On the sedimentation process in a trailing suction hopper dredger : Over het sedimentatie proces in een sleephopperzuiger

In the last decades and in the near future, large areas of land, especially in the Far East, were and will be reclaimed using trailing suction hopper dredgers. During the overflow phase of the loading stage of the dredging cycle, a part of the dredged volume of sand will not settle in the hopper but will be transported with the overflow discharge overboard. For production, sand quality and environmental reasons it is important to predict the amount of these so-called overflow losses. The total volume of losses as the influence on the loaded (and lost) particle size distribution (PSD) is important. In 1997 a research programme was started to get more understanding of the sedimentation process onboard a hopper dredger. The goal of the programme was to develop a numerical model that can be used to predict the influence of the relevant parameters as hopper geometry, sand, discharge and concentration on the overflow losses (and which fractions of the PSD will be lost). The research programme consists of three parts: laboratory experiments, development of numerical models and full-scale validation of the models. In this article the developed 1DV numerical model will be presented. The 1DV-model is one-dimensional, but in contrast to most existing models in the vertical direction. The influence of the PSD distribution is modelled using a coupled system of transport equations (convection-diffusion) for the different grain sizes. The numerical results will be compared with experiments. The financial support of the VBKO (Vereniging van Waterbouwers in Bagger-, Kust en Oeverwerken) for this research is gratefully acknowledged.