Interpretation of free-fall cone penetrometer test (FFCPT) data in soft cohesive seabeds remains challenging due to the coupled effects of inertia, strain rate, and soil sensitivity. This study develops and validates an integrated framework to improve the estimation of undrained shear strength from FFCPT measurements. Field tests were conducted at three Baltic Sea offshore sites, and complementary triaxial tests on high-quality samples provided reference undrained shear strengths. The analysis of large-deformation simulations using the Generalised Interpolation Material Point Method (GIMP) to reproduce the penetration process gave insights into the influence of rate and sensitivity on the measured soil resistance. These led to a refined analytical formulation, implemented in MATLAB, for direct strength profiling from FFCPT acceleration–depth data. The predicted undrained shear strengths show improved agreement with laboratory measurements compared with existing analytical interpretations, typically within ±[jls-end-space/]20%–25%. The proposed physics-based and computationally efficient methodology improves the reliability of seabed characterisation and provides a practical tool for offshore geotechnical investigations, supporting more reliable foundation, anchor, and pipeline design in soft marine sediments. ... Read more

The MIDASclay project (Monopile Improved Design via Advanced Cyclic Soil Modelling in Clay) aims to evaluate the cyclic lateral behaviour of monopiles in clays and clay-sand mixtures, focusing on developing a cyclic soil reaction model that captures cyclic ratcheting and operational stiffness in cohesive soils. Together with the MIDAS project – aimed at cyclic behaviour of monopiles in sand, it seeks to establish a comprehensive framework for modelling the cyclic lateral response of monopiles across diverse soil conditions. To address knowledge gaps, the project employs centrifuge testing of monopiles under cyclic lateral loads, aiming to produce a soil reaction model tailored to cohesive soils. This paper outlines the project setup, research plan, and initial findings. Early results from an auxiliary centrifuge test highlight the preparation of highly over-consolidated samples and provide insights into the influence of clay properties on monopile behaviour. MIDASclay is expected to support and advance design methodologies for monopiles in cohesive soils. ... Read more