An Experimental Study for Analysis of the Self-Burial of Pipelines with Spoilers in Current

Abstract

Abstract This experimental study deals with the mechanism of spoilers that cause scouring around pipelines. The design methodology was applied to spoilers for accelerating pipelines that undergo self-burial into the sand-bed and evaluated using approaching experimental analysis. The experimental study was conducted to investigate the self-burial ability of submarine pipelines with two types of sand-bed models: silt and sand. Spoilers of different heights were attached to the top of the pipeline for each experiment case. The relationship between the relative scour depth and spoiler height was evaluated by applying different flow velocities and sand diameters and com-parative analysis was performed with values obtained from similarity experiments and theory. The experimental study will be useful in establishing a database for the design of spoilers. Keywords: Spoiler, Self Burial, Scour, Scour Depth, Equilibrium Scour Depth, Model similarity 1. Introduction Submarine pipelines are adversely affected by the marine environment. Especially, current velocity is rela-tively high in shallow water where pipeline installation and operation are expected. Flow around submarine pipelines transforms the sand-bed according to local scour induced vortex shedding and results in additional static or dynamic loads on pipelines, with potential structural damage. Consequently, special regard is re-quired in the design and maintenance of pipelines that are fully capable of accomplishing coastal processes during the onset of scour. Spoilers are convenient during pipeline installation due to the self-burial effect. Pipelines attached to spoil-ers experience lower pressure on the bottom, increasing the inlet velocity of the current between the sand-bed and the bottom of the pipe to a velocity faster than normal. After the pipeline descends, the current de-livers soil and sediment cover to the top of the pipeline, which accounts for the self-burial of the pipeline. Flume tests for similarity models have been conducted and compared to experimental and calculated values for scour depth by Kjeldsen et al. (1974) and by Bijker & Leeuwenstein (1984). 2. Similarity Model