The 4th District Port Construction Bureau, Ministry of Transport
KEYWORDS : Kumamoto Port, soft ground dike, waterway submerged dike, high density air compressed transport
ABSTRACT
Kumamoto port is constructed as offshore artificial in Ariake Bay off the coast of Kumamoto city. Kumamoto port is subject to great tidal range of up to some 4.5m. The site of the port is in fact in the midst of a coastal area experiencing great tide level variation. A thick 40in soft earth layer, known as Ariake clay, lies under the seabed. Furthermore, the port is at the center of the tidal flat of Ariake Bay boasting of the largest size in Japan. Moreover this area is famous for green layer farming. To overcome technical difficulties, engineers have developed, and put to practical use, original technologies and methods such as "Moundless Breakwater with Wide Footing on Soft Ground (hereinafter referred to as soft ground dike) - , "Waterway Submerged Dike" and "High density Air compressed Transport Method" . The soft ground dike obtains stability from adhesion between the dike bottom slab and clayey earth layer and from lateral resistance of piles driven down from the slab against horizontal wave force to the breakwater. The design greatly reduces the dike weight, consequently eliminating foundation improvement even in the case of soft ground. The waterway submerged dike is a measure against waterway siltation. The effects of the dikes include their role as a weir to hinder the fluid mud layer that is formed in stormy weather, and to prevent deposition in a waterway by carrying out the suspended sediment with the upwelling currents developed behind the dikes. the high density air -compressed transport process is a method of transporting dredged spoil pneumatically, Capable of transporting spoil as is in high density without adding water thereto, this method features that waste water does not occur, thus eliminating waste water treatment facilities and preventing marine pollution, and that the resulting land dries sooner than otherwise, thus permitting early service of the land.
