Chapter 11: Displacement response to axial cycling of piles driven in sand

The axial cyclic response of driven-pile foundations can be important in the design of conventional offshore oil and gas platforms and onshore facilities such as towers and pylons (Jardine, 1991; Poulos, 1988). It may be still more critical in offshore wind turbines that rely on tripods or jacket structures. Turbines commissioned in relatively shallow waters (< 30 m) are currently mostly founded on monopiles (75%) or gravity-based structures (20%) (Gavin et al., 2011), whose axial response is often not a significant concern. With deeper water sites, jacket and tripod structures founded on open-ended driven pipe-piles become more attractive (e.g. Seidel, 2007). The lateral and moment loads imposed by wind or wave action can be large in comparison with self-weights, leading to multiple modes of axial and lateral cyclic loading acting on the foundation piles. While lateral loading model test data have been reported for monopiles (Leblanc et al., 2010), less guidance is available regarding full-scale displacement accumulation and stiffness responses under axial cycling.