Effects of vertical loading on lateral screw pile performance

The offshore wind energy sector faces new challenges as it moves into deeper water deployment. To meet these challenges new and efficient foundation solutions are required. One potential solution is to upscale onshore screw piles but they require verification of performance for new geometries and demanding loading regimes. This paper presents a 3D Finite Element Analysis (3D-FEA) investigation of screw pile behaviour when subjected to combined vertical and lateral loading in sand. The investigation varied screw pile length (L) and helical plate diameter (Dh) on piles with fixed core diameter (Dp) whilst subjecting the piles to combined axial and lateral loading. The results were compared to straight shafted piles with the same core diameter. The results of the analysis show that vertical compression loads increase the lateral capacity of screw piles whereas vertical uplift loads marginally reduce the lateral capacity. The down side of this enhanced lateral capacity is that the screw piles experience higher bending moments. This suggest that when using screw piles for offshore foundation applications structures should be designed to maintain axial compressive loads on the piles and that induced bending moments need to be adequately assessed when deciding on appropriate structural sections.