This paper presents a three-dimensional numerical investigation of the undrained capacity of suction piles subjected to moment loading using finite element analysis. The model was first verified by comparing the results against well-established results in literature. The model was then used to investigate the effect of moment loading on vertical and torsional capacity by performing a sensitivity analysis by varying soil heterogeneity and suction pile geometry. The parametric study was carried out for suction piles with L/D ratios varying between 1 to 7 embedded in soils with constant and linearly varying shear strength.
Suction piles have been widely used in offshore energy industry to support various structures used for exploitation of oil and gas, e.g. for temporary or permanent mooring of floating offshore facilities, as well as offshore wind turbines. They have advantages over other conventional offshore foundation systems because of their large capacity and their relatively simple installation procedure. They are installed by pressure drawdown within the cylinder, referred to as ‘suction’, after partial penetration of the pile due to its submerged weight.
The behaviour of suction piles can be examined using experimental, analytical or numerical approaches. Physical experiments are generally time-consuming and costly. Analytical methods are constrained to idealised cases. However, numerical simulations provide a suitable alternative to study the behaviour of suction piles under complex loading conditions.
A number of researchers have employed numerical approaches to study the behaviour of suction piles. These approaches have been extensively applied to shallow foundations in the past (Abyaneh et al., 2015; Abyaneh et al., 2017; Bransby and Randolph, 2003). Zdravkovic et al. (2001) employed numerical analysis to investigate the effect of load inclination, skirt length, foundation diameter, soil adhesion and soil anisotropy on the pull-out capacity of bucket foundations in soft clay. Taiebat and Carter (2005) carried out three-dimensional finite-element analyses to investigate the behaviour of caissons embedded in a homogeneous soil deforming under undrained conditions. The performance of the caisson under separate axial (vertical), lateral and torsional forces was investigated first, followed by the interaction of these forces with each other. However, to the authors knowledge, the effect of moment on the capacity of suction piles has not been investigated using numerical approaches.