Case studies

Keller was first choice ground engineering contractor at the extraordinary Palm- Jumeirah Island project in Dubai.

Unlikely as it may sound, Dubai’s Palm-Jumeirah Island is an artificial island that has been reclaimed from the sea in the shape of a palm tree. It is hypothetically visible from the moon with a naked eye and is the self-proclaimed Eighth Wonder of the World.

It is yet another prestigious project for Dubai development company Nakheel, and will unquestionably help Dubai in its quest to diversify its economy into upmarket tourism.

World famous celebrities, such as Formula 1 driver Ralf Schumacher and England’s football captain David Beckham, have already bought villas – and did so even before the island was created.

Palm-Jumeirah Island is located about 20km southwest of Dubai city centre, next to Royal Miraj Hotel. A series of 5km-long crescent shaped “branches” extend off the central “trunk”. This trunk will have a luxurious shopping mall, a resort, water theme park and a 1.5km long canal. It will be connected to the mainland by a bridge.

The lower branches will contain the luxury villas, complete with beach-fronts and swimming pools. The 11km beach strip across the top of the palm will be developed with luxurious hotels, apartments and leisure facilities including a diving club.

Three old aeroplanes have been stripped of environmentally harmful materials and will be sunk to create an artificial reef, encouraging marine life and providing something interesting for divers to explore.

The island was created using sand fill placed directly onto the (typically) 10.5m deep seabed using bottom dump dredgers. Above sea level, the top 3m of the reclamation was achieved using a dredging technique known as “rainbowing” in which the sand fill was sprayed over the surface of the emerging island.

The reclamation was made of calcareous sand, which was locally cemented into a soft sandstone. Although Dubai is a low risk earthquake zone, Nakheel’s design consultant mitigated the risk of liquefaction by specifying vibro compaction ground improvement - this will also help to control differential settlements across the reclamation.

The scale of the project means a number of the world’s leading ground engineering contractors were involved, but Keller was the client’s first choice to tender for the vibro compaction work.

Keller’s target was to achieve a bearing capacity of 150 kN/square metre and 60% relative density within the reclaimed fill. Keller’s solution was to create a grid of dense columns on a regular 3.75m spacing using a giant vibrating poker. The average compaction depth was 13m.

Keller was on site, working double shifts, within two weeks of receiving the client’s letter of intent.

Leading up to completion of the ground improvement work in July 2004, Keller had 12 vibro units working around the clock. And with beachside site offices located on the junction of the palm’s trunk and crown, Keller’s engineers, operatives and support team were all in agreement that it was not a bad place to work for a few months.