ABSTRACT:

Water waves propagating on the ocean create an oscillating pressure on the seafloor, inducing stress and pore pressure fields in the fluid-filled porous seabed, which must be known for the evaluation of seabed instability. In this paper, a general semi-analytical method is formulated for the analysis of response of seabed under wave action during a storm. The seabed is idealized as a poro-elastic medium of finite thickness filled with a single compressible fluid with anisotropIc flow. The coupled process of fluid flow and deformation of soil skeleton is formulated in the framework of BioI's theory. The formulation for the three-dimensional response of seabed is developed for a general wave field. Later, the analyses for seabed response to two-dimensional progressive is presented. The effects of various wave and soil parameters on seabed response are also studied. Numerical results are presented. The extensions for the analyses for seabed response understanding wave and short-crested wave are outlined.

INTRODUCTION

The evaluation of response and stability of seabed subjected to loadings associated with a wave storm are important for various offshore installations involved in ocean resource exploitation (buried pipelines, gravity and platform structures) as well as coastal development. The wave-induced stresses and the pore fluid pressure in a porous bed have been studied by various authors. Early studies were based on the assumption of incompressible pore-fluid and soil skeleton and the flow in porous bed governed by Darcy's Law (putnam, 1949; Reid and Kajiura, 1957 and Liu, 1973). Madsen (1978) and Yamamoto et. aI., (1978) were the first to develop analytical solutions for the problem, using Biot's theory (Biot 1941) of coupled flow and deformation. Later more complete formulation of the problem including the wave-seabed interactions, the inertial effects and vertical variation of soil properties were developed by Yamamoto (1981, 1984).

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