| 摘要 |
A method of assembling a floating platform comprising in combination a semisubmersible vessel 54 having two or more pontoons, buoyant columns upstanding from those pontoons and a deck supported on the columns (the semi-submersible vessel being of a kind known per se), and a raft 53 having a hull portion with a planform greater than the planform of the vessel; which method comprises the steps of ballasting a raft (of the kind described) so that the raft 53 rests on a prepared subsea surface 51 with the upper surface of its hull submerged to a depth greater than the deballasted draft of the vessel, floating the vessel 54 over the hull of the raft, deballasting the raft 53 so that the pontoons of the vessel are raised above water level, and then securing the vessel 54 to the upper surface of the raft 53. The raft may be ballasted to sink to the subsea surface on a falling tide, with the vessel being floated over the raft near high tide, and the raft being subsequently deballasted on a rising tide. Furrows or trenches may be provided to avoid suction forming between the raft and subsea bed during deballasting. Alternatively water jetting may be used. |
