Performance of silt-curtain in three dimensional sea is investigated through a series of experiments. It is found that there are three mechanisms to reduce concentration and flux of turbidity generated by the construction work from flowing out of the construction site enclosed with silt curtains. The first is the temporal storage of turbidity and retardation of the flow of turbidity around the curtain. The second is the acceleration of dispassion of turbidity caused by the turbulence generated around the curtain that decreases the peak value of concentration of turbidity. The last one is the reduction of flow velocity in the enclosed area. As a result, the diffusion time increases and the amount of turbidity settled down in the enclosed region increases. Taking these mechanisms into account a simple procedure to predict reduction of flow velocity and the flux of turbidity is proposed. The applicability of the proposed procedure is examined using experimental results.
Generation of turbidity in the coastal region is unavoidable in the construction work of various kind of coastal structures. Turbidity caused by the dredging, sand damping for sand mat and so on often has fatal effects for fish habitation and ecosystem especially in the semienclosed sea. To prevent from dispersing and spreading out SS from the construction site, a silt curtain has been usually used. Although some experimental studies have been carried out to investigate the performance of silt-curtain in a two-dimensional wave tank (Kano et. al., 1987, Sawaragi et.al., 1988 and Oda et. al., 1990) and field (Furudoi, 1989), any investigation of the performance of silt curtain has not been done in three-dimensional sea. At present, there is not any definite guide line for the plane arrangement and expansion of silt curtain in the sea.
