or late and end of life management of an asset. Whole life geotechnical design seeks to predict soil-structure responses across the design life by considering the whole life of imposed actions coupled with geotechnical properties that evolve with each action. In contrast, traditional geotechnical design considers the ‘worst case’ single value of minimum resistance or stiffness coupled with the ‘worst case’ single value of maximum action over the design life. The emerging philosophy of whole life geotechnical design checks limit states at different stages of the ‘whole life’ against ‘current’ geotechnical properties, updated based on the processes that have occurred and the responses that have accumulated earlier in the design life. Consideration of whole life geotechnical response provides greater insight, enabling forecasting of the response of a supported structure through and beyond its design life. Insights can be applied at the initial design stage for optimal sizing; through life for assessing or predicting cumulative displacements or changes in resistance, and assumptions in the initial design against observed performance. By extension, these insights can be used to predict actual remaining design life; for re-lifing or re-purposing; and decommissioning. This paper presents the overarching philosophy of whole life geotechnical design, theory underpinning the evolution of geotechnical properties, derivation of the appropriate parameters, and some applications. This paper demonstrates the potential of whole life design, particularly to the emerging opportunities of offshore renewable energy infrastructure.

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Shallow penetrometer tests: theoretical and experimental modelling of the rotation stage

Cited by 3 publications

References 27 publications

Load-controlled cyclic T-bar tests: a new method to assess effects of cyclic loading and consolidation

Load-controlled cyclic T-bar tests: a new method to assess effects of cyclic loading and consolidation

Shallow penetrometer tests: theoretical and experimental modelling of penetration and dissipation stages

Whole Life Design: Theory and Applications of This New Approach to Offshore Geotechnics

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