A review of a CPT based axial capacity prediction of screw piles in sand

Screw piles are widely used in onshore engineering applications and have recently been considered as an alternative foundation solution for offshore wind turbines (OWTs) supported on jacket structures. The high loads required to support such structures demand a considerable up-scaling of the screw pile geometry typically used onshore. Driven piles followed a similar upscaling process for their use in offshore structures and the CPT tip resistance (q_c) value is now commonly used directly in design methods for both onshore and offshore driven piles. This paper evaluates the performance of a new CPT-based design method (UWA-SP-21) to predict the axial capacity of screw piles in tension and compression. To achieve this, a database of single helix load tested screw piles sand is collated and used for assessment of the method. The development of this CPT design approach reflects the process that was following for driven piles. UWA-SP21 has been developed through studies of onshore piles. The findings from this study can in the future be extrapolated appropriately to the larger pile sizes required offshore, in the same way that driven pile design has evolved.