Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Installation of suction bucket foundations in layered soils in Southern China
Zhaorong Maa, Donghua Liua, Bo Liua, Youhu Zhangb*, Knut H. AndersencbaGuangdong Electric Power Design Institute, Guangzhou, Guangdong, China
Southeast University (formerly Norwegian Geotechnical Institute), Nanjing, Jiangsu, ChinacNorwegian Geotechnical Institute, Oslo, Norway*Corresponding author

supported by jacket structures and a large portion of them are expected
to be supported by suction bucket jackets.

ABSTRACT
Suction bucket jacket foundations are novel foundation solutions forbottom-fixed offshore wind farms and are gaining popularity in China.
However, in many Chinese offshore wind farm sites, layered clay andsand ground conditions are frequently encountered which pose
installation risks for suction bucket foundations. This paper presents
recent installation experience of two suction bucket jackets in Southern
China with an aim to provide guidance to future installations in similarsoil conditions.

Suction buckets are installed by self-weight first and then by negative
pressure difference (i.e., suction) between inside the skirt and outside of
the skirt which is created by pumping water out from the bucket
foundation. Suction bucket, when used as anchoring solution for offshore
floating facilities, known as suction anchor, has been used by theoffshore oil and gas industry since the late 1980s. Extensive experiencehas been gained on suction installation in pure clay or pure sand soil
profiles and installation methods are well established (Houlsby et al.
2005, Andersen et al. 2008, DNVGL-RP-C212). The installation
resistance and potential risks are relatively well understood. However, inlayered seabed, the mechanism and installation risks are less wellunderstood (Aas et al., 2009, Saue et al., 2017 and Andersen et al., 2020).
This is manifested by limited guidance in design guideline documents.
This is particular the case when a sand layer underlies a clay layer. Dueto its low permeability, the clay layer may act as barrier to seepage flow,
resulting in increased tip resistance when the skirt tip reaches the sandlayer compared to the pure sand scenario. It may also lead to potential
internal soil plug uplift which describes the scenario where the internalsoil plug above the sand surface is lifted up as a piston, leading topremature termination of the installation process. This is illustrated byFigure 1.

KEY WORDS: suction bucket jacket; suction installation; layeredsoils; offshore wind

INTRODUCTION
The offshore wind industry is fast-growing in China due to thegovernment’s push for energy structure transition and commitment to thestrategic goal of carbon peaking in 2030 and carbon neutral in 2060. In2021, China saw an added offshore wind capacity of 12 GW and the total
accumulated capacity reached 23 GW by the end of 2021. Strong growthis projected in the coming years and the total installed capacity is
forecasted to reach 40 GW by the end of 2026.
Suction bucket jacket (SBJ) is a relative new support structure type forbottom fixed offshore wind farms. It offers several advantages overconventional jacket structures on piles due to its efficient installation
with the jacket and bucket foundations installed in one go and its superior
adaptability to sites with shallow bedrock. The first of its type intyphoon-prone offshore Southern China was installed in August 2020
(Liu et al. 2020) and several new projects with either a single
demonstrator (Houhu Offshore Wind Farm), small scale application(Yuedian Shapa Offshore Wind Farm with six turbines on SBJ) and massapplication (Fujian Changle Offshore Wind Farm with 72 turbines onSBJ) are installed since then. With the industry expanding to deeper
waters (>35m) and greater distance to the shore and application of largerwind turbines (10+ MW), more and more offshore turbines will be

Figure 1. Plug uplift mechanism in clay over sand (Ragni et al., 2020)

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