Formwork: Dubai Metro
RMD Kwikform Middle East's role on the Dubai Metro
Of all the infrastructure developments undertaken in the Emirates, the Dubai Metro is undoubtedly the most important public transport project in terms of its strategic implications. RMD Kwikform Middle East secured the contract for the temporary support work for construction of the Metro’s elevated tracks.
The VFR JV comprises two post-tensioned pre-stressing specialists, VSL and Freyssinet, together with Italian contractor Rizzani. Their expertise was critical to the successful creation of the 52km Red Line with its 29 stations, which were completed first, as well as another 22km of track and 18 stations for the Green Line.
RMD Kwikform project manager David Barrington explains: “While there was serious competition for this contract, a number of members of the project team had come to Dubai from building a similar transport scheme in Hong Kong, where they had come to realise the benefits of Megashor.
“So although we were up against heavy competition from a variety of businesses, we had the equipment that the client trusted already on the ground, and the designers to provide the drawings for each location.
“Essentially we had to complete a drawing and component list for every different height of the track units above the existing ground level, to ensure the installation went ahead smoothly and safely; and these had to be turned around within a couple of days to keep the work on schedule,” said Barrington.
So colossal was the scale of the scheme undertaken by VFR that the consortium had up to a dozen sections of the route under construction at any one time, with RMD Kwikform being called upon to supply Megashor towers to site for erection within a very short timeframe.
Barrington continues: “We supplied the first pieces of equipment from stock in November 2006, with the larger orders delivered early in 2007, and continuing on a regular basis thereafter.”
The Megashor support system offers a load-carrying capacity of 100 tonnes a leg, and it was used to carry the very heavy, U-shaped precast concrete sections to the Metro’s tracks wherever the main contractor was unable to use its standard launching system.
This may be due to there being restricted headroom, perhaps due to a road coming over the top, or the presence of electricity cables. Then they were making use of Megashor as support from below.
One of the key attributes of Megashor is the fact that the integral jacks provide up to 400mm adjustment top and bottom. With the towers set to millimeter accuracy, the main contractor’s operatives took over installing a series of bolted and welded steel beams across the top bearing plates, which then carried the track sections.
Depending on the distance from one abutment to the next, the Megashor system was being employed to erect double rows of towers to carry as many as eight or nine precast units: each one 4m in length and 10m wide, to make up the span.
These were then jointed together and the prestressing tendons passed through the cast-in ducts that determine their correct profile or path. Hydraulic jacks then tensioned the cables in sequence and the Megashor supports could be lowered ready for reuse.