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Sunday, June 27, 2010 |
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Diving under Moma Sands
:: News
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Source: Leon van der Merwe
The Moma Sands Project is a recently completed multi-million US$ project on the coast of Mozambique established to process mineral sands by means of a proven dredging, concentrating and separation method. The primary mineral extracted is Titanium Dioxide. The material is transported from the facility on land along a pier conveyor system (extending 450m into the ocean), onto a barge that shuttles between the jetty and sea-going bulk carriers moored about seven nautical miles offshore.
The Stefanutti Stocks Civils structural rehabilitation section was approached by Bateman Engineering to assist with the underwater repair to the Berthing Dolphin Pile at the end of the pier, which had been damaged by the impact of the barge
during unusually stormy conditions.
“The challenge was to place self-compacting grout around the 1m-diameter steel dolphin pile at a depth of four metres below sea level, working from a platform eight metres above sea level” says Leon van der Merwe, contracts manager.
Divers were used to install a four metre long steel form around the pile creating a 100mm annulus for grouting. The grout used was a specially formulated thixotropic grout incorporating additives to prevent cement washout and enhance cohesiveness specifically for underwater placement.
This grout was pumped by means of a double diaphragm pump into steel pipes, which extended to the bottom of the steel forms. The pipes were slowly extracted as the pumping operation progressed. A continuous pumping operation had to be maintained until the entire annulus was filled to avoid any air pockets developing in the grout and ensuring full displacement of all water within the steel form.
“The project was completed in five days,” says Leon, “and we look forward to the next project Bateman Engineering will challenge us with!”
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