Abstract
There are terrible problems that the organic sediments on the sea bed destroy the ecosystem all around the closed water. Generally, the two improving methods for the bottom sediments which target such the organic sediments are executed. The one is a dredging method which removes them outside, and the other is a capping sand method which covers the sea bed with the sand. This paper describes the sand deposition characteristics of thin sand capping when the sand was dumped by either a backhoe or a grab bucket into shallow water, because the construction demands the sand piled up as thinly and uniformly as possible. They were clarified through the field research at our construction site. Finally, the average layer thicknesses were almost equal to the planned layer thicknesses in any case of the dumping either the dredged sand or the pit sand. The coefficient of variation of the layer thickness became larger as the planned layer thickness decreased. Thus in the thin sand capping, it found that we have to set more surcharge for the quantity of sands, because the error of layer thickness would grow.
