Stress effects due to different installation methods for pipe piles in sand

Abstract

Impact driven pipe piles are commonly used in offshore structures but vibratory driving is becoming more popular due to advantages regarding noise emissions, material fatigue and installation time. In offshore practice, crane-guided vibratory driving is used for maximum control over the installation process. Regarding the load-bearing behaviour of piles, the influence of the installation method is currently subject to research. To contribute to this question, comparative scale model investigations were carried out with impact driven, jacked, and vibratory driven piles in dense sand. The tests focussed on variations of vibratory installation parameters, including ‘crane-guided’ and ‘free’ vibratory driving. Based on measurements at the pile and in the soil, the influence of dynamic pile motions on the soil stress development could be analysed. The well-known increase of radial effective soil stresses due to impact driving could be reproduced. The tests showed that the same effects could be evoked by ‘free’ vibratory driving if certain vibration parameters were met. Increased soil stresses may be beneficial for the lateral or axial pile behaviour, but on the other hand cause problems regarding drivability. A sequential application of ‘crane-guided’ and ‘free’ vibratory driving may optimise both the installation process and the bearing behaviour.