Prediction of Breakout Forces for Deepwater Seafloor Objects

Bouwmeester, Diederick; Peuchen, Joek; Wal, T. van der; Sarata, Brenn; Willemse, C.; Baars, Stefan Van; Peelen, Ruud

doi:10.4043/19925-ms

Cited by 8 publications

(4 citation statements)

References 9 publications

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“…The uplift forces required for removal from the seabed are resisted not only by the self-weight of the submerged mudmat, but also by the suction forces potentially developing at the mudmat invert. In soft soil with low permeability, such as the clays or silts commonly encountered in deep waters, these suction forces can be equal to twice the submerged weight of the mudmat (Bouwmeester et al, 2009). In extreme cases, the suction forces may be greater than the lifting capacity of the vessel and lead to hazards during removal (Reid, 2007).…”

Section: Introductionmentioning

confidence: 99%

Effect of perforations on uplift capacity of skirted foundations on clay

Gaudin

Tian

et al. 2014

Can. Geotech. J.

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The retrieval of deep water subsea installations resting on soft soil, such as “mudmat” shallow foundations, can be a difficult and costly operation if significant resistance to uplift is experienced. At the mudmat invert, suctions may develop, increasing the uplift resistance to greater than the weight of the mat. In this paper, a series of centrifuge model tests are performed to determine the uplift resistance of rectangular mudmats resting on lightly overconsolidated kaolin clay. The study investigates the influence of perforation, in combination with skirt length and eccentric uplift, on the uplift resistance and suction generation at the foundation invert. The outcomes demonstrate that the central and eccentric uplift of mudmats have different failure mechanisms, resulting in a different distribution of excess pore pressure at the foundation invert. In contrast, perforations do not change the failure mechanism and only alter the magnitude of suction generated. The two different configurations of perforation investigated significantly reduce the suction at the mat invert and the uplift resistance, and may potentially shorten the operating time for centred uplift. The combination of perforation and eccentric uplift has the most beneficial effect on the reduction of the uplift resistance.

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Section: Introductionmentioning

confidence: 99%

Effect of perforations on uplift capacity of skirted foundations on clay

Gaudin

Tian

et al. 2014

Can. Geotech. J.

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“…Reasonable accuracy in predicting the magnitude of this uplift resistance is required so that appropriate scales of vessels and lifting equipment can be selected. Field data reported by Bouwmeester et al (2009) indicate the ratio of uplift resistance to submerged weight of the mudmat could be up to 2·5, whereas centrifuge data reported by Chen et al (2012) show that this ratio depends on the location of the load attachment point (relative to the centre of the mudmat), the skirt length and the uplift velocity, with the least favourable combination resulting in a ratio of 5. A large body of literature examines the variation in penetration resistance with velocity, prompted by concerns regarding the appropriate penetration rate for penetrometers used to measure soil strength (Chung et al, 2006;House et al, 2001;Lehane et al, 2009;Randolph and Hope, 2004).…”

Section: Mudmats Under Upliftmentioning

confidence: 88%

Session report: offshore geotechnics at ICPMG 2014

O’Loughlin¹

2015

International Journal of Physical Modelling in Geotechnics

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This paper provides an overview of the contributions to offshore geotechnics at the 8th International Conference on Physical Modelling in Geotechnics 2014. The problems addressed in the conference contributions are a reflection on the focus of the offshore industry, which is expanding into new geographical regions and marketplaces. This expansion brings a fresh set of geotechnical challenges, including seabed stratification that presents risks for the installation of mobile jack-up platforms, strict serviceability criteria for the foundations of offshore wind turbines, complex loading on shallow foundations used to support seabed infrastructure and protecting offshore pipelines from ice gouging. These problems, as addressed in the conference proceedings and elsewhere in the literature, are discussed with notable contributions highlighted.

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“…(3) where log R=log R o -m logt where R o and m depends on the in-situ rest time and soil characteristics t is the time taken to breakout q d is the contact pressure Bowmeester studied about 35 cases of immediate break out events of a sea floor template in very soft clay and observed that the immediate breakout force varied from 1.1 to 2.5 times the submerged weight [9]. The vertical adhesive resistance during breakout was studied by Yamazaki [10] and it was observed that the effect of suction force is negligible in case of sea floor mining operations.…”

Section: Sinkage and Breakout Forcesmentioning

confidence: 99%

Estimation of sinkage and breakout forces for tracked vehicle for soft soils

Amudha

Reshma

Ramesh

et al. 2014

Oceans 2014 - Taipei

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Deep seabed polymetallic nodule mining machines have to operate in extremely soft ocean floor having soils of shear strength in the order of 1-3 kPa. The extent of sinkage and pullout force or breakout force required to lift the mining machine from the seafloor bottom needs to be evaluated for the successful operation and retrieval of the mining machine. In most of the cases the breakout force exceeds the submerged weight of object. Most of the empirical equations for estimating breakout forces are based on the bearing capacity phenomena. In the present study experimental investigations have been carried for obtaining undrained or immediate breakout forces on flat plates, plates with involute grousers and single track unit of Undercarriage unit. The magnitude of forces so obtained from the experiments has been compared to those calculated from the empirical equations. Studies on the extent of sinkage in soft sediments is critical for quantification of resistances encountered by the mining machine which influences the maneuverability of the mining machine. Experimental investigations have been carried out on flat plates, flat plates with grousers and single track of undercarriage unit as a part of sinkage studies. Sinkage has also been studied by Finite Element Methods using MohrCoulomb material model neglecting angle of internal friction angle as soils were fully cohesive and solving through explicit methods.

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Prediction of Breakout Forces for Deepwater Seafloor Objects

Cited by 8 publications

References 9 publications

Effect of perforations on uplift capacity of skirted foundations on clay

Effect of perforations on uplift capacity of skirted foundations on clay

Session report: offshore geotechnics at ICPMG 2014

Estimation of sinkage and breakout forces for tracked vehicle for soft soils

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