Sunday, September 25, 2011

Palm Island













                                The Palm Islands are an artificial archipelago(a chain or cluster of islands) in Dubai, United Arab Emirates one of the major commercial and residential infrastructure. Crown prince Shekh Mahamad bin rashid ahmad 2 wants to increase tourists to Dubai. He want to make Dubai No. 1 luxurious tourist destination in the world. 5 million tourist visit annually and prince wants to increase it by 15. Coast of Dubai is 72km which is not enough for 15 million people. So the crown prince plan is to build massive islands into the sea.
Palm Islands are constructed by Nakheel Properties, a property developer in the United Arab Emirates, who hired Belgian and Dutch dredging and marine contractor Jan De Nul and Van Oord, some of the world's specialists in land reclamation (Land reclamation is the process to create new land from sea or riverbeds). The Dutch had increased Holland’s land by 35%.
The crown price wanted the island in the shape of palm tree and to be built by only sand and rocks. The construction started in August 2001. Arabian gulf is a perfect place to build such a mega structure. It is on average only 30m deep and 160km wide. It is too short for catastrophic waves to build up. But it should bear with massive waves in winter and a worst case scenario storm which hit once in 100 years should also be considered.


 

              To protect the island break water around the palm tree shaped island must be built. The team do the final calculation to built a break water 3m above sea level and 11.5 km long. 9 barges, 15 tank boats,  4 dredgers, 30 heavy land base machines and 10 floating cranes were needed to construct the massive island.



                        First step of building break water was to construct sea floor. 3 massive dredger dump the sand up to 7.4m thick. To keep it in place floor of rocks were dropped on it up to 3m above sea level, total thickness of 7m. 5.5 million cubic meter of rock was required by the 11.5m long break water which is enough to build two Egyptian pyramids. The heavy land base machines put 14000 cubic meters of rock in place per day. These rocks must interlock with each other to bear with sea waves. The constant check to ensure the break water is in place and standing firm was done by sending divers.

                March 2002 storm hits and a section of break water is in the sea. For 3 weeks work had to be stopped. But the break water stands firm. Crown prince wanted the island and city on it to be build by2006. Only way to meet the deadline is to build break water and island at same time. But this is not an ideal situation. The island will have bad effects of sea waves without complete break water. But the deadline had to be met.


               The island construction team had to find 94 million cubic meters of sand to build the palm tree island. Dubai has more sand, but desert sand is not the suitable for constructing island. Its particles are too fine and won’t stick together firmly. It means it will be easily washed away. The best sand was found 6 nautical miles(11km) out of sea. This was the best suitable sand. It packs densely and more resistant to waves.




                Dredgers scoop up 8000 ton of sand less than an hour and spray the sand into the place. The process is called rain bowing. But it was difficult to say that sand was falling at right place.  It was achieved by GPS technology. Dubai has access to only privately owned satellite in the world, the Ikonos. 







Mobile receivers on the island make grid reference and receiving signals from satellite and from a fixed position on land, height and position of island is recorded. With these records dredgers rainbow the sand at place with pin point accuracy.

                October 2002, 2/3 of break water and 9 palm fronds rise above the sea level. But then engineers discovered a problem that could put the whole project in danger. The water inside the sea wall (break water) was not circulating resulting in dirty water being stored inside.







 Luckily the solution is found just in time. Making two breaks in sea wall (break water) made it easy for sea to push clean water inside.
                
                 August 2003 break water completes. Two months later island reclamation completes. 94 million cubic meter of sand and 5.5 million cubic meters of rock holds back full force of sea. Now to fulfil crown prince’s dream  4500 houses and apartments, 200 hotels and shopping malls are to be build on the island.

The sand island must support an entire city on it. But sand is not an easy platform to build on. Because the sand is sprayed it is loose and not compactable. Over time sand will compact naturally, but it will take time.



 The solution was to use process called vibro-compaction. January 2004 fifteen vibro-compacting machines work around the clock to firm up the land. These shafts vibrate shaking the ground around it and compact the land. As the land compacts and sink more sand is poured in.  It took 8 months to stabilize the land. March 2004, the palm Jumairah is ready to be and building site.

When the palm first released to the public all the houses were sold just in 3 days. Most expensive go for 1.2 million dollars. 






         
           There was another problem, beach erosion. Normally sea current push the beach sand evenly. By building massive structure on shore line current will change its shape resulting in at some place shore will extend and other place it will erode.  Naturally problem will be solved but it will take time. Mean time developers used dredgers to suck up sand where it has deposited and pour into place where it had erode. 





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