Effects of Dynamic Soil Permeability on the Wave-Induced Oscillatory Seabed Response

Wu, Sheng (Griffith University) | Jeng, Dong-Sheng (Griffith University)

OnePetro 

ABSTRACT

Soil permeability is one of key factors in the prediction of the wave- induced seabed response, which will directly affect the design of foundation around marine installations. Most previous studies in the field treated the soil permeability as a constant, although it depends on numerous soil parameters. In this study, the soil permeability is considered as a function of pore water pressure as reported in the literature, with this new feature, the governing equation will become non-linear differential equations. Numerical examples demonstrate the significant influence of dynamic soil permeability on the wave-induced pore pressure and effective stresses.

INTRODUCTION

In the past a few decades, considerable efforts have been devoted to the phenomenon of the wave-soil interactions. One of the major reason is that the evaluation of the wave-induced soil response and its resultant seabed instability is particularly important for coastal geotechnical engineers involved in the design of foundation of the offshore installations (Rahman, 1991; Sumer, 2014). Another reason is that the poro-elastic theories for wave-soil interaction have been applied to field measurements such as determination of the shear modulus of seabed (Yamamoto et al., 1991) and the direction spectra of ocean waves (Nye and Yamamoto, 1994), as well as acoustic waves propagating through porous media (Yamamoto and Turgut, 1988).

Based on Biot's poro-elastic theory (Biot, 1941), several classic investigations for the wave-induced soil response have been carried out since the 1970s. Among these, Yamamoto et al (1978) proposed an exact closed-form analytical solutions for the wave-induced oscillatory soil response in an isotropic, poro-elastic and infinite seabed. This model was further extended to three-dimensional cases by Hsu and Jeng (1994) for various soil conditions. Another different approximation, so-called boundary layer approximation, was proposed by Mei and Foda (1981), which provided a simple formulations of the wave-induced soil response. This approximation can provide precise prediction of soil response in fine sand rather than coarse sand, as reported in Hsu and Jeng (1994). Okusa (1985) investigated the effects of degree of saturation on the wave-induced soil response based on plane stress conditions. A detailed review of previous relevant research can be found in Jeng (2003).