A CPT-based design framework for uplifted open-ended piles installed in spatially variable sandy soils. I: Soil resistance design line optimization

Due to the mechanical properties of the seabed exhibiting horizontal and vertical spatial variability, an important challenge in offshore geotechnical design lies in the selection of the relevant soil strength profile for foundation sizing, called hereafter the “design line.” Design values are most often selected depth-wise using existing field data, through knowledge of the volume and distance of the field data from the designed infrastructure and considering the relevant limit state and targeted level of reliability. The cone penetration test (CPT) is well-suited to this purpose given the quasi-continuity and high repeatability of its measurements. This paper proposes a statistical CPT-based method to identify the design line for the design of open-ended piles under drained uplift loading to achieve a target reliability. Application of the proposed method reveals that the statistical procedure used to select the design line is dependent on the proximity of the nearest CPTs to the piles, and the horizontal and vertical scales of fluctuation and the coefficient of variation of the cone tip resistance. This information is used in a companion paper to inform optimization and selection of site investigation strategies for the design of uplifted piles for offshore wind farms.