Answer by Rakshita Nagayach:
I believe the Palm Island (Palm Jumeirah), Dubai was the most audacious project of its time. Building an island in the middle of an ocean was the bravest thing to do. The island has a breath-taking aerial view,along with the infrastructure built on it. But a lot of hurdles came in the way during the construction of the then largest man made island.
1) Foundation construction: The Palm developers wanted the foundations to be made with natural building materials i.e. only sand and rocks. The problem was that sand gets eroded as soon as it hits the water. Also to protect the island, a backwaters wall was to be constructed so as to prevent direct impact of waves on the island.
94 million cubic meters of sand and 5.5 million cubic meters of hard rock were needed to make a 2.5 meters wall above the sea level.
2) Climatic Factors: Massive sea waves, persistent winds and large currents are relevant in the Arabian Gulf. Though the Gulf is quite shallow near the coastline of Dubai (on an average, the depth in only 30 meters), But thecoming in winters bring 2 meters high waves,becoming a threat to the project.
This threat was overcome by constructing breakwaters 3 m above the expected wave height and 11.5 km long.
3) Political Pressure: It was both on the engineers and the Palm Developers. The construction began in August 2001 and a month later, the World Trade Center attack wiped out almost all the tourism in the Middle East for about 3 months.
Also the engineers were given exactly 5 years to complete the project,which demands 15 years actually.
4) Massive Construction Equipment required: 9s, 15 s, 13 Heavy land Bar machines and 10 floating cranes were used for the construction of the sea wall. The first step was to build the sea floor, by 3 , laying 7.4 m thick layer of sand when the sea is at the calmest. Rocks are immediately dropped to raise the breakwater.
5) Wave Action: Waves have an eroding nature of whatever comes in their way. The sloping layer of the sand laid takes out the force of the wave as they hit the water. Rubble formed the core of breakwater outer armour of rock pieces protect the entire wall.
Constant checks had to be made by the divers pinpointing every rock and crack, as every crack was dangerous. Every 27 m of the wall was checked by a diver periodically.
6) Shamal arrives: Storms with a speed upto 56 kmph bring torrential rains and violent thunderstorms with them, delaying the breakwaters by 3 weeks.
7) Availability of Sand: Although Dubai’s desert has abundant sand to be used for construction,the problem with desert sand is that its too fine to construct a city of a hundred thousand people. Marine sand available 6 nautical miles from the site has the properties of being resistant to wave impact, coarse and densely packed.
Dredges sucked up the sand from the Gulf sea bed and sprayed it on the site within 3 hours time. It took less than an hour to fill the 8000 tonnes tank with sand in the dredges.
Pumping, technically known as Rainbowing is the spraying of sand on the site.
8) Synchronicity in Wall building and Island building: If the breakwaters work progresses too quickly, it will cut-off the access for reclamation project, and if reclamation is done too fast, it is in direct contact with the sea waves.
9) Accuracy in shape of the Island: A single mistake in the shape would lead to failure of entire project. To keep a check on it, Dubai used it privately owned space satellite (only nation in the world to have a private satellite).GPS was used by daily perimetering the surface and create a grid reference by reading the signals from space and fixed position on land to check location of sand bars.
10) Water blockage: As the breakwaters trapped the island, the water was supposed to become stagnant,and ultimately home to algae and other unwanted biological hazards. So, 2 breaks in the sea wall were made, by making 4-lane road bridges over it on the observation that tides enter the wall twice a day and in 2 weeks, the entire water is replenished. A team of environmentalists keeps checking the water content on a regular basis.
11) Liquefaction of Sand due to seismic activities: Due to spraying, the sand is loose and not compact, which might lead to complete sinking of the island due to the occurrence of earthquakes.
Sand layers are compacted 12 m deep using 15 Vibrocompactors; probes drilling 200000 holes, shaking the ground around it and making it compact. As sand compacts and sinks, more sand is poured in.
12) Building the city in just 2 years: 40000 Asian workers in two 12-hours shift worked under 51 contractors building hundreds of villas, hotels and shopping malls.
13) Beach erosion and coast line depletion: The engineers have made sure that the beaches facing erosion will continuously be examined and sand would be sprayed on them.
Normally the waves keep the beach in a line but due to an obstacle, the wave pattern changes. In dome places,sand is deposited extending out of the sea,and in some places it is eroded away.
A dredger is appointed to suck up the sand where it is built across the coast and deposit it in areas where it has been eroded,thus maintaining the coastline.
14) Aquatic Life: To check the condition of fishes and corals, every 6 weeks divers check the waters. It was expected that the aquatic life would be affected badly, but to a surprise the results were completely opposite. Marine life is not only unaffected, the breakwaters have provided shelter for fish, attracting many other species.
Now the Palm developers plan to develop largest artificial reef in the world! In June 2004, 2 Jet planes were dropped in sea for people to dive on,and there’s a plan to drop a London’s Red double-decker bus!
Long live the spirit of Engineers!