Desert snow

25 April 2008

The strand jacking system is set up while the slope rests on its support towers

The strand jacking system is set up while the slope rests on its support towers

The Snow Centre is part of Mall of the Emirates project and is the signature feature of developer Majid Al Futtaim in Dubai, United Arab Emirates. It is the first indoor ski slope in the Middle East. The actual slope, which has a 15% gradient, is 400 m long, 60 m wide, has an unsupported 90 m span and starts at a height of 83 m. At the bottom end of the slope, a five star hotel with views of the attraction, is under construction. The slope will cater both for novice and expert skiers as well as snow boarders. A chairlift system to transport skiers to the top of the slope will be installed at a later date.

Once the 80 m high support tower where the attraction starts was completed, the angled slope had to be lifted into place. Some of the steel components for the slope were manufactured at a workshop 40 km from the site and delivered on a fleet of hydraulic multi axle trailers and flat or low bed dollies. Several permits for oversized loads needed to be obtained from local authorities for this stage of the job.

The final fabrication was carried out on site with the slope assembled on a series of temporary support steel towers constructed from structural steel members and a mega truss. The finished slope weighed 2,850 tonnes, a portion of which was cast concrete floor decking and insulated wall and roof cladding.

The lift

To perform the lift VSL (Switzerland) Ltd. Heavy Lifting, working for main contractor Hyder Consulting, developed a system comprising eight hydraulic pumps, 16 strand jacks, each with four-lifting points, and around 20 km of steel lifting strands. The strand jacks had a lifting capacity of 3,224 kN, a 200 mm stroke and a working pressure of 360 bar. Powering the strand jacks were hydraulic pumps with a maximum pressure of 450 bar. The lifting system took four weeks to install on site with the aid of a tower crane, a 5 tonne capacity mobile crane and a 3 tonne capacity telescopic handler. In total, the entire erection package was valued by VSL at around US$3 million.

The operation to jack the slope was done as a four-point lift with each corner of the structure supported by four strand jacks. These jacks were hydraulically linked to act as one group (lift point) controlled by computer. The lift started by pulling all four points simultaneously but, when 80% of the expected load had been taken up, it was halted to make final checks. For safety this load testing procedure was carried out several times during the lift. The slope was attached to the temporary support towers that it was constructed on until final checks for each stage of lifting had been completed and the load could be transferred to the strand jacks. After three days of lifting the claimed record lift for the region was in place and the dismantling of the jacking system and support tower began.

The attraction opened at the beginning of 2006, with 22,500 m2 of manufactured snow and the facility includes 3,000 m2 Snow Park, also claimed to be the world's largest. There are five different ski runs for skiers of varying skill and a 90 m long quarter pipe for snow boarders and stunt skiers. The park holds a maximum of 1,500 people. •

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