ABSTRACT:

This paper briefly reviews results of the current work undertaken by Universiti Teknologi Malaysia in the field of fluid structure- seabed interactions, in particular around pipelines laid horizontally on a bed of sand with shell fragments. The approach adopted in the study was directed mainly towards the collection of data to establish the influence of several variables on the development of local scour. It is evident from the study that the equilibrium scour depth decreases due to the pronounced effect of the armouring phenomenon when sand with shell fragments were used in the experiments.

INTRODUCTION

Increasing activities offshore with regards to the petroleum industry has created a widening interest in research in this field lately. Since it is anticipated that a continued increase of offshore pipelines will be laid in future in several parts of the world, relevant studies pertaining to these pipelines have been undertaken by various researchers. As a direct consequence of this, is the study of the local scour beneath submarine pipelines under current only or wave superimposed on current flow conditions. A practical method which have been exploited by a number of investigators was the application of analytical methods to deal with the real problem in which comparisons were made with experimental results and observations. Many such attempts have been made in recent years to evaluate and describe the local scour process beneath pipelines subjected to a current or wave field or a combination of both. This is apparent from reports written by researchers such as Herbich (1981), Bijker & Leeuwestein (i983), and Ibrahim & Nalluri (1981). Basically, they studied local scour beneath pipelines laid in granular and fine sediments that have been subjected to either this current/wave field or both.

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