Watching the periodic floods surge down the Wadi Dayqah in Muscat was not only an awesome sight, but one to fill farmers and other inhabitants of the region with frustration at the precious resource racing out to be lost in the sea. No more, however, as the Gulf’s largest irrigation dam project to date nears completion.

 

The Wadi Dayqah Dam is set to harness the 60 million cubic metres of potentially potable water that flow down the deep desert canyon each year; with RMD Kwikform having played a pivotal role in assisting the joint venture company with the construction of a 390 metre long, roller compacted concrete dam.

 

While the client – the Sultanate of Oman Ministry of Regional Municipalities, Environment and Water Resources – estimated that just 15 per cent of the perennial flow was utilised through existing irrigation channels, the new dam will be able to store up 100 million cubic metres of water.

 

Thanks to the work of Vinci Construction and Consolidated Contractors Company Oman LLC, a series of pipelines will in the future carry treated water to the villages of Hayl al Ghaf, Daghmar and Quriyat. While these downstream settlements will gain some 10 million cubic metres of water for mainly agricultural use, another 5,700,000 and 19.300,000 cubic metres will be consumed as drinking water by the Quriyat and Muscat Governorates respectively.

 

The development of the Wadi Dayqah Dam has provided RMD Kwikform the opportunity to demonstrate its ability to supply the very largest civil engineering projects with both stock and specialist formwork systems. While in many instances, clients find hiring formwork is more economic, the scale and duration of the dam project meant that the contractors chose to purchase all of the equipment; the site being supplied through RMD Kwikform’s huge Dubai depot.

 

At its highest point the dam stands 73.6 metre high, spanning between its bedrock abutments in the wadi walls. Its construction was begun in 2007 with RMD Kwikform supplying its first components in the April for the casting of a diversion channel which runs centrally beneath the dam wall.

 

For this RMD Kwikform delivered sufficient quantities of its well proven and widely used GTX Beams and Superslim Soldiers to facilitate the casting of the 55.4 by 15.53 metre wide structure. These products were employed to form single sided shutters for the massive, 4.0 metre thick base section to the channel. These were propped using adjustable struts.

 

The walls, at a slightly more modest 2.5 metres thick were formed in two lifts using GTX Beams and Superslim Soldiers again, but this time with pairs of shutters linked using RMD Kwikform Rapid Ties. Finally single sided forms were employed again to cast the 2.5 metre thick roof slab to the diversion channel.

 

Possibly the most complex aspect to the construction of the Wadi Dayqah Dam concerned the Intake Tower which was erected in advance of the dam wall. Standing off-centre to the dam itself, it rises 56 metres above the canyon floor and has a base 8.0 metres thick.

 

Complicating the construction sequence, and preventing the RMD Kwikform shutters from being tied through from face to face in many instances, were the proliferation of intake pipes and sluice gate assemblies that are accommodated within the tower.

 

The solution devised by RMD Kwikform’s technical design department involved adopting a 2.25 metre high, single sided shutter arrangement, to reduce the pressures and avoid the need for continuous ties. Once the concrete gains sufficient strength, the shutters are struck and raised to the next position using RMD Kwikform Jump Form brackets secured to the manufacturer’s 24 x 280 mm Anchor Screws, cast into the top quartile of the previous section. Man access platforms with handrails are an essential component of the system.

 

Despite the imposing size of the Wadi Dayqah Dam wall, the method of construction actually means the concrete pressures are far lower during placement than is normally experienced when concrete is poured or pumped into shutters. As the core of the dam is compacted using 30 tonne vibrating road rollers to compact concrete with a slump of just 20 mm (?), the operatives shoot a much more fluid mix along the edge zone, some 400 mm wide behind the formwork. This face area is compacted conventionally with vibrating pokers.

 

Nevertheless, RMD Kwikform’s design office carried out full calculations for all of the loading conditions relating to the various formwork elements and supplied its clients with comprehensive detail drawings, plus method statements where appropriate. And to ensure that there were no problems with the interpretation of the drawings, one of RMD Kwiform’s most experienced engineers spent two weeks on site at the beginning of the project to train the labour force and give guidance on health and safety issues.

 

For the upstream wall of the dam which will mainly be hidden beneath the waters of the new reservoir, a similar construction method was adopted to that for the Intake Tower. The downstream face, however, steps back like the sides of an ancient pyramid, and featured the use of 1.2 metre forms assembled using GTX walers and supported using more of the Anchor Screws with brackets and telescopic shores. At the top of the downstream face, an overhang was constructed by casting a Rapid Tie nut and plate into the last step, and then cantilevering out at an angle before the shutters rise vertically again. Telescopic props and access platforms were again provided by RMD Kwikform.

 

An important aspect to the level of service and functionality which RMD Kwikform is able to offer compared to its competitors is the company’s capability to respond to customer’s project specific requirements: particularly with regard to the fabrication of special components.

 

In the case of the Wadi Dayqah Dam the need for bespoke formwork elements focussed the ogee curves to the spillways, and the ‘splitter teeth’ which encourage the flow across the top to do so smoothly.

 

The second stage of the ambitious infrastructure project also got under way in 2007 with work involving the construction of a huge treatment works some seven and a half kilometres downstream of the dam site. This is predicted to be able to process 125,000 cubic metres of water per day. An enclosed reservoir is also being built.