The global market for offshore wind energy is currently experiencing tremendous growth, which is expected to continue in the coming decades. Monopiles are one of the most frequently used foundations for Offshore Wind Turbines (OWTs) and are commonly driven into the seabed using impact hammering. The demand for higher capacity OWTs requires the installation of larger monopiles. As monopiles, however, become bigger their installation with hammering and mitigation of generated noise becomes challenging and costly. To optimize installation and to limit noise emissions, an innovative installation technique known as the Gentle Driving of Piles, GDP, has been developed. This technique combines vertical and torsional vibrations under different frequencies with the main driving assistance coming from the torsional force. This paper presents and discusses the results from a series of lab-scale pile driving tests performed in dense sand using the GDP method. For these tests, a lab-scale GDP shaker has been mobilized. During installation of the scaled piles, the frequencies and amplitudes of the vertical and torsional excitation were varied independently with the objective to increase the penetration speed. The results show improved pile driveability with high-frequency, low-amplitude torsional vibrations and showcase the potential of the GDP method in improving installation performance.

The rapid expansion of the offshore wind industry into regions with complex geomaterials, such as glauconite sands, presents significant geotechnical challenges. Glauconite sands, commonly found in shallow marine environments, are characterized by their susceptibility to particle crushing and complex shearing behavior, which can lead to high soil resistance and pile driving refusal during monopile (MP) installation. Current drivability prediction models often fail to account for these unique behaviors, leading to uncertainties and inefficiencies in offshore wind farm planning and construction. This research initiative, led by Deltares, seeks to address these challenges through a comprehensive 3-year program combining advanced experimental and numerical modeling. The project involves soil characterization via laboratory tests, calibration chamber testing, and Cone Penetration Test (CPT) simulations. The development of constitutive and drivability models tailored for glauconite sands aims to improve MP installation predictability and optimize offshore operations. The research will also establish soil classification guidelines for glauconite deposits, addressing gaps in current practices. The project’s findings are expected to provide actionable insights for both the scientific and industrial communities, enhancing the design and installation of offshore monopiles (MPs) in glauconite-bearing soils.

Due to the rapid expansion of the offshore wind industry, wind farms are being developed in areas where glauconite soils are encountered. Of particular interest for the development of windfarms in regions dominated by glauconite sand deposits is the risk associated with the presence of this geomaterial. It is acknowledged that glauconitic soils pose significant challenges during pile installation due to their high susceptibility to particle crushing at relatively low stress levels. This transforms the sand into a low-permeable fine-grained clay-like material, leading to a complex response upon shearing as a result of the change in soil behaviour. In this study, the geotechnical behaviour of a glauconite sand from the Antwerp region in Belgium is investigated by means of a laboratory testing program comprising of index classification tests, compression, direct shear and interface shear strength tests. The laboratory test data are interpreted to improve understanding of the geotechnical properties of this peculiar geomaterial and evaluate its potential implications during pile driving.

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.