Effect of Padeye Depth on the Behavior of Offshore Anchor Piles Under Mooring Forces

Offshore anchor piles are usually loaded at a padeye on pile surface. The padeye depth can be at the seabed or below it. Using a padeye below the seabed is widely used in case of suction caissons. However, anchor piles are more flexible and the mode of failure will be different from that for suction caissons. In the current parametric study, the effect of padeye depth on the behavior of offshore anchor pile subjected to mooring forces in dense sand was studied. Finite Element Model (FEM) had been established. The model had been calibrated based on the centrifuge tests that were carried out by the authors. Three piles of different soil-pile rigidity covering a wide range of pile flexibility were used in the study. The piles were pulled out at an angle of 15° to horizontal. In all cases the padeye depth was changed from at the ground surface to a depth of four times the pile diameter. From this parametric study, it was found that pulling out an offshore anchor pile at a level below the seabed has some advantages of increasing the ultimate capacity of the pile, decreasing pile deflection, and decreasing bending moment. An optimum depth of padeye was recommended.