Bow thruster velocities at multiple bank slope configurations and the stability of slope material

Master thesis (2017)

Authors

R.F.A. van Noort Civil Engineering & Geosciences

Contributors

T. Vellinga (supervisor 1)
H.J. Verheij (supervisor 2)
H.J. Verhagen (supervisor 2)
A. van der Hout (supervisor 2)
T Blokland (supervisor 2)
Faculty
Civil Engineering & Geosciences
Copyright: © 2017 Roel van Noort
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Published Date

30-06-2017

Language

English

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Faculty

Civil Engineering & Geosciences

Abstract

When sea-going or inland vessels berth along a mooring location they use their bow thruster to manoeuvre. When the induced propeller jet is directed towards a slope it might affect the stability of the slope material and this can lead to damage when the loads are too large.

The objective of this research was to extend and validate a method to determine hydraulic bed loads on slopes induced by bow thrusters and a method to determine the stability of slope material. In order to answer this objective scale model tests are conducted at the test facilities of Deltares. Velocity and stability measurements are performed during multiple test scenarios that contain variations in slope angle, axial distance and pile configuration. From the obtained data of the velocity measurements the time-averaged velocities and the turbulence intensities are determined. For example, the time-averaged slope velocities measured in the scale model that consists of an 1 : 3 slope with an open quay pile configuration and a rough bed (test scenario T10 in the research) are shown in Figure 1. These values are compared to the values according to the Dutch guidelines and a correction factor for the underestimation of the hydraulic bed load on a slope is defined for each test scenario. After that the consequences for a design of a slope protection are evaluated. Furthermore, for the stability tests it is determined what the critical slope velocity is. This is done for multiple criteria of initiation of motion. With these critical slope velocities a stability parameter for the stability relations can be determined that is applicable at situations similar to the scenario tested. These determined stability parameters are compared to the recommended stability parameters and the differences are evaluated. Finally recommendations are formulated for correction factors for the slope velocities induced by bow thrusters and recommendations are formulated for a proposed stability formula by an earlier research.