The Influence of Seabed Trench on Suction Pile’s Holding Capacity

Abstract Suction piles have been widely used as anchor points for semi-taut and taut mooring systems in deepwater sites for the last decade as this technique has advantages in both technical and economic aspects. Recently, large-size trenches were found in front and near the suction piles in some offshore areas, i.e., West Africa, which may greatly affect the pile’s holding capacity. As this is a relatively new issue, very few studies related to this problem have been carried out. In order to investigate the influence of a trench on a suction pile’s holding capacity, a three-Dimensional Finite Element Analysis (3D FEA) model using Finite Element Code PLAXIS 3D was developed. This paper presents the development of this 3D FEA model to investigate the influence of a trench on a suction pile’s holding capacity in deepwater marine clay. Using this model, a series of FEA runs were carried out. Firstly, the FEA model was used to investigate the remaining capacity of suction piles with trench depth assuming soil behavior was not influenced by the development of a trench. Secondly, the FEA model was used to investigate the remaining capacity of suction piles considering an influence on soil behavior due to the development of a trench. Finally, discussions and recommendations on suction pile’s holding capacity and structural impacts due to a seabed trench were provided to take the trench influence into consideration for suction pile geotechnical designs in similar soil conditions in West Africa offshore.