Engineers today righted the shipwrecked Costa Concordia in a $400 million, 19-hour operation involving a technique called parbuckling.
The word parbuckling has leapt into everyday conversation all around the world. So what is it?
Parbuckling has been used for centuries to raise or lower cylindrical objects like barrels and logs.
It involves building a ramp between the two heights, looping a rope under the object and rolling it up the ramp, which is far easier than lifting a heavy object vertically.
Here’s the technique being used to load a log onto a truck:
Parbuckling been used to salvage large ships since as far back as 1943, when the 35,000-tonne USS Oklahoma was righted in Pearl Harbor.
The Parbuckling Project for Costa Concordia, which sank off the coast the Italian island of Giglio in January 2012, commenced last May.
A ship isn’t exactly a cylinder so parbuckle salvage is more about rotating it into the right position than rolling a wreck up a ramp.
The Costa Concordia salvage, which was successfully executed today, involved rotating the ship upright onto an underwater platform, so it could be towed away.
The wreck originally rested at an angle of 65 degrees from the vertical axis; engineers needed it to rotate to about 40 degrees before they could rely on gravity to right the ship.
Parbuckling is risky because it involves exerting a diagonal force on the ship. If wreck slides sideways instead of rotating, it may not be possible to return the ship into a position where it can be levered upright.
Water depth has a major impact on the engineering around the ship; Simon Boxall of the National Oceanography Centre wrote on the Conversation this week that even an additional 10 metres of water could have made Parbuckling Project unfeasible.
The Costa Concordia is nearly 300m long and weighs more than 114,000 tonnes.
It was also filled with water and had a a huge gash across one side, so parts of the structure had to be reinforced and forces had to be carefully balanced throughout the parbuckling operation so the ship wouldn’t fall apart.
Salvage materials weighed some 30,000 tonnes in total.
Until today’s operation, 65% of the ship rested underwater, in the middle of a nationally protected marine park and coral reef, where it would have remained if the salvage operation failed.
The next step is to attach floatation structures onto Costa Concordia, and pump water out of the ship, after which time only about 18 metres of the ship will remain submerged.
It is expected to be towed away next year.
Here’s a video describing the Parbuckling Project plan:
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