LARGE-SCALE MODEL EXPERIMENTAL STUDY ON MECHANISM OF SINGLE PILE HYDRAULIC HAMMER DRIVING FOR OFFSHORE WIND POWER

Zhu Huailong; Zhu Bitang; Luo Ruping; Xu Changjie

doi:10.19912/j.0254-0096.tynxb.2024-0655

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Acta Energiae Solaris Sinica ›› 2025, Vol. 46 ›› Issue (8) : 120-129. DOI: 10.19912/j.0254-0096.tynxb.2024-0655

LARGE-SCALE MODEL EXPERIMENTAL STUDY ON MECHANISM OF SINGLE PILE HYDRAULIC HAMMER DRIVING FOR OFFSHORE WIND POWER

Zhu Huailong^1-3, Zhu Bitang^1,2, Luo Ruping^1,2, Xu Changjie^1,2,4

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Abstract

Offshore wind turbine pile foundations are primarily constructed using open-ended pipe piles, which are driven into the ground using hydraulic hammer, This construction method leads to changes in the stress and displacement fields of both the pile body and the surrounding soil. These changes occur due to the large diameter of the pile and the high energy used during the penetration process. In order to investigate the mechanism of hydraulic hammer driving of offshore wind turbine piles, a large scale （1∶10） model test of hydraulic hammer driving of open-ended steel pipe piles （diameter D=0.273 m） was carried out in sandy soils with 70% densification by adopting the monitoring techniques of fibre-optic grating （FBG） strain transducers and thin-film pressure transducers. The study focused on the variation of soil plug height, pile axial force, and lateral friction resistance, pile-soil interface stress, and stress in sand during pile driving. The results show that the FBG strain sensor can withstand high-energy hydraulic impact during pile driving, and effectively monitor strain changes in steel pipe piles under dynamic loading. The maximum impact acceleration reaches 100 g during installation, and the maximum strain of the FBG sensor was 450×10^-6. With an increase in pile driving depth, there is little change in the Plug Length Ratio （PLR）. The Incremental Filling Ratio （IFR） value is close to 1, indicating that the soil plugging effect is not significant. The normal stress at the pile tip and the side of the pile decreases with the increase of h/R（where h is the height of the monitoring point from the pile tip and R is the pile radius）. Additionally, the normal residual stress at the pile side is significantly smaller than the normal stress during vibration. During the process of pile driving, the soil stress experiences a sharp increase as the pile tip approaches. This stress gradually decreases as the pile passes through the soil, and eventually stabilize. The principal stress distribution during this process follows the pattern of "radial stress > vertical stress > circumferential stress". At the same level, the farther away from the pile, the smaller soil stress. Therefore, it is necessary to consider the effect of pile driving on the marine pile foundation with strict stiffness and deformation control.

Key words

offshore wind turbine / hydraulic vibration / open pipe pile / FBG strain sensor / soil plugging effect / pile-soil interface stress

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Zhu Huailong, Zhu Bitang, Luo Ruping, Xu Changjie. LARGE-SCALE MODEL EXPERIMENTAL STUDY ON MECHANISM OF SINGLE PILE HYDRAULIC HAMMER DRIVING FOR OFFSHORE WIND POWER[J]. Acta Energiae Solaris Sinica. 2025, 46(8): 120-129 https://doi.org/10.19912/j.0254-0096.tynxb.2024-0655

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