Consistent preload calculations for jackup spudcan penetration in clays

Dean, E. T. R.

doi:10.1139/t07-108

Cited by 14 publications

(7 citation statements)

References 19 publications

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“…Previous studies on spudcan-footprint interaction, however, have not considered the jack-up operational period, or any elapsed time between the initial and final installation (Stewart & Finnie, 2001;Gaudin et al, 2007;Dean, 2008;Gan et al, 2008;Cassidy et al, 2009). In this paper, the duration of the jack-up operational period and the elapsed time between previous spudcan extraction and spudcan reinstallation were systematically investigated using a centrifuge modelling technique.…”

Section: Introductionmentioning

confidence: 99%

Effect of time on spudcan–footprint interaction in clay

Gan¹,

Leung²,

Cassidy³

et al. 2012

Géotechnique

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Mobile drilling platforms often return to sites where previous installation, operation and extraction have formed footprints on the seabed. Owing to soil consolidation during the jack-up operational period and the intervening period before reinstallation, the interaction between a new spudcan installation and an existing footprint is complex and time dependent. This paper presents a series of drum centrifuge model tests to investigate the changes in the shear strength of soils beneath and adjacent to a spudcan footprint in normally and overconsolidated clays. The changes with time after two different jack-up operational periods are presented. The results reveal that the soil beneath a footprint generally loses some strength initially, owing to soil remoulding, but it subsequently regains its strength with time as it reconsolidates. The soil remoulding and subsequent strength gain are found to be more significant in normally consolidated clay than in overconsolidated clay. A longer jack-up operational period has an effect of strengthening the underlying soil below the spudcan in both clays. The vertical load, induced horizontal load and moment on a spudcan during its reinstallation into an existing footprint at different times after footprint formation are studied. Compared with the load for installing a spudcan for the first time, the load required to reinstall the same spudcan to the same depth is smaller in normally consolidated clay if the elapsed time between footprint formation and spudcan reinstallation is relatively short. The required load for spudcan reinstallation subsequently increases with footprint elapsed time. For overconsolidated clay, the load required for spudcan reinstallation is always smaller than that for initial spudcan installation, irrespective of the time between installations. The effects of original in situ soil strength, changes in soil strength with time and footprint elapsed time on the interaction between spudcan and footprint are examined.Les plates-formes de forage mobiles reviennent souvent sur des sites où des installations, l'exploitation, et des opérations d'extraction précédentes ont formé des empreintes sur le fond marin. Du fait de la consolidation du sol survenue au cours des périodes opérationnelles sur installations de forage autoélévatrices, et de la période qui s'écoule avant la réinstallation, l'interaction entre l'installation d'un nouveau caisson d'enfichage et une empreinte existante est à la fois complexe et tributaire du temps. La présente communication illustre une série d'essais sur maquette centrifuge à tambour effectués pour examiner les variations de résistance au cisaillement des sols sousjacents et adjacents à l'empreinte du caisson d'enfichage, dans des argiles à consolidation normale ou surconsolidées. Les changements survenus en fonction en temps, à la suite de deux périodes opérationnelles avec installations de forage autoélévatrices, sont présentés. Les résultats révèlent que le sol situé sous une empreinte perd génér-alement, dans un premier temps, ...

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Section: Introductionmentioning

confidence: 99%

Effect of time on spudcan–footprint interaction in clay

Gan¹,

Leung²,

Cassidy³

et al. 2012

Géotechnique

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“…Later more related works on the use of upper bound method in some tenacious patterns are reported, notably, the work of Bona (2004), Es-Saheb (2004) and Moller et al (2004), as well as Ebrahimi and Najafizadeh (2004). Also, in the civil engineering field, the upper bound method is widely used in predicting and estimating the loads in the foundations and footings of different shapes, as reported in the last few years, by Zhu and Michalowski (2005), Merifield and Nguyen (2006), Gourvenec et al (2006), Gourvenec (2007), Zhang (2008), Dean (2008) and Yilmaz and Bakir (2009) and most recently by Arabshahi et al (2010), as well as Majidi et al (2011) and Veiskarami et al (2011).…”

Section: Introductionmentioning

confidence: 99%

Analyses of Plane-strain Compression Using the Upper Bound Method

Es-Saheb¹,

Al-Witry²,

Albedah³

2013

RJASET

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Traditional upper bound analyses for plane-strain compression leads to low load prediction values, for a large ratio range of contact Length (L) to thickness (h). These predicted load values are based on deformation fields consisted of rigid regions separated by planes upon which discrete shear occurs. In this study, the relatively simple deformation fields consisted of odd number of triangles such like, 1, 3 and 5, are used. A general minimum solution for this class of upper bounds is derived and found to occur when the base of the center triangle (w) [= 2L/ (n+1)], where n is an odd integer ≥3. Consequently, whether still lower values would occur with this class of field when the ratio(R), of the field triangles side lengths is varied, has been systematically investigated. Thus, the upper bound loads are calculated over a wide range of the ratio (R) and the deformation field parameters. These parameters include the thickness (h) the contact Length (L) and the base of the center triangle (w). It is found that, all the minimum load values occur at unity R ratio and the minimum values of h, L and w. The minimum values obtained for hopt, Lopt and wopt are 1.466, 3.266 and 2.0 units, respectively. Also, the corresponding overall minimum optimal upper bound value found is P/2k = 1.93.

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“…6,[14][15][16][17][18] However, limited studies in the literature for solving the bearing capacity problems of conical footing have been reported. 19,20 As seen in Figure 1, the jack-up structure is utilized for drilling and maintenance works in the oil and gas industry, 21,22 and each of its legs is standing on spudcan, [23][24][25][26][27][28] which has a diameter ranging from 5 to 20 m. 21,29 With the use of the flat base theory, Meyerhof 30 proposed the bearing capacity theory for the conical footing by conducting the loading tests on cones and indicated that when the wedge angle F I G U R E 1 Jack-up rig model (β) increases, the point resistance of a pile with smooth and rough tips are increased and decreased, respectively. By solving the differential equations derived from the combination of the equilibrium equation and yield condition, Houlsby 31 computed the ultimate load of the wedge-shaped footing with the cone test of clayey soil, and the author found that the bearing capacity is considerably influenced by the wedge angle.…”

Section: Introductionmentioning

confidence: 99%

Bearing capacity factors of cone‐shaped footing in meshfree

Phuor

Ganz

Trapper

2022

Num Anal Meth Geomechanics

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Unlike the flat base foundations, the determination of the bearing resistance of the cone-shaped footing in finite element analysis (FEA) might not be carried out without considering the interface model. In addition, the simulations of the FEA is hardly achieved with a large system due to the assembly technique. So, the alternative should be considered. Therefore, this paper proposes a new method for computing the 𝑁 𝑐 , 𝑁 𝑞 and 𝑁 𝛾 factors of the bearing capacity of the rough and smooth cone-shaped foundations by combining the skew boundary condition as the interface model incorporated with the viscoplastic strain method-based meshfree obeying the yield equation of the Mohr-Coulomb (MC). Thus, the factors can be determined exclusively and reported to reach a close agreement with the published data; nevertheless, the discrepancies are also provided. The plastic flow of the soil mechanics is discussed thoroughly. In addition, the effects of soil friction angle (𝜙) and cone-shaped angle (𝛽) on the factors are inspected systematically. Accordingly, the conservation of the Terzaghi's superposition assumption is confirmed, and the bearing capacity factor charts can be established for various combinations of 𝜙 = 5 o -45 o and 𝛽 = 30 o -180 o . Therefore, it may conclude that the results produced by these techniques and the techniques themselves may be applied confidently for solving geotechnical problems, especially for computing the bearing resistance of the soil.

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Consistent preload calculations for jackup spudcan penetration in clays

Cited by 14 publications

References 19 publications

Effect of time on spudcan–footprint interaction in clay

Effect of time on spudcan–footprint interaction in clay

Analyses of Plane-strain Compression Using the Upper Bound Method

Bearing capacity factors of cone‐shaped footing in meshfree

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