Skirted foundation to mitigate spudcan punch-through on sand-over-clay

Abstract

Mitigation of spudcan punch-through is one of the principal aspects for inclusion in the ISO standard 19905-1. This paper investigates the potential for using skirted foundations as an alternative to spudcans in an attempt to mitigate punch-through failure of jack-up rigs during installation and preloading in sand-over-clay deposits. A series of centrifuge model tests is undertaken on a spudcan and two skirted foundations, varying the length of the skirt relative to the foundation diameter. The thickness of the sand layer is also varied to cover a range of practical interest. The results from this study confirm that the use of skirted foundations as an alternative to spudcans can eliminate the potential of punch-through failure on sand-over-clay deposits. The degree of post-peak bearing reduction, one of the key measures of the severity of punch-through failure, is shown to be linked directly to the effective sand layer thickness beneath the foundations. Skirted foundations assist in mitigating the severity of punch-through failure by reducing the effective sand layer thickness.

Mitigating punch-through on sand-over-clay using skirted foundations

“…Mitigating Punch-Through on Sand-over-Clay using Skirted Foundation Lee et al Submitted Nov 2018, Revised Oct 2019Re-revised Feb 2020 6 the skirt thickness in the typical range of 0.1 -1% of the foundation diameter (Hossain et al, 2014). The penetration depth of the spudcan base with largest area relative to the original seabed surface was denoted as d.…”

“…The scope of this paper is restricted to two-layer sandover-clay deposits. 5 foundations to mitigate punch-through failure, Teh et al (2008b), Gan et al (2011) and Hossain et al (2014) have carried out centrifuge model tests on medium-dense and dense (relative density; ID = 44%, 50% and 95%) sand-over-soft clay deposits, considering skirt length of L = 0D -0.5D (see Fig. 1).…”

Finite Element Analysis and Parametric Study of Spudcan Footing Geometries Penetrating Clay Near Existing Footprints

“…The geometries of typical fusiform spudcan footings are shown in Figure 2. The investigations from some research shows that, by comparing with fusiform spudcan footing, skirted footing may have a higher bearing capacity [7] and have some potential in mitigating punch-through failure [10,11]. the initial installation.…”

On Cubic Spudcan Deep Penetration in Dense Sand Overlying Non-Uniform Clay

“…Spudcan penetration in strong-over-soft sediments has been addressed by a number of researchers, with particular focus on the mechanism of punch-through failure and methods for predicting the (post) peak penetration resistance and the corresponding depth [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In addition, mitigating measures for possible punch-through failure of spudcans have been explored [21][22][23][24][25]. However, most research on punch-through failure of spudcans mainly focus on generic spudcans (characterized by typical axisymmetric inverse conical characteristics; Figure 1a), although some modifications (e.g., varying bottom profile and holes through the footing) of generic spudcans have been explored [24].…”