Silent Installation of MonoPiLEs in prevailing Clay and Sand soils (SIMPLECS)

WHY

Many future European wind farm zones, including the Dutch wind farms Nederwiek, Doordewind and IJmuiden Ver, are characterised by challenging subsoil conditions. These include very dense sand layers and very high-strength clay layers that extend over several metres. Such soil conditions create significant difficulties for conventional monopile installation methods, such as impact driving and vibro-hammering. These methods either exceed underwater noise limits imposed to protect marine life or encounter early refusal, preventing monopiles from reaching their target penetration depths.

Pre-tender geotechnical investigations illustrate the scale of this challenge. For example, at Nederwiek I-A, nearly all investigated locations contain either very dense sands, very high-strength clays, or both, leaving no areas where traditional installation methods can be applied without constraints. Investments and costs for noise mitigation during impact driving increase substantially along with the increasing size and power of wind turbines. As offshore wind development moves into these more complex soil environments, alternative installation techniques become essential to protect marine life, increase the speed of installation and lower installation costs and investments.

At the same time, traditional foundation installation methods generate significant environmental impacts, including high underwater noise levels and substantial CO₂ emissions due to extensive noise mitigation measures and the need for heavier monopiles withstanding the loads of the impact hammer. The current Vibrojet® technology, for the first time applied at scale in Hollandse Kust West in March 2026, offers a promising alternative, enabling quieter monopile installation while reducing overall CO₂ emissions by eliminating the need for noise mitigation measures and enabling slimmer monopile designs from lower peak energy transfer. To fully realise these benefits, the applicability of new jetting solutions, enhanced vibro solutions and combined in the Vibrojet® must be extended to very high-strength clays and very dense sands. Addressing this challenge is essential to support the continued, sustainable expansion of offshore wind in the Netherlands.

WHAT

This project aims to develop a new jetting solution, a new vibro solution, and an optimal combination of the next-level Vibrojet® so that the new jetting-based installation solution can be used in more challenging offshore soil conditions, in particular, very high-strength clays and very dense sands. The focus is on demonstrating reliable performance in these difficult soils and improving the tools needed to predict and design jetting-based installations.

The technical work is divided into two main tracks: clay and sand. For clayey soils, the project will develop and test the solutions’ penetration into very high-strength clays with undrained shear strengths of up to 300 kPa. Scaled prototypes will be designed, built and tested in realistic field conditions, such as onshore or nearshore locations. The prototypes will combine both clay and sand penetration techniques to reflect typical offshore soil profiles. Field testing will focus on driveability and axial bearing capacity, supported by geotechnical modelling, data analysis and reporting. The results will be used to define how the prototype performance can be scaled up to full-size offshore monopiles.

For sandy soils, the project will extend Vibrojet®, jetting-only and enhanced vibro-capabilities to very dense sands with cone resistances of up to 125 MPa. This work builds on existing Vibrojet® models and experience from earlier projects, SIMPLE II, SIMPLE-IIB, and SIMPLE-III. Laboratory tests will be carried out at Deltares using flumes and calibration chambers to simulate dense and very dense sand under realistic stress conditions. Different installation methods will be compared, and the piles and surrounding soil will be heavily instrumented to better understand pile–soil interaction and bearing capacity behaviour. Numerical modelling will support the interpretation of the test results.

The project will conclude with an integrated analysis and clear recommendations for future large-scale offshore application of Vibrojet® technology, including the analysis of the individual contributions of the vibro and the jetting.

EXPECTED RESULTS

Upon completion of the SIMPLECS project, several key results will be achieved for jetting-based pile installation in both clay and sand. For clay soils, the project will deliver proof of the optimal Vibrojet® driveability in very high-strength clays, reaching a Technology Readiness Level (TRL) of 6. In addition, geotechnical calculation models will be developed to predict clay driveability and the governing failure mechanisms during Vibrojet® installation. The results will be documented in detailed reports, including lessons learned on geotechnical behaviour, operational optimisation, and the mechanical performance of the prototype.

For sandy soils, the project will demonstrate Vibrojet® driveability in very dense sands, achieving a final TRL of 7. The performance of Vibrojet® will be compared with conventional vibro-hammering through lateral and axial bearing capacity tests. An extended geotechnical model will be delivered to predict sand driveability and fluidisation behaviour. The findings will be consolidated into an integrated design representative of full-scale offshore installation, enabling rapid progression towards commercial deployment.