Bearing capacity on sand overlying clay soils: a simplified conceptual model

Lee, K.K.; Randolph, Mark; Cassidy, Mark

doi:10.1680/geot.12.p.176

Cited by 81 publications

(58 citation statements)

References 17 publications

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“…For assessing spudcan penetration resistance in a sandover-clay layering system, four existing design methods are compared in this study, including: (a) load spread method; (b) punching shear method; (c) the method by Lee et al (2013aLee et al ( , 2013b, referred to herein as the ' Lee et al method'; and (d) the method by Hu et al, (2014aHu et al, ( , 2014bHu et al, ( , 2015, referred to herein as the 'Hu et al method'. The first two methods are recommended in the current design guidelines -ISO standard 19905-1 (ISO, 2012)while the other two were proposed recently.…”

Section: Design Methods Existing Design Methods For Sand-over-clay: Pmentioning

confidence: 99%

“…This is termed as 'punch-through' failure, implying a rapid rate of penetration. New mechanism-based design methods (Lee et al, 2013a(Lee et al, , 2013bHu et al, 2014aHu et al, , 2014bHu et al, , 2015 have recently been proposed for estimating the peak bearing capacity in the surface sand layer and the bearing capacity in the underlying clay layer. However, their applicability in multi-layer soils with an overlying clay layer (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigation of spudcan penetration in multi-layer deposits with an interbedded sand layer

2017

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For calculating spudcan penetration resistance in an interbedded sand layer between two clay layers, the recently developed mechanism-based design methods for surface sand-over-clay deposits are extended to account for the influence of the overlying clay layer. A series of large-deformation finite-element (LDFE) analyses were carried out, varying layer geometries and strength parameters. The numerical results and existing centrifuge test data are used to calibrate the extended design methods. The performance of the modified design methods and those suggested in the ISO standard 19905-1 is compared, confirming the accuracy of the former methods in estimating the peak penetration resistance in the sand layer. LDFE analyses were also carried out adding a strong fourth layer, with the corresponding effects on the increasing peak resistance in the second (sand) layer and squeezing behaviour (or limiting squeezing depth) in the third (soft clay) layer discussed. Design formulas are also developed to estimate the increase of peak resistance and limiting squeezing depth due to the presence of the strong fourth layer.

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Section: Design Methods Existing Design Methods For Sand-over-clay: Pmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical investigation of spudcan penetration in multi-layer deposits with an interbedded sand layer

2017

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“…The reason lies in that the increasing bearing capacity of the foundation induced by a soil plug trapped below the spudcan is not accounted for in the guideline. A new calculation method accounting for the new failure mechanism was first proposed by Lee et al [54] and was further improved by Hu et al [55]. The peak resistance is the sum of the frictional resistance in sand and the bearing capacity of the underlying clay (the first term in eq.…”

Section: Penetration Of Spudcans (1) Bearing Capacity Failure In Unifmentioning

confidence: 99%

On the instability of offshore foundations: theory and mechanism

Gao

et al. 2015

Sci. China Phys. Mech. Astron.

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As the offshore engineering moving from shallow to deep waters, the foundation types for fixed and floating platforms have been gradually evolving to minimize engineering costs and structural risks in the harsh offshore environments. Particular focus of this paper is on the foundation instability and its failure mechanisms as well as the relevant theory advances for the prevailing foundation types in both shallow and deep water depths. Piles, spudcans, gravity bases, suction caissons, and plate anchors are detailed in this paper. The failure phenomena and mechanisms for each type of foundations are identified and summarized, respectively. The theoretical approaches along with sophisticated empirical solutions for the bearing capacity problems are then presented. The major challenges are from flow-structure-soil coupling processes, rigorous constitutive modeling of cyclic behaviors of marine sediments, and the spatial variability of soil properties for large-spreading structures. Further researches are suggested to reveal the instability mechanisms for underpinning the evolution of offshore foundations. Citation:Gao F P, Li J H, Qi W G, et al. On the instability of offshore foundations: theory and mechanism.

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“…A new conceptual model has been derived, based on this, and is detailed in Lee et al (2013). This paper also discusses the effect of having a surcharge above the sand layer.…”

Section: Development Of a New Conceptual Modelmentioning

confidence: 99%

Bearing capacity on sand overlying clay soils: experimental and finite-element investigation of potential punch-through failure

Lee

Cassidy²,

Randolph³

2013

Géotechnique

Self Cite

108

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When a jack-up spudcan foundation is installed on seabeds consisting of a sand layer overlying soft clay, the potential for 'punch-through' failure exists. This happens as a result of an abrupt reduction in bearing resistance when the foundation punches a block of sand into the underlying soft clay in an uncontrolled manner. This paper details an extensive series of 30 tests of flat circular and spudcan foundations continuously penetrated through samples of sand overlying clay, and performed under relevant stress conditions using a drum centrifuge. The large testing area of the drum centrifuge was used advantageously to produce test results that could be compared directly with tests covering a sand thickness over foundation diameter of 0 . 21 to 1 . 12. Results from retrospective finite-element analysis of the experiments are also described, with back-calculated values of the stress-level-dependent friction and dilation angles in the sand during peak penetration resistance shown to fit correlations in the literature. The back-analysis showed that larger values of peak resistance gave lower friction and dilation angles, which is consistent with gradual suppression of dilatancy under high confining stress. When compared with published results from visualisation experiments, the finite-element analysis showed a similar failure mechanism during peak resistance, with a frustum of sand forced into the underlying clay at an angle reflecting the dilation in the sand.

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Bearing capacity on sand overlying clay soils: a simplified conceptual model

Cited by 81 publications

References 17 publications

Numerical investigation of spudcan penetration in multi-layer deposits with an interbedded sand layer

Numerical investigation of spudcan penetration in multi-layer deposits with an interbedded sand layer

On the instability of offshore foundations: theory and mechanism

Bearing capacity on sand overlying clay soils: experimental and finite-element investigation of potential punch-through failure

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