The results of dumping stones on a slope by a side stone-dumping vessel

Abstract

The bed and bank of a river, enclosing structures and other works where water is involved are exposed to waves, currents and water level changes. Bed and bank protection works are necessary to prevent eroding of the bed, bank or structure. Bed and bank protection works, on fascine mattresses, geotextile or on a granular filter, are important hydraulic engineering works. They are constructed out of thin layers of granular material. For the construction of these protection works stone-dumping vessels are often used. Granular material dumped by a side stone-dumping vessel will hit the bottom at a certain place and cover it with a thin layer. Repeated thin layers of dumped material will eventually form the bed or bank protection work of a certain thickness. The protection works are constructed in sections, which should all be of equal thickness to ensure a regular protection layer. Therefore it is important to know where stones, if dumped overboard, will hit the bottom and what happens when they hit the bottom. A theoretical model has been developed for the distribution of stones dumped in stationary water, based on a flat bottom. This theoretical model has already been validated by experiments done on a flat bottom. Bed and bank protection works, however, are often constructed on a slope. It is unknown whether the theoretical model is valid in this situation. In this model based on a flat bottom, the Single Stone Model, the stones are dumped at one spot. This theory can be rewritten to the Line Distribution model in which stones are dumped into the water over a certain length, like in the case of a side stone-dumping vessel. Like the Single Stone Model, this theory is based on dumping stones on a flat bottom. Experiments researching this theory have been performed (figure 1). In this thesis, results of experiments investigating the influence of slopes on the distribution of the stones dumped by a side stone-dumping vessel are reported and the validity of the Line Distribution Model on a slope is verified. In the experiments three different slope angles were used to investigate the influence of them. The distribution of stones dumped on a slope of 1:4 can be described by the Line Dumping Model without slope correction, for all water depths and stone diameters as used in the experiments. Apparently this slope angle is too small to influence the dumping process.