Dubai: Nakheel, the real estate company developing the Palm Jumeirah, has revealed the engineering details of its sub-sea tunnel, which links the main body of the Palm to the crescent.
The six lane tunnel is 1.4 kilometres long, 40 metres wide and 25 metres below sea level. It includes two cells for traffic - three lanes in each direction - and a service/emergency cell in between.
To build the tunnel, a three kilometre long coffer dam - a type of dam that is constructed to exclude water from an area that is normally submerged - was built, with construction starting in October 2004.
The dam was made by driving sheet piles deep into the seabed. Once the dam was built, more than 4.3 million cubic metres of seawater was discharged at a rate of 1,000 cubic metres per hour, from the cofferdam in 45 days
Once the dam was entirely drained of water, construction of the tunnel got underway. Around 200,000 cubic metres of reinforced concrete, 260,000 cubic metres of sand back-filling and 50,000 tonnes of rock armour were used in the creation of the tunnel.
Currently, piers of the monorail are being constructed on the tunnel.
To stabilise the weight, light-weight polystyrene sheets are placed over the tunnel before sand and rock are used to firm up the piers.
