Numerical Analysis of Fin Effects on Lateral Load Behavior of Monopile Foundations in Sand and Clay

Monopile foundations are subjected to large environmental loads in the form of lateral loads from wind, seismic, water currents, which would exceed more than 30% of gravity loads. Providing fins to monopiles is one of the most viable options to decrease the foundation cost for wind turbine foundations and improve its lateral load carrying capacity in poor ground conditions. Numerical analyses were performed on monopiles with and without fins embedded in loose sand and soft clay. Pile material is considered as mild steel for all analyses. Initially, fins length, width, orientation and position were varied to evaluate the optimum fins size, position and orientation. After establishing optimum fin dimensions, position and orientations, lateral load analyses were performed on finned piles embedded in loose sand and soft clay. The results have shown that fins placed near the top portion of the piles are more effective than fins placed near the middle and bottom portions of the piles. Among various fin orientations, straight fins (or fins placed orthogonally) are the most effective ones and for the optimum fin efficiency as well as to avoid buckling, the fin width shall be 0.5 times pile diameter, and the fin length shall be half the pile length and this is found to be valid for finned piles embedded in both loose sand and soft clay. The monopile embedded in sand with fins placed at top carry 42% higher lateral load and whereas in soft clay it is 48% than monopiles.