Critical Skirt Spacing for Shallow Foundations under General Loading

Mana, Divya S. K.; Gourvenec, Susan; Martin, Christopher M.

doi:10.1061/(asce)gt.1943-5606.0000882

Cited by 61 publications

(21 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is apparent that the greatest number of internal skirts is generally that required for mobilising maximum combined Hx(y)-My(x) loading capacity. The number of internal skirts required for maximum load-carrying capacity has been shown to increase with increasing vertical load mobilisation for plane strain conditions [11] and is verified in this study, as illustrated later in Figure 15. Therefore, it is concluded that in-plane V-M-H loading is the critical case for determining optimal internal skirt spacing and it may be asserted that the critical number of internal skirts for mudmats subjected to in-plane V-M-H loading can be used for selection of internal skirt spacing for mudmats under…”

Section: V-m 2 -H 2 -T Loadingsupporting

confidence: 53%

“…The effect of interface roughness of the internal skirts on the optimal number of skirts for maximum capacity was explored by comparing results for this study with results for strip foundations with all smooth interfaces, including the skirt-soil interface and at the underside of the base plate [11]. A comparison is shown in Figure 14 and in general one additional skirt is required for foundations with a completely smooth foundation-soil interface to mobilise the maximum available capacity.…”

Section: Effects Of Foundation Shape and Roughness On Optimal Number mentioning

confidence: 99%

“…The method does not extend to general combined loading conditions and the recommended spacing is considerably closer than commonly adopted in practice. A systematic study of optimal skirt spacing has been proposed for skirted foundations under combined in-plane V-M-H loading, but the study was restricted to conditions of plane strain and to only the limits of soil strength heterogeneity [11]. Subsea mudmats are generally threedimensional in geometry and subjected to loading in six degrees-of-freedom (see Figure 1 -T load capacity of square skirted mudmats was investigated for limiting cases of soil strength heterogeneity [5], but to date there has been no systematic study to define optimal skirt spacing across a full range of foundation aspect ratios and embedment ratios for practical intervals of soil strength heterogeneity.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optimal skirt spacing for subsea mudmats under loading in six degrees of freedom

Feng

Gourvenec

Randolph

2014

Applied Ocean Research

View full text Add to dashboard Cite

Two-and three-dimensional finite element analyses are performed to identify the optimal internal skirt spacing for the maximum undrained capacity of subsea skirted mudmats. Fully three-dimensional loading (vertical, biaxial horizontal, biaxial moment and torsion) is considered for subsea mudmats with skirt embedment ranging from 5 to 20% of the foundation breadth in soil with a range of linearly increasing strength with depth. The results have identified the governing case for determining the optimal skirt spacing for mudmats subjected to fully three-dimensional loading. It is also shown that optimal skirt spacing for rectangular or square mudmats can be determined in plane strain conditions using the equivalent foundation embedment ratio. The number of internal skirts required to ensure soil plug rigidity under fully three-dimensional loading is presented as a function of skirt embedment ratio, soil heterogeneity index and vertical load mobilisation. Results also indicate that effects of skirt roughness become negligible as foundation embedment increases in terms of determining the optimal skirt spacing.

show abstract

Section: V-m 2 -H 2 -T Loadingsupporting

confidence: 53%

Section: Effects Of Foundation Shape and Roughness On Optimal Number mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optimal skirt spacing for subsea mudmats under loading in six degrees of freedom

Feng

Gourvenec

Randolph

2014

Applied Ocean Research

View full text Add to dashboard Cite

show abstract

“…The skirt penetrates the seabed until the top plate comes into contact with the seabed confining a soil plug within the skirted compartment. Internal skirts may be provided to increase foundation stiffness and effective rigidity of the soil plug (Mana et al 2013a). Skirted foundations have a wide range of applications in the offshore oil and gas sector, for example to support gravity based structures, steel jacket structures for offshore wind turbines, as anchors for floating structures, and support for a variety of subsea infrastructure such as manifolds, pipeline end terminations and valve protection systems (e.g.…”

Section: Skirted Foundationsmentioning

confidence: 99%

Experimental investigation of reverse end bearing of offshore shallow foundations

2013

Self Cite

View full text Add to dashboard Cite

An experimental investigation of Mana/Gourvenec/Randolph reverse end bearing of offshore shallow foundations 2 ABSTRACT Shallow skirted foundations can mobilise uplift resistance from end bearing in the short to medium term. However, uncertainty exists over the magnitude of reverse end bearing resistance compared with resistance in compression, and how this might be affected by a gap between the external face of the foundation skirt and the adjacent soil. The study presented in this paper explored the problem through centrifuge model tests, investigating the effect of skirt embedment ratio on (i) the magnitude of reverse end bearing capacity compared to compression capacity (ii) the uplift displacement associated with spontaneous loss of suction during uplift, and (iii) the effect of a vertical gap on the external skirt-soil interface.The results show that (i) peak uplift capacity equivalent to compression capacity can be mobilised for a fully sealed foundation with an intact skirt-soil interface,(ii) suction required for reverse end bearing can be maintained through considerable foundation displacement, even for low skirt embedment ratio, and (iii) the presence of a vertical gap along the external skirt-soil interface causes abrupt loss of suction beneath the top plate after minimal foundation displacement, with subsequent uplift capacity being markedly reduced.

show abstract

“…It is well established that the embedment provided by the skirts increases the bearing capacity significantly. For vertical loading only and uniform soil, skirted foundations are equivalent to shallow foundations with a foundation depth equal to the skirt length [5]. The peripheral skirt also resists lateral movement, and consequently increases the lateral bearing capacity.…”

mentioning

confidence: 99%

Undrained bearing capacity of tripod skirted foundations under eccentric loading

2015

View full text Add to dashboard Cite

The undrained bearing capacity of a group of three rigidly connected skirted foundations (tripod) under vertical, moment or combined vertical-moment IntroductionSkirted foundations designed to sustain strong environmental forces such as winds, waves and currents have been extensively used for offshore structures (e.g. oil and gas platforms) in past decades. Although other types of foundation are also very common, skirted foundations have been shown to be cost-efficient and easy to install. Recently, their application has been investigated for the foundations to offshore wind turbines. In such structures the foundation, commonly a monopile, accounts for up to 35 % of the total cost [1] and therefore the use of suction caissons is an attractive alternative solution. Skirted foundations are shallow foundations with a peripheral vertical skirt that penetrates to depth B below the seabed, as shown in Fig. 1. The undrained vertical bearing capacity of such foundations has been investigated by several researchers using analytical, numerical and experimental methods [2], [3], [4]. It is well established that the embedment provided by the skirts increases the bearing capacity significantly. For vertical loading only and uniform soil, skirted foundations are equivalent to shallow foundations with a foundation depth equal to the skirt length [5]. The peripheral skirt also resists lateral movement, and consequently increases the lateral bearing capacity. It also increases the uplift capacity due to the development of suction within the skirt, and therefore also increases overturning moment capacity in the case of groups of skirted foundations (as considered in this study). Since such foundations are employed in offshore applications, most studies available consider combined loading, either through equivalent two-dimensional or full three-dimensional modelling [5]− [9]. Based primarily on numerical analysis, several normalized failure load surfaces have been proposed in order to take account of the effect of inclined and/or eccentric loading on the undrained bearing capacity of skirted foundations [10]− [18].Offshore wind turbines are subjected to very large overturning moments because of the horizontal wind pressures acting high above foundation level [19]− [22]. Very large foundation dimensions are generally required to carry these highly eccentric loads. As a consequence, the use of skirted foundations for offshore wind turbines is more challenging than in the case of oil and gas platforms, where vertical loading is dominant. An alternative to single skirted foundations (monopods) is the use of rigidly connected groups of three or four skirted foundations (tripods and tetrapods), which provides increased bearing capacity and drastically reduces the required minimum diameter of each footing, especially under eccentric loading. In this case, however, possible interactions between the footings need to be taken into account in the design.Unlike the case of single foundations, very few published studies consider the undrain...

show abstract

Critical Skirt Spacing for Shallow Foundations under General Loading

Cited by 61 publications

References 21 publications

Optimal skirt spacing for subsea mudmats under loading in six degrees of freedom

Optimal skirt spacing for subsea mudmats under loading in six degrees of freedom

Experimental investigation of reverse end bearing of offshore shallow foundations

Undrained bearing capacity of tripod skirted foundations under eccentric loading

Contact Info

Product

Resources

About