Interpretative framework for CPT p-y module tests in drained sands: a practical model for end effect elimination considering sand relative density and surcharge pressure

Accelerating the current timeline of offshore wind projects is imperative to achieve global decarbonisation plans. In response, a novel in-situ site characterisation tool ROBOCONE is being developed to make the geotechnical design of offshore pile foundations more efficient by directly providing lateral p-y response data, reducing the need for offshore sampling and onshore laboratory testing. This device expands the kinematic range of standard cone penetrometer testing by integrating a robotic cylindrical section capable of horizontal translation, referred to as a p-y module. However, due to the finite length of p-y module, it is necessary to quantify ‘end effects’ to accurately derive p-y curves from the direct measurements of the p-y module. This paper presents detailed three-dimensional finite element analyses of the p-y module in sands, utilizing a bounding surface elastoplastic model that accounts for variations in stress–strain behaviour due to relative density and stress level. The resulting end effect model is underpinned by a two-stage optimisation process that considers key factors such as overburden pressure and relative density. The model's predictive accuracy is proven through additional finite element analyses different to the calibration cases. The research outcomes offer a robust interpretative framework to accurately determine p-y curves for the design of laterally loaded offshore piles, using the ROBOCONE p-y module.