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.

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.

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.