Experimental investigation of frequency–amplitude decoupling in axial-torsional vibratory pile driving by means of laboratory-scale testing

This paper presents the development and testing of a lab-scale Gentle Driving of Piles (GDP) shaker. Conventional impact piling for offshore monopile installation faces challenges due to noise regulations and its adverse marine environmental impacts. The GDP method, which integrates high-frequency torsional vibrations with low-frequency axial vibrations, aims to mitigate these issues. In this work, a new GDP shaker is designed and tested to enhance vibratory pile driving by independently controlling torsional and vertical vibration amplitudes and frequencies. Laboratory tests were conducted using the newly designed shaker for pile driving in sandy soil to evaluate its performance. The results indicate a significant reduction in power consumption and improved pile drivability with high-frequency, low-amplitude torsional vibrations. This study highlights the importance of optimizing dynamic inputs for enhanced pile penetration and reduced environmental impact, showcasing the potential of the GDP method as a promising alternative to traditional impact piling techniques. •A lab-scale GDP shaker has been developed with frequency-amplitude decoupling.•High-frequency torsion does not require large amplitudes for efficient driving.•Inversion of GDP inputs showcases that torsion is the most effective driving mode.•The decoupled design facilitates fast installation at lower power consumption.