LOCAL SCOUR NEAR OFFSHORE PIPELINES

Abstract

The present investigation of local scour treats model tests with scour from a uniform flow near pipelines resting on the bottom and pipelines more or less buried. Two different flumes with uniform flow perpendicular to the longitudinal axis of the pipes were used for the experiments. The following mean flow velocities were used: V equals 0.25 m/s, 0.35 m/s and 0.45 m/s. The mean diameter of the bed material was 74 microns. Thirty-two experiments including 4 diameters D = 6.0 cm, 11.0 cm, 22.5 cm and 50.0 cm were carried out. On the basis of these model experiments the following has been estimated for a uniform flow: 1. The development with time of the scouring processes. 2. The different scour patterns near the pipes when they are resting on the bottom and when they are more or less buried in the sand. 3. Possibilities with relevant parameters to extend the observed results for use on prototypes. If test facilities available the experience gained will be used in a further work investigating scour from waves and scour from a combination of currents and waves.