Author(s): Su Jason C. C.; Perng Arthur T. H.; Capart Herve

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Keywords: Jet trenching; Turbidity current; Moving jet

Abstract: Laboratory experiments are performed to investigate the water and sediment motions due to needle jets moved steadily along a submerged bed of fine sand. These point-like jets represent small-scale analogues of the jetting swords used by Remotely Operated Vehicles (ROVs) to bury submarine cables and pipelines under a protective sand cover. The features observed in the experiments include the longitudinal flow structure and bed profile within the jet-incised trench, as well as the turbid overspill induced when the jet-induced sediment-laden current flows over the lateral walls of the trench. Distinct overspill patterns are observed depending on the power and travelling speed of the moving jets. For a given power, slow speeds induce overflow turbidity currents that radiate outward and propagate ahead of their point of emergence from the trench. Fast travelling speeds, by contrast, induce swept back turbid plumes that spread only in the downstream direction, away from the jets. Overspill patterns are important in practice because they control the loss of sediment from the trench, the resulting loss of sand cover for the buried product, and possible adverse environmental effects due to the stirring and dispersal of turbid plumes.

DOI:

Year: 2007