TOWARDS A COMPREHENSIVE DESIGN FOR SILT SCREENS IN OPEN CONFIGURATION FROM THE HYDRAULICS PERSPECTIVE

摘要

Silt screens have been considered the "best management practice" to control dispersal of sediment at dredging and land reclamation sites. However, reported performance of the screen in terms of sediment containment is inconsistent. The author believes that such inconsistency could be attributable to two major shortcomings of the current practice of silt screen development. Firstly, the design of silt screen is one that emphasises structural and stability design. The effects of a silt screen on sediment redistribution have often been overlooked in the process. Secondly, despite reported as being successfully executed at several dredging sites, the effects of silt screens on sediment redistribution is not fully understood. It remains unclear how sediment is contained and redistributed in the presence of a silt screen. In this paper, the physics of sediment containment in the presence of a silt screen is first analyzed. From the results obtained from a comprehensive study on the hydraulics and sediment movement patterns around a silt screen through laboratory experiments and numerical simulation, the desirable hydraulics conditions around a silt screen for sediment containment are identified. It has been found that the performance of a silt screen deployed in an open configuration depends on both the vertical geometrical parameters such as screen penetration depth the distance of silt screen from the source, and the length of the silt screen in the transverse direction.