<；P>；PROBLEM TO BE SOLVED: To provide a sand cover structure that appropriately inhibits the elution of hydrogen sulfide and nutritive salts from the bottom material and retains high stability causing scarce sinking. <；P>；SOLUTION: The sand cover structure at the water bottom comprises the lower sand cover layer of finely granulated blast furnace slag and the upper sand cover layer formed on the lower sand cover layer with other sand cover material than the finely granulated blast furnace slag. Since the lower sand cover layer is consolidated by the finely granulated blast furnace slag, the lower sand cover layer plays the role of the lid for the bottom material to inhibit the elution of hydrogen sulfide and nutritive salts and also whole or partial sinking of the sand cover layer are suppressed. <；P>；COPYRIGHT: (C)2007,JPO&INPIT
