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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

Wave-induced soil response in a porous seabed around a free spanning pipeline: Two-way coupling model
Hualing Zhai1 and Dong-Sheng Jeng1,2,#12

School of Civil Engineering, Southwest Jiao Tong University, Chengdu, China
School of Engineering & Built Environment, Griffith University Gold Coast Campus, Queensland, Australia#Corresponding author.

ABSTRACTwave

The problem of the wave-seabed interactions around a pipeline has become an important issue in the field of coastal geotechnical engineering, due to the exploitation of oil and gas industry. To date, most existing studies adopted one-way coupling algorithm to integrate wave andseabed sub-model, which violated the physical phenomena. In the study,
a new two-way coupling algorithm for the wave–seabed interactions
around a pipeline is proposed. The numerical results indicate that thewater surface elevation, pore-pressures, soil displacements and effective
normal stresses obtained by two-way coupling model are smaller thanthat of the conventional one-way coupling model generally. However,the Shields number by two-way coupling model is extremely larger thanthat of one-way coupling model, which implies that two-way couplingis required for the prediction of the scour. Meanwhile, the existence ofpipeline would increase the influences of two coupling models on wave
and seabed characteristics.

current

fluidliquefied soil
depthliquefaction zone
seepageσ'z
τ zx

σ'xueτ xz

σ'0

porous seabed(a) Problem of wave-seabed interactions.

KEY WORDS:fluidTwo-way coupling model; fluid-seabed-pipeline interaction; soil response; OpenFOAM

Uimpermeable
dynamic wave pressure

INTRODUCTION
Pipelines has been one of the key offshore installations for the exploitation and transportation of offshore oil and gas industry with thegrowth demand for marine energy resources. Therefore, the problem of
fluid-seabed interactions around the pipeline has become an important
issue in the offshore project regarding the seabed stability around thepipeline (Sumer, 2014; Jeng, 2018).

interfaceporous medium(seabed)(b) One-way coupling model

To date, most existing investigations for the wave–seabed interactions
have adopted one-way coupling process, as shown in Fig. 1. In theseapproaches, the dynamic water pressures were treated as the only
external loading for the seabed model, but ignored the feedback ofseabed response to the flow field. At the early stage of the theoreticaldevelopment of the wave-induced soil response, Yamamoto et al. (1978)and Hsu and Jeng (1994) obtained 2-D and 3-D analytical solutions,based on Biot’s poro-elastic theory (Biot, 1941) with linear wave theory.
Later, numerous numerical studies for the wave-seabed interaction haveFig. 1 (a) Sketch of problem for wave-seabed interactions and (2)the conventional one-way integrated model.

been available in the literature. Among these, Liu and Garcia (2007)
established a fluid-seabed interaction numerical model to investigate theseabed response and the coupling between fluid and seabed was throughstress and continuity condition on common boundaries. Later, Jeng et1576