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2 - Basic Seabed Mechanisms

Published online by Cambridge University Press:  28 April 2018

Dong-Sheng Jeng
Affiliation:
Griffith University, Queensland
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Summary

Introduction

Considerable efforts from researchers in the field of marine geotechnics have been devoted to the phenomenon of the wave-induced soil response since the 1970s. One reason for the growing interest is that many coastal/offshore structures (such as vertical walls, caissons, offshore monopiles and pipelines) have been damaged by the waveinduced seabed response, rather than from construction deficiencies (Christian et al. 1974; Smith & Gordon 1983; Lundgren et al. 1989).

As mentioned in Chapter 1, two mechanisms of the wave-induced soil response have been reported in the literature. Both oscillatory (transient) and residual mechanisms of the wave-induced soil response have been intensively studied since the 1970s with two different approaches: the Yamamoto–Madsen model (Madsen 1978; Yamamoto et al. 1978) for the oscillatory mechanism and the Seed–Rahman model (Seed & Rahman 1978) for the residual mechanism. Following these approaches, numerous models have been proposed in the literature. In this chapter, the basic concepts and some key results of the previous models for wave-seabed interaction will be summarised.

Oscillatory Mechanism

Basically, previous studies of the wave-induced oscillatory soil response can be classified into three categories: the Yamamoto–Madsen model, the boundary-layer approximation and the dynamic model. We outline the contribution of several key publications available in the literature here.

  • (a) Yamamoto–Madsen model (YM model, or Biot's consolidation model): Yamamoto et al. (1978) proposed an analytical solution for an infinite seabed with hydraulic isotropy, while Madsen (1978) derived an analytical solution for a similar problem but with hydraulic anisotropy (i.e., permeabilities in all directions are different). Different seabed conditions, such as a seabed of finite thickness (Yamamoto 1977) and a layered seabed (Yamamoto 1981), were considered. Based on the plane stress conditions, Okusa (1985b) further reduced the sixth-order governing equation in the YM model to a fourth-order governing equation. Later, the YM model was further extended to more complicated wave conditions such as three-dimensional (3D) short-crested wave systems (Hsu et al. 1993, 1995; Hsu & Jeng 1994) or seabed conditions such as cross-anisotropic soil behaviour (Jeng 1997b) or a non-homogeneous seabed profile (Jeng & Seymour 1997a; Kitano & Mase 2001). Some numerical models have been developed with this framework, which were reviewed in Chapter 1.

  • (b) Boundary-layer approximation: Based on the mixture theory, Mei & Foda (1981) proposed the boundary-layer approximation for the wave-induced soil response.

  • Type
    Chapter
    Information
    Mechanics of Wave-Seabed-Structure Interactions
    Modelling, Processes and Applications
    , pp. 34 - 108
    Publisher: Cambridge University Press
    Print publication year: 2018

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    • Basic Seabed Mechanisms
    • Dong-Sheng Jeng, Griffith University, Queensland
    • Book: Mechanics of Wave-Seabed-Structure Interactions
    • Online publication: 28 April 2018
    • Chapter DOI: https://doi.org/10.1017/9781316672266.003
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    • Basic Seabed Mechanisms
    • Dong-Sheng Jeng, Griffith University, Queensland
    • Book: Mechanics of Wave-Seabed-Structure Interactions
    • Online publication: 28 April 2018
    • Chapter DOI: https://doi.org/10.1017/9781316672266.003
    Available formats
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    To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

    • Basic Seabed Mechanisms
    • Dong-Sheng Jeng, Griffith University, Queensland
    • Book: Mechanics of Wave-Seabed-Structure Interactions
    • Online publication: 28 April 2018
    • Chapter DOI: https://doi.org/10.1017/9781316672266.003
    Available formats
    ×