Applicability of the strain accumulation procedure for the geotechnical foundation design of zero-radius bend triggers

Zografou, Dimitra; Gourvenec, Susan; O’Loughlin, Conleth; Banimahd, Meysam

doi:10.1016/j.oceaneng.2019.05.044

Cited by 2 publications

(3 citation statements)

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“…The cyclic stresses in the uniform cyclic tests -symmetrical and nonsymmetrical with CSR = 1 -were selected such that there would be sufficient data to fit strain contours in the respective contour diagrams. Non-symmetrical tests with uniform amplitudes and τave > τcyc were also conducted, and in particular with CSR = 0.26 and 0.42, with shear stresses representative of the loading conditions of a subsea zero-radius bend trigger during pipe-laying (Peek & Kristiansen 2009, Zografou et al 2018. The cyclic shear stresses in the staged tests, with the exception of one test [StCs1], were chosen so that failure would not occur in any of the parcels, allowing the effect of cyclic stress history to be investigated.…”

Section: Testing Proceduresmentioning

confidence: 99%

“…The dataset of contour diagrams developed in this study provides a useful tool for the interpretation of model test data, as kaolin is a material used extensively for research and a large existing dataset of physical modelling results involving cyclic loading on kaolin is available in the public domain (e.g. Clukey et al 1995, Chen & Randolph 2007, Acosta-Martinez & Gourvenec 2008, Zografou et al 2018.…”

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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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Section: Testing Proceduresmentioning

confidence: 99%

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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 normalised shear stress and number of cycles at failure are also plotted on the contour diagram on Figure 10 for the centrifuge test with low-level cyclic loading followed by a consolidation period and a parcel of cyclic loading of high magnitude [LOW_CONS_HIGH] (q V,max/qV,ult = -0.95 and N = 41). It is noted that the first parcel with qV,max/qV,ult = -0.36 (-0.10 ± 0.30) and N = 1080 plots near the horizontal contour of 1% and is not considered in the accumulation procedure (Zografou et al 2018a, Zografou et al 2018b. As shown in Figure 9 and discussed above, T-bar tests through the foundation footprint in the cyclic test with the same sequence until the end of consolidation period [LOW_CONS indicated that the increase in s u is between 20%, close to the centre of the foundation and up to 70% close to the edges of the foundation.…”

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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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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Applicability of the strain accumulation procedure for the geotechnical foundation design of zero-radius bend triggers

Cited by 2 publications

References 35 publications

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

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

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

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