International Journal of Ocean and Coastal Engineering

A better understanding of soil behavior in a seabed foundation around submerged breakwaters under combined wave and current loadings has become crucial regarding the design and maintenance for such breakwaters. Bragg effect is considered in this study, which is one of the important factors that influence the flow field and soil response in the vicinity of multiple breakwaters. The wave-current induced dynamic soil response (effective stresses, pore pressures and displacements) and its resultant residual liquefaction in a loosely deposited seabed foundation around multiple breakwaters are investigated. In this study, the wave motion is governed by VARANS equation and the Biot’s $u$–$p$ approximation is used to govern soil-fluid interactions in porous medium. The elasto-plastic constitutive model (PZIII) is used to reproduce the plastic soil behavior in seabed foundation under long-term cyclic ocean loading. Numerical results show that the flow motion can be largely changed due to Bragg effects. The construction of breakwaters significantly change the stress field in seabed foundation. Parametric study shows that, under the strongest Bragg effect, the presence of currents, soil properties and wave characteristics have great impact on the liquefaction potential.

This paper presents the results of an integrated mathematical modeling exercise for sinking of Drag Embedment Anchors (DEA) in a seabed liquefied by waves. The mathematical model consists of three elements (sub-models): (1) Mathematical model for residual liquefaction under waves; (2) Mathematical model for sinking of DEAs in the liquefied soil; and (3) Mathematical model for upward progression of compaction front in the post-liquefaction stage. The study demonstrates the implementation of the model with reference to a selected group of real-life DEAs. The results generally show that the ultimate sinking depths of DEAs are rather large (tens of centimeters short of the liquefaction depth), and accordingly, the ultimate sinking times of DEAs are rather small (O(10min)) as a result of the massive weights of these anchors. The paper presents a parametric study carried out in a systematic way to understand the influence of parameters such as the relative density of soil, the soil depth, and the grain size on the end results.