| 摘要 |
PURPOSE:To permit the use of a rig even in brittle seabed ground by piercing the body of a double cylinder having vertically movable excavation means with the charge and discharge of water on its upper and lower parts into a through hole provided in a pontoon. CONSTITUTION:The cylindrical body 3 having an excavation means, e.g., an excavating tower 8, etc., vertically movable by the charge and discharge of water on its upper part is pierced into a through hole 2 provided at the center of a pontoon 1, and a working hole 18 through which an excavating tube 17 is passed is provided at the cylindrical body 3. After the mooring, water is charged into a ballast tank in the body 3 and then the wire 6 of a winch 4 is pulled out, whereupon the body 3 goes down and reaches the seabed. Then, a necessary earth-contacting pressure is secured by controlling the amount of water to be charged into the ballast tank of the body 3 according to the conditions of the seabed. Thus, the rig can be safely set on the brittle place of the seabed ground in shallow sea area. |
