Numerical modelling of wave induced soil liquefaction around buried pipelines and cables

Abstract

In this thesis at first, the concept of soil liquefaction is researched in terms of physics, and the reasons & consequences of this phenomenon are investigated. Besides, the conditions (occurrence in which type of loadings, in which type of soils, and so on.) that cause this phenomenon is mentioned. In short, there are two different types of liquefaction failure of soil; residual and momentary liquefaction. Then, both type of liquefaction is mentioned. However, in this thesis, the residual liquefaction of soil is investigated for the design aspects of submarine pipelines and offshore cables. Besides, the effect of this phenomenon on the structures especially buried objects is scrutinized in many ways. Then generally, it is stated that the buried objects heavier than the liquefied soil sink deeper in the soil, while lighter objects float to the surface when the soil is liquefied. These are called sinking and floatation failures too. In addition, numerous articles and research about this failure are reviewed in the literature. In these researches, the mechanism of the marine soil, the liquefaction/compaction process of the soil (life cycle of the soil), the stress-strain relationship of the soil under loadings, and the relevant conditions (wave or earthquake loading, soil type, so on) are stated in this thesis as theoretical (with analytical & numerical models) and experimental works. Particularly, the disturbance effect on the soil by buried objects such as offshore pipelines/cables is scrutinized comprehensively based on the relevant articles.