A joint academia-industry project, the Pile Soil Analysis (PISA) project, resulted in an empirical method for assessing the monotonic lateral loading response of large diameter monopiles. The method predicts four soil reactions, namely the distributed load and the distributed moment along the pile shaft, the pile base shear and the pile base moment. The method considers pile load test data and 3D numerical modelling. A 1D framework allows prediction of the four soil reactions. In this paper, a CPT-based approach is proposed to derive the four soil reaction components for use in a 1D model for conceptual design of monopiles in sand subject to monotonic lateral loading. The approach relies on results from 3D finite element analyses that were performed considering soil conditions for a sand site used in the PISA project (Dunkirk site). The results are compared to pile load test data from the PISA project, showing good agreement, particularly for load levels related to the serviceability limit state.

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Offshore wind turbine generators (WTG) are commonly founded on single large diameter piles, named monopiles. These monopiles are subjected to significant lateral loads and thereby sizeable overturning bending moments mainly due to action of wind and wave forces; thus the critical geotechnical design situation for monopiles supporting WTGs is often related to lateral loading conditions. The Pile Soil Analysis (PISA) joint industry research project [1] has recently proposed a monopile design method which encompasses finite element (FE) calculations under a specific design framework. Soil reaction curves that are crucial for monopile design (i.e. lateral force and moment reactions along the shaft and at the base of the pile) are derived from FE calculations, subsequently calibrated and entered into a 1D model which is then used for design optimisation. This method is implemented within the PLAXIS MoDeTo (Monopile Design Tool) software. This paper presents results of a concept monopile design study under lateral monotonic loading with the use of the PLAXIS MoDeTo method. @en