The vibratory installation of monopiles as foundation for offshore wind turbines is considered a plausible solution next to the conventional installation method (impact-hammering). One of the main advantages is the lower noise emissions, reducing harm to the marine life. However, knowledge on the effects of the vibratory installation parameters on the lateral response of monopiles – and how these effects differ from those caused by impact-driving – is limited. This paper presents the results from an ongoing Joint Industry Project (SIMOX) with focus on 1g laboratory tests carried out in a 9.0m x 5.5m x 2.5m tank with saturated sand at Deltares, the Netherlands. The tests involve the installation (impact and vibratory) of scaled piles with 32 cm diameter, embedment length of 1.5 m and two wall thicknesses. The lateral loading regime consisted of monotonic and cyclic lateral loading. The results show the effect of soil density and different installation parameters of vibratory installation on the lateral response of the piles compared to a conventional impact installation.

Gentle Driving of Piles (GDP) is a new technology for the vibratory installation of tubular (mono)piles. Its founding principle is that both efficient installation and low noise emission can be achieved by applying to the pile a combination of axial and torsional vibrations. Preliminary development and demonstration of the proposed technology are the main objectives of the GDP research programme. To this end, onshore medium-scale tests in sand have been performed on piles installed using both impact and vibratory driving methods (including GDP). After presenting the development of a purpose-built GDP driving device and the geotechnical characterisation of the site, this paper covers the execution of GDP installation tests. Focus is on the installation performance of GDP-driven piles, which is discussed with the aid of structural and ground monitoring data. The comparison between piling data associated with GDP and standard axial vibro-driving points out the potential of the proposed installation technology, particularly with regard to the beneficial effect of the torsional vibration component. The findings of this study encourage further development of the GDP method and its future extension to offshore full-scale conditions.

Gentle Driving of Piles (GDP) is a new technology for the vibratory installation of tubular (mono)piles. Its founding principle is that both efficient installation and low noise emission can be achieved by applying to the pile a combination of axial and torsional vibrations. Preliminary development and demonstration of the proposed technology are the main objectives of the GDP research programme. To this end, onshore medium-scale tests in sand have been performed on piles installed using both impact and vibratory driving methods (including GDP). While the results of the installation tests are presented by Tsetas et al. (2023), this work focuses on the post-installation performance of GDP-driven piles under a sequence of slow/large-amplitude (cyclic) and faster/low-amplitude (dynamic) load parcels. The field data point out the influence of onshore unsaturated soil conditions, which result in complex cyclic pile stiffness trends due to the interplay of pile–soil gapping and soil's fabric changes. The pile stiffness under small-amplitude vibrations is strongly correlated with the previous response to large load cycles, and noticeably frequency-dependent for load cycles with a period lower than 1 s. Overall, the post-installation performance of GDP-driven piles appears to be satisfactory, which encourages further development and demonstration at full scale.

The response of monopiles to lateral loading has attracted considerable research interest in recent years. As monopile foundations are exposed to ever-harsher environmental conditions, the engineering tools used for their simulation should continually update and improve. Recently, the challenge of simulating the behaviour of monopiles under lateral loads has been addressed to a significant extent through a combination of numerical modelling and experimental data. Although monotonic response calculations are still relevant to monopile design, it should be acknowledged that offshore environmental loads are inherently cyclic. To improve the engineering tools for the simulation of cyclic monopile behaviour and our understanding of the relevant geotechnical mechanisms, this study presents and discusses the outcome of advanced 1D cyclic soil reaction modelling of monopile-soil interactions employed to simulate centrifuge data conducted as part of the MIDAS research project. The memory-enhanced p-y model proves capable of simulating cyclic ratcheting behaviour in complex loading histories, which promotes the discussion for the evolution of relevant soil reaction mechanisms during cyclic loads. Finally, preliminary calibration strategies for the employed cyclic soil reaction models are presented.

A novel pile-driving technique, named Gentle Driving of Piles (GDP), that combines axial low-frequency and torsional high-frequency vibrations has been developed and tested recently. During the experimental campaign, several piles were installed onshore, making use of the GDP shaker. Besides those, a number of additional piles were installed using conventional pile-driving techniques, i.e. impact piling and axial vibratory driving. After the completion of the installation phase, the installed piles have been subjected to impact hammer tests with the following goals. First, the in-situ dynamic properties of the pile-soil system have been identified. Second, the post-installation soil state has been investigated, along with its evolution in time for each pile driving scenario. Preliminary analyses, of the data collected during the impact tests show dissimilar trends in the overall dynamic response between the piles installed with impact hammer and those installed with the axial and the GDP shakers.This observation suggests a difference in the post-installation dynamic behaviour of the pile-soil systems related to different pile-driving techniques. In this paper, a first attempt is made to identify the differences in the overall pile-soil dynamic behaviour of the piles installed by means of the three different pile-driving techniques.