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Middle East: Coming clean

High-rise formwork construction techniques are being used to develop a much needed new underground wastewater containment and treatment system for the expanding Dubai suburb Burj.

Now standing tall at over 800m, construction work on the Buji Dubai has passed its peak. Nearby, however, work is racing along on another impressive high rise that will service it.

Aimed at servicing the whole of the Burj Dubai area, home to some of the largest and most impressive structures in Dubai, not least the world’s tallest building the Burj Dubai, the Dubai Municipality funded project at a cost in excess of 1.56bn Dirhams (£257M) will transform the way wastewater is handled in the area.

Turning construction on its head

The solution to tackling this issue has taken multi-storey construction and turned it on its head, with the construction of a vast concrete underground pumping station known as DS164 to contain and distribute wastewater to the new Jebel Ali treatment works. Wastewater from DS164 will link by a pipeline discharging to another pumping station DS161 that will forward sewage to the treatment plant along a predefined pipeline route.

Infrastructure and excavation works to prepare for construction of the massive phased Jebel Ali wastewater treatment plant and pumping projects began in early 2007, with the contract for the development of a major pumping station awarded to construction firm Wade Adams Middle East’s drainage and sewage team.

“This project will ensure residents and visitors have all the amenities they would expect of a World class city.”

Ashraf Hanna, Wade Adams

To build the underground high-rise style pumping station, the Wade Adams engineering team worked with formwork provider RMD Kwikform to design a safe and fast formwork solution, using its Rapidclimb system.

This approach to adopting the principles of high-rise construction underground, led to the recent completion of the concrete work for the 22m deep, 700m³ pumping station, ahead of schedule.

The complete project DS164, including the pumping station, was due for completion in May 2010, but is already ahead of schedule with 75% of the work completed in just 55% of the time.

“Even though this project will not been seen by residents and visitors to Dubai, it will certainly play an important role in ensuring they have all the amenities they would expect of a World class city,” says Wade Adams construction manager Ashraf Hanna.

“Having developed a speciality in this sector, working on a number of drainage and sewage projects of this kind, but on a smaller scale, when we were tendering for the job.

“We knew that the success of the project would rely heavily upon achieving a high level of build quality,” he says. “After all, the one thing you do not need from a system that is carrying sewage is leakage, or worse still system failure.”

Meeting challenges

When looking at the overall design of the main 22m deep pumping station, Wade Adams focused on determining whether the formwork equipment and suggested solutions from suppliers could meet the pressures and tolerances exerted upon it by the self compacting concrete that it had to use.

“Although this was the core challenge, we also had to factor in the three key points that are relevant to any project − the programme time, cost and staff safety,” says Hanna. “Even before we were awarded the project November 2007 we worked with RMD Kwikform engineers to develop a system that could meet these challenges, so that once we had secured the project we could move quickly to begin work.”

Following a construction specification put together by design consultant Khatib and Alami, the Wade Adams engineering team worked together with RMD Kwikform engineers to design a modular system based solution.

The important restrictions placed on the design related to its manoeuvrability, as the weight of the individual panel and Rapidclimb system sections could not exceed the 2.5t lifting capability of the site’s 6t tower crane.

“Unlike a high-rise project where you tend to have numerous cranes and plenty of room for supporting access systems, when you are working underground you have much more to contend with, not least the safety aspect.”

Stuart Bland, RMD Kwikform

“From a design perspective, unlike a high-rise project where you tend to have numerous cranes and plenty of room for supporting access systems, when you are working underground you have much more to contend with, not least the safety aspect of protecting workers from potential of falling debris,” says RMD Kwikform key account manager Stuart Bland.

“That is why in the main design we went for the Rapidclimb system as it is in this case a descending system that supports its own weight and can be moved simply from pour to pour using a crane.”

Due to crane restrictions the panels that make up the system using RMD Kwikform standard formwork were converted into a crane-handled climbing system.

The system consists of Alform aluminium secondary beams and Soldier primary beams in conjunction with the Rapidclimb frames, with each panel 3.5m high by 6m wide to suite the customer’s pour sequence.

Quality and accuracy

From a practical perspective, once the panels are moved into place Rapidclimb can be anchored to the existing concrete construction using reusable high load Rapidclimb anchors.

Mounted on a trolley, the formwork panel can then easily be retracted from the form face to allow for cleaning and steel fixing to take place. Access platforms and formwork are lifted as one, increasing safety, while reducing the need for additional labour.

“We made the trailing platform wider in size to give staff an added reassurance, as working underground at height is probably even more daunting than being on top of a high rise building.”

Stuart Bland, RMD Kwikform

“Because in this case we were descending, the platform design for second fixing was reversed and to increase safety we made the trailing platform wider in size to give staff an added reassurance, as working underground at height is probably even more daunting than being on top of a high rise building.

“From a quality and accuracy perspective, because we needed to achieve a very good finish for obvious reasons, spillage was out of the question − we trained the team on how to take advantage of the system design layout,” says Bland.

“For example, due to the makeup of Rapidclimb, fine adjustments of the form face can be made during construction, to make sure accurate alignment of the face is achieved both vertically and laterally.

“Similarly the ratchet turnbuckle system used to retract the form from the wall makes it easy to strike the shutter from the concrete face and move to the next pour.”

With the entire pumping station requiring 20 pours, the formwork allowed the second fix to go ahead while the next pour was underway. Waterproof grout was used to ensure that no leaks were possible.

“With the completion of the concrete phase of the pumping station, we are now pushing hard to complete the pipe work and engineering required to get the system up and running, so that we can deliver our own impressive world-class sewage system that visitors won’t see, but will certainly benefit from,” says Hanna.

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